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Unusual Red Arcs Spotted on Icy Saturn Moon

Like graffiti sprayed by an unknown artist, unexplained arc-shaped, reddish streaks are visible on the surface of Saturn's icy moon Tethys in new, enhanced-color images from NASA's Cassini spacecraft.
The red arcs are narrow, curved lines on the moon's surface, and are among the most unusual color features on Saturn's moons to be revealed by Cassini's cameras.
Images taken using clear, green, infrared and ultraviolet spectral filters were combined to create the enhanced-color views, which highlight subtle color differences across the icy moon's surface at wavelengths not visible to human eyes.
A few of the red arcs can be seen faintly in observations made earlier in the Cassini mission, which has been in orbit at Saturn since 2004. But the color images for this observation, obtained in April 2015, are the first to show large northern areas of Tethys under the illumination and viewing conditions necessary to see the arcs clearly. As the Saturn system moved into its northern hemisphere summer over the past few years, northern latitudes have become increasingly well illuminated. As a result, the arcs have become clearly visible for the first time.
"The red arcs really popped out when we saw the new images," said Cassini participating scientist Paul Schenk of the Lunar and Planetary Institute in Houston. "It's surprising how extensive these features are."
The origin of the features and their reddish color is a mystery to Cassini scientists. Possibilities being studied include ideas that the reddish material is exposed ice with chemical impurities, or the result of outgassing from inside Tethys. They could also be associated with features like fractures that are below the resolution of the available images.
Except for a few small craters on Saturn's moon Dione, reddish-tinted features are rare on other moons of Saturn. Many reddish features do occur, however, on the geologically young surface of Jupiter's moon Europa.
"The red arcs must be geologically young because they cut across older features like impact craters, but we don't know their age in years." said Paul Helfenstein, a Cassini imaging scientist at Cornell University, Ithaca, New York, who helped plan the observations. "If the stain is only a thin, colored veneer on the icy soil, exposure to the space environment at Tethys' surface might erase them on relatively short time scales."
The Cassini team is currently planning follow-up observations of the features, at higher resolution, later this year.
"After 11 years in orbit, Cassini continues to make surprising discoveries," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "We are planning an even closer look at one of the Tethys red arcs in November to see if we can tease out the source and composition of these unusual markings."

New Names and Insights at Ceres

 Colorful new maps of Ceres, based on data from NASA's Dawn spacecraft, showcase a diverse topography, with height differences between crater bottoms and mountain peaks as great as 9 miles (15 kilometers).
Scientists continue to analyze the latest data from Dawn as the spacecraft makes its way to its third mapping orbit.
"The craters we find on Ceres, in terms of their depth and diameter, are very similar to what we see on Dione and Tethys, two icy satellites of Saturn that are about the same size and density as Ceres. The features are pretty consistent with an ice-rich crust," said Dawn science team member Paul Schenk, a geologist at the Lunar and Planetary Institute, Houston.
Some of these craters and other features now have official names, inspired by spirits and deities relating to agriculture from a variety of cultures. The International Astronomical Union recently approved a batch of names for features on Ceres.
The newly labeled features include Occator, the mysterious crater containing Ceres' brightest spots, which has a diameter of about 60 miles (90 kilometers) and a depth of about 2 miles (4 kilometers). Occator is the name of the Roman agriculture deity of harrowing, a method of leveling soil.
Colorful new maps of Ceres, based on data from NASA's Dawn spacecraft, showcase a diverse topography, with height differences between crater bottoms and mountain peaks as great as 9 miles (15 kilometers).
Scientists continue to analyze the latest data from Dawn as the spacecraft makes its way to its third mapping orbit.
"The craters we find on Ceres, in terms of their depth and diameter, are very similar to what we see on Dione and Tethys, two icy satellites of Saturn that are about the same size and density as Ceres. The features are pretty consistent with an ice-rich crust," said Dawn science team member Paul Schenk, a geologist at the Lunar and Planetary Institute, Houston.
Some of these craters and other features now have official names, inspired by spirits and deities relating to agriculture from a variety of cultures. The International Astronomical Union recently approved a batch of names for features on Ceres.
The newly labeled features include Occator, the mysterious crater containing Ceres' brightest spots, which has a diameter of about 60 miles (90 kilometers) and a depth of about 2 miles (4 kilometers). Occator is the name of the Roman agriculture deity of harrowing, a method of leveling soil.
A smaller crater with bright material, previously labeled "Spot 1," is now identified as Haulani, after the Hawaiian plant goddess. Haulani has a diameter of about 20 miles (30 kilometers). Temperature data from Dawn's visible and infrared mapping spectrometer show that this crater seems to be colder than most of the territory around it.
Dantu crater, named after the Ghanaian god associated with the planting of corn, is about 75 miles (120 kilometers) across and 3 miles (5 kilometers) deep. A crater called Ezinu, after the Sumerian goddess of grain, is about the same size. Both are less than half the size of Kerwan, named after the Hopi spirit of sprouting maize, and Yalode, a crater named after the African Dahomey goddess worshipped by women at harvest rites.
"The impact craters Dantu and Ezinu are extremely deep, while the much larger impact basins Kerwan and Yalode exhibit much shallower depth, indicating increasing ice mobility with crater size and age," said Ralf Jaumann, a Dawn science team member at the German Aerospace Center (DLR) in Berlin.
Almost directly south of Occator is Urvara, a crater named for the Indian and Iranian deity of plants and fields. Urvara, about 100 miles (160 kilometers) wide and 3 miles (6 kilometers) deep, has a prominent central pointy peak that is 2 miles (3 kilometers) high.
Dawn is currently spiraling toward its third science orbit, 900 miles (less than 1,500 kilometers) above the surface, or three times closer to Ceres than its previous orbit. The spacecraft will reach this orbit in mid-August and begin taking images and other data again.
Ceres, with a diameter of 584 miles (940 kilometers), is the largest object in the main asteroid belt, located between Mars and Jupiter. This makes Ceres about 40 percent the size of Pluto, another dwarf planet, which NASA's New Horizons mission flew by earlier this month.
On March 6, 2015, Dawn made history as the first mission to reach a dwarf planet, and the first to orbit two distinct extraterrestrial targets. It conducted extensive observations of Vesta in 2011-2012.

NASA's Curiosity Rover Inspects Unusual Bedrock

Approaching the third anniversary of its landing on Mars, NASA's Curiosity Mars rover has found a target unlike anything it has studied before -- bedrock with surprisingly high levels of silica. Silica is a rock-forming compound containing silicon and oxygen, commonly found on Earth as quartz.
This area lies just downhill from a geological contact zone the rover has been studying near "Marias Pass" on lower Mount Sharp.
In fact, the Curiosity team decided to back up the rover 46 meters (151 feet) from the geological contact zone to investigate the high-silica target dubbed "Elk." The decision was made after they analyzed data from two instruments, the laser-firing Chemistry & Camera (ChemCam) and Dynamic Albedo of Neutrons (DAN), which show elevated amounts of silicon and hydrogen, respectively. High levels of silica in the rock could indicate ideal conditions for preserving ancient organic material, if present, so the science team wants to take a closer look.

"One never knows what to expect on Mars, but the Elk target was interesting enough to go back and investigate," said Roger Wiens, the principal investigator of the ChemCam instrument from the Los Alamos National Laboratory in New Mexico. ChemCam is coming up on its 1,000th target, having already fired its laser more than 260,000 times since Curiosity landed on Mars Aug. 6, 2012, Universal Time (evening of Aug. 5, Pacific Time).
In other news, an engineering test on the rover's sample-collecting drill on July 18 is aiding analysis of intermittent short circuits in the drill's percussion mechanism, in preparation for using the drill in the area where the rover has been working for the past two months. The latest test did not result in any short circuits, so the team plans to continue with more tests, performed on the science targets themselves.
Before Curiosity began further investigating the high-silica area, it was busy scrutinizing the geological contact zone near Marias Pass, where a pale mudstone meets darker sandstone.
"We found an outcrop named Missoula where the two rock types came together, but it was quite small and close to the ground. We used the robotic arm to capture a dog's-eye view with the MAHLI camera, getting our nose right in there," said Ashwin Vasavada, the mission's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. MAHLI is short for Mars Hand Lens Imager.
The rover had reached this area after a steep climb up a 20-foot (6-meter) hill. Near the top of the climb, the ChemCam instrument fired its laser at the target Elk, and took a spectral reading of its composition.
"ChemCam acts like eyes and ears of the rover for nearby objects," said Wiens.
The rover had moved on before the Elk data were analyzed, so a U-turn was required to obtain more data. Upon its return, the rover was able to study a similar target, "Lamoose," up close with the MAHLI camera and the arm-mounted Alpha Particle X-ray Spectrometer (APXS).
Curiosity has been working on Mars since early August 2012. It reached the base of Mount Sharp last year after fruitfully investigating outcrops closer to its landing site and then trekking to the mountain. The main mission objective now is to examine successively higher layers of Mount Sharp.

Finding Another Earth





The discovery of a super-Earth-sized planet orbiting a sun-like star brings us closer than ever to finding a twin of our own watery world. But NASA's Kepler space telescope has captured evidence of other potentially habitable planets amid the sea of stars in the Milky Way galaxy.
To take a brief tour of the more prominent contenders, it helps to zero in on the "habitable zone" around their stars. This is the band of congenial temperatures for planetary orbits -- not too close and not too far. Too close and the planet is fried (we're looking at you, Venus). Too far and it's in deep freeze. But settle comfortably into the habitable zone, and your planet could have liquid water on its surface -- just right. Goldilocks has never been more relevant. Scientists have, in fact, taken to calling this water-friendly region the "Goldilocks zone."
The zone can be a wide band or a narrow one, and nearer the star or farther, depending on the star's size and energy output. For small, red-dwarf stars, habitable zone planets might gather close, like marshmallow-roasting campers around the fire. For gigantic, hot stars, the band must retreat to a safer distance.
About a dozen habitable zone planets in the Earth-size ballpark have been discovered so far -- that is, 10 to 15 planets between one-half and twice the diameter of Earth, depending on how the habitable zone is defined and allowing for uncertainties about some of the planetary sizes.
The new discovery, Kepler-452b, fires the planet hunter's imagination because it is the most similar to the Earth-sun system found yet: a planet at the right temperature within the habitable zone, and only about one-and-a-half times the diameter of Earth, circling a star very much like our own sun. The planet also has a good chance of being rocky, like Earth, its discoverers say.
Kepler-452b is more similar to Earth than any system previously discovered. And the timing is especially fitting: 2015 marks the 20th anniversary of the first exoplanet confirmed to be in orbit around a typical star.
But several other exoplanet discoveries came nearly as close in their similarity to Earth.
Before this, the planet Kepler-186f held the "most similar" distinction (they get the common moniker, "Kepler," because they were discovered with the Kepler space telescope). About 500 light-years from Earth, Kepler-186f is no more than 10 percent larger than Earth, and sails through its star's habitable zone, making its surface potentially watery.
But its 130-day orbit carries it around a red-dwarf star that is much cooler than our sun and only half its size. Thus, the planet is really more like an "Earth cousin," says Thomas Barclay of the Bay Area Environmental Research Institute at NASA's Ames Research Center, Moffett Field, California, a co-author of the paper announcing the discovery in April 2014.
Kepler-186f gets about one-third the energy from its star that Earth gets from our sun. And that puts it just at the outside edge of the habitable zone. Scientists say that if you were standing on the planet at noon, the light would look about as bright as it does on Earth an hour before sunset.
That doesn't mean the planet is bereft of life, although it doesn't mean life exists there, either.
Before Kepler-186f, Kepler-62f was the exoplanet known to be most similar to Earth. Like the new discovery, Kepler-62f is a "super Earth," about 40 percent larger than our home planet. But, like Kepler-186f, its 267-day orbit also carries it around a star that is cooler and smaller than the sun, some 1,200 light-years away in the constellation Lyra. Still, Kepler-62f does reside in the habitable zone.
Kepler-62f's discovery was announced in April 2013, about the same time as Kepler-69c, another super Earth -- though one that is 70 percent larger than our home planet. That's the bad news; astronomers are uncertain about the planet's composition, or just when a "super Earth" becomes so large that it diminishes the chance of finding life on its surface. That also moves it farther than its competitors from the realm of a potential Earth twin. The good news is that Kepler-69c lies in its sun's habitable zone, with a 242-day orbit reminiscent of our charbroiled sister planet, Venus. Its star is also similar to ours in size with about 80 percent of the sun's luminosity. Its planetary system is about 2,700 light-years away in the constellation Cygnus.
Kepler-22b also was hailed in its day as the most like Earth. It was the first of the Kepler planets to be found within the habitable zone, and it orbits a star much like our sun. But Kepler-22b is a sumo wrestler among super Earths, about 2.4 times Earth's size. And no one knows if it is rocky, gaseous or liquid. The planet was detected almost immediately after Kepler began making observations in 2009, and was confirmed in 2011. This planet, which could have a cloudy atmosphere, is 600 light-years away, with a 290-day orbit not unlike Earth's.
Not all the planets jostling to be most like Earth were discovered using Kepler. A super Earth known as Gliese 667Cc also came to light in 2011, discovered by astronomers combing through data from the European Southern Observatory's 3.6-meter telescope in Chile. The planet, only 22 light-years away, has a mass at least 4.5 times that of Earth. It orbits a red dwarf in the habitable zone, though closely enough -- with a mere 28-day orbit -- to make the planet subject to intense flares that could erupt periodically from the star's surface. Still, its sun is smaller and cooler than ours, and Gliese 667Cc's orbital distance means it probably receives around 90 percent of the energy we get from the sun. That's a point in favor of life, if the planet's atmosphere is something like ours. The planet's true size and density remain unknown, however, which means it could still turn out to be a gas planet, hostile to life as we know it. And powerful magnetic fluxes also could mean periodic drop-offs in the amount of energy reaching the planet, by as much as 40 percent. These drop-offs could last for months, according to scientists at the University of Oslo's Institute of Theoretical Astrophysics in Norway.
Deduct two points.
Too big, too uncertain, or circling the wrong kind of star: Shuffle through the catalog of habitable zone planets, and the closest we can come to Earth -- at least so far -- appears to be the new kid on the interstellar block, Kepler-452b.

NASA's Kepler Mission Discovers Bigger, Older Cousin to Earth

NASA's Kepler mission has confirmed the first near-Earth-size planet in the "habitable zone" around a sun-like star. This discovery and the introduction of 11 other new small habitable-zone candidate planets mark another milestone in the journey to finding another "Earth."
The newly discovered Kepler-452b is the smallest planet to date discovered orbiting in the habitable zone -- the area around a star where liquid water could pool on the surface of an orbiting planet -- of a G2-type star, like our sun. The confirmation of Kepler-452b brings the total number of confirmed planets to 1,030.
"On the 20th anniversary year of the discovery that proved other suns host planets, the Kepler exoplanet explorer has discovered a planet and star which most closely resemble the Earth and our sun," said John Grunsfeld, associate administrator of NASA's Science Mission Directorate at the agency's headquarters in Washington. "This exciting result brings us one step closer to finding an Earth 2.0."
Kepler-452b has a diameter 60 percent larger than Earth and is considered a super-Earth-size planet. While its mass and composition are not yet determined, previous research suggests that planets the size of Kepler-452b have a good chance of being rocky.
While Kepler-452b is larger than Earth, its 385-day orbit is only 5 percent longer. The planet is 5 percent farther from its parent star, Kepler-452, than Earth is from the sun. Kepler-452 is 6 billion years old, 1.5 billion years older than our sun, has the same temperature, and is 20 percent brighter, with a diameter 10 percent larger.
"We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth's evolving environment," said Jon Jenkins, Kepler data analysis lead at NASA's Ames Research Center in Moffett Field, California, who led the team that discovered Kepler-452b. "It's awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That's substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet."
To help confirm the finding and better determine the properties of the Kepler-452 system, the team conducted ground-based observations at the University of Texas at Austin's McDonald Observatory, the Fred Lawrence Whipple Observatory on Mt. Hopkins, Arizona, and the W. M. Keck Observatory atop Mauna Kea in Hawaii. These measurements were key for the researchers to confirm the planetary nature of Kepler-452b, to refine the size and brightness of its host star and to better pin down the size of the planet and its orbit.
The Kepler-452 system is located 1,400 light-years away in the constellation Cygnus. The research paper reporting this finding has been accepted for publication in The Astronomical Journal.
In addition to confirming Kepler-452b, the Kepler team has increased the number of new exoplanet candidates by 521 from their analysis of observations conducted from May 2009 to May 2013, raising the number of planet candidates detected by the Kepler mission to 4,696. Candidates require follow-up observations and analysis to verify they are actual planets.
Twelve of the new planet candidates have diameters between one to two times that of Earth, and orbit in their star's habitable zone. Of these, nine orbit stars that are similar to our sun in size and temperature.
"We've been able to fully automate our process of identifying planet candidates, which means we can finally assess every transit signal in the entire Kepler dataset quickly and uniformly," said Jeff Coughlin, Kepler scientist at the SETI Institute in Mountain View, California, who led the analysis of a new candidate catalog. "This gives astronomers a statistically sound population of planet candidates to accurately determine the number of small, possibly rocky planets like Earth in our Milky Way galaxy."
These findings, presented in the seventh Kepler Candidate Catalog, will be submitted for publication in the Astrophysical Journal. These findings are derived from data publicly available on the NASA Exoplanet Archive.
Scientists now are producing the last catalog based on the original Kepler mission's four-year data set. The final analysis will be conducted using sophisticated software that is increasingly sensitive to the tiny telltale signatures of Earth-size planets.

Could 'Windbots' Someday Explore the Skies of Jupiter?

Among designers of robotic probes to explore the planets, there is certainly no shortage of clever ideas. There are concepts for robots that are propelled by waves in the sea. There are ideas for tumbleweed bots driven by wind, rolling across Antarctica or Mars. Recently a team of engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, wondered if a probe could be buoyant in the clouds of Earth or a distant gas giant planet, like Jupiter.
That team has recently begun studying their question, thanks to a one-year, $100,000 study, funded by NASA's Innovative Advanced Concepts (NIAC) program. They're investigating the feasibility of creating a windbot, a new class of robotic probe designed to stay aloft in a planet's atmosphere for a long time without wings or hot-air balloons. The NASA-funded study will systematically investigate how future spacecraft of this kind could stay airborne and harvest energy.
Although no mission is currently scheduled to utilize windbots, the researchers hope their study will open new avenues for atmospheric science on gas giant planets using high-mobility robotic explorers.
Unlike the moon and Mars, which have already been explored by robotic rovers, gas giant planets like Jupiter and Saturn have no solid surface on which a probe to land on. In 1995, NASA's Galileo spacecraft dropped off an atmospheric probe that descended into Jupiter under a parachute. The battery-powered probe survived only about an hour before succumbing to high heat and pressure as it fell into the planet's ponderously deep atmosphere. In contrast to the plummeting probe, a windbot could have rotors on several sides of its body that could spin independently to change direction or create lift.
Adrian Stoica, principal investigator for the windbots study at JPL, points to a great example to think about from nature: a dandelion seed. "A dandelion seed is great at staying airborne. It rotates as it falls, creating lift, which allows it to stay afloat for long time, carried by the wind. We'll be exploring this effect on windbot designs."
Stoica and colleagues think that, to stay airborne for a long time, a windbot would need to be able to use energy available in the planet's atmosphere. That energy might not be solar, because the probe could find itself on the planet's night side for an extended period. Nuclear power sources also could be a liability for a floating probe because of their weight. But winds, temperature variations and even a planet's magnetic field could potentially be sources of energy an atmospheric probe could exploit.
As they begin their study, the team suspects the best bet for an atmospheric robot to harvest energy is turbulence -- wind that's frequently changing direction and intensity. The key is variability. High wind velocity isn't enough. But in a dynamic, turbulent environment there are gradients -- differences in energy from high to low -- that can be used.
"It's a spring of energy a probe could drink from," said Stoica, who thinks a windbot might generate power in a similar way to some wristwatches that can be wound by shaking.
Embracing turbulence to make power and stay aloft is a departure from the approach taken by conventional aircraft, which carry their own internal power sources and perform best in smooth air. Commercial airliners, for example, cruise in Earth's stratosphere, where winds tend to be much smoother and flow faster than in the dense air closer to the ground.
The JPL team is starting out by characterizing winds among the clouds of Jupiter to understand what kinds of places might be best for sending a windbot and to determine some of the technical requirements for its design. "There are lots of things we don't know," Stoica said. "Does a windbot need to be 10 meters in diameter or 100? How much lift do we need from the winds in order to keep a windbot aloft?"
One thing the team is pretty certain of is that a windbot would need to be able to sense the winds around itself in order to live off the turbulence. To that end, they plan to build a simple windbot model as part of their study. The aerodynamic modeling for this type of craft is particularly difficult, so Stoica thinks having a physical model will be important.
The model windbot would be subjected to carefully controlled turbulent airflows to determine how best to design systems that react and reorient the robot to keep it aloft. After that, the team would move on to investigating means, such as electronic sensors, for a windbot to perceive the wind field in the environment around itself. Putting these capabilities together into a functional prototype would be left for a future study.
If the cost of building windbots turned out to be sufficiently affordable, Stoica thinks it would be useful to have multiple units sending back data from different places in a planet's atmosphere. "One could imagine a network of windbots existing for quite a long time on Jupiter or Saturn, sending information about ever-changing weather patterns," he said. "And, of course, what we learn about the atmospheres of other planets enriches our understanding of Earth's own weather and climate."
In fact, windbots might also come in handy as an additional tool to help scientists understand turbulent weather phenomena on Earth, such as hurricanes, without venturing beyond our planet's atmosphere. A windbot designed to sense and feed off turbulence might not only survive such hazardous environments, but also transmit valuable data all the while.
Despite its potential, the windbot concept is not without its tradeoffs. The buoyant probe might have to sacrifice travel time in moving to interesting destinations on a planet to simply stay alive -- trading a shorter route from point A to point B to follow the energy available from winds to stay aloft. At other times, when it has sufficient energy, it might be able to head to its destination via a more direct path.
The windbot concept is a long way from being ready to launch to Jupiter, but Stoica and colleagues are excited to dive into their initial study. "We don't yet know if this idea is truly feasible. We'll do the research to try and find out," he said. "But it pushes us to find other ways of approaching the problem, and that kind of thinking is extremely valuable."

NASA's Curiosity Mars Rover Tracks Sunspots

While busily investigating bedrock types on Mars' Mount Sharp and preparing for a drill test, NASA's Curiosity Mars rover has also been looking up frequently to monitor sunspots on the face of the sun that is turned away from Earth.
Large sunspots are evident in views from Curiosity's Mast Camera (Mastcam). Scientists temporarily have no other resource providing views of the sun from the opposite side of the solar system from Earth. The sun completes a rotation about once a month -- faster near its equator than near its poles. Information about sunspots that develop before they rotate into view of Earth and Earth-orbiting spacecraft is helpful in predicting space-weather effects of solar emissions related to sunspots.
A series of images from Curiosity showing sunspots rotating eastward in late June and early July is online at:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19801
One sunspot or cluster that rotated out of Curiosity's view over the July 4 weekend showed up by July 7 as a source area of a solar eruption observed by NASA's Earth-orbiting Solar Dynamics Observatory, as seen at:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19680
Another sunspot being tracked by Curiosity is on pace to face Earthward next week.
NASA's STEREO-A spacecraft, which monitors the sun, is currently almost exactly behind the sun from Earth's perspective, but for precisely that reason it is temporarily out of communication. The sun disrupts radio transmissions that pass too close to it. Communication with Curiosity was also suspended last month when Mars passed nearly behind the sun, but the rover resumed full communication and operations in late June. Daily information from STEREO-A is expected to begin again this month.
"Tracking the sunspot activity on the far side of the sun is useful for space-weather forecasting," said Yihua Zheng, project leader for NASA Space Weather Services at NASA Goddard Space Flight Center, Greenbelt, Maryland. "It helps us monitor how the sunspots evolve and grow before they become visible from this side."
Space weather forecasting aids in anticipating and taking precautions against possible effects of solar storms on spacecraft orbiting Earth and elsewhere in the solar system. Intense space weather can degrade telephone communications, broadcasting and other electronic technology on Earth.
The main purpose for most imaging of the sun by Curiosity and other Mars rovers has been to monitor how its apparent brightness is affected by dust in Mars' atmosphere above the rovers. Mark Lemmon of Texas A&M University, College Station, is a Mastcam team member who studies the Martian atmosphere. Three months ago, he coordinated sunset imaging by Curiosity for a Martian evening when Mercury was passing directly in front of the sun from Mars' viewpoint.
"We saw sunspots in the images during the Mercury transit, and I was trying to distinguish Mercury from a sunspot," Lemmon said. "I checked with heliophysicists who study sunspots and learned that STEREO-A was out of communications, so there was no current information about sunspots on that side of the sun. That's how we learned it would be useful for Curiosity to monitor sunspots."
In addition to its sunspot viewing, Curiosity is examining rocks near "Marias Pass." A test is planned this month for the percussion mechanism of the rover's sample-collecting drill, which exhibited a transient short circuit during transfer of sample material collected four months ago. The test is designed to provide diagnostic information for use in planning the rover's next drilling operation, possibly in the Marias Pass area.
Curiosity has been working on Mars since early August 2012. It reached the base of Mount Sharp last year after fruitfully investigating outcrops closer to its landing site and then trekking to the mountain. The main mission objective now is to examine successively higher layers of Mount Sharp.

Rosetta's lander Philae wakes up from hibernation (14 June)

Rosetta's lander Philae has woken up after seven months in hibernation on the surface of Comet 67P/Churyumov-Gerasimenko.
The signals were received at ESA's European Space Operations Centre in Darmstadt at 22:28 CEST on 13 June. More than 300 data packets have been analysed by the teams at the Lander Control Center at the German Aerospace Center (DLR).
"Philae is doing very well: It has an operating temperature of -35ºC and has 24 Watts available," explains DLR Philae Project Manager Dr. Stephan Ulamec. "The lander is ready for operations."
For 85 seconds Philae "spoke" with its team on ground, via Rosetta, in the first contact since going into hibernation in November.
When analysing the status data it became clear that Philae also must have been awake earlier: "We have also received historical data – so far, however, the lander had not been able to contact us earlier."
Now the scientists are waiting for the next contact. There are still more than 8000 data packets in Philae’s mass memory which will give the DLR team information on what happened to the lander in the past few days on Comet 67P/Churyumov-Gerasimenko.
Philae shut down on 15 November 2014 at 1:15 CET after being in operation on the comet for about 60 hours. Since 12 March 2015 the communication unit on orbiter Rosetta was turned on to listen out for the lander.

Ceres Spots Continue to Mystify in Latest Dawn Images

 

 

 

 

 Dawn has been studying the dwarf planet in detail from its second mapping orbit, which is 2,700 miles (4,400 kilometers) above Ceres. A new view of its intriguing bright spots, located in a crater about 55 miles (90 kilometers) across, shows even more small spots in the crater than were previously visible.

At least eight spots can be seen next to the largest bright area, which scientists think is approximately 6 miles (9 kilometers) wide. A highly reflective material is responsible for these spots -- ice and salt are leading possibilities, but scientists are considering other options, too.

Dawn's visible and infrared mapping spectrometer allows scientists to identify specific minerals present on Ceres by looking at how light is reflected. Each mineral reflects the range of visible and infrared-light wavelengths in a unique way, and this signature helps scientists determine the components of Ceres. So, as the spacecraft continues to send back more images and data, scientists will learn more about the mystery bright spots.

In addition to the bright spots, the latest images also show a mountain with steep slopes protruding from a relatively smooth area of the dwarf planet's surface. The structure rises about 3 miles (5 kilometers) above the surface.

Ceres also has numerous craters of varying sizes, many of which have central peaks. There is ample evidence of past activity on the surface, including flows, landslides and collapsed structures. It seems that Ceres shows more remnants of activity than the protoplanet Vesta, which Dawn studied intensively for 14 months in 2011 and 2012.

Dawn is the first mission to visit a dwarf planet, and the first to orbit two distinct targets in our solar system. It arrived at Ceres, the largest object in the main asteroid belt between Mars and Jupiter, on March 6, 2015.

Dawn will remain in its current altitude until June 30, continuing to take images and spectra of Ceres in orbits of about three days each. It then will move into its next orbit at an altitude of 900 miles (1,450 kilometers), arriving in early August.

 

 

Helium-Shrouded Planets May Be Common in Our Galaxy

They wouldn't float like balloons or give you the chance to talk in high, squeaky voices, but planets with helium skies may constitute an exotic planetary class in our Milky Way galaxy. Researchers using data from NASA's Spitzer Space Telescope propose that warm Neptune-size planets with clouds of helium may be strewn about the galaxy by the thousands.
"We don't have any planets like this in our own solar system," said Renyu Hu, NASA Hubble Fellow at the agency's Jet Propulsion Laboratory in Pasadena, California, and lead author of a new study on the findings accepted for publication in the Astrophysical Journal. "But we think planets with helium atmospheres could be common around other stars."
Prior to the study, astronomers had been investigating a surprising number of so-called warm Neptunes in our galaxy. NASA's Kepler space telescope has found hundreds of candidate planets that fall into this category. They are the size of Neptune or smaller, with tight orbits that are closer to their stars than our own sizzling Mercury is to our sun. These planets reach temperatures of more than 1,340 degrees Fahrenheit (1,000 Kelvin), and orbit their stars in as little as one or two days.
In the new study, Hu and his team make the case that some warm Neptunes -- and warm sub-Neptunes, which are smaller than Neptune -- could have atmospheres enriched with helium. They say that the close proximity of these planets to their searing stars would cause the hydrogen in their atmospheres to boil off.
"Hydrogen is four times lighter than helium, so it would slowly disappear from the planets' atmospheres, causing them to become more concentrated with helium over time," said Hu. "The process would be gradual, taking up to 10 billion years to complete." For reference, our planet Earth is about 4.5 billion years old.
Warm Neptunes are thought to have either rocky or liquid cores, surrounded by gas. If helium is indeed the dominant component in their atmospheres, the planets would appear white or gray. By contrast, the Neptune of our own solar system is a brilliant azure blue. The methane in its atmosphere absorbs the color red, giving Neptune its blue hue.
A lack of methane in one particular warm Neptune, called GJ 436b, is in fact what led Hu and his team to develop their helium planet theory. Spitzer had previously observed GJ 436b, located 33 light-years away, and found evidence for carbon but not methane. This was puzzling to scientists, because methane molecules are made of one carbon and four hydrogen atoms, and planets like this are expected to have a lot of hydrogen. Why wasn't the hydrogen linking up with carbon to produce methane?
According to the new study, the hydrogen might have been slow-cooked off the planet by radiation from the host stars. With less hydrogen around, the carbon would pair up with oxygen to make carbon monoxide. In fact, Spitzer found evidence for a predominance of carbon monoxide in the atmosphere of GJ 436b.
The next step to test this theory is to look at other warm Neptunes for signs of carbon monoxide and carbon dioxide, which are indicators of helium atmospheres. The team says this might be possible with the help of NASA's Hubble Space Telescope, and NASA's upcoming James Webb Space Telescope may one day directly detect that helium.
Meanwhile, the wacky world of exoplanets continues to surprise astronomers.
"Any planet one can imagine probably exists, out there, somewhere, as long as it fits within the laws of physics and chemistry," said co-author Sara Seager of the Massachusetts Institute of Technology in Cambridge and JPL. "Planets are so incredibly diverse in their masses, sizes and orbits that we expect this to extend to exoplanet atmospheres."

Stellar Sparklers That Last

While fireworks only last a short time here on Earth, a bundle of cosmic sparklers in a nearby cluster of stars will be going off for a very long time. NGC 1333 is a star cluster populated with many young stars that are less than 2 million years old -- a blink of an eye in astronomical terms for stars like these expected to burn for billions of years.
This new composite image combines X-rays from NASA's Chandra X-ray Observatory (shown in pink) with infrared data from NASA's Spitzer Space Telescope (shown in red) as well as optical data from the Digitized Sky Survey and the National Optical Astronomical Observatories' Mayall 4-meter telescope on Kitt Peak (red, green, blue). The Chandra data reveal 95 young stars glowing in X-ray light, 41 of which had not been seen previously using Spitzer because they lacked infrared emission from a surrounding disk.
To make a detailed study of the X-ray properties of young stars, a team of astronomers, led by Elaine Winston from the University of Exeter, United Kingdom, analyzed the Chandra X-ray data of both NGC 1333, located about 780 light-years from Earth, and the Serpens cloud, a similar cluster of young stars about 1,100 light-years away. They then compared the two datasets with observations of the young stars in the Orion Nebula Cluster, perhaps the most well-studied young star cluster in the Milky Way galaxy.
The researchers found that the X-ray brightness of the stars in NGC 1333 and the Serpens cloud depends on the total brightness of the stars across the electromagnetic spectrum, as found in previous studies of other clusters. They also found that the X-ray brightness mainly depends on the size of the star. In other words, the bigger the stellar sparkler, the brighter it will glow in X-rays.

Second Mountain Range Rises from Pluto's 'Heart'

A second mountain range on Pluto that rises from the dwarf planet's heart-shaped region, nicknamed Tombaugh Regio, is seen in this stunning image from NASA's New Horizons spacecraft. NASA unveiled the image on July 21, 2015.

Pluto has a big heart — big enough to accommodate at least two sets of mountains, a new photo from NASA's New Horizons spacecraft reveals.

New Horizons has spotted a second mountain range inside Tombaugh Regio, the 1,200-mile-wide (2,000 kilometers) heart-shaped feature that mission team members named after Pluto's discoverer, Clyde Tombaugh.

This newfound range rises up to 1 mile (1.6 km) above Pluto's frigid surface, making it comparable in height to the Appalachian Mountains of the eastern United States, NASA officials said. Tombaugh Regio's other known mountain range, by contrast, is more similar to the tall and jagged Rocky Mountains, topping out at more than 2 miles (3.2 km) in elevation.
The newly discovered range lies just west of the ice plains known as Sputnik Planum and is 68 miles (110 km) northwest of the taller mountain range, which mission scientists are calling Norgay Montes after Sherpa Tenzing Norgay, who along with Edmund Hillary completed the first-ever ascent of Mt. Everest, in 1953. (Tombaugh Regio, Norgay Montes and other such names remain informal monikers until they're officially approved by the International Astronomical Union.)

The new photo, which New Horizons captured during its historic Pluto flyby on July 14, shows a startling complexity of terrain within Tombaugh Regio, researchers said.

"There is a pronounced difference in texture between the younger, frozen plains to the east and the dark, heavily cratered terrain to the west," Jeff Moore, leader of New Horizons' geology, geophysics and imaging team, said in a statement today (July 21) upon the photo's release.


"There's a complex interaction going on between the bright and the dark materials that we're still trying to understand," added Moore, who's based at at NASA's Ames Research Center in Moffett Field, California.

The lack of craters on Sputnik Planum suggests the icy plains are extremely young in geological terms — 100 million years or less, mission team members have said. But the darker terrain to the west is probably several billion years old.

Features as small as 0.5 miles (0.8 km) wide are visible in the new photo, which New Horizons took from a distance of 48,000 miles (77,000 km). But the spacecraft zoomed to within just 7,800 miles (12,500 km) of Pluto's surface on July 14, so even more spectacular images of the dwarf planet should be coming down to Earth in the future.

All of New Horizons' close-approach data should be in researchers' hands in compressed form by the end of 2015, while it may take another year to get the complete flyby dataset down to Earth, team members have said.

Europa's Elusive Water Plume Paints Grim Picture For Life

A meteorite may have been responsible for a water plume briefly spotted above Europa two years ago, implying it takes a very rare event to breach the ice on the Jovian moon.

Astrobiologists worldwide received news in December 2013 that water vapor was detected in Hubble Space Telescope observations of Jupiter's moon Europa, which is considered one of the top potential locations in our solar system for life. Those results were published in the journal Science and led by Lorenz Roth, a planetary scientist at the Southwest Research Institute in Texas.

However, follow-up observations of Europa have found no plume emanating from the moon. A new paper based on observations made by NASA's Saturn-orbiting Cassini spacecraft reveals that Europa's atmosphere is 100 times less dense than claims in previous publications, and composed mainly of atomic rather than molecular oxygen.
Furthermore, the magnetosphere plasma, or superheated gas, at Europa’s orbit is very hot, with properties indicating that the plasma is mainly composed of ions, or charged particles, from the nearby moon Io.

Based on the plasma properties, the rate of injection of neutral gas from the surface of Europa is probably very low. This means the plasma in Europa's atmosphere has a low density, and a low escape rate into its magnetic field or magnetosphere.

No one knew what the plasma was made of before Cassini's measurements, which led some researchers previously to believe that the plasma came from Europa. Plasma can be comprised of different molecules, including hydrogen and oxygen, but Cassini's spectroscope was not designed to measure which species of molecules were present in the gas.

Because molecular hydrogen and atomic hydrogen were not found in Cassini's measurement of the plasma, this means that the plasma did not come from Europa as was previously suspected. The plasma that as detected was made of sulfur dioxide — a product of volcanoes on Io.

“Our conclusion was that almost everything we were seeing was plasma from Io,” said Don Shemansky, chief scientist of the planetary and space science division of space weather company Space Environment Technologies (PSSD/SET).

However, a meteorite that briefly threw water aloft from Europa's surface cannot be ruled out, he said

Furthest Galaxy Imaged at 13.1bn LYs Away

A galaxy far, far away — farther, in fact, than any other known galaxy — has been measured by astronomers.

The galaxy EGS-zs8-1 lies 13.1 billion light-years from Earth, the largest distance ever measured between Earth and another galaxy.

The universe is thought to be about 13.8 billion years old, so galaxy EGS-zs8-1 is also one of the earliest galaxies to form in the cosmos. Further studies could provide a glimpse at how these early galaxies helped produce the heavy elements that are essential for building the diversity of life and landscapes we see on Earth today.
EGS-zs8-1 is one of the brightest objects observed in this region, which is around 13 billion light-years from Earth. The authors of the new research say other galaxies likely lie at similar distances or even further from Earth, but they are too faint for scientists to measure their exact distance.

"We have a lot of sources that we can see with Hubble that are probably farther way" than EGS-zs8-1, said Pascal Oesch, a postdoctoral researcher at Yale and lead author of the new study. "But we cannot measure their exact distance yet."

To measure the separation between Earth and a far-off cosmic object, astronomers often look at how quickly those objects are moving away from Earth. The universe is expanding; space itself is growing like a balloon or a loaf of bread in the oven. Objects in the universe thus move away from each other, like raisins in the bread dough.

As these objects move away from Earth, the light they emit becomes shifted. The more far-flung an object is, the faster it appears to move away from Earth, and the more the light is shifted. So, by measuring the degree of shifting — known as "redshift" — astronomers can also measure distance. A higher redshift equals a larger distance, and galaxy EGS-zs8-1 has the highest redshift ever measured, according to the new research (the previous record holder has a redshift that is only slightly smaller).

Galaxy EGS-zs8-1 was originally identified by the Hubble Space Telescope and the infrared Spitzer Space Telescope, and stood out because of the unique colors it emitted. The new research used observations conducted with the MOSFIRE instrument on the W.M. Keck Observatory's 10-meter (33 feet) telescope in Hawaii.
The light from EGS has traveled a distance of 13.1 billion light-years, so the light shows EGS-zs8-1 as it was 13.1 billion years ago. At that time, the universe was only about 670 million years old, or about 5 percent its current age of about 13.8 billion years, according to a statement from Yale. The first stars began forming about 200 million to 300 million years after the Big Bang, according to Oesch.

By combining observations from Keck, Spitzer and Hubble, the researchers say they can estimate that the stars in EGS-zs8-1 are "between 100 [million] and 300 million years old." But Oesch said it is difficult to know how old EGS-zs8-1 is compared to other galaxies at a similar distance from Earth. It is, however, one of the oldest galaxies yet measured.

The new observations also show that EGS-zs8-1 is forming stars 80 times faster than the Milky Way. In addition, the still-growing galaxy has "already built more than 15 percent of the mass of our own Milky Way today," Oesch said in a statement from Yale University.

The unique colors observed in EGS and other early galaxies by the Spitzer Space Telescope present questions about what took place in these primeval environments. According to the statement, these colors could have been caused by the rapid formation of massive, young stars that interacted with the primordial gas in these galaxies. Oesch said further study of the galaxy could reveal the types and amounts of heavy elements that formed there.

"By looking at different galaxies as a function of time, we can reconstruct the build-up of the heavy elements that we see around us today and that we're all made of," Oesch said. In addition, the new observations provide "an indication of how the stars were forming at these extreme distances, and they seem to be forming differently than the local universe. Every discovery opens up a whole new set of questions."

NASA's NuSTAR Captures Possible 'Screams' from Zombie Stars

Peering into the heart of the Milky Way galaxy, NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) has spotted a mysterious glow of high-energy X-rays that, according to scientists, could be the "howls" of dead stars as they feed on stellar companions.
"We can see a completely new component of the center of our galaxy with NuSTAR's images," said Kerstin Perez of Columbia University in New York, lead author of a new report on the findings in the journal Nature. "We can't definitively explain the X-ray signal yet -- it's a mystery. More work needs to be done."
The center of our Milky Way galaxy is bustling with young and old stars, smaller black holes and other varieties of stellar corpses -- all swarming around a supermassive black hole called Sagittarius A*.
NuSTAR, launched into space in 2012, is the first telescope capable of capturing crisp images of this frenzied region in high-energy X-rays. The new images show a region around the supermassive black hole about 40 light-years across. Astronomers were surprised by the pictures, which reveal an unexpected haze of high-energy X-rays dominating the usual stellar activity.
"Almost anything that can emit X-rays is in the galactic center," said Perez. "The area is crowded with low-energy X-ray sources, but their emission is very faint when you examine it at the energies that NuSTAR observes, so the new signal stands out."
Astronomers have four theories to explain the baffling X-ray glow, three of which involve different classes of stellar corpses. When stars die, they don't always go quietly into the night. Unlike stars like our sun, collapsed dead stars that belong to stellar pairs, or binaries, can siphon matter from their companions. This zombie-like "feeding" process differs depending on the nature of the normal star, but the result may be an eruption of X-rays.
According to one theory, a type of stellar zombie called a pulsar could be at work. Pulsars are the collapsed remains of stars that exploded in supernova blasts. They can spin extremely fast and send out intense beams of radiation. As the pulsars spin, the beams sweep across the sky, sometimes intercepting Earth, like lighthouse beacons.
"We may be witnessing the beacons of a hitherto hidden population of pulsars in the galactic center," said co-author Fiona Harrison of the California Institute of Technology in Pasadena, principal investigator of NuSTAR. "This would mean there is something special about the environment in the very center of our galaxy."
Other possible culprits include heavy-set stellar corpses called white dwarfs, which are the collapsed, burned-out remains of stars not massive enough to explode in supernovae. Our sun is such a star, and is destined to become a white dwarf in about five billion years. Because these white dwarfs are much denser than they were in their youth, they have stronger gravity and can produce higher-energy X-rays than normal. Another theory points to small black holes that slowly feed off their companion stars, radiating X-rays as material plummets down into their bottomless pits.
Alternatively, the source of the high-energy X-rays might not be stellar corpses at all, astronomers say, but rather a diffuse haze of charged particles called cosmic rays. The cosmic rays might originate from the supermassive black hole at the center of the galaxy as it devours material. When the cosmic rays interact with surrounding, dense gas, they emit X-rays.
However, none of these theories match what is known from previous research, leaving the astronomers largely stumped.
"This new result just reminds us that the galactic center is a bizarre place," said co-author Chuck Hailey of Columbia University. "In the same way people behave differently walking on the street instead of jammed on a crowded rush-hour subway, stellar objects exhibit weird behavior when crammed in close quarters near the supermassive black hole."
The team says more observations are planned. Until then, theorists will be busy exploring the above scenarios or coming up with new models to explain what could be giving off the puzzling high-energy X-ray glow.
"Every time that we build small telescopes like NuSTAR, which improve our view of the cosmos in a particular wavelength band, we can expect surprises like this," said Paul Hertz, the astrophysics division director at NASA Headquarters in Washington.

Saturn Moon's Activity Could Be 'Curtain Eruptions'

New research using data from NASA's Cassini mission suggests most of the eruptions from Saturn's moon Enceladus might be diffuse curtains rather than discrete jets. Many features that appear to be individual jets of material erupting along the length of prominent fractures in the moon's south polar region might be phantoms created by an optical illusion, according to the new study.
The research is being published on Thursday, May 7, in the journal Nature.
"We think most of the observed activity represents curtain eruptions from the 'tiger stripe' fractures, rather than intermittent geysers along them," said Joseph Spitale, lead author of the study and a participating scientist on the Cassini mission at the Planetary Science Institute in Tucson, Arizona. "Some prominent jets likely are what they appear to be, but most of the activity seen in the images can be explained without discrete jets."
In analyzing Cassini's images of the eruptions on Enceladus, Spitale and colleagues took particular note of the faint background glow present in most images. The brightest eruption features, which appear to be discrete jets, look to them to be superimposed intermittently upon this background structure.
The researchers modeled eruptions on Enceladus as uniform curtains along the tiger stripe fractures. They found that phantom brightness enhancements appear in places where the viewer is looking through a "fold" in the curtain. The folds exist because the fractures in Enceladus' surface are more wavy than perfectly straight. The researchers think this optical illusion is responsible for most of what appear to be individual jets.
"The viewing direction plays an important role in where the phantom jets appear," said Spitale. "If you rotated your perspective around Enceladus' south pole, such jets would seem to appear and disappear."
Phantom jets in simulated images produced by the scientists line up nicely with some of the features in real Cassini images that appear to be discrete columns of spray. The correspondence between simulation and spacecraft data suggests that much of the discrete-jet structure is an illusion, according to the researchers.
Curtain eruptions occur on Earth where molten rock, or magma, gushes out of a deep fracture. These eruptions, which often create spectacular curtains of fire, are seen in places such as Hawaii, Iceland and the Galapagos Islands.
"Our understanding of Enceladus continues to evolve, and we've come to expect surprises along the way," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California, who was not involved in the study. "This little ice world is becoming more exciting, not less, as we tease out new details about its subsurface ocean and astonishing geophysical activity."

Bright Spots Shine in Newest Dawn Ceres Images

New images of dwarf planet Ceres, taken by NASA's Dawn spacecraft, show the cratered surface of this mysterious world in sharper detail than ever before. These are among the first snapshots from Dawn's second mapping orbit, which is 2,700 miles (4,400 kilometers) above Ceres.
The region with the brightest spots is in a crater about 55 miles (90 kilometers) across. The spots consist of many individual bright points of differing sizes, with a central cluster. So far, scientists have found no obvious explanation for their observed locations or brightness levels.
"The bright spots in this configuration make Ceres unique from anything we've seen before in the solar system. The science team is working to understand their source. Reflection from ice is the leading candidate in my mind, but the team continues to consider alternate possibilities, such as salt. With closer views from the new orbit and multiple view angles, we soon will be better able to determine the nature of this enigmatic phenomenon," said Chris Russell, principal investigator for the Dawn mission based at the University of California, Los Angeles
Numerous other features on Ceres intrigue scientists as they contrast this world with others, including protoplanet Vesta, which Dawn visited for 14 months in 2011 and 2012. Craters abound on both bodies, but Ceres appears to have had more activity on its surface, with evidence of flows, landslides and collapsed structures.
Additionally, new images from Dawn's visible and infrared mapping spectrometer (VIR) show a portion of Ceres' cratered northern hemisphere, taken on May 16, including a true-color view and a temperature image. The temperature image is derived from data in the infrared light range. This instrument is also important in determining the nature of the bright spots.
Having arrived in its current orbit on June 3, Dawn will observe the dwarf planet from 2,700 miles (4,400 kilometers) above its surface until June 28. In orbits of about three days each, the spacecraft will conduct intensive observations of Ceres. It will then move toward its next orbit of altitude 900 miles (1,450 kilometers), arriving in early August.
On March 6, 2015, Dawn made history as the first mission to visit a dwarf planet, and the first to orbit two distinct extraterrestrial targets. At its previous target, Vesta, Dawn took tens of thousands of images and made many observations about the body's composition and other properties

NASA Spacecraft Detects Impact Glass on Surface of Mars

NASA's Mars Reconnaissance Orbiter (MRO) has detected deposits of glass within impact craters on Mars. Though formed in the searing heat of a violent impact, such deposits might provide a delicate window into the possibility of past life on the Red Planet.
During the past few years, research has shown evidence about past life has been preserved in impact glass here on Earth. A 2014 study led by scientist Peter Schultz of Brown University in Providence, Rhode Island, found organic molecules and plant matter entombed in glass formed by an impact that occurred millions of years ago in Argentina. Schultz suggested that similar processes might preserve signs of life on Mars, if they were present at the time of an impact.
Fellow Brown researchers Kevin Cannon and Jack Mustard, building on the previous research, detail their data about Martian impact glass in a report now online in the journal Geology.
"The work done by Pete and others showed us that glasses are potentially important for preserving biosignatures," Cannon said. "Knowing that, we wanted to go look for them on Mars and that's what we did here. Before this paper, no one had been able to definitively detect them on the surface."
Cannon and Mustard showed large glass deposits are present in several ancient, yet well-preserved, craters on Mars. Picking out the glassy deposits was no easy task. To identify minerals and rock types remotely, scientists measured the spectra of light reflected off the planet's surface. But impact glass doesn't have a particularly strong spectral signal.
"Glasses tend to be spectrally bland or weakly expressive, so signature from the glass tends to be overwhelmed by the chunks of rock mixed in with it," said Mustard. "But Kevin found a way to tease that signal out."
In a laboratory, Cannon mixed together powders with a similar composition of Martian rocks and fired them in an oven to form glass. He then measured the spectral signal from that glass.
Once Mustard had the signal from the lab glass, he used an algorithm to pick out similar signals in data from MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), for which he is the deputy principal investigator.
The technique pinpointed deposits in several Martian crater central peaks, the craggy mounds that often form in the center of a crater during a large impact. The fact the deposits were found on central peaks is a good indicator that they have an impact origin.
Knowing that impact glass can preserve ancient signs of life -- and now knowing that such deposits exist on the Martian surface today -- opens up a potential new strategy in the search for ancient Martian life.
"The researchers' analysis suggests glass deposits are relatively common impact features on Mars," said Jim Green, director of NASA's planetary science division at the agency's headquarters in Washington. "These areas could be targets for future exploration as our robotic scientific explorers pave the way on the journey to Mars with humans in the 2030s."
One of the craters containing glass, called Hargraves, is near the Nili Fossae trough, a 400-mile-long (about 650-kilometer-long) depression that stretches across the Martian surface. The region is one of the landing site contenders for NASA's Mars 2020 rover, a mission to cache soil and rock samples for possible return to Earth.
Nili Fossae trough is already of scientific interest because the crust in the region is thought to date back to when Mars was a much wetter planet. The region also is rife with what appear to be ancient hydrothermal fractures, warm vents that could have provided energy for life to thrive just beneath the surface.
"If you had an impact that dug in and sampled that subsurface environment, it's possible that some of it might be preserved in a glassy component," Mustard said. "That makes this a pretty compelling place to go look around, and possibly return a sample."
MRO has been examining Mars with CRISM and five other instruments since 2006.
"This significant new detection of impact glass illustrates how we can continue to learn from the ongoing observations by this long-lived mission," said Richard Zurek, MRO project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California.

Dawn Spirals Closer to Ceres, Returns a New View (May 2015)

A new view of Ceres, taken by NASA's Dawn spacecraft on May 23, shows finer detail is becoming visible on the dwarf planet. The spacecraft snapped the image at a distance of 3,200 miles (5,100 kilometers) with a resolution of 1,600 feet (480 meters) per pixel. The image is part of a sequence taken for navigational purposes.

NASA's WISE Spacecraft Discovers Most Luminous Galaxy in Universe

A remote galaxy shining with the light of more than 300 trillion suns has been discovered using data from NASA's Wide-field Infrared Survey Explorer (WISE). The galaxy is the most luminous galaxy found to date and belongs to a new class of objects recently discovered by WISE -- extremely luminous infrared galaxies, or ELIRGs.
"We are looking at a very intense phase of galaxy evolution," said Chao-Wei Tsai of NASA's Jet Propulsion Laboratory in Pasadena, California, lead author of a new report appearing in the May 22 issue of The Astrophysical Journal. "This dazzling light may be from the main growth spurt of the galaxy's black hole."
The brilliant galaxy, known as WISE J224607.57-052635.0, may have a behemoth black hole at its belly, gorging itself on gas. Supermassive black holes draw gas and matter into a disk around them, heating the disk to roaring temperatures of millions of degrees and blasting out high-energy, visible, ultraviolet and X-ray light. The light is blocked by surrounding cocoons of dust. As the dust heats up, it radiates infrared light.
Immense black holes are common at the cores of galaxies, but finding one this big so "far back" in the cosmos is rare. Because light from the galaxy hosting the black hole has traveled 12.5 billion years to reach us, astronomers are seeing the object as it was in the distant past. The black hole was already billions of times the mass of our sun when our universe was only a tenth of its present age of 13.8 billion years.
The new study outlines three reasons why the black holes in the ELIRGs could have grown so massive. First, they may have been born big. In other words, the "seeds," or embryonic black holes, might be bigger than thought possible.
"How do you get an elephant?" asked Peter Eisenhardt, project scientist for WISE at JPL and a co-author on the paper. "One way is start with a baby elephant."
The other two explanations involve either breaking or bending the theoretical limit of black hole feeding, called the Eddington limit. When a black hole feeds, gas falls in and heats up, blasting out light. The pressure of the light actually pushes the gas away, creating a limit to how fast the black hole can continuously scarf down matter. If a black hole broke this limit, it could theoretically balloon in size at a breakneck pace. Black holes have previously been observed breaking this limit; however, the black hole in the study would have had to repeatedly break the limit to grow this large.
Alternatively, the black holes might just be bending this limit.
"Another way for a black hole to grow this big is for it to have gone on a sustained binge, consuming food faster than typically thought possible," said Tsai. "This can happen if the black hole isn't spinning that fast."
If a black hole spins slowly enough, it won't repel its meal as much. In the end, a slow-spinning black hole can gobble up more matter than a fast spinner.
"The massive black holes in ELIRGs could be gorging themselves on more matter for a longer period of time," said Andrew Blain of University of Leicester in the United Kingdom, a co-author of this report. "It's like winning a hot-dog-eating contest lasting hundreds of millions of years."
More research is needed to solve this puzzle of these dazzlingly luminous galaxies. The team has plans to better determine the masses of the central black holes. Knowing these objects' true hefts will help reveal their history, as well as that of other galaxies, in this very crucial and frenzied chapter of our cosmos.
WISE has been finding more of these oddball galaxies in infrared images of the entire sky captured in 2010. By viewing the whole sky with more sensitivity than ever before, WISE has been able to catch rare cosmic specimens that might have been missed otherwise.
The new study reports a total of 20 new ELIRGs, including the most luminous galaxy found to date. These galaxies were not found earlier because of their distance, and because dust converts their powerful visible light into an incredible outpouring of infrared light.
"We found in a related study with WISE that as many as half of the most luminous galaxies only show up well in infrared light," said Tsai.

Star Explosion is Lopsided, Finds NASA's NuSTAR

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has found evidence that a massive star exploded in a lopsided fashion, sending ejected material flying in one direction and the core of the star in the other.
The findings offer the best proof yet that star explosions of this type, called Type II or core-collapse supernovae, are inherently asymmetrical, a phenomenon that had been difficult to prove before now.
"Stars are spherical objects, but apparently the process by which they die causes their cores to be turbulent, boiling and sloshing around in the seconds before their demise," said Steve Boggs of the University of California, Berkeley, lead author of a new study on the findings, appearing in the May 8 issue of Science. "We are learning that this sloshing leads to asymmetrical explosions."
The supernova remnant in the study, called 1987A, is 166,000 light-years away. Light from the blast that created the remnant lit up skies above Earth in 1987. While other telescopes had found hints that this explosion was not spherical, NuSTAR found the "smoking gun" in the form of a radioisotope called titanium-44.
"Titanium is produced in the very heart of the explosion, so it traces the shape of the engine driving the disassembly of the star," said Fiona Harrison, the principal investigator of NuSTAR at the California Institute of Technology in Pasadena. "By looking at the shift of the energy of the X-rays coming from titanium, the NuSTAR data revealed that, surprisingly, most of the material is moving away from us."
Last year, NuSTAR created detailed titanium-44 maps of another supernova remnant, called Cassiopeia A, also finding evidence of an asymmetrical explosion, though not to as great an extent as in 1987A. Together, these results suggest that lopsidedness is at the very root of core-collapse supernova.
When supernova 1987A first lit up our skies decades ago, telescopes around the world had a unique opportunity to watch the event unfold and evolve. Outer, ejected materials lit up first, followed by the innermost materials powered by radioactive isotopes, such as cobalt-56, which decayed into iron-56. In 2012, the European Space Agency's Integral satellite detected titanium-44 in 1987A. Titanium-44 continues to blaze in the supernova remnant due to its long lifetime of 85 years.
"In some ways, it is as if 1987A is still exploding in front of our eyes," said Boggs.
NuSTAR brought a new tool to the study of 1987A. Thanks to the observatory's sharp high-energy X-ray vision, it has made the most precise measurements of titanium-44 yet. This radioactive material is produced at the core of a supernova, so it provides astronomers with a direct probe into the mechanisms of a detonating star.
The NuSTAR spectral data reveal that titanium-44 is moving away from us with a velocity of 1.6 million mph (2.6 million kilometers per hour). That indicates ejected material flung outward in one direction, while the compact core of the supernova, called a neutron star, seems to have kicked off in the opposite direction.
"These explosions are driven by the formation of a compact object, the remaining core of the star, and this seems to be connected to the core blasting one direction, and the ejected material, the other," said Boggs.
Previous observations have hinted at the lopsided nature of supernova blasts, but it was impossible to confirm. Telescopes like NASA's Chandra X-ray Observatory, which sees lower-energy X-rays than NuSTAR, had spotted iron that had been heated in the 1987A blast, but it was not clear if the iron was generated in the explosion or just happened to have been in the vicinity.
"Radioactive titanium-44 glows in the X-rays no matter what and is only produced in the explosion," said Brian Grefenstette, a co-author of the study at Caltech. "This means that we don't have to worry about how the environment influenced the observations. We are able to directly observe the material ejected in the explosion."
Future studies by NuSTAR and other telescopes should further illuminate the warped nature of supernovae. Is 1987A particularly askew, or in line with other objects in its class? A decades-old mystery continues to unravel before our eyes

Dawn Glimpses Ceres' North Pole (April 2015)

After spending more than a month in orbit on the dark side of dwarf planet Ceres, NASA's Dawn spacecraft has captured several views of the sunlit north pole of this intriguing world. These images were taken on April 10 from a distance of 21,000 miles (33,000 kilometers), and they represent the highest-resolution views of Ceres to date.
Subsequent images of Ceres will show surface features at increasingly better resolution.
Dawn arrived at Ceres on March 6, marking the first time a spacecraft has orbited a dwarf planet. Previously, the spacecraft explored giant asteroid Vesta for 14 months from 2011 to 2012. Dawn has the distinction of being the only spacecraft to orbit two extraterrestrial targets.
Ceres, with an average diameter of about 590 miles (950 kilometers), is the largest body in the main asteroid belt between Mars and Jupiter. Dawn has been using its ion propulsion system to maneuver to its first science orbit at Ceres, which it will reach on April 23. The spacecraft will remain at a distance of 8,400 miles (13,500 kilometers) from the dwarf planet until May 9. Afterward, it will make its way to lower orbits.

Icy Tendrils Reaching into Saturn Ring Traced to Their Source (April 2015)

Long, sinuous, tendril-like structures seen in the vicinity of Saturn's icy moon Enceladus originate directly from geysers erupting from its surface, according to scientists studying images from NASA's Cassini spacecraft.
This result is published online today in a study in the Astronomical Journal, along with additional insights into the nature of the structures.
"We've been able to show that each unique tendril structure can be reproduced by particular sets of geysers on the moon's surface," said Colin Mitchell, a Cassini imaging team associate at the Space Science Institute in Boulder, Colorado, and lead author of the paper. Mitchell and colleagues used computer simulations to follow the trajectories of ice grains ejected from individual geysers. The geysers, which were discovered by Cassini in 2005, are jets of tiny water ice particles, water vapor and simple organic compounds.
Under certain lighting conditions, Cassini's wide-view images showing icy material erupting from Enceladus reveal faint, finger-like features, dubbed "tendrils" by the imaging team. The tendrils reach into Saturn's E ring -- the ring in which Enceladus orbits -- extending tens of thousands of miles (or kilometers) away from the moon. Since the tendrils were discovered, scientists have thought they were the result of the moon's geysering activity and the means by which Enceladus supplies material to the E ring. But the ghostly features had never before been traced directly to geysers on the surface.
Because the team was able to show that tendril structures of different shapes correspond to different sizes of geyser particles, the team was able to zero in on the sizes of the particles forming them. They found the tendrils are composed of particles with diameters no smaller than about a millionth of a meter (one meter is about 3 feet), a size consistent with the measurements of E-ring particles made by other Cassini instruments.
As the researchers examined images from different times and positions around Saturn, they also found that the detailed appearance of the tendrils changes over time. "It became clear to us that some features disappeared from one image to the next," said John Weiss, an imaging team associate at Saint Martin's University in Lacey, Washington, and an author on the paper.
The authors suspect that changes in the tendrils' appearance likely result from the cycle of tidal stresses -- squeezing and stretching of the moon as it orbits Saturn -- and its control of the widths of fractures from which the geysers erupt. The stronger the tidal stresses raised by Saturn at any point on the fractures, the wider the fracture opening and the greater the eruption of material. The authors will investigate in future work whether this theory explains the tendrils' changing appearance.
There is even more that can be extracted from the images, the scientists say. "As the supply lanes for Saturn's E ring, the tendrils give us a way to ascertain how much mass is leaving Enceladus and making its way into Saturn orbit," said Carolyn Porco, team leader for the imaging experiment and a coauthor on the paper. "So, another important step is to determine how much mass is involved, and thus estimate how much longer the moon's sub-surface ocean may last." An estimate of the lifetime of the ocean is important in understanding the evolution of Enceladus over long timescales.
Because of its significance to the investigation of possible extraterrestrial habitable zones, Enceladus is a major target of investigation for the final years of the Cassini mission. Many observations, including imaging of the plume and tendril features, and thermal observations of the surface of its south polar geyser basin, are planned during the next couple of years.

NASA's Spitzer Spots Planet Deep Within Our Galaxy (April 2015)

NASA's Spitzer Space Telescope has teamed up with a telescope on the ground to find a remote gas planet about 13,000 light-years away, making it one of the most distant planets known.
The discovery demonstrates that Spitzer -- from its unique perch in space -- can be used to help solve the puzzle of how planets are distributed throughout our flat, spiral-shaped Milky Way galaxy. Are they concentrated heavily in its central hub, or more evenly spread throughout its suburbs?
"We don't know if planets are more common in our galaxy's central bulge or the disk of the galaxy, which is why these observations are so important," said Jennifer Yee of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, and a NASA Sagan fellow. Yee is the lead author of one of three new studies that appeared recently in the Astrophysical Journal describing a collaboration between astronomers using Spitzer and the Polish Optical Gravitational Lensing Experiment, or OGLE.
OGLE's Warsaw Telescope at the Las Campanas Observatory in Chile scans the skies for planets using a method called microlensing. A microlensing event occurs when one star happens to pass in front of another, and its gravity acts as a lens to magnify and brighten the more distant star's light. If that foreground star happens to have a planet in orbit around it, the planet might cause a blip in the magnification.
Astronomers are using these blips to find and characterize planets tens of thousands of light-years away in the central bulge of our galaxy, where star crossings are more common. Our sun is located in the suburbs of the galaxy, about two-thirds of the way out from the center. The microlensing technique as a whole has yielded about 30 planet discoveries so far, with the farthest residing about 25,000 light-years away.
"Microlensing experiments are already detecting planets from the solar neighborhood to almost the center of the Milky Way," said co-author Andrew Gould of The Ohio State University, Columbus. "And so they can, in principle, tell us the relative efficiency of planet formation across this huge expanse of our galaxy."
Microlensing complements other planet-hunting tools, such as NASA's Kepler mission, which has found more than 1,000 planets closer to home. But it faces one key problem: This method can't always precisely narrow down the distance to the stars and planets being observed. While a passing star may magnify the light of a more distant star, it rarely can be seen itself, making the task of measuring how far away it is challenging.
Of the approximately 30 planets discovered with microlensing so far, roughly half cannot be pinned down to a precise location. The result is like a planetary treasure map lacking in X's.
That's where Spitzer can help out, thanks to its remote Earth-trailing orbit. Spitzer circles our sun, and is currently about 128 million miles (207 million kilometers) away from Earth. That's farther from Earth than Earth is from our sun. When Spitzer watches a microlensing event simultaneously with a telescope on Earth, it sees the star brighten at a different time, due to the large distance between the two telescopes and their unique vantage points. This technique is generally referred to as parallax.
"Spitzer is the first space telescope to make a microlens parallax measurement for a planet," said Yee. "Traditional parallax techniques that employ ground-based telescopes are not as effective at such great distances."
Using space telescopes to observe microlensing events is tricky. Ground telescopes send out alerts to the astronomy community when an event starts, but the activity can quickly fade, lasting on average about 40 days. The Spitzer team has scrambled to start microlensing campaigns as soon as three days after receiving an alert.
In the case of the newfound planet, the duration of the microlensing event happened to be unusually long, about 150 days. Both Spitzer and OGLE's telescopes detected the telltale planetary blip in the magnification, with Spitzer seeing it 20 days earlier.
This time delay between viewing of the event by OGLE and Spitzer was used to calculate the distance to the star and its planet. Knowing the distance allowed the scientists also to determine the mass of the planet, which is about half that of Jupiter.
Spitzer has eyed 22 other microlensing events in collaboration with OGLE and several other ground-based telescopes. While these observations have not turned up new planets, the data are essential to learning the population statistics of stars and planets at the heart of our galaxy. Spitzer will watch approximately 120 additional microlensing events this summer.
"We've mainly explored our own solar neighborhood so far," said Sebastiano Calchi Novati, a Visiting Sagan Fellow at NASA's Exoplanet Science Institute at the California Institute of Technology, Pasadena. "Now we can use these single lenses to do statistics on planets as a whole and learn about their distribution in the galaxy."

NASA-funded Study Explains Saturn's Epic Tantrums (April 2015)

The long-standing mystery of why Saturn seethes with enormous storms every 30 years may have been solved by scientists working with data from NASA's Cassini mission. The tempests, which can grow into bright bands that encircle the entire planet, are on a natural timer that is reset by each subsequent storm, the researchers report.
In 140 years of telescope observations, great storms have erupted on Saturn six times. Cassini and observers on Earth tracked the most recent of these storms from December 2010 to August 2011. During that time, the storm exploded through the clouds, eventually winding its way around Saturn.
In a paper published online today in the journal Nature Geoscience, scientists describe the effect they believe is responsible for the periodic outbursts. The basic idea is that water vapor is heavier than the hydrogen and helium that make up the bulk of Saturn's atmosphere, so once each giant storm dumps its huge mass of rain, the air within the clouds is left lighter than the atmosphere below. For a time, this situation shuts off the process of convection -- in which warm, moist air rises, and cool, dense air sinks -- that creates new clouds and storms.
"For decades after one of these storms, the warm air in Saturn's deep atmosphere is too wet, and too dense, to rise," said Cheng Li, a graduate student at the California Institute of Technology in Pasadena, who led the study. "The air above has to cool off, radiating its heat to space, before its density is greater than that of the hot, wet air below. This cooling process takes about 30 years, and then come the storms."
Li thinks the episodic nature of the storms indicates Saturn's deep atmosphere contains more water, relative to the other atmospheric constituents, than Jupiter. The researchers suggest Saturn's extra-wet interior might explain why the planet has such epic tantrums, whereas Jupiter does not. If Saturn's deep atmosphere were drier, scientists would expect continuous, smaller storms, as observed on Jupiter, Li said. Instead, Saturn's outbursts are episodic and quite explosive.
Other observations by ground and space-based telescopes have hinted at a wet interior for Saturn. "Previous studies using spectroscopy have shown that Saturn's interior is enriched in methane and other volatiles, by two or three times, compared to Jupiter. From there, it's a short leap to expect that Saturn is also rich in oxygen, which is also a volatile and a big part of every H2O molecule," said Andrew Ingersoll, a member of the Cassini science team, also at Caltech, who co-authored the paper with Li. Volatiles are elements and chemical compounds that change from solid to liquid or gas at relatively low temperatures.
Scientists are interested in understanding the amount of oxygen and other volatile ingredients in Saturn and Jupiter. These ingredients provide important clues about the formation of the two planets -- which are thought to have formed before all the others -- and conditions in the early solar system.

Dawn's Ceres Color Map Reveals Surface Diversity (April 2015)

A new color map of dwarf planet Ceres, which NASA's Dawn spacecraft has been orbiting since March, reveals the diversity of the surface of this planetary body. Differences in morphology and color across the surface suggest Ceres was once an active body, Dawn researchers said today at the 2015 General Assembly of the European Geosciences Union in Vienna.
"This dwarf planet was not just an inert rock throughout its history. It was active, with processes that resulted in different materials in different regions. We are beginning to capture that diversity in our color images," said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.
The Dawn mission made history on March 6 as the first spacecraft to reach a dwarf planet, and the first spacecraft to orbit two extraterrestrial targets. Previously, Dawn studied giant asteroid Vesta from 2011 to 2012, uncovering numerous insights about its geology and history. While Vesta is a dry body, Ceres is believed to be 25 percent water ice by mass. By comparing Vesta and Ceres, scientists hope to gain a better understanding of the formation of the solar system.
Ceres' surface is heavily cratered, as expected, but appears to have fewer large craters than scientists anticipated. It also has a pair of very bright neighboring spots in its northern hemisphere. More detail will emerge after the spacecraft begins its first intensive science phase on April 23, from a distance of 8,400 miles (13,500 kilometers) from the surface, said Martin Hoffmann, investigator on the Dawn framing camera team, based at the Max Planck Institute for Solar System Research, Göttingen, Germany.
The visible and infrared mapping spectrometer (VIR), an imaging spectrometer that examines Ceres in visible and infrared light, has been examining the relative temperatures of features on Ceres' surface. Preliminary examination suggests that different bright regions on Ceres' surface behave differently, said Federico Tosi, investigator from the VIR instrument team at the Institute for Space Astrophysics and Planetology, and the Italian National Institute for Astrophysics, Rome.
Based on observations from NASA's Hubble Space Telescope, planetary scientists have identified 10 bright regions on Ceres' surface. One pair of bright spots, by far the brightest visible marks on Ceres, appears to be located in a region that is similar in temperature to its surroundings. But a different bright feature corresponds to a region that is cooler than the rest of Ceres' surface.
The origins of Ceres' bright spots, which have captivated the attention of scientists and the public alike, remain unknown. It appears the brightest pair is located in a crater 57 miles (92 kilometers) wide. As Dawn gets closer to the surface of Ceres, better-resolution images will become available.
"The bright spots continue to fascinate the science team, but we will have to wait until we get closer and are able to resolve them before we can determine their source," Russell said.
Both Vesta and Ceres are located in the main asteroid belt between Mars and Jupiter. The Dawn spacecraft will continue studying Ceres through June 2016.