NEOWISE Observes Carbon Gases in Comets (NASA)

An expanded view of comet C/2006 W3 (Christensen)


After its launch in 2009, NASA's NEOWISE spacecraft observed 163 comets during the WISE/NEOWISE prime mission. This sample from the space telescope represents the largest infrared survey of comets to date. Data from the survey are giving new insights into the dust, comet nucleus sizes, and production rates for difficult-to-observe gases like carbon dioxide and carbon monoxide. Results of the NEOWISE census of comets were recently published in the Astrophysical Journal.
Carbon monoxide (CO) and carbon dioxide (CO2) are common molecules found in the environment of the early solar system, and in comets. In most circumstances, water-ice sublimation likely drives the activity in comets when they come nearest to the sun, but at larger distances and colder temperatures, other common molecules like CO and CO2 may be the main drivers. Spaceborne carbon dioxide and carbon monoxide are difficult to directly detect from the ground because their abundance in Earth's own atmosphere obscures the signal. The NEOWISE spacecraft soars high above Earth's atmosphere, making these measurements of a comet's gas emissions possible.
"This is the first time we've seen such large statistical evidence of carbon monoxide taking over as a comet's gas of choice when they are farther out from the sun," said James Bauer, deputy principal investigator of the NEOWISE mission from NASA's Jet Propulsion Laboratory in Pasadena, California, and author of a paper on the subject. "By emitting what is likely mostly carbon monoxide beyond four astronomical units (4 times the Earth-Sun distance; about 370 million miles, 600 million kilometers) it shows us that comets may have stored most of the gases when they formed, and secured them over billions of years. Most of the comets that we observed as active beyond 4 AU are long-period comets, comets with orbital periods greater than 200 years that spend most of their time beyond Neptune's orbit."
While the amount of carbon monoxide and dioxide increases relative to ejected dust as a comet gets closer to the sun, the percentage of these two gases, when compared to other volatile gases, decreases.
"As they get closer to the sun, these comets seem to produce a prodigious amount of carbon dioxide," said Bauer. "Your average comet sampled by NEOWISE would expel enough carbon dioxide to provide the bubble power for thousands of cans of soda per second."

Earth Might Have Hairy Dark Matter (NASA)

A new study publishing this week in the Astrophysical Journal by Gary Prézeau of NASA's Jet Propulsion Laboratory, Pasadena, California, proposes the existence of long filaments of dark matter, or "hairs."
Dark matter is an invisible, mysterious substance that makes up about 27 percent of all matter and energy in the universe. The regular matter, which makes up everything we can see around us, is only 5 percent of the universe. The rest is dark energy, a strange phenomenon associated with the acceleration of our expanding universe.
Neither dark matter nor dark energy has ever been directly detected, although many experiments are trying to unlock the mysteries of dark matter, whether from deep underground or in space.
Based on many observations of its gravitational pull in action, scientists are certain that dark matter exists, and have measured how much of it there is in the universe to an accuracy of better than one percent. The leading theory is that dark matter is "cold," meaning it doesn't move around much, and it is "dark" insofar as it doesn't produce or interact with light.
Galaxies, which contain stars made of ordinary matter, form because of fluctuations in the density of dark matter. Gravity acts as the glue that holds both the ordinary and dark matter together in galaxies.
According to calculations done in the 1990s and simulations performed in the last decade, dark matter forms "fine-grained streams" of particles that move at the same velocity and orbit galaxies such as ours.
"A stream can be much larger than the solar system itself, and there are many different streams crisscrossing our galactic neighborhood," Prézeau said.
Prézeau likens the formation of fine-grained streams of dark matter to mixing chocolate and vanilla ice cream. Swirl a scoop of each together a few times and you get a mixed pattern, but you can still see the individual colors.
"When gravity interacts with the cold dark matter gas during galaxy formation, all particles within a stream continue traveling at the same velocity," Prézeau said.
But what happens when one of these streams approaches a planet such as Earth? Prézeau used computer simulations to find out.
His analysis finds that when a dark matter stream goes through a planet, the stream particles focus into an ultra-dense filament, or "hair," of dark matter. In fact, there should be many such hairs sprouting from Earth.
A stream of ordinary matter would not go through Earth and out the other side. But from the point of view of dark matter, Earth is no obstacle. According to Prézeau's simulations, Earth's gravity would focus and bend the stream of dark matter particles into a narrow, dense hair.
Hairs emerging from planets have both "roots," the densest concentration of dark matter particles in the hair, and "tips," where the hair ends. When particles of a dark matter stream pass through Earth's core, they focus at the "root" of a hair, where the density of the particles is about a billion times more than average. The root of such a hair should be around 600,000 miles (1 million kilometers) away from the surface, or twice as far as the moon. The stream particles that graze Earth's surface will form the tip of the hair, about twice as far from Earth as the hair's root.
"If we could pinpoint the location of the root of these hairs, we could potentially send a probe there and get a bonanza of data about dark matter," Prézeau said.
A stream passing through Jupiter's core would produce even denser roots: almost 1 trillion times denser than the original stream, according to Prézeau's simulations.
"Dark matter has eluded all attempts at direct detection for over 30 years. The roots of dark matter hairs would be an attractive place to look, given how dense they are thought to be," said Charles Lawrence, chief scientist for JPL's astronomy, physics and technology directorate.
Another fascinating finding from these computer simulations is that the changes in density found inside our planet - from the inner core, to the outer core, to the mantle to the crust - would be reflected in the hairs. The hairs would have "kinks" in them that correspond to the transitions between the different layers of Earth.
Theoretically, if it were possible to obtain this information, scientists could use hairs of cold dark matter to map out the layers of any planetary body, and even infer the depths of oceans on icy moons.
Further study is needed to support these findings and unlock the mysteries of the nature of dark matter.

Mars Rover Finds Rich Mineral Stew in Fractured Rock (space.com)

hemical analysis by NASA's Mars rover Curiosity indicates that water made several repeat appearances to create the rich mineral veins at a site called "Garden City" in the lower part of Mount Sharp.
The veins form in places where fluids have move through fractured rocks, depositing minerals and leaving telltale chemical fingerprints on surrounding areas. Some of the mineral veins at Garden City protrude the equivalent of two finger widths above the now-eroded bedrock in which they formed.
The site was not accessible to Curiosity's drill, but in March the rover zapped 17 targets with its ChemCam laser and discovered a diverse chemical stew.
"I think this has some of the most extreme chemistry that we've seen in a very localized area. There's been other places where we've seen very strong chemistry, but in this kind of meter-square area, up until this point I don't think we've seen anywhere with this much variability and this much unexpected chemistry," Curiosity scientist Diana Blaney, with NASA's Jet Propulsion Laboratory in Pasadena, Calif, told Discovery News.
Many of the veins contain rich deposits of calcium sulfate. Others are laced with magnesium sulfate or fluorine. Levels of iron vary.
The three-mile-high Mount Sharp rises from the floor of a huge impact basin that once held water. The Garden City veins were created after mud in the lake had hardened into rock and cracked.
"At Garden City, because there's such good preservation and we get the cross-cutting, we're able to start pulling out some chemical signatures that we saw at different places into distinct fluids. And by looking at the cross-cutting relationships and the difference in chemistries, I think we have really strong evidence that they're distinct fluid events," Blaney said.
"We don't know how far apart in time these different events occurred, or what was driving them," she added. "I think as we get more information on what it's going to take to chemically evolve these fluids, we might be able to pin that down."
Curiosity is scouring Mount Sharp to look for habitats that could have supported past life and for places suitable to preserve organics.
"Veins have a good potential — because it's a fluid and there is crystallization — to include things as inclusions, but the organic preservation has a lot of factors," Blaney said.

Pluto Goes Psychedelic in Brilliant New Photo (space.com)

Pluto's the prettiest dwarf planet at the party in this new, brilliantly colored image recently released by NASA.
Researchers used a process called principal component analysis to create the false-colored photo of Pluto, which highlights the subtle color differences among the different regions, NASA officials said in a statement. The original image was captured by the Ralph/MVIC color camera on NASA's New Horizons spacecraft as it passed within about 22,000 miles (35,000 kilometers) from Pluto during its flyby in July.
Pluto's geography has already proven astonishingly varied as New Horizons continues to send back detailed observations from its flyby. Flattened, icy plains; jagged ridges; deep craters; and even enormous mountains that are potential icy volcanoes all have been spotted on the dwarf planet.

First gamma-ray pulsar detected in another galaxy (Science News)

Researchers using NASA's Fermi Gamma-ray Space Telescope have discovered the first gamma-ray pulsar in a galaxy other than our own. The object sets a new record for the most luminous gamma-ray pulsar known.

The pulsar lies in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a small galaxy that orbits our Milky Way and is located 163,000 light-years away. The Tarantula Nebula is the largest, most active and most complex star-formation region in our galactic neighborhood. It was identified as a bright source of gamma rays, the highest-energy form of light, early in the Fermi mission. Astronomers initially attributed this glow to collisions of subatomic particles accelerated in the shock waves produced by supernova explosions.
"It's now clear that a single pulsar, PSR J0540-6919, is responsible for roughly half of the gamma-ray brightness we originally thought came from the nebula," said lead scientist Pierrick Martin, an astrophysicist at the National Center for Scientific Research (CNRS) and the Research Institute in Astrophysics and Planetology in Toulouse, France. "That is a genuine surprise."
When a massive star explodes as a supernova, the star's core may survive as a neutron star, where the mass of half a million Earths is crushed into a magnetized ball no larger than Washington, D.C. A young isolated neutron star spins tens of times each second, and its rapidly spinning magnetic field powers beams of radio waves, visible light, X-rays and gamma rays. If the beams sweep past Earth, astronomers observe a regular pulse of emission and the object is classified as a pulsar.
The Tarantula Nebula was known to host two pulsars, PSR J0540-6919 (J0540 for short) and PSR J0537?6910 (J0537), which were discovered with the help of NASA's Einstein and Rossi X-ray Timing Explorer (RXTE) satellites, respectively. J0540 spins just under 20 times a second, while J0537 whirls at nearly 62 times a second -- the fastest-known rotation period for a young pulsar.
Nevertheless, it took more than six years of observations by Fermi's Large Area Telescope (LAT), as well as a complete reanalysis of all LAT data in a process called Pass 8, to detect gamma-ray pulsations from J0540. The Fermi data establish upper limits for gamma-ray pulses from J0537 but do not yet detect them.
Martin and his colleagues present these findings in a paper to be published in the Nov. 13 edition of the journal Science.
"The gamma-ray pulses from J0540 have 20 times the intensity of the previous record-holder, the pulsar in the famous Crab Nebula, yet they have roughly similar levels of radio, optical and X-ray emission," said coauthor Lucas Guillemot, at the Laboratory for Physics and Chemistry of Environment and Space, operated by CNRS and the University of Orléans in France. "Accounting for these differences will guide us to a better understanding of the extreme physics at work in young pulsars."
J0540 is a rare find, with an age of roughly 1,700 years, about twice that of the Crab Nebula pulsar. By contrast, most of the more than 2,500 known pulsars are from 10,000 to hundreds of millions of years old.
Despite J0540's luminosity, too few gamma rays reach the LAT to detect pulsations without knowing the period in advance. This information comes from a long-term X-ray monitoring campaign using RXTE, which recorded both pulsars from the start of the Fermi mission to the end of 2011, when RXTE operations ceased.
"This campaign began as a search for a pulsar created by SN 1987A, the closest supernova seen since the invention of the telescope," said co-author Francis Marshall, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "That search failed, but it discovered J0537."
Prior to the launch of Fermi in 2008, only seven gamma-ray pulsars were known. To date, the mission has found more than 160

Rosetta detects oxygen on comet 67P (Chemistry World)

Molecular oxygen has been detected in the cloud of gas surrounding comet 67P/Churyumov-Gerasimenko by the Rosetta space probe, which has been orbiting the comet for over a year. It is the first time molecular oxygen has ever been detected on a comet.

The measurements were taken by the ROSINA-DFMS mass spectrometer on board Rosetta between September 2014 and March 2015. In the areas sampled, the abundance of oxygen relative to water ranged from one to 10%.
Molecular oxygen has never been detected on a comet before, although it has been observed in the atmospheres of icy moons orbiting Saturn and Jupiter. Measurements taken by other spacecraft show the coma of a comet – the cloud of gas surrounding the nucleus – is usually made up of water vapour, carbon dioxide and carbon monoxide.
The observations may help shape new models of how the comet formed. Measurements of the ratios of different gases indicate that the oxygen in 67P’s coma comes from its icy nucleus, which in turn suggests that ‘primordial’ oxygen, present in the giant molecular cloud that gave rise to the solar system, was incorporated into the comet as it formed.

Radar Images Provide New Details on Halloween Asteroid (NASA)

The highest-resolution radar images of asteroid 2015 TB145's safe flyby of Earth have been processed. NASA scientists used giant, Earth-based radio telescopes to bounce radar signals off the asteroid as it flew past Earth on Oct. 31 at 10 a.m. PDT (1 p.m. EDT) at about 1.3 lunar distances (300,000 miles, or 480,000 kilometers) from Earth. Asteroid 2015 TB145 is spherical in shape and approximately 2,000 feet (600 meters) in diameter.
"The radar images of asteroid 2015 TB145 show portions of the surface not seen previously and reveal pronounced concavities, bright spots that might be boulders, and other complex features that could be ridges," said Lance Benner of NASA's Jet Propulsion Laboratory in Pasadena, California, who leads NASA's asteroid radar research program. "The images look distinctly different from the Arecibo radar images obtained on Oct. 30 and are probably the result of seeing the asteroid from a different perspective in its three-hour rotation period."
Radar images of asteroid 2015 TB145 acquired by Arecibo Observatory are available at these sites:
http://on.fb.me/1MahsY8
https://twitter.com/AreciboRadar/status/661293813713928192
To obtain these highest-resolution radar images of the asteroid, scientists used the 230-foot (70-meter) DSS-14 antenna at Goldstone, California, to transmit high-power microwaves toward the asteroid. The signal bounced off the asteroid, and its radar echoes were received by the National Radio Astronomy Observatory's 100-meter (330-foot) Green Bank Telescope in West Virginia. The radar images achieve a spatial resolution as fine as 13 feet (4 meters) per pixel.
The next time that asteroid 2015 TB145 will be in Earth's neighborhood will be in September 2018, when it will make a distant pass at about 24 million miles (38 million kilometers), or about a quarter the distance between Earth and the sun.
Radar is a powerful technique for studying an asteroid's size, shape, rotation, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than would be possible otherwise.
NASA places a high priority on tracking asteroids and protecting our home planet from them. In fact, the U.S. has the most robust and productive survey and detection program for discovering near-Earth objects (NEOs). To date, U.S. assets have discovered about 98 percent of known NEOs.
In addition to the resources NASA puts into understanding asteroids, it also partners with other U.S. government agencies, university-based astronomers, and space science institutes across the country, often with grants, interagency transfers and other contracts from NASA, and also with international space agencies and institutions that are working to track and better understand these objects. In addition, NASA values the work of numerous highly skilled amateur astronomers, whose accurate observational data helps improve asteroid orbits after they are found.

Whopping Galaxy Cluster Spotted with Help of NASA Telescopes (NASA)

Astronomers have discovered a giant gathering of galaxies in a very remote part of the universe, thanks to NASA's Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE). The galaxy cluster, located 8.5 billion light-years away, is the most massive structure yet found at such great distances.
Galaxy clusters are gravitationally bound groups of thousands of galaxies, which themselves each contain hundreds of billions of stars. The clusters grow bigger and bigger over time as they acquire new members.
How did these clusters evolve over time? What did they look like billions of years ago? To answer these questions, astronomers look back in time to our youthful universe. Because light takes time to reach us, we can see very distant objects as they were in the past. For example, we are seeing the newfound galaxy cluster -- called Massive Overdense Object (MOO) J1142+1527 -- as it existed 8.5 billion years ago, long before Earth formed.
As light from remote galaxies makes its way to us, it becomes stretched to longer, infrared wavelengths by the expansion of space. That's where WISE and Spitzer help out.
For infrared space telescopes, picking out distant galaxies is like plucking ripe cherries from a cherry tree. In the infrared images produced by Spitzer, these distant galaxies stand out as red dots, while closer galaxies look white. Astronomers first combed through the WISE catalog to find candidates for clusters of distant galaxies. WISE catalogued hundreds of millions of objects in images taken over the entire sky from 2010 to 2011.
They then used Spitzer to narrow in on 200 of the most interesting objects, in a project named the "Massive and Distant Clusters of WISE Survey," or MaDCoWS. Spitzer doesn't observe the whole sky like WISE, but can see more detail.
"It's the combination of Spitzer and WISE that lets us go from a quarter billion objects down to the most massive galaxy clusters in the sky," said Anthony Gonzalez of the University of Florida in Gainesville, lead author of a new study published in the Oct. 20 issue of the Astrophysical Journal Letters.
From these observations, MOO J1142+1527 jumped out as one of the most extreme.
The W.M. Keck Observatories and Gemini Observatory on Mauna Kea in Hawaii were used to measure the distance to the cluster at 8.5 billion light-years. Using data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) telescopes near Owens Valley in California, the scientists were then able to determine that the cluster's mass is a quadrillion times that of our sun -- making it the most massive known cluster that far back in space and time.
MOO J1142+1527 may be one of only a handful of clusters of this heft in the early universe, according to the scientists' estimates.
"Based on our understanding of how galaxy clusters grow from the very beginning of our universe, this cluster should be one of the five most massive in existence at that time," said co-author Peter Eisenhardt, the project scientist for WISE at NASA's Jet Propulsion Laboratory in Pasadena, California.
In the coming year, the team plans to sift through more than 1,700 additional galaxy cluster candidates with Spitzer, looking for biggest of the bunch.
"Once we find the most massive clusters, we can start to investigate how galaxies evolved in these extreme environments," said Gonzalez.

Saturn's Geyser Moon Shines in Close Flyby Views (NASA)

NASA's Cassini spacecraft has begun transmitting its latest images of Saturn's icy, geologically active moon Enceladus, acquired during the dramatic Oct. 28 flyby in which the probe passed about 30 miles (49 kilometers) above the moon's south polar region. The spacecraft will continue transmitting its data from the encounter for the next several days.
"Cassini's stunning images are providing us a quick look at Enceladus from this ultra-close flyby, but some of the most exciting science is yet to come," said Linda Spilker, the mission's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
Researchers will soon begin studying data from Cassini's gas analyzer and dust detector instruments, which directly sampled the moon's plume of gas and dust-sized icy particles during the flyby. Those analyses are likely to take several weeks, but should provide important insights about the composition of the global ocean beneath Enceladus' surface and any hydrothermal activity occurring on the ocean floor. The potential for such activity in this small ocean world has made Enceladus a prime target for future exploration in search of habitable environments in the solar system beyond Earth.
In addition to the processed images, unprocessed, or "raw," images appear on the Cassini mission website at:
http://saturn.jpl.nasa.gov/mission/flybys/enceladus20151028
Cassini's next and final close Enceladus flyby will take place on Dec. 19, when the spacecraft will measure the amount of heat coming from the moon's interior. The flyby will be at an altitude of 3,106 miles (4,999 kilometers).
Additional information and multimedia products for Cassini's final Enceladus flybys are available at:
http://solarsystem.nasa.gov/finalflybys

Voyager 1 Helps Solve Interstellar Medium Mystery (NASA)

NASA's Voyager 1 spacecraft made history in 2012 by entering interstellar space, leaving the planets and the solar wind behind. But observations from the pioneering probe were puzzling with regard to the magnetic field around it, as they differed from what scientists derived from observations by other spacecraft.
A new study offers fresh insights into this mystery. Writing in the Astrophysical Journal Letters, Nathan Schwadron of the University of New Hampshire, Durham, and colleagues reanalyzed magnetic field data from Voyager 1 and found that the direction of the magnetic field has been slowly turning ever since the spacecraft crossed into interstellar space. They believe this is an effect of the nearby boundary of the solar wind, a stream of charged particles that comes from the sun.
"This study provides very strong evidence that Voyager 1 is in a region where the magnetic field is being deflected by the solar wind," said Schwadron, lead author of the study.
Researchers predict that in 10 years Voyager 1 will reach a more "pristine" region of the interstellar medium where the solar wind does not significantly influence the magnetic field.
Voyager 1's crossing into interstellar space meant it had left the heliosphere -- the bubble of solar wind surrounding our sun and the planets. Observations from Voyager's instruments found that the particle density was 40 times greater outside this boundary than inside, confirming that it had indeed left the heliosphere.
But so far, Voyager 1's observation of the direction of the local interstellar magnetic field is more than 40 degrees off from what other spacecraft have determined. The new study suggests this discrepancy exists because Voyager 1 is in a more distorted magnetic field just outside the heliopause, which is the boundary between the solar wind and the interstellar medium.
"If you think of the magnetic field as a rubber band stretched around a beach ball, that band is being deflected around the heliopause," Schwadron said.
In 2009, NASA's Interstellar Boundary Explorer (IBEX) discovered a "ribbon" of energetic neutral atoms that is thought to hold clues to the direction of the pristine interstellar magnetic field. The so-called "IBEX ribbon," which forms a circular arc in the sky, remains mysterious, but scientists believe it is produced by a flow of neutral hydrogen atoms from the solar wind that were re-ionized in nearby interstellar space and then picked up electrons to become neutral again.
The new study uses multiple data sets to confirm that the magnetic field direction at the center of the IBEX ribbon is the same direction as the magnetic field in the pristine interstellar medium. Observations from the NASA/ESA Ulysses and SOHO spacecraft also support the new findings.
"All of these different data sets that have been collected over the last 25 years have been pointing toward the same meeting point in the field," Schwadron said.
Over time, the study suggests, at increasing distances from the heliosphere, the magnetic field will be oriented more and more toward "true north," as defined by the IBEX ribbon. By 2025, if the field around Voyager 1 continues to steadily turn, Voyager 1 will observe the same magnetic field direction as IBEX. That would signal Voyager 1's arrival in a less distorted region of the interstellar medium.
"It's an interesting way to look at the data. It gives a prediction of how long we'll have to go before Voyager 1 is in the medium that's no longer strongly perturbed," said Ed Stone, Voyager project scientist, based at the California Institute of Technology in Pasadena, who was not involved in this study.
While Voyager 1 will continue delivering insights about interstellar space, its twin probe Voyager 2 is also expected to cross into the interstellar medium within the next few years. Voyager 2 will make additional observations of the magnetic field in interstellar space and help scientists refine their estimates.
Voyager 1 and Voyager 2 were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft. Voyager 1 is the most distant object touched by human hands.

Astronomers find disk of young stars near center of Milky Way (AAAS)

Astronomers have long thought that the bulge at the center of our Milky Way galaxy is populated with very old stars. But a survey of the area has revealed an unexpected feature: a disk of much younger stars hidden among the veterans. A team of astronomers used survey data taken by the European Southern Observatory’s VISTA telescope at Cerro Paranal in Chile. VISTA is able to observe at infrared wavelengths, which can penetrate the clouds of dust that normally shroud the galactic center. The astronomers were looking for variable stars call Cepheids, which pulse at a rate related to their brightness. This allows astronomers to calculate how far away they are. As the team reports today in Astrophysical Journal Letters, among the 655 Cepheids they found, there were 35 examples of a subset known as classical Cepheids (red dots; the yellow star is our sun), which are typically young stars. The 35 varied in age from 25 million to 100 million years old, striplings compared with the much more elderly stars all around them. Even more surprising, all of the 35 were arranged in a thin disk slicing through the central bulge (see above). The discovery suggests there has been a constant supply of young stars to the galactic center, but where do they come from? The galactic center is thought to have used up its supply of gas from which to make stars long long ago, so astronomers will have to figure out some mechanism by which young stars are moved inward from farther out in the galaxy.

Black Hole Has Major Flare

The baffling and strange behaviors of black holes have become somewhat less mysterious recently, with new observations from NASA's Explorer missions Swift and the Nuclear Spectroscopic Telescope Array, or NuSTAR. The two space telescopes caught a supermassive black hole in the midst of a giant eruption of X-ray light, helping astronomers address an ongoing puzzle: How do supermassive black holes flare?
The results suggest that supermassive black holes send out beams of X-rays when their surrounding coronas -- sources of extremely energetic particles -- shoot, or launch, away from the black holes.
"This is the first time we have been able to link the launching of the corona to a flare," said Dan Wilkins of Saint Mary's University in Halifax, Canada, lead author of a new paper on the results appearing in the Monthly Notices of the Royal Astronomical Society. "This will help us understand how supermassive black holes power some of the brightest objects in the universe."
Supermassive black holes don't give off any light themselves, but they are often encircled by disks of hot, glowing material. The gravity of a black hole pulls swirling gas into it, heating this material and causing it to shine with different types of light. Another source of radiation near a black hole is the corona. Coronas are made up of highly energetic particles that generate X-ray light, but details about their appearance, and how they form, are unclear.
Astronomers think coronas have one of two likely configurations. The "lamppost" model says they are compact sources of light, similar to light bulbs, that sit above and below the black hole, along its rotation axis. The other model proposes that the coronas are spread out more diffusely, either as a larger cloud around the black hole, or as a "sandwich" that envelops the surrounding disk of material like slices of bread. In fact, it's possible that coronas switch between both the lamppost and sandwich configurations.
The new data support the "lamppost" model -- and demonstrate, in the finest detail yet, how the light-bulb-like coronas move. The observations began when Swift, which monitors the sky for cosmic outbursts of X-rays and gamma rays, caught a large flare coming from the supermassive black hole called Markarian 335, or Mrk 335, located 324 million light-years away in the direction of the constellation Pegasus. This supermassive black hole, which sits at the center of a galaxy, was once one of the brightest X-ray sources in the sky.
"Something very strange happened in 2007, when Mrk 335 faded by a factor of 30. What we have found is that it continues to erupt in flares but has not reached the brightness levels and stability seen before," said Luigi Gallo, the principal investigator for the project at Saint Mary's University. Another co-author, Dirk Grupe of Morehead State University in Kentucky, has been using Swift to regularly monitor the black hole since 2007.
In September 2014, Swift caught Mrk 335 in a huge flare. Once Gallo found out, he sent a request to the NuSTAR team to quickly follow up on the object as part of a "target of opportunity" program, where the observatory's previously planned observing schedule is interrupted for important events. Eight days later, NuSTAR set its X-ray eyes on the target, witnessing the final half of the flare event.
After careful scrutiny of the data, the astronomers realized they were seeing the ejection, and eventual collapse, of the black hole's corona.
"The corona gathered inward at first and then launched upwards like a jet," said Wilkins. "We still don't know how jets in black holes form, but it's an exciting possibility that this black hole's corona was beginning to form the base of a jet before it collapsed."
How could the researchers tell the corona moved? The corona gives off X-ray light that has a slightly different spectrum -- X-ray "colors" -- than the light coming from the disk around the black hole. By analyzing a spectrum of X-ray light from Mrk 335 across a range of wavelengths observed by both Swift and NuSTAR, the researchers could tell that the corona X-ray light had brightened -- and that this brightening was due to the motion of the corona.
Coronas can move very fast. The corona associated with Mrk 335, according to the scientists, was traveling at about 20 percent the speed of light. When this happens, and the corona launches in our direction, its light is brightened in an effect called relativistic Doppler boosting.
Putting this all together, the results show that the X-ray flare from this black hole was caused by the ejected corona.
"The nature of the energetic source of X-rays we call the corona is mysterious, but now with the ability to see dramatic changes like this we are getting clues about its size and structure," said Fiona Harrison, the principal investigator of NuSTAR at the California Institute of Technology in Pasadena, who was not affiliated with the study.
Many other black hole brainteasers remain. For example, astronomers want to understand what causes the ejection of the corona in the first place.

Only 8% of the universe’s habitable worlds have formed so far (AAAS)

There are likely hundreds of millions of Earth-like planets in the Milky Way today, but that’s a small fraction of the number that may form throughout the universe in the future, a new study suggests. Using data from the Hubble Space Telescope, researchers estimated the rates of past star and planet formation in the universe, which is now about 13.8 billion years old. They then combined that information with data from previous surveys that estimated the amounts of hydrogen and helium left over from the big bang that still haven’t collapsed to form stars. At the time our solar system formed about 4.6 billion years ago, only about 39% of the hydrogen and helium in our galaxy had collapsed into clouds that then evolved into stars, they say. That means that the remaining 61% is available to form future solar systems that may include Earth-like planets in their habitable zones, the researchers report online today in Monthly Notices of the Royal Astronomical Society. In the universe as a whole, the researchers suggest, only 8% of its original starmaking gases was locked up in stars by Earth’s first birthday. The rest will, over the remaining trillions of years of the universe’s lifetime, coalesce into stars whose solar systems will contain a myriad of Earth-like planets

NASA's K2 Finds Dead Star Vaporizing a Mini 'Planet' (NASA & Nature)

Vanderburg et al.¹ analysed data from the white dwarf star WD 1145+017 taken by the Kepler space observatory and ground-based telescopes. The data revealed transit features (periodic attenuations of the stellar brightness) that are best explained by the passage in front of the star of one or several disintegrating minor planets. The authors performed simulations of this process in which a minor planet that orbits very close to the star loses mass in the form of dust particles that generate leading and trailing cometary tails (colours indicate dust density). The various phases of the transit (leading tail, minor planet core and trailing tail) induce attenuations of the stellar brightness of different magnitudes and durations. Adapted from Fig. S7 of ref. 1.


Scientists using NASA's repurposed Kepler space telescope, known as the K2 mission, have uncovered strong evidence of a tiny, rocky object being torn apart as it spirals around a white dwarf star. This discovery validates a long-held theory that white dwarfs are capable of cannibalizing possible remnant planets that have survived within its solar system.
"We are for the first time witnessing a miniature "planet" ripped apart by intense gravity, being vaporized by starlight and raining rocky material onto its star," said Andrew Vanderburg, graduate student at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and lead author of the paper published in Nature.
As stars like our sun age, they puff up into red giants and then gradually lose about half their mass, shrinking down to 1/100th of their original size to roughly the size of Earth. This dead, dense star remnant is called a white dwarf.
The devastated planetesimal, or cosmic object formed from dust, rock, and other materials, is estimated to be the size of a large asteroid, and is the first planetary object to be confirmed transiting a white dwarf. It orbits its white dwarf, WD 1145+017, once every 4.5 hours. This orbital period places it extremely close to the white dwarf and its searing heat and shearing gravitational force.
During its first observing campaign from May 30 to Aug. 21, 2014, K2 trained its gaze on a patch of sky in the constellation Virgo, measuring the minuscule change in brightness of the distant white dwarf. When an object transits, or passes in front of a star from the vantage point of the space telescope, a dip in starlight is recorded. The periodic dimming of starlight indicates the presence of an object in orbit about the star.
A research team led by Vanderburg found an unusual, but vaguely familiar pattern in the data. While there was a prominent dip in brightness occurring every 4.5 hours, blocking up to 40 percent of the white dwarf's light, the transit signal of the tiny planet did not exhibit the typical symmetric U-shaped pattern. It showed an asymmetric elongated slope pattern that would indicate the presence of a comet-like tail. Together these features indicated a ring of dusty debris circling the white dwarf, and what could be the signature of a small planet being vaporized.
"The eureka moment of discovery came on the last night of observation with a sudden realization of what was going around the white dwarf. The shape and changing depth of the transit were undeniable signatures," said Vanderburg.
In addition to the strangely shaped transits, Vanderburg and his team found signs of heavier elements polluting the atmosphere of WD 1145+017, as predicted by theory.
Due to intense gravity, white dwarfs are expected to have chemically pure surfaces, covered only with light elements of helium and hydrogen. For years, researchers have found evidence that some white dwarf atmospheres are polluted with traces of heavier elements such as calcium, silicon, magnesium and iron. Scientists have long suspected that the source of this pollution was an asteroid or a small planet being torn apart by the white dwarf's intense gravity.
Analysis of the star's atmospheric composition was conducted using observations made by the University of Arizona's MMT Observatory near Tucson.
"For the last decade we've suspected that white dwarf stars were feeding on the remains of rocky objects, and this result may be the smoking gun we're looking for," said Fergal Mullally, staff scientist of K2 at SETI and NASA's Ames Research Center in Moffett Field, California. "However, there's still a lot more work to be done figuring out the history of this system."
"This discovery highlights the power and serendipitous nature of K2. The science community has full access to K2 observations and is using these data to make a wide range of unique discoveries across the full range of astrophysics phenomena," said Steve Howell, K2 project scientist at Ames

Closest Northern Views of Saturn's Moon Enceladus (NASA)

NASA's Cassini spacecraft has begun returning its best-ever views of the northern extremes of Saturn's icy, ocean-bearing moon Enceladus. The spacecraft obtained the images during its Oct. 14 flyby, passing 1,142 miles (1,839 kilometers) above the moon's surface. Mission controllers say the spacecraft will continue transmitting images and other data from the encounter for the next several days.
Scientists expected the north polar region of Enceladus to be heavily cratered, based on low-resolution images from the Voyager mission, but the new high-resolution Cassini images show a landscape of stark contrasts. "The northern regions are crisscrossed by a spidery network of gossamer-thin cracks that slice through the craters," said Paul Helfenstein, a member of the Cassini imaging team at Cornell University, Ithaca, New York. "These thin cracks are ubiquitous on Enceladus, and now we see that they extend across the northern terrains as well."
In addition to the processed images, unprocessed, or "raw," images are posted on the Cassini mission website at:
http://saturn.jpl.nasa.gov/mission/flybys/enceladus20151014
Cassini's next encounter with Enceladus is planned for Oct. 28, when the spacecraft will come within 30 miles (49 kilometers) of the moon's south polar region. During the encounter, Cassini will make its deepest-ever dive through the moon's plume of icy spray, sampling the chemistry of the extraterrestrial ocean beneath the ice. Mission scientists are hopeful data from that flyby will provide evidence of how much hydrothermal activity is occurring in the moon's ocean, along with more detailed insights about the ocean's chemistry -- both of which relate to the potential habitability of Enceladus.
Cassini's final close Enceladus flyby will take place on Dec. 19, when the spacecraft will measure the amount of heat coming from the moon's interior. The flyby will be at an altitude of 3,106 miles (4,999 kilometers).
An online toolkit for all three final Enceladus flybys is available at:
http://solarsystem.nasa.gov/finalflybys

Mars' Mysterious South Pole Revealed in New Photo (ESA)

The swirling white dot toward the bottom of the photo, which was taken by the European Space Agency's Mars Express spacecraft, is the Red Planet’s south polar ice cap. The cap is composed of both frozen water and frozen carbon dioxide, and it changes shape with Mars' seasons.
In 2004, Mars Express confirmed that the south polar cap contains water ice, according to the European Space Agency (ESA).

NASA's Curiosity Rover Team Confirms Ancient Lakes on Mars (NASA)

A new study from the team behind NASA's Mars Science Laboratory/Curiosity has confirmed that Mars was once, billions of years ago, capable of storing water in lakes over an extended period of time.
Using data from the Curiosity rover, the team has determined that, long ago, water helped deposit sediment into Gale Crater, where the rover landed more than three years ago. The sediment deposited as layers that formed the foundation for Mount Sharp, the mountain found in the middle of the crater today.
"Observations from the rover suggest that a series of long-lived streams and lakes existed at some point between about 3.8 to 3.3 billion years ago, delivering sediment that slowly built up the lower layers of Mount Sharp," said Ashwin Vasavada, Mars Science Laboratory project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and co-author of the new Science article to be published Friday, Oct. 9.
The findings build upon previous work that suggested there were ancient lakes on Mars, and add to the unfolding story of a wet Mars, both past and present. Last month, NASA scientists confirmed current water flows on Mars.
"What we thought we knew about water on Mars is constantly being put to the test," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at NASA Headquarters in Washington. "It's clear that the Mars of billions of years ago more closely resembled Earth than it does today. Our challenge is to figure out how this more clement Mars was even possible, and what happened to that wetter Mars."
Before Curiosity landed on Mars in 2012, scientists proposed that Gale Crater had filled with layers of sediments. Some hypotheses were "dry," suggesting that sediment accumulated from wind-blown dust and sand. Others focused on the possibility that sediment layers were deposited in ancient lakes.
The latest results from Curiosity indicate that these wetter scenarios were correct for the lower portions of Mount Sharp. Based on the new analysis, the filling of at least the bottom layers of the mountain occurred mostly by ancient rivers and lakes over a period of less than 500 million years.
"During the traverse of Gale, we have noticed patterns in the geology where we saw evidence of ancient fast-moving streams with coarser gravel, as well as places where streams appear to have emptied out into bodies of standing water," Vasavada said. "The prediction was that we should start seeing water-deposited, fine-grained rocks closer to Mount Sharp. Now that we've arrived, we're seeing finely laminated mudstones in abundance that look like lake deposits."
The mudstone indicates the presence of bodies of standing water in the form of lakes that remained for long periods of time, possibly repeatedly expanding and contracting during hundreds to millions of years. These lakes deposited the sediment that eventually formed the lower portion of the mountain.
"Paradoxically, where there is a mountain today there was once a basin, and it was sometimes filled with water," said John Grotzinger, the former project scientist for Mars Science Laboratory at the California Institute of Technology in Pasadena, and lead author of the new report. "We see evidence of about 250 feet (75 meters) of sedimentary fill, and based on mapping data from NASA's Mars Reconnaissance Orbiter and images from Curiosity's camera, it appears that the water-transported sedimentary deposition could have extended at least 500 to 650 feet (150 to 200) meters above the crater floor."
Furthermore, the total thickness of sedimentary deposits in Gale Crater that indicate interaction with water could extend higher still, perhaps up to one-half mile (800 meters) above the crater floor.
Above 800 meters, Mount Sharp shows no evidence of hydrated strata, and that is the bulk of what forms Mount Sharp. Grotzinger suggests that perhaps this later segment of the crater's history may have been dominated by dry, wind-driven deposits, as was once imagined for the lower part explored by Curiosity.
A lingering question surrounds the original source of the water that carried sediment into the crater. For flowing water to have existed on the surface, Mars must have had a thicker atmosphere and warmer climate than has been theorized for the ancient era when Gale Crater experienced the intense geological activity. However, current models of this paleoclimate have, literally, come up dry.
At least some of the water may have been supplied to the lakes by snowfall and rain in the highlands of the Gale Crater rim. Some have made the argument that there was an ocean in the plains north of the crater, but that does not explain how the water managed to exist as a liquid for extended periods of time on the surface.
"We have tended to think of Mars as being simple," Grotzinger mused. "We once thought of the Earth as being simple too. But the more you look into it, questions come up because you're beginning to fathom the real complexity of what we see on Mars. This is a good time to go back to reevaluate all our assumptions. Something is missing somewhere."
More information about Mars Science Laboratory is online at:
http://www.nasa.gov/msl

Rosetta's First Peek at the Comet's Dark Side (NASA/ESA)

Since its arrival at comet 67P/Churyumov-Gerasimenko, the European Space Agency's Rosetta spacecraft has been surveying the surface and the environment of this curiously shaped body. But for a long time, a portion of the nucleus -- the dark, cold regions around the comet's south pole -- remained inaccessible to almost all instruments on the spacecraft.
Due to a combination of its double-lobed shape and the inclination of its rotation axis, Rosetta's comet has a very peculiar seasonal pattern over its 6.5-year-long orbit. Seasons are distributed very unevenly between the two hemispheres. Each hemisphere comprise parts of both comet lobes and the "neck."
For most of the comet's orbit, the northern hemisphere experiences a very long summer, lasting over 5.5 years, while the southern hemisphere undergoes a long, dark and cold winter. However, a few months before the comet reaches perihelion -- the closest point to the sun along its orbit -- the situation changes, and the southern hemisphere transitions to a brief and very hot summer.
When Rosetta arrived at 67P/C-G in August 2014, the comet was still experiencing its long summer in the northern hemisphere, and regions on the southern hemisphere received very little sunlight. Moreover, a large part of this hemisphere, close to the comet's south pole, was in polar night and had been in total darkness for almost five years.
With no direct illumination from the sun, these regions could not be imaged with Rosetta's OSIRIS (the Optical, Spectroscopic, and Infrared Remote Imaging System) science camera, or its Visible, InfraRed and Thermal Imaging Spectrometer (VIRTIS). For the first several months after Rosetta's arrival at the comet, only one instrument on the spacecraft could observe and characterize the cold southern pole of 67P/C-G: the Microwave Instrument for Rosetta Orbiter (MIRO).
In a paper accepted for publication in the journal Astronomy and Astrophysics, scientists report on the data collected by MIRO over these regions between August and October 2014.
"We observed the 'dark side' of the comet with MIRO on many occasions after Rosetta's arrival at 67P/C-G, and these unique data are telling us something very intriguing about the material just below its surface," said Mathieu Choukroun from NASA's Jet Propulsion Laboratory (JPL), Pasadena, California, lead author of the study.
Observing the comet's southern polar regions, Choukroun and colleagues found significant differences between the data collected with MIRO's millimeter and sub-millimeter wavelength channels. These differences might point to the presence of large amounts of ice within the first few tens of centimeters below the surface of these regions.
"Surprisingly, the thermal and electrical properties around the comet's south pole are quite different than what is found elsewhere on the nucleus," said Choukroun. "It appears that either the surface material or the material that's a few tens of centimeters below it is extremely transparent, and could consist mostly of water ice or carbon-dioxide ice."
The difference between the surface and subsurface composition of this part of the nucleus and that found elsewhere might originate in the comet's peculiar cycle of seasons. One of the possible explanations is that water and other gases that were released during the comet's previous perihelion, when the southern hemisphere was the most illuminated portion of the nucleus. The water condensed again and precipitated on the surface after the season changed and the southern hemisphere plunged again into its long and cold winter.
These are, however, preliminary results, because the analysis depends on the detailed shape of the nucleus. At the time the measurements were made, the shape of the dark, polar region was not known with great accuracy.
"We plan to revisit the MIRO data using an updated version of the shape model, to verify these early results and refine the interpretation of the measurements," added Choukroun.
Rosetta scientists will be testing these and other possible scenarios using data that were collected in the subsequent months, leading to the comet's perihelion, which took place on Aug. 13, 2015 and beyond.
In May 2015, the seasons changed on 67P/C-G and the brief, hot southern summer, which will last until early 2016, began. As the formerly dark southern polar regions started to receive more sunlight, it has been possible to observe them with other instruments on Rosetta, and the combination of all data might eventually disclose the origin of their curious composition.
"In the past few months, Rosetta has flown over the southern polar regions on several occasions, starting to collect data from this part of the comet after summer began there," said Matt Taylor, ESA Rosetta project scientist. "At the beginning of the southern summer, we had a paucity of observations in these regions as Rosetta's trajectory focused on the northern hemisphere due to ongoing communication with the lander, Philae. However, closer to perihelion we were able to begin observing the south."
Rosetta is currently on an excursion out to about 930 miles (1,500 kilometers) from the nucleus to study the comet's environment at large. But the spacecraft will soon come closer to the comet, focusing on full orbits to compare the northern and southern hemispheres, as well as some slower passes in the south to maximize observations there. In addition, as activity will start to wane later this year, the team hopes to get closer to the nucleus and gain higher-resolution observations of the surface.
"First, we observed these dark regions with MIRO, the only instrument able to do so at the time, and we tried to interpret these unique data. Now, as these regions became warmer and brighter around perihelion, we can observe them with other instruments, too."
Mark Hofstadter, MIRO principal investigator at JPL, adds, "We hope that, by combining data from all these instruments, we will be able to confirm whether or not the south pole had a different composition and whether or not it is changing seasonally."
The MIRO instrument is a small, lightweight spectrometer that can map the abundance, temperature and velocity of cometary water vapor and other molecules that the nucleus releases. It can also measure the temperature up to about one inch (three centimeters) below the surface of the comet's nucleus. One reason the subsurface temperature is important is that the observed gases likely come from sublimating ices beneath the surface. By combining information on the gas and the subsurface, MIRO is able to study this process in detail.
Comets are time capsules containing primitive material left over from the epoch when the sun and its planets formed. Rosetta is the first spacecraft to witness at close proximity how a comet changes as it is subjected to the increasing intensity of the sun's radiation. Observations will help scientists learn more about the origin and evolution of our solar system and the role comets may have played in the formation of planets.

NASA Confirms Evidence That Liquid Water Flows on Today's Mars (NASA - Oct 2015 Announcement)

New findings from NASA's Mars Reconnaissance Orbiter (MRO) provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.
Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet. These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at colder times.
"Our quest on Mars has been to 'follow the water,' in our search for life in the universe, and now we have convincing science that validates what we've long suspected," said John Grunsfeld, astronaut and associate administrator of NASA's Science Mission Directorate in Washington. "This is a significant development, as it appears to confirm that water -- albeit briny -- is flowing today on the surface of Mars."
These downhill flows, known as recurring slope lineae (RSL), often have been described as possibly related to liquid water. The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly. Scientists say it's likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening.
"We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," said Lujendra Ojha of the Georgia Institute of Technology (Georgia Tech) in Atlanta, lead author of a report on these findings published Sept. 28 by Nature Geoscience.
Ojha first noticed these puzzling features as a University of Arizona undergraduate student in 2010, using images from the MRO's High Resolution Imaging Science Experiment (HiRISE). HiRISE observations now have documented RSL at dozens of sites on Mars. The new study pairs HiRISE observations with mineral mapping by MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide. When the researchers looked at the same locations and RSL weren't as extensive, they detected no hydrated salt.
Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius). On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.
Perchlorates have previously been seen on Mars. NASA's Phoenix lander and Curiosity rover both found them in the planet's soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This also is the first time perchlorates have been identified from orbit.
MRO has been examining Mars since 2006 with its six science instruments.
"The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are," said Rich Zurek, MRO project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
For Ojha, the new findings are more proof that the mysterious lines he first saw darkening Martian slopes five years ago are, indeed, present-day water.
"When most people talk about water on Mars, they're usually talking about ancient water or frozen water," he said. "Now we know there's more to the story. This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL."
The discovery is the latest of many breakthroughs by NASA's Mars missions.
"It took multiple spacecraft over several years to solve this mystery, and now we know there is liquid water on the surface of this cold, desert planet," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at the agency's headquarters in Washington. "It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future."

'Hinners Point' Above Floor of 'Marathon Valley' on Mars (NASA)

This Martian scene shows contrasting textures and colors of "Hinners Point," at the northern edge of "Marathon Valley," and swirling reddish zones on the valley floor to the left.
The view combines six frames taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity on Aug. 14, 2015, during the 4,108th Martian day, or sol, of the rover's work on Mars.
The summit takes its informal name as a tribute to Noel Hinners (1935-2014). For NASA's Apollo program, Hinners played important roles in selection of landing sites on the moon and scientific training of astronauts. He then served as NASA associate administrator for space science, director of the Smithsonian National Air and Space Museum, director of NASA's Goddard Space Flight Center, NASA chief scientist and associate deputy administrator of NASA. Subsequent to responsibility for the Viking Mars missions while at NASA, he spent the latter part of his career as vice president for flight systems at Lockheed Martin, where he had responsibility for the company's roles in development and operation of NASA's Mars Global Surveyor, Mars Reconnaissance Orbiter, Mars Odyssey, Phoenix Mars Lander, Stardust and Genesis missions.
Marathon Valley cuts generally east-west through the western rim of Endeavour Crater. The valley's name refers to the distance Opportunity drove from its 2004 landing site to arrival at this location in 2014. The valley was a high-priority destination for the rover mission because observations from orbit detected clay minerals there.
Dark rocks on Hinners Point show a pattern dipping downward toward the interior of Endeavour, to the right from this viewing angle. The strong dip may have resulted from the violence of the impact event that excavated the crater.
Brighter rocks make up the valley floor. The reddish zones there may be areas where water has altered composition. Inspections by Opportunity have found compositions there are higher in silica and lower in iron than the typical composition of rocks on Endeavour's rim.
The scene spans from west-southwest at left to northwest at right. The larger of two stones close to each other in the foreground left of center is about 5 inches (12 centimeters) wide. On bright bedrock to the right of those stones, Opportunity inspected a target informally named "Pvt. George Gibson." Another inspected target, "Pvt. Silas Goodrich," is on the valley floor near the left edge of this scene. The informal names for these targets refer to members of the Lewis and Clark expedition's Corps of Discovery.
This version of the image is presented in approximate true color by combing exposures taken through three of the Pancam's color filters, centered on wavelengths of 753 nanometers (near-infrared), 535 nanometers (green) and 432 nanometers (violet). An enhanced-color version making differences in surface materials easier to see is at PIA19820. A stereo version is at PIA19911.
JPL manages the Mars Exploration Rover Project for NASA's Science Mission Directorate in Washington. For more about Opportunity's mission, see http://mars.nasa.gov/mer.

Funky Light Signal From Colliding Black Holes Explained (NASA)

Entangled by gravity and destined to merge, two candidate black holes in a distant galaxy appear to be locked in an intricate dance. Researchers using data from NASA's Galaxy Evolution Explorer (GALEX) and NASA's Hubble Space Telescope have come up with the most compelling confirmation yet for the existence of these merging black holes and have found new details about their odd, cyclical light signal.
The candidate black hole duo, called PG 1302-102, was first identified earlier this year using ground-based telescopes. The black holes are the tightest orbiting pair detected so far, with a separation not much bigger than the diameter of our solar system. They are expected to collide and merge in less than a million years, triggering a titanic blast with the power of 100 million supernovae.
Researchers are studying this pair to better understand how galaxies and the monstrous black holes at their cores merge -- a common occurrence in the early universe. But as common as these events were, they are hard to spot and confirm.
PG 1302-102 is one of only a handful of good binary black hole candidates. It was discovered and reported earlier this year by researchers at the California Institute of Technology in Pasadena, after they scrutinized an unusual light signal coming from the center of a galaxy. The researchers, who used telescopes in the Catalina Real-Time Transient Survey, demonstrated that the varying signal is likely generated by the motion of two black holes, which swing around each other every five years. While the black holes themselves don't give off light, the material surrounding them does.
In the new study, published in the Sept. 17 issue of Nature, researchers found more evidence to support and confirm the close-knit dance of these black holes. Using ultraviolet data from GALEX and Hubble, they were able to track the system's changing light patterns over the past 20 years.
"We were lucky to have GALEX data to look through," said co-author David Schiminovich of Columbia University in New York. "We went back into the GALEX archives and found that the object just happened to have been observed six times."
Hubble, which sees ultraviolet light in addition to visible and other wavelengths of light, had likewise observed the object in the past.
The ultraviolet light was important to test a prediction of how the black holes generate a cyclical light pattern. The idea is that one of the black holes in the pair is giving off more light -- it is gobbling up more matter than the other one, and this process heats up matter that emits energetic light. As this black hole orbits around its partner every five years, its light changes and appears to brighten as it heads toward us.
"It's as if a 60-Watt light bulb suddenly appears to be 100 Watts," explained Daniel D'Orazio, lead author of the study from Columbia University. "As the black hole light speeds away from us, it appears as a dimmer 20-Watt bulb."
What's causing the changes in light? One set of changes has to do with the "blue shifting" effect, in which light is squeezed to shorter wavelengths as it travels toward us in the same way that a police car's siren squeals at higher frequencies as it heads toward you. Another reason has to do with the enormous speed of the black hole.
The brighter black hole is, in fact, traveling at nearly seven percent the speed of light -- in other words, really fast. Though it takes the black hole five years to orbit its companion, it is traveling vast distances. It would be as if a black hole lapped our entire solar system from the outer fringes, where the Oort cloud of comets lies, in just five years. At speeds as high as this, which are known as relativistic, the light becomes boosted and brighter.
D'Orazio and colleagues modeled this effect based on a previous Caltech paper and predicted how it should look in ultraviolet light. They determined that, if the periodic brightening and dimming previously seen in the visible light is indeed due to the relativistic boosting effect, then the same periodic behavior should be present in ultraviolet wavelengths, but amplified 2.5 times. Sure enough, the ultraviolet light from GALEX and Hubble matched their predictions.
"We are strengthening our ideas of what's going on in this system and starting to understand it better," said Zoltan Haiman, a co-author from Columbia University who conceived the project.
The results will also help researchers understand how to find even closer-knit merging black holes in the future, what some consider the holy grail of physics and the search for gravitational waves. In the final moments before the ultimate union of two black holes, when they are tightly spinning around each other like ice skaters in a "death spiral," they are predicted to send out ripples in space and time. These so-called gravitational waves, whose existence follows from Albert Einstein's gravity theory published 100 years ago, hold clues about the fabric of our universe.
The findings are also a doorway to understanding other merging black holes across the universe, a widespread population that is only now beginning to yield its secrets.

Cassini Finds Global Ocean in Saturn's Moon Enceladus (NASA)

A global ocean lies beneath the icy crust of Saturn's geologically active moon Enceladus, according to new research using data from NASA's Cassini mission.
Researchers found the magnitude of the moon's very slight wobble, as it orbits Saturn, can only be accounted for if its outer ice shell is not frozen solid to its interior, meaning a global ocean must be present.
The finding implies the fine spray of water vapor, icy particles and simple organic molecules Cassini has observed coming from fractures near the moon's south pole is being fed by this vast liquid water reservoir. The research is presented in a paper published online this week in the journal Icarus.
Previous analysis of Cassini data suggested the presence of a lens-shaped body of water, or sea, underlying the moon's south polar region. However, gravity data collected during the spacecraft's several close passes over the south polar region lent support to the possibility the sea might be global. The new results -- derived using an independent line of evidence based on Cassini's images -- confirm this to be the case.
"This was a hard problem that required years of observations, and calculations involving a diverse collection of disciplines, but we are confident we finally got it right," said Peter Thomas, a Cassini imaging team member at Cornell University, Ithaca, New York, and lead author of the paper.
Cassini scientists analyzed more than seven years' worth of images of Enceladus taken by the spacecraft, which has been orbiting Saturn since mid-2004. They carefully mapped the positions of features on Enceladus -- mostly craters -- across hundreds of images, in order to measure changes in the moon's rotation with extreme precision.
As a result, they found Enceladus has a tiny, but measurable wobble as it orbits Saturn. Because the icy moon is not perfectly spherical -- and because it goes slightly faster and slower during different portions of its orbit around Saturn -- the giant planet subtly rocks Enceladus back and forth as it rotates.
The team plugged their measurement of the wobble, called a libration, into different models for how Enceladus might be arranged on the inside, including ones in which the moon was frozen from surface to core.
"If the surface and core were rigidly connected, the core would provide so much dead weight the wobble would be far smaller than we observe it to be," said Matthew Tiscareno, a Cassini participating scientist at the SETI Institute, Mountain View, California, and a co-author of the paper. "This proves that there must be a global layer of liquid separating the surface from the core."
The mechanisms that might have prevented Enceladus' ocean from freezing remain a mystery. Thomas and colleagues suggest a few ideas for future study that might help resolve the question, including the surprising possibility that tidal forces due to Saturn's gravity could be generating much more heat within Enceladus than previously thought.
"This is a major step beyond what we understood about this moon before, and it demonstrates the kind of deep-dive discoveries we can make with long-lived orbiter missions to other planets," said co-author Carolyn Porco, Cassini imaging team lead at Space Science Institute, Boulder, Colorado, and visiting scholar at the University of California, Berkeley. "Cassini has been exemplary in this regard."
The unfolding story of Enceladus has been one of the great triumphs of Cassini's long mission at Saturn. Scientists first detected signs of the moon's icy plume in early 2005, and followed up with a series of discoveries about the material gushing from warm fractures near its south pole. They announced strong evidence for a regional sea in 2014, and more recently, in 2015, they shared results that suggest hydrothermal activity is taking place on the ocean floor.
Cassini is scheduled to make a close flyby of Enceladus on Oct. 28, in the mission's deepest-ever dive through the moon's active plume of icy material. The spacecraft will pass a mere 30 miles (49 kilometers) above the moon's surface.

Mars Panorama from Curiosity Shows Petrified Sand Dunes (NASA)

Large-scale crossbedding in the sandstone of this ridge on a lower slope of Mars' Mount Sharp is typical of windblown sand dunes that have petrified. Image credit: NASA/JPL-Caltech/MSSS

Some of the dark sandstone in an area being explored by NASA's Curiosity Mars rover shows texture and inclined bedding structures characteristic of deposits that formed as sand dunes, then were cemented into rock.
A panorama from Curiosity's Mast Camera (Mastcam) that includes a ridge made of this sandstone is online at:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19818
This sandstone outcrop -- part of a geological layer that Curiosity's science team calls the Stimson unit -- has a structure called crossbedding on a large scale that the team has interpreted as deposits of sand dunes formed by wind. Similar-looking petrified sand dunes are common in the U.S. Southwest. Geometry and orientation of the crossbedding give information about the directions of the winds that produced the dunes.
The Stimson unit overlies a layer of mudstone that was deposited in a lake environment. Curiosity has been examining successively higher and younger layers of Mount Sharp, starting with the mudstone at the mountain's base, for evidence about changes in the area's ancient environment.
The dozens of individual Mastcam images combined into this panorama were taken on Aug. 27, 2015. Curiosity has driven about 103 yards (94 meters) in the subsequent two weeks, generally southward. Outcrops of the Stimson unit sandstone are still accessible to the rover, and researchers plan to use the rover to collect and analyze a drilled sample of Stimson unit sandstone this month.
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.

NASA Telescopes Find Galaxy Cluster with Vibrant Heart (NASA)

Astronomers have discovered a rare beast of a galaxy cluster whose heart is bursting with new stars. The unexpected find, made with the help of NASA's Spitzer and Hubble space telescopes, suggests that behemoth galaxies at the cores of these massive clusters can grow significantly by feeding off gas stolen from another galaxy.
"Usually, the stars at the centers of galaxy clusters are old and dead, essentially fossils," said Tracy Webb of McGill University, Montreal, Canada, lead author of a new paper on the findings accepted for publication in the Astrophysical Journal. "But we think the giant galaxy at the center of this cluster is furiously making new stars after merging with a smaller galaxy."
Galaxy clusters are vast families of galaxies bound and grouped by the ties of gravity. Our own Milky Way resides in a small galaxy group, called the Local Group, which itself is on the periphery of the vast Laniakea supercluster of 100,000 galaxies. (Laniakea is Hawaiian for "immeasurable heaven.")
The cluster in the new study, referred to by astronomers as SpARCS1049+56, has at least 27 galaxy members, and a combined mass equal to nearly 400 trillion suns. It is located 9.8 billion light-years away in the Ursa Major constellation. The object was initially discovered using Spitzer and the Canada-France-Hawaii telescope, located on Mauna Kea in Hawaii, and confirmed using the W.M. Keck Observatory, also on Mauna Kea.
What makes this cluster unique is its luminous heart of new stars. At the core of most massive galaxy clusters lies one hulking galaxy that usually doesn't produce new stars very quickly. The galaxy dominating the cluster SpARCS1049+56 is rapidly spitting out an enormous number of stars -- about 860 new ones a year. For reference, our Milky Way makes only about one to two stars per year.
"With Spitzer's infrared camera, we can actually see the ferocious heat from all these hot young stars," said co-author Jason Surace from NASA's Spitzer Science Center at the California Institute of Technology in Pasadena. Spitzer detects infrared light, so it can see the warm glow of hidden, dusty regions where stars form.
Follow-up studies with Hubble in visible light helped confirm the source of the fuel, or gas, for the new stars. A smaller galaxy seems to have recently merged with the monster galaxy in the middle of the cluster, lending its gas to the larger galaxy and igniting a fury of new stars.
"Hubble found a train wreck of a merger at the center of this galaxy," said Webb.
Hubble specifically detected features in the smaller, merging galaxy called "beads on a string," which are pockets of gas that condense where new stars are forming. Beads on a string are telltale signs of collisions between gas-rich galaxies, a phenomenon known to astronomers as wet mergers, where "wet" refers to the presence of gas. In these smash-ups, the gas is quickly converted to new stars.
Dry mergers, by contrast, occur when galaxies with little gas collide and no new stars are formed. Typically, galaxies at the centers of clusters grow in mass through dry mergers at their core, or by siphoning gas into their centers.
The new discovery is one of the first known cases of a wet merger at the core of a distant galaxy cluster. Hubble previously discovered another closer galaxy cluster containing a wet merger, but it wasn't forming stars as vigorously.
The researchers are planning more studies to find out how common galaxy clusters like SpARCS1049+56 are. The cluster may be an outlier, or it may represent an early time in our universe when gobbling up gas-rich galaxies was the norm.

Philae poses comet chemistry conundrum (Chemistry World)

The estimated landing points of Philae as it bounced its way across comet 67P © ESA/ROSETTA/NAVCAM/SONC/DLR

As the Philae lander bounced across comet 67P/Churyumov–Gerasimenko’s surface in November last year, two chemical instruments were able to take tentative – but intriguingly contradictory – sniffs of its environment. Those mass spectrometry measurements provide compositional details important for deciphering the origins of life on Earth, a key aim of the Rosetta mission that carried Philae. But while the cometary sampling and composition (COSAC) instrument detected 16 organic molecules1, half of which contain nitrogen atoms, Ptolemy reports very low concentrations of nitrogen-containing compounds2.

Nevertheless, Jen Blank, a senior scientist at the Nasa Ames Research Center in California, US, highlights the historic achievement of syncing orbit with a comet and sending a lander down to the surface. ‘The Philae data are amazing,’ enthuses Blank, who’s studied how comets may have supplied Earth with molecules needed for life, but wasn’t involved in Rosetta or Philae. ‘These are the first measurements of organic compounds collected directly on a comet or asteroid.’

Philae was programmed to take sniffs shortly after touching down on 67P as an ‘insurance policy’, explains Ian Wright from the Open University in Milton Keynes, UK, and principal investigator for Ptolemy. That was well planned, because the touchdown became a rebound that sent Philae out of communication range, preventing further measurements to date.

The lander was also therefore in motion in the minutes between the instruments doing their respective basic analyses, or sniffs, of whatever material happened to have entered them. One potential explanation for the distinct results is therefore that they reflect differences between locations on the comet, Wright suggests. The fact that COSAC’s sample port is on Philae’s underside, and Ptolemy’s is on its top is another. ‘Have we analysed separate grains?’ Wright asks. ‘We’ve no reason to expect that the surface would be homogenous.’

Exhausting serendipity

COSAC’s best sniff happened automatically 25 minutes after Philae’s first contact, while the lander was around 150 metres above the surface. The instrument consists of a gas chromatograph and a time-of-flight mass spectrometer intended to analyse organic compounds in samples drilled from the comet’s surface. Though Philae couldn’t drill, the impact threw up some solid material, part of which apparently entered COSAC’s two exhaust pipes. The COSAC team, headed by Fred Goesmann from the Max Planck Institute for Solar System Research in Göttingen, Germany, thinks the exhaust’s warmth evaporated volatile compounds, allowing their detection. 

The compounds COSAC identified included methyl isocyanate, acetone, propionaldehyde and acetamide, which have not previously been reported in comets. Acetamide is also one of four compounds detected that can produce important biological molecules like amino acids, sugars and DNA bases. Blank is especially excited by acetamide’s presence. ‘It's easy to imagine a pathway to an amino acid,’ she says.  However, Goesmann is cautious not to read too much into their presence. ‘Comets with such a composition do not work against life,’ he tells Chemistry World. ‘In the right environment, emerging life could make use of it.’

However, the small amount of material COSAC was looking at meant it couldn’t detect anything but the smallest compounds. That means it wouldn’t have seen any ‘molecules of life’, such as amino acids, even if they were present. And although it could have, it didn’t see much ammonia, formaldehyde or carbon dioxide, which are common components of cometary ice, or any sulfur compounds. The COSAC scientists link the lack of ice to measurements previously made by Rosetta showing 67P’s surface is covered in a carbon-based coat rather than frozen.  

Icy isolation

To determine isotope ratios of chemicals on 67P and establish their origins, Ptolemy’s gas chromatograph and ion trap mass spectrometer were also supposed to be fed drilled samples. However, it was reduced to making six sniffs at 14 second intervals about 20 minutes after Philae hit 67P. Like COSAC, it failed to find any signs of sulfur. Ptolemy saw mostly water and carbon dioxide, ice components expected on comets, but no significant indication of ammonia, and very low levels of nitrogen compounds overall. The COSAC scientists suggest that the absence of this key source of nitrogen could be because it has evaporated or been used up in reactions.

Ptolemy also found hints of polyoxymethylene, a polymer thought to be produced from formaldehyde by cosmic radiation, previously detected on Halley’s Comet. This source of formaldehyde is another important potential resource for origin-of-life chemistry, Wright underlines. ‘It can produce simple sugars like ribose,’ he says. ‘These are things that we hope will be picked up by astrobiologists in refining their ideas.’

This Photo of Saturn's Moon Dione Crossing the Planet Is Simply Jaw-Dropping (space.com)

Saturn's moon Dione crosses the face of the ringed planet in an image obtained on May 21, 2015

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Credit: NASA/JPL-Caltech/Space Science Institute

How 'Starshades' Could Aid Search for Alien Life (space.com)

Nineteen different subscale versions of a light-blocking "starshade" were tested recently in the Nevada desert.

The next step in the exoplanet revolution may be an in-space "starshade" that lets alien worlds step out of a blinding glare.
Researchers are testing designs for a starshade, which would fly in formation with a future space-based telescope. The starshade, also known as an "external occulter," would block the light from a star while allowing the scope to spot emissions from much dimmer orbiting planets.
Scientists are conducting desert tests of the technology on Earth. They're using the McMath-Pierce Solar Telescope at Kitt Peak National Observatory in Arizona to model a starshade's ability to help future instruments find and characterize rocky, Earth-like alien worlds.
A starshade may be used on NASA's potential Wide-Field Infrared Survey Telescope (WFIRST), a space-based instrument that would feature a primary mirror 8 feet (2.4 meters) wide, the same size as that of the agency's iconic Hubble Space Telescope.
Several years ago, the U.S. National Reconnaissance Office (NRO) donated two space telescopes to NASA. In 2013, the space agency announced it hoped to use one of these scopes for WFIRST. That move spurred anticipation in the U.S. astronomical community for Hubble-quality imaging over an area of sky 100 times larger than that viewed by Hubble. This version of the mission is called WFIRST-AFTA (for "Astrophysics-Focused Telescope Assets").
The WFIRST-AFTA mission would carry out exoplanet exploration, dark energy research, and galactic and extragalactic surveys.
Small-scale versions of starshades have undergone nighttime desert testing in Nevada and California and, more recently, at the McMath-Pierce Solar Telescope site.
The sites selected for evaluating starshade designs each have pros and cons, but collectively the evaluations are complementary and help to validate optical modeling of the idea, said Steve Warwick, Starshade program manager at Northrop Grumman Aerospace Systems.
"We can't do everything we can do in space on the ground in terms of optics, but the tests add a lot of confidence to how the starshade will work on orbit," Warwick told Space.com.
McMath operators said testing sharshades with the telescope, which was dedicated in 1962, was the craziest way that anyone had used the facility to date, Warwick said.
"They were extremely helpful and excited to see what we could do with their facility," Warwick said of the McMath team. Starshade testing at the Arizona site has been done twice so far, in late March and then in June.
The hope is to return to that location in the November-December time period; the exact timing will depend partly on other McMath users' schedules, Warwick said.
A mix of NASA funding and Northrop Grumman funding has enabled the starshade test program to move forward.


http://www.space.com/30429-starshade-alien-life-search-wfirst-tech.html?cmpid=NL_SP_weekly_2015-09-02