Interesting Temperature Patterns on MImas

March 29, 2010

PASADENA, Calif. -- The highest-resolution-yet temperature map and images of Saturn's icy moon Mimas obtained by NASA's Cassini spacecraft reveal surprising patterns on the surface of the small moon, including unexpected hot regions that resemble "Pac-Man" eating a dot, and striking bands of light and dark in crater walls.

"Other moons usually grab the spotlight, but it turns out Mimas is more bizarre than we thought it was," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It has certainly given us some new puzzles."

Cassini collected the data on Feb. 13, during its closest flyby of the moon, which is marked by an enormous scar called Herschel Crater and resembles the Death Star from "Star Wars."

Scientists working with the composite infrared spectrometer, which mapped Mimas' temperatures, expected smoothly varying temperatures peaking in the early afternoon near the equator. Instead, the warmest region was in the morning, along one edge of the moon's disk, making a sharply defined Pac-Man shape, with temperatures around 92 Kelvin (minus 294 degrees Fahrenheit). The rest of the moon was much colder, around 77 Kelvin (minus 320 degrees Fahrenheit). A smaller warm spot - the dot in Pac-Man's mouth - showed up around Herschel, with a temperature around 84 Kelvin (minus 310 degrees Fahrenheit).

The warm spot around Herschel makes sense because tall crater walls (about 5 kilometers, or 3 miles, high) can trap heat inside the crater. But scientists were completely baffled by the sharp, V-shaped pattern.

"We suspect the temperatures are revealing differences in texture on the surface," said John Spencer, a Cassini composite infrared spectrometer team member based at Southwest Research Institute in Boulder, Colo. "It's maybe something like the difference between old, dense snow and freshly fallen powder."

Denser ice quickly conducts the heat of the sun away from the surface, keeping it cold during the day. Powdery ice is more insulating and traps the sun's heat at the surface, so the surface warms up.

Even if surface texture variations are to blame, scientists are still trying to figure out why there are such sharp boundaries between the regions, Spencer said. It is possible that the impact that created Herschel Crater melted surface ice and spread water across the moon. That liquid may have flash-frozen into a hard surface. But it is hard to understand why this dense top layer would remain intact when meteorites and other space debris should have pulverized it by now, Spencer said.

Icy spray from the E ring, one of Saturn's outer rings, should also keep Mimas relatively light-colored, but the new visible-light images from the flyby paint a picture of surprising contrasts. Cassini imaging team scientists didn't expect to see dark streaks trailing down the bright crater walls or a continuous, narrow pile of concentrated dark debris tracing the foot of each wall.

The pattern may appear because of the way the surface of Mimas ages, said Paul Helfenstein, a Cassini imaging team associate based at Cornell University, Ithaca, N.Y. Over time, the moon's surface appears to accumulate a thin veil of silicate minerals or carbon-rich particles, possibly because of meteor dust falling onto the moon, or impurities already embedded in surface ice.

As the sun's warming rays and the vacuum of space evaporate the brighter ice, the darker material is concentrated and left behind. Gravity pulls the dark material down the crater walls, exposing fresh ice underneath. Although similar effects are seen on other moons of Saturn, the visibility of these contrasts on a moon continually re-paved with small particles from the E ring helps scientists estimate rates of change on other satellites.

"These processes are not unique to Mimas, but the new high-definition images are like Rosetta stones for interpreting them," Helfenstein said.

Associated images also;
http://photojournal.jpl.nasa.gov/catalog/?IDNumber=PIA12572
http://photojournal.jpl.nasa.gov/catalog/?IDNumber=PIA12571 (Streaked crater image)

Dust From Supernova Engulfes Other Stars

March 29, 2010

PASADENA, Calif. -- A new image from NASA's Chandra and Spitzer space telescopes shows the dusty remains of a collapsed star. The dust is flying past and engulfing a nearby family of stars.

"Scientists think the stars in the image are part of a stellar cluster in which a supernova exploded," said Tea Temin of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., who led the study. "The material ejected in the explosion is now blowing past these stars at high velocities."

The composite image of G54.1+0.3 is online at http://photojournal.jpl.nasa.gov/catalog/?IDNumber=pia12982 . It shows the Chandra X-ray Observatory data in blue, and data from the Spitzer Space Telescope in green (shorter wavelength) and red-yellow (longer). The white source near the center of the image is a dense, rapidly rotating neutron star, or pulsar, left behind after a core-collapse supernova explosion. The pulsar generates a wind of high-energy particles -- seen in the Chandra data -- that expands into the surrounding environment, illuminating the material ejected in the supernova explosion.

The infrared shell that surrounds the pulsar wind is made up of gas and dust that condensed out of debris from the supernova. As the cold dust expands into the surroundings, it is heated and lit up by the stars in the cluster so that it is observable in infrared. The dust closest to the stars is the hottest and is seen glowing in yellow in the image. Some of the dust is also being heated by the expanding pulsar wind as it overtakes the material in the shell.

The unique environment into which this supernova exploded makes it possible for astronomers to observe the condensed dust from the supernova that is usually too cold to emit in infrared. Without the presence of the stellar cluster, it would not be possible to observe this dust until it becomes energized and heated by a shock wave from the supernova. However, the very action of such shock heating would destroy many of the smaller dust particles. In G54.1+0.3, astronomers are observing pristine dust before any such destruction.

G54.1+0.3 provides an exciting opportunity for astronomers to study the freshly formed supernova dust before it becomes altered and destroyed by shocks. The nature and quantity of dust produced in supernova explosions is a long-standing mystery, and G54.1+0.3 supplies an important piece to the puzzle

Cassinni - Ring Dynamics & Weather/Magnetosphere Activity. Influence of Enceladus

March 18, 2010

From our vantage point on Earth, Saturn may look like a peaceful orb with rings worthy of a carefully raked Zen garden, but NASA's Cassini spacecraft has been shadowing the gas giant long enough to see that the rings are a rough and tumble roller derby. It has also revealed that the planet itself roils with strange weather and shifting patterns of charged particles. Two review papers to be published in the March 19 issue of the journal Science synthesize Cassini's findings since arriving at Saturn in 2004.

"This rambunctious system gives us a new feel for how an early solar system might have behaved," said Linda Spilker, a planetary scientist and the new Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This kind of deep, rich data can only be collected by an orbiting spacecraft, and we look forward to the next seven years around Saturn bringing even more surprises."

In the paper describing the elegant mess of activity in the rings, lead author Jeff Cuzzi, Cassini's interdisciplinary scientist for rings and dust who is based at NASA Ames Research Center, Moffett Field, Calif., describes how Cassini has shown us that collisions are routine and chunks of ice leave trails of debris in their wakes. Spacecraft data have also revealed how small moons play tug-of-war with ring material and how bits of rubble that would otherwise join together to become moons are ultimately ripped apart by the gravitational pull that Saturn exerts.

During equinox, the period when sunlight hits the rings exactly edge-on, Cassini witnessed rings that are normally flat - about tens of meters (yards) thick - being flipped up as high as the Rocky Mountains.

The spacecraft has also shown that the rings are composed mostly of water ice, with a mysterious reddish contaminant that could be rust or small organic molecules similar to those found in red vegetables on Earth.

"It has been amazing to see the rings come to life before our very eyes, changing even as we watch, being colorful and taking on a tangible, 3-D nature," Cuzzi said. "The rings were still a nearly unstructured object in even the best telescopes when I was a grad student, but Cassini has brought us an intimate familiarity with them."

Cuzzi said Cassini scientists were surprised to find such fine-scale structure nearly everywhere in the rings, forcing them to be very careful about generalizing their findings across the entire ring disk. The discovery that the rings are clumpy has also called into question some of the previous estimates for the mass of the rings because there might be clusters of material hidden inside of the clumps that have not yet been measured.

In the review paper on Saturn's atmosphere, ionosphere and magnetosphere, lead author Tamas Gombosi, Cassini's interdisciplinary scientist for magnetosphere and plasma science who is based at the University of Michigan in Ann Arbor, describes how Cassini helped scientists understand a south polar vortex that has a diameter 20 to 40 times that of a terrestrial hurricane, and the bizarrely stable hexagon-shaped jet stream at the planet's north pole. Cassini scientists have also calculated a variation in Saturn's wind speeds at different altitudes and latitudes that is 10 times greater than the wind speed variation on Earth.

According to Gombosi's paper, Cassini has also shown us that the small moon Enceladus, not the sun or Saturn's largest moon Titan, is the biggest contributor of charged particles to Saturn's magnetic environment. The charged particles from Enceladus, a moon that features a plume of water vapor and other gases spraying from its south polar region, also contribute to the auroras around the poles of the planet.

"We learned from Cassini that the Saturnian magnetosphere is swimming in water," Gombosi said. "This is unique in the solar system and makes Saturn's plasma environment particularly fascinating."

Of course, Cassini's intense investigation has opened up a host of new mysteries. For example, Cassini has shown us images of occasional cannon-ball-like objects that rocket across one of the outer rings known as the F ring, without many clues about where they came from or why they quickly disappear.

Learning more about a kind of radio emission known as "kilometric radiation" at Saturn has unsettled debates about the planet's rotation rate rather than settled them. While the regular periods of kilometric radiation have given scientists a sense of the rotation rate at Jupiter, Saturn has clocked different periods for the radiation during NASA's Voyager flybys in 1980 and 1981 and the nearly six years of Cassini's investigations. The modulations vary by about 30 seconds to a minute, but they shouldn't be varying at all. The inconsistency may be related to a source in the magnetic bubble around the planet rather than the core of the gas giant, but scientists are still debating.

"Cassini has answered questions we were not even smart enough to ask when the mission was planned and raised a lot of new ones," Cuzzi said. "We are hot on the trail, though."

NASA's Spitzer Unearths Primitive Black Holes - First Generation Quasars Born in Dust Free Universe

March 17, 2010

Astronomers have come across what appear to be two of the earliest and most primitive supermassive black holes known. The discovery, based largely on observations from NASA's Spitzer Space Telescope, will provide a better understanding of the roots of our universe, and how the very first black holes, galaxies and stars came to be.

"We have found what are likely first-generation quasars, born in a dust-free medium and at the earliest stages of evolution," said Linhua Jiang of the University of Arizona, Tucson. Jiang is the lead author of a paper announcing the findings in the March 18 issue of Nature.

Black holes are beastly distortions of space and time. The most massive and active ones lurk at the cores of galaxies, and are usually surrounded by doughnut-shaped structures of dust and gas that feed and sustain the growing black holes. These hungry, supermassive black holes are called quasars.

As grimy and unkempt as our present-day universe is today, scientists believe the very early universe didn't have any dust -- which tells them that the most primitive quasars should also be dust-free. But nobody had seen such immaculate quasars -- until now. Spitzer has identified two -- the smallest on record -- about 13 billion light-years away from Earth. The quasars, called J0005-0006 and J0303-0019, were first unveiled in visible light using data from the Sloan Digital Sky Survey. That discovery team, which included Jiang, was led by Xiaohui Fan, a coauthor of the recent paper at the University of Arizona. NASA's Chandra X-ray Observatory had also observed X-rays from one of the objects. X-rays, ultraviolet and optical light stream out from quasars as the gas surrounding them is swallowed.

"Quasars emit an enormous amount of light, making them detectable literally at the edge of the observable universe," said Fan.

When Jiang and his colleagues set out to observe J0005-0006 and J0303-0019 with Spitzer between 2006 and 2009, their targets didn't stand out much from the usual quasar bunch. Spitzer measured infrared light from the objects along with 19 others, all belonging to a class of the most distant quasars known. Each quasar is anchored by a supermassive black hole weighing more than 100 million suns.

Of the 21 quasars, J0005-0006 and J0303-0019 lacked characteristic signatures of hot dust, the Spitzer data showed. Spitzer's infrared sight makes the space telescope ideally suited to detect the warm glow of dust that has been heated by feeding black holes.

"We think these early black holes are forming around the time when the dust was first forming in the universe, less than one billion years after the Big Bang," said Fan. "The primordial universe did not contain any molecules that could coagulate to form dust. The elements necessary for this process were produced and pumped into the universe later by stars."

The astronomers also observed that the amount of hot dust in a quasar goes up with the mass of its black hole. As a black hole grows, dust has more time to materialize around it. The black holes at the cores of J0005-0006 and J0303-0019 have the smallest measured masses known in the early universe, indicating they are particularly young, and at a stage when dust has not yet formed around them.

Other authors include W.N. Brandt of Pennsylvania State University, University Park; Chris L. Carilli of the National Radio Astronomy Observatory, Socorro, N.M.; Eiichi Egami of the University of Arizona; Dean C. Hines of the Space Science Institute, Boulder, Colo.; Jaron D. Kurk of the Max Planck Institute for Extraterrestrial Physics, Germany; Gordon T. Richards of Drexel University, Philadephia, Pa.; Yue Shen of the Harvard Smithsonian Center for Astrophysics, Cambridge, Mass.; Michael A. Strauss of Princeton, N.J.; Marianne Vestergaard of the University of Arizona and Niels Bohr Institute in Denmark; and Fabian Walter of the Max Planck Institute for Astronomy, Germany. Fan and Kurk were based in part at the Max Planck Institute for Astronomy when this research was conducted.

The Spitzer observations were made before the telescope ran out of its liquid coolant in May 2009, beginning its "warm" mission

Planck Mission Images Galactic Web of Cold Dust

March 17, 2010

Tendrils of the coldest stuff in our galaxy can be seen in a new, large image from Planck, a mission surveying the whole sky to learn more about the birth of our universe.

Planck, a European Space Agency-led mission with important participation from NASA, launched into space in May 2009 from Kourou, French Guiana. The space telescope has almost finished its first of at least four separate scans of the entire sky, a voluminous task that will be completed in early 2012.

The new image available online at http://photojournal.jpl.nasa.gov/catalog/PIA12964, highlights a swath of our Milky Way galaxy occupying about one-thirteenth of the entire sky. It shows the bright band of our galaxy's spiral disk amidst swirling clouds where gas and dust mix together and, sometimes, ignite to form new stars. The data were taken in the so-called far-infrared portion of the light spectrum, using two of nine different frequencies available on Planck.

"We've got huge amounts of data streaming down from space," said Ulf Israelsson, the NASA project manager for the mission at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The intricate process of sorting through all of it has begun."

The mission's primary objective is to map the cosmic microwave background -- relic radiation left over from the Big Bang that created our universe about 13.7 billion years ago. Planck's state-of-the-art technology will provide the most detailed information yet about the size, mass, age, geometry, composition and fate of the universe.

In addition to cosmological questions like these, the mission will address such astronomy topics as star formation and galactic structure. Its observations will be used in synergy with data from other missions, such as the Herschel Space Observatory, another ESA mission with important NASA participation, and NASA's Spitzer Space Telescope.

"Planck is the first big cosmology mission that will also have a large impact on our understanding of our galaxy, the Milky Way," said Charles Lawrence, the mission's NASA project scientist at JPL. "We can see the cold dust and gas that permeate our galaxy on very large scales, while other missions like Herschel can zoom in to see the detail."

Planck is scheduled to release a first batch of astronomy data, called the Early Release Compact Source Catalog, in Jan. 2011. Cosmology results on the first two years' worth of data are expected to be released in Dec. 2012.

Thermal Images of Jupiter's "Red Spot"

New thermal images from powerful ground-based telescopes show swirls of warmer air and cooler regions never seen before within Jupiter's Great Red Spot, enabling scientists to make the first detailed interior weather map of the giant storm system.

The observations reveal that the reddest color of the Great Red Spot corresponds to a warm core within the otherwise cold storm system, and images show dark lanes at the edge of the storm where gases are descending into the deeper regions of the planet. These types of data, detailed in a paper appearing in the journal Icarus, give scientists a sense of the circulation patterns within the solar system's best-known storm system.

"This is our first detailed look inside the biggest storm of the solar system," said Glenn Orton, a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who was one of the authors of the paper. "We once thought the Great Red Spot was a plain old oval without much structure, but these new results show that it is, in fact, extremely complicated."

Sky gazers have been observing the Great Red Spot in one form or another for hundreds of years, with continuous observations of its current shape dating back to the 19th century. The spot, which is a cold region averaging about 110 Kelvin (minus 260 degrees Fahrenheit) is so wide about three Earths could fit inside its boundaries.

The thermal images obtained by giant 8-meter (26-foot) telescopes used for this study -- the European Southern Observatory's Very Large Telescope in Chile, the Gemini Observatory telescope in Chile and the National Astronomical Observatory of Japan's Subaru telescope in Hawaii -- have provided an unprecedented level of resolution and extended the coverage provided by NASA's Galileo spacecraft in the late 1990s. Together with observations of the deep cloud structure by the 3-meter (10-foot) NASA Infrared Telescope Facility in Hawaii, the level of thermal detail observed from these giant observatories is comparable to visible-light images from NASA's Hubble Space Telescope for the first time.

One of the most intriguing findings shows the most intense orange-red central part of the spot is about 3 to 4 Kelvin (5 to 7 degrees Fahrenheit) warmer than the environment around it, said Leigh Fletcher, the lead author of the paper, who completed much of the research as a postdoctoral fellow at JPL and is currently a fellow at the University of Oxford in England. This temperature differential might not seem like a lot, but it is enough to allow the storm circulation, usually counter-clockwise, to shift to a weak clockwise circulation in the very middle of the storm. Not only that, but on other parts of Jupiter, the temperature change is enough to alter wind velocities and affect cloud patterns in the belts and zones.

"This is the first time we can say that there's an intimate link between environmental conditions -- temperature, winds, pressure and composition - and the actual color of the Great Red Spot," Fletcher said. "Although we can speculate, we still don't know for sure which chemicals or processes are causing that deep red color, but we do know now that it is related to changes in the environmental conditions right in the heart of the storm."

Unlocking the secrets of Jupiter's giant storm systems will be one of the targets for infrared spacecraft observations from future missions including NASA's Juno mission

Cassini Data Show Ice and Rock Mixture Inside Titan

March 11, 2010

PASADENA, Calif. -- By precisely tracking NASA's Cassini spacecraft on its low swoops over Saturn's moon Titan, scientists have determined the distribution of materials in the moon's interior. The subtle gravitational tugs they measured suggest the interior has been too cold and sluggish to split completely into separate layers of ice and rock.

The finding, to be published in the March 12 issue of the journal Science, shows how Titan evolved in a different fashion from inner planets such as Earth, or icy moons such as Jupiter's Ganymede, whose interiors have split into distinctive layers.

"These results are fundamental to understanding the history of moons of the outer solar system," said Cassini Project Scientist Bob Pappalardo, commenting on his colleagues' research. Pappalardo is with NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We can now better understand Titan's place among the range of icy satellites in our solar system."

Scientists have known that Titan, Saturn's largest moon, is about half ice and half rock, but they needed the gravity data to figure out how the materials were distributed. It turns out Titan's interior is a sorbet of ice studded with rocks that probably never heated up beyond a relatively lukewarm temperature. Only in the outermost 500 kilometers (300 miles) is Titan's ice devoid of any rock, while ice and rock are mixed to various extents at greater depth.

"To avoid separating the ice and the rock, you must avoid heating the ice too much," said David J. Stevenson, one of the paper's co-authors and a professor of planetary science at the California Institute of Technology in Pasadena. "This means that Titan was built rather slowly for a moon, in perhaps around a million years or so, back soon after the formation of the solar system."

This incomplete separation of ice and rock makes Titan less like Jupiter's moon Ganymede, where ice and rock have fully separated, and perhaps more like another Jovian moon, Callisto, which is believed to have a mixed ice and rock interior. Though the moons are all about the same size, they clearly have diverse histories.

The Cassini measurements help construct a gravity map, which may help explain why Titan has a stunted topography, since interior ice must be warm enough to flow slowly in response to the weight of heavy geologic structures, such as mountains.

Creating the gravity map required tracking minute changes in Cassini's speed along a line of sight from Earth to the spacecraft as it flew four close flybys of Titan between February 2006 and July 2008. The spacecraft took paths between about 1,300 to 1,900 kilometers (800 to 1,200 miles) above Titan.

"The ripples of Titan's gravity gently push and pull Cassini along its orbit as it passes by the moon and all these changes were accurately recorded by the ground antennas of the Deep Space Network within 5 thousandths of a millimeter per second [0.2 thousandths of an inch per second] even as the spacecraft was over a billion kilometers [more than 600 million miles] away," said Luciano Iess, a Cassini radio science team member at Sapienza University of Rome in Italy, and the paper's lead author. "It was a tricky experiment."

The results don't speak to whether Titan has an ocean beneath the surface, but scientists say this hypothesis is very plausible and they intend to keep investigating. Detecting tides induced by Saturn, a goal of the radio science team, would provide the clearest evidence for such a hidden water layer.

A Cassini interdisciplinary investigator, Jonathan Lunine, said of his colleagues' findings, "Additional flybys may tell us whether the crust is thick or thin today." Lunine is with the University of Rome, Tor Vergata, Italy, and the University of Arizona, Tucson. "With that information we may have a better understanding of how methane, the ephemeral working fluid of Titan's rivers, lakes and clouds, has been resupplied over geologic time. Like the history of water on Earth, this is fundamental to a deep picture of the nature of Titan through time."

Is That Saturn's Moon Titan or Utah?

Planetary scientists have been puzzling for years over the honeycomb patterns and flat valleys with squiggly edges evident in radar images of Saturn's moon Titan. Now, working with a "volunteer researcher" who has put his own spin on data from NASA's Cassini spacecraft, they have found some recognizable analogies to a type of spectacular terrain on Earth known as karst topography. A poster session today, Thursday, March 4, at the Lunar and Planetary Science Conference in The Woodlands, Texas, displays their work.

Karst terrain on Earth occurs when water dissolves layers of bedrock, leaving dramatic rock outcroppings and sinkholes. Comparing images of White Canyon in Utah, the Darai Hills of Papua New Guinea, and Guangxi Province in China to an area of connected valleys and ridges on Titan known as Sikun Labyrinthus yields eerie similarities. The materials may be different - liquid methane and ethane on Titan instead of water, and probably some slurry of organic molecules on Titan instead of rock - but the processes are likely quite similar.

"Even though Titan is an alien world with much lower temperatures, we keep learning how many similarities there are to Earth," said Karl Mitchell, a Cassini radar team associate at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The karst-like landscape suggests there is a lot happening right now under the surface that we can't see."

Indeed, Mitchell said, if the karst landscape on Titan is consistent with Earth's, there could very well be caves under the Titan surface.

Work on these analogies was spearheaded by Mike Malaska of Chapel Hill, N.C., an organic chemist by trade and a contributor in his spare time to unmannedspaceflight.com, a Web site for amateur space enthusiasts to try their hand at visualizing NASA data. Malaska approached radar team member Jani Radebaugh at Brigham Young University in Provo, Utah, about collaborative work after meeting her at last year's Lunar and Planetary Science Conference.

"I've been in love with Titan since Cassini beamed down the first images of Titan's Shangri-La sand sea," Malaska said. "It's been amazing for the public to see data come down so quickly and get data sets so rich that you can practically imagine riding along with the spacecraft."

Radebaugh steered Malaska toward a swath of landscape imaged by the radar instrument on Dec. 20, 2007. Malaska traced out patterns in the landscape on his computer and classified them into different types of valley patterns. He saw that some of the valleys had no apparent outlets and wondered where the fluid and material went.

Searching geological literature, he found that such closed valleys were typical of karst terrain and was led to examples of karst in Papua New Guinea, Indonesia, Utah and China. He pulled down images of these places from Google Earth. He got input from other Cassini team members and associates, including Ralph Lorenz of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., and Tom Farr of JPL.

Malaska also wanted to make 3-D images and an animation of the area, so he collaborated with Bjorn Jonsson and Doug Ellison, two other "volunteer researchers" involved with the Web site. Malaska used a ruddy color palette derived from Cassini's imaging science subsystem and the descent imaging and spectral radiometer on the European Space Agency's Huygens probe. He also used some artistic license to model the elevations of the ridges and dendritic drainage basins, taking as his basic assumption that liquid flows downward.

"My artistic model seems to fit the current data," Malaska said. "Of course, Cassini could do another pass and blow the model away. I'm hoping it will be confirmed, though."

Mars Dunes: On the Move?

PASADENA, Calif. -- New studies of ripples and dunes shaped by the winds on Mars testify to variability on that planet, identifying at least one place where ripples are actively migrating and another where the ripples have been stationary for 100,000 years or more.

Patterns of dunes and the smaller ripples present some of the more visually striking landforms photographed by cameras orbiting Mars. Investigations of whether they are moving go back more than a decade.

Two reports presented at the 41st Lunar and Planetary Sciences Conference near Houston this week make it clear that the answer depends on where you look. Both reports used images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, which allows examination of features as small as about a meter, or yard, across.

One report is by Simone Silvestro of the International Research School of Planetary Sciences at Italy's G. d'Annunzio University, and his collaborators. They investigated migration of ripples and other features on dark dunes within the Nili Patera area of Mars' northern hemisphere. They compared an image taken on Oct. 13, 2007, with another of the same dunes taken on June 30, 2007. Most of the dunes in the study area are hundreds of meters long. Ripples form patterns on the surfaces of the dunes, with crests of roughly parallel ripples spaced a few meters apart.

Careful comparison of the images revealed places where ripples on the surface of the dunes had migrated about 2 meters (7 feet) -- the largest movement ever measured in a ripple or dune on Mars. The researchers also saw changes in the shape of dune edges and in streaks on the downwind faces of dunes.

"The dark dunes in this part of Mars are active in present-day atmospheric conditions," Silvestro said. "It is exciting to have such high-resolution images available for comparisons that show Mars as an active world."

The other report is by Matthew Golombek of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and collaborators. They checked whether ripples have been moving in the southern-hemisphere area of Mars' Meridiani Planum where the Mars Exploration Rover Opportunity has been working since 2004. They used observations by Opportunity as well as by HiRISE, surveying an area of about 23 square kilometers (9 square miles). Examination of ripples at the edges of craters can show whether the ripples were in place before the crater was excavated or moved after the crater formed.

"HiRISE images are so good, you can tell if a crater is younger than the ripple migration," Golombek said. "There's enough of a range of crater ages that we can bracket the age of the most recent migration of the ripples in this area to more than 100,000 years and probably less than 300,000 years ago."

Winds are still blowing sand and dust at Meridiani. Opportunity has seen resulting changes in its own wheel tracks revisited several months after the tracks were first cut.

Golombek has a hypothesis for why the ripples at Meridiani are static, despite winds, while those elsewhere on Mars may be actively moving. Opportunity has seen that the long ripples in the region are covered with erosion-resistant pebbles, nicknamed "blueberries," which the rover first observed weathering out of softer matrix rocks beside the landing site. These spherules -- mostly about 1 to 3 millimeters (0.04 to 0.12 inches) in diameter -- may be too large for the wind to budge.

"The blueberries appear to form a armoring layer that shields the smaller sand grains beneath them from the wind," he said.

HiRISE Principal Investigator Alfred McEwen, of the University of Arizona, Tucson, said, "The more we look at Mars at the level of detail we can now see, the more we appreciate how much the planet differs from one place to another."

Galactic Lenses Confirm Universe's Age, Size

The size and age of the universe, as well as how fast it is expanding, has been confirmed with a new, precise method that uses galaxies as lenses to look at other galaxies.

The new measurement confirmed the age of the universe as 13.75 billion years old, to within 170 million years, and also confirmed the strength of dark energy, which is responsible for the accelerating expansion of the universe.

When looking out at the cosmos, it can be difficult for scientists to distinguish between a very bright light far away and a dimmer source much closer to Earth.

To circumvent this problem, a team of researchers used a technique called gravitational lensing to measure the distances light traveled from a bright, active galaxy to the Earth along different paths, along with data from the Hubble Space Telescope. Researchers can use the observations to infer not just how far away the galaxy lies but also the overall scale of the universe and some details of its expansion.

Size and age

The size of the universe is often expressed by astrophysicists in terms of a quantity called Hubble's constant, which describes the rate at which galaxies in the universe are flying away from each other.

"We've known for a long time that lensing is capable of making a physical measurement of Hubble's constant," said team member Phil Marshall of the researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). But gravitational lensing had never before been used in such a precise way.

The new measurement provides an equally precise measurement of Hubble's constant as long-established tools such as observation of supernovas (often used as "standard candles" of cosmic distance) and the cosmic microwave background, the remnant radiation of the Big Bang.

The most widely accepted value for the Hubble constant right now is 72 kilometers per second per megaparsec, obtained by the Hubble Space Telescope.

"Gravitational lensing has come of age as a competitive tool in the astrophysicist's toolkit," Marshall said.

Radar Map of Buried Martian Ice Adds to Climate Record

PASADENA, Calif. -- Extensive radar mapping of the middle-latitude region of northern Mars shows that thick masses of buried ice are quite common beneath protective coverings of rubble.

The ability of NASA's Mars Reconnaissance Orbiter to continue charting the locations of these hidden glaciers and ice-filled valleys -- first confirmed by radar two years ago -- adds clues about how these deposits may have been left as remnants when regional ice sheets retreated.

The subsurface ice deposits extend for hundreds of kilometers, or miles, in the rugged region called Deuteronilus Mensae, about halfway from the equator to the Martian north pole. Jeffrey Plaut of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleagues prepared a map of the region's confirmed ice for presentation at this week's 41st Lunar and Planetary Science Conference near Houston.

The Shallow Radar instrument on the orbiter has obtained more than 250 observations of the study area, which is about the size of California.

"We have mapped the whole area with a high density of coverage," Plaut said. "These are not isolated features. In this area, the radar is detecting thick subsurface ice in many locations." The common locations are around the bases of mesas and scarps, and confined within valleys or craters.

Plaut said, "The hypothesis is the whole area was covered with an ice sheet during a different climate period, and when the climate dried out, these deposits remained only where they had been covered by a layer of debris protecting the ice from the atmosphere."

The researchers plan to continue the mapping. These buried masses of ice are a significant fraction of the known non-polar ice on Mars. The ice could contain a record of environmental conditions at the time of its deposition and flow, making the ice masses an intriguing possible target for a future mission with digging capability.

Elusive Dark Matter May Be Hidden on Earth

Scientists are hot on the tail of one of nature's most elusive substances, the mysterious dark matter that is thought to make up the bulk of the universe. Many scientists think dark matter might even be hiding right under our noses here on Earth.

Dark matter is especially tricky to find because of its dark nature. In fact, scientists don't know what it is. It doesn't emit or reflect any light, so the most powerful telescopes have no hope of spying it directly. It has been thought to exist since the 1970s based on observations of gravity's effects on large-scales, such as among and between galaxies – regular matter can't account for the amount of gravity at work.

And dark matter doesn't often interact with most other matter, scientists theorize. One idea is that it flies right through the Earth, your house, and your body without bouncing off atoms.

Some scientists have taken to underground searches in hopes of catching just a few out of the multitude of dark matter particles in a rare instance of actually bouncing off of a regular particle.

"They're just streaming right though us, and every once in while there's an interaction," said Angela Reisseter of the University of Minnesota, a member of a project called the Cryogenic Dark Matter Search (CDMS). She spoke this month at the meeting of the American Physical Society in Washington, D.C.

Dark matter detected...or was it?

In a recent issue of the journal Science Express, Reisseter and her colleagues reported finding two possible events that may or may not be dark matter impacts on their detectors.

"Our previous results have been no, no, no," Reisseter said. "This is our first maybe – that is all it is."

The CDMS is buried in a mine in Minnesota underneath about 766 yards (700 meters) of rock, plastic, lead, copper and other materials designed to stop everything but dark matter from reaching the experiment — thus cosmic rays and other particles that might be confused for dark matter particles will mostly be eliminated.

The detectors themselves are basically small, hockey-puck shaped blocks of the elements germanium and silicon. If the nucleus from one of the germanium or silicon atoms is hit by a dark matter particle, then it will rebound and send a signal to the detector.

However the researchers can't be absolutely sure that the two signals they measured were dark matter and not some other particle, which they call background. Two signals is just too few to be confident of, they said, because their calculations predicted about one false event from background.

"If it was one, we'd say 'Oh, it's the background.' If it was three you start to say 'Oh, it's a signal,'" Reisseter said. "We can't call it background and we can't call it signal."

The CDMS team intends to keep running their experiment at ever more sensitive levels in hopes that a more substantial signal is discovered.

Dark matter hunt goes on

Other attempts to track down dark matter on Earth have focused on powerful particle accelerators that speed up subatomic particles to close to the speed of light and then smash them together, hoping the incredibly high collision energies create exotic particles, including dark matter.

But even with our increasingly powerful atom smashers, no sign of dark matter has yet been spotted.

"You have to ask why would this be?" said Sarah Eno of the University of Maryland. "Why would the particle that makes up most of the matter in the universe never have been seen in our accelerators?"

One reason could be that they just aren't powerful enough. Scientists aren't sure how massive the dark matter particle might be, and certain possibilities require extremely high energies to create them in the laboratory. Or it might be impossible find at any accelerator.

"We don't know for a fact that the dark mater particle is a particle we would be able to produce and detect," Eno said.

The best hope now could be a new particle accelerator — the Large Hadron Collider (LHC) near Geneva, Switzerland — that is the largest ever built. It opened recently and isn't yet running at full speed. When it does, many are holding out hope that dark matter will finally be pinned down.

"It could be that now we have this new machine we'll finally have enough energy to make this dark matter particle and see it in our collisions," Eno said. She is a member of the Compact Muon Solenoid experiment team at the LHC

Cassini Finds Plethora of Plumes, Hotspots at Enceladus

February 23, 2010


Newly released images from last November's swoop over Saturn's icy moon Enceladus by NASA's Cassini spacecraft reveal a forest of new jets spraying from prominent fractures crossing the south polar region and yield the most detailed temperature map to date of one fracture.

The new images from the imaging science subsystem and the composite infrared spectrometer teams also include the best 3-D image ever obtained of a "tiger stripe," a fissure that sprays icy particles, water vapor and organic compounds. There are also views of regions not well-mapped previously on Enceladus, including a southern area with crudely circular tectonic patterns.

The images and additional information are online at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

"Enceladus continues to astound," said Bob Pappalardo, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "With each Cassini flyby, we learn more about its extreme activity and what makes this strange moon tick."

For Cassini's visible-light cameras, the Nov. 21, 2009 flyby provided the last look at Enceladus' south polar surface before that region of the moon goes into 15 years of darkness, and includes the most detailed look yet at the jets.

Scientists planned to use this flyby to look for new or smaller jets not visible in previous images. In one mosaic, scientists count more than 30 individual geysers, including more than 20 that had not been seen before. At least one jet spouting prominently in previous images now appears less powerful.

"This last flyby confirms what we suspected," said Carolyn Porco, imaging team lead based at the Space Science Institute in Boulder, Colo. "The vigor of individual jets can vary with time, and many jets, large and small, erupt all along the tiger stripes."

A new map that combines heat data with visible-light images shows a 40-kilometer (25-mile) segment of the longest tiger stripe, known as Baghdad Sulcus. The map illustrates the correlation, at the highest resolution yet seen, between the geologically youthful surface fractures and the anomalously warm temperatures that have been recorded in the south polar region. The broad swaths of heat previously detected by the infrared spectrometer appear to be confined to a narrow, intense region no more than a kilometer (half a mile) wide along the fracture.

In these measurements, peak temperatures along Baghdad Sulcus exceed 180 Kelvin (minus 135 degrees Fahrenheit), and may be higher than 200 Kelvin (minus 100 degrees Fahrenheit). These warm temperatures probably result from heating of the fracture flanks by the warm, upwelling water vapor that propels the ice-particle jets seen by Cassini's cameras. Cassini scientists will be testing this idea by investigating how well the hot spots correspond with the jet sources.

"The fractures are chilly by Earth standards, but they're a cozy oasis compared to the numbing 50 Kelvin (-370 Fahrenheit) of their surroundings," said John Spencer, a composite infrared spectrometer team member based at Southwest Research Institute in Boulder, Colo. "The huge amount of heat pouring out of the tiger stripe fractures may be enough to melt the ice underground. Results like this make Enceladus one of the most exciting places we've found in the solar system."

Some of Cassini's scientists infer that the warmer the temperatures are at the surface, the greater the likelihood that jets erupt from liquid. "And if true, this makes Enceladus' organic-rich, liquid sub-surface environment the most accessible extraterrestrial watery zone known in the solar system," Porco said.

The Nov. 21 flyby was the eighth targeted encounter with Enceladus. It took the spacecraft to within about 1,600 kilometers (1,000 miles) of the moon's surface, at around 82 degrees south latitude.

Buzz Lightyear Sets Duration Record Aboard Space Station

Yes, that's right, Buzz Lightyear is on his way home.

The animated astronaut has been on a real space mission in the form of a 12-inch tall action figure since launching last year aboard Discovery's STS-124 mission, as part of an educational partnership between NASA and the Walt Disney Company.


Buzz is returning with the STS-128 crew, including space station flight engineer Tim Kopra who spent 44 days living on the ISS. By comparison, Lightyear will have logged 467 days in space, assuming that the weather in Florida does not delay his scheduled landing on Thursday evening.


That is a record, says Disney, pointing out that Lightyear's stay surpasses the longest duration space mission set in 1995 by Russian cosmonaut Valery Polyakov by a month.


During his time on-board the station, with the help of his crewmates, Lightyear has been the star of recorded videos that are aimed at exciting children about spaceflight, while teaching them the basics of working in weightlessness.

Out There: A Strange Zoo of Other Worlds

More than 400 worlds have been found beyond the reach of our sun, and the tally is rising rapidly. From super-Earths to giants dwarfing Jupiter, our galaxy is a zoo of different kinds of planets.

Hot Jupiters

The first discovery of an extrasolar planet around a sun-like star was 51 Pegasi B, an exoplanet roughly 50 light-years away, unofficially named Bellerophon after the tamer of the mythical Pegasus.

Like many alien worlds found after it, 51 Pegasi B was a "hot Jupiter," a gas giant as close or closer to its star than Mercury is to our sun, unlike "cold Jupiters" that orbit farther away such as Saturn or, naturally, Jupiter.

Of the 429 exoplanets discovered to date, 89 have been hot Jupiters, likely because their large size and proximity to their stars makes them easier to spot by current techniques.

Pulsar planets

The first true discovery of extrasolar planets came in 1994, when radio astronomers discovered worlds around the pulsar PSR B1257+12 some 980 light-years away in the Virgo constellation. A pulsar is not a normal star, but a dense, rapidly spinning remnant of a supernova explosion. As of 2007, three extrasolar planets have been confirmed in orbit around this pulsar.

The oldest exoplanet known yet, PSR B1620-26 b, nicknamed Methuselah, is also a pulsar planet, located 5,600 light years from Earth in the Scorpius constellation. Methuselah is roughly twice Jupiter's mass and is estimated to be some 12.7 billion years old, and it suggested planets as potential habitats for life arose early in the universe's history. It is also a circumbinary planet, orbiting around a binary system composed of the pulsar PSR B1620-26 A and the white dwarf WD B1620-26.

All these worlds cannot support life as we know it, permanently bathed as they are in the pulsar's high-energy radiation.

Super-Earths

A super-Earth is a planet with a mass larger than Earth's, roughly up to 10 times greater. The first super-Earths ever found were two of the planets around PSR B1257+12.

Super-Earths might be more geologically active than our planet.

Astronomers at the Harvard-Smithsonian Center for Astrophysics suggest they experience more vigorous plate tectonics because they possess thinner plates under more stress. Such activity is essential to life as we know it, because it helps enable complex chemistry and recycles substances like carbon dioxide into the atmosphere, which keeps Earth warm.

Eccentric planets

In our solar system, planets for the most part have fairly uniform circular orbits. The exoplanets found so far, however, can have far more eccentric orbits, moving in close and then far from their stars. Where a perfect circle has an eccentricity value of zero, roughly half of exoplanets seen thus far have an eccentricity of 0.25 or greater.

These eccentric orbits can lead exoplanets to extreme heat waves. For instance, HD 80606b, which is about four times the mass of Jupiter and is located some 200 light-years from Earth, has an eccentricity of roughly 0.93, "so it goes from an orbital distance close to that of Earth's to come hurtling in well inside the orbit of Mercury, essentially getting blasted with a blowtorch every 111 days," said astronomer Charles Beichman, executive director of NASA's ExoPlanet Science Institute.

"One thing we're trying hard to understand now is whether planets with eccentric orbits are the unusual ones, or whether it's our system that's the oddball out," Beichman said. "These eccentric orbits would essentially lead planets to interfere with each other, scattering them around."

Hot Neptunes

Hot Neptunes are planets some 10 to 20 times the mass of Earth's – about the mass of "cold Neptunes" such as Uranus and, naturally, Neptune – yet are as close or closer to their stars than Mercury is to our sun. The first hot Neptune discovered was Gliese 436b some 33.4 light years away in the constellation Leo, which orbits its star a thousand times closer than Neptune orbits our Sun. It might have a surface of "hot ice" – water that remains solid despite its heat because it gets compressed by the planet's gravity. So far about 25 hot Neptunes have been found so far, Beichman said.

Water worlds

There are two kinds of worlds that might be entirely covered with water. "One is a terrestrial Earth-like planet that's just covered with a lot more water than our world, like the Kevin Costner movie, but is otherwise still familiar," Beichman said. "Or you can imagine a hot Neptune which is almost totally composed of water that is close enough to its star to not be frozen, but instead have an ocean thousands of kilometers deep and perhaps an atmosphere like a gas giant's, with lots of hydrogen and water vapor."

Chthonian planets

Sometimes hot Jupiters or hot Neptunes live too close to their stars for comfort. Once their stars roast these exoplanets and rip at them with their gravity, they might blow the gas completely off them, leaving behind rocky cores scientists have dubbed chthonian planets or evaporated remnant cores. Their proximity to their stars could mean they are covered in lava.

The super-Earth COROT-7b may well be a chthonian planet, orbiting 23 times closer to its star than Mercury is to our sun. The first evaporating planet discovered, HD209458b, nicknamed Osiris, might be on its way to becoming a chthonian planet.

Free-floating planets

Normally planets are thought of as orbiting stars, but there are hints a number of bodies with the mass of gas giants might be free-floating. These might either have escaped from their suns or never had a star to begin with, born in star-forming regions without the mass needed to ignite.

Roughly a half-dozen candidate free-floating planets have been found so far, either still glowing from the heat released as their gravity contracts their mass, or from the rare times one passes in front of a star and magnifies the light from the background star. "It's not clear whether you call them planets because they formed as part of a planetary system and were subsequently ejected or formed as super-small brown dwarf stars with the mass of planets," Beichman said.

Exo-Earths

Although vast majority of the 429 exoplanets found to date have been gas or ice giants, it is likely that terrestrial exoplanets outnumber these behemoths, and upcoming missions may soon finally discover rocky worlds the size of Earth.

"This is the decade when the first real confirmed exo-Earths are likely to come," Beichman said. "We've already found objects three to five times the mass of Earth."

The Kepler mission launched in 2009 is already on track to finding such planets, he noted, and the James Webb Space Telescope currently scheduled to launch in 2014 will be able to characterize the atmospheres of at least a few super-Earths.

An obvious hope is to find a Goldilocks planet just right for life – a planet at the right distance from its star to not roast or freeze and just the right size to retain an atmosphere but not so large as to become a gas giant. "We're on a quest with a very high probability of success of finding a planet that's habitable or even inhabited with primitive life around other stars," Beichman said. "As we're progressing on that path, every time we round the bend along the way, we're finding fantastic new vistas."

What Makes Supernovas Go Boom

The trigger that ignites a common type of stellar explosion has finally been uncovered with observations from NASA's Chandra X-ray Observatory, providing a major advance in the understanding of supernovas.

These supernovas, called Type 1a, result from the explosion of a white dwarf star. These types of supernovas are used as cosmic mile markers, and knowing what causes these stellar blow-ups is a critical key to studying the mysterious dark energy that astronomers think pervades the universe.

"These are such critical objects in understanding the universe. It was a major embarrassment that we did not know how they worked," said Marat Gilfanov of the Max Plank Institute for Astrophysics in Germany and a member of the team that made the new findings. "Now we are beginning to understand what lights the fuse of these explosions."

Type Ia supernovas are generally thought to go off when a white dwarf star — the remnant core of a red giant star that has sloughed off its outer gas layers and cooled down — exceeds its weight limit, becomes unstable and explodes.

But just what causes it to tip the scale and get blown to smithereens hadn't been pinned down. Two possibilities for pushing a white dwarf over the edge were considered the main contenders: accretion, in which a white dwarf siphons off material from a sun-like companion star until it exceeds its weight limit; and the merging of two white dwarfs into a bigger mass.

One way for telling which process was the culprit was looking at the X-ray light emission from supernovas, as each scenario would generate different amounts of X-rays. A Type Ia supernova caused by accreting material produces significant X-ray emission prior to the explosion, while a supernova from a merger of two white dwarfs would create significantly less.

To see which scenario was likely the cause of Type 1a supernovas, Gilfanov and his team used the Chandra Observatory to observe five nearby elliptical galaxies and the central region of the Andromeda Galaxy (or M31).

The scientists found that the observed X-ray emission was a factor of 30 to 50 times smaller than expected from the accretion scenario, effectively ruling out this mechanism and making white dwarf mergers the main suspect in these galaxies.

"Our results suggest that the supernovas in the galaxies we studied almost all come from two white dwarfs merging," said team member Akos Bogdan, also of Max Planck. "This is probably not what many astronomers would expect."

The unexpectedness stems partly from the fact that few double white dwarf systems seemed to exist and that such pairs are difficult to see even with the best telescopes.

"Now this path to supernovas will have to be investigated in more detail," Gilfanov said.

The difference between these two scenarios may have implications for how these supernovas can be used as "standard candles" to track vast cosmic distances. Type 1a supernovas have generally been thought to be excellent distance guides because they can be seen to large distances and follow a reliable brightness pattern.

But because white dwarfs can come in a range of masses, it means that the merger of two of them could result in explosions that vary somewhat in brightness.

One question that remains to be answered is whether this trigger that seems to be the cause of Type 1a supernovas in elliptical galaxies is also the fuse for these stellar explosions in spiral galaxies.

Primitive Stars Lurking Near Milky Way Found (Plus, Biggest Star Ever "Weighed")

A new panorama of a cosmic nebula offers an up-close glimpse of baby stars being born.

The nebula, dubbed NGC 3603, is called a starburst region because stars are coming into being in feverish bursts of activity. It lies about 22,000 light-years away from the sun, making it the closest region of the kind known in our galaxy. This near view offers astronomers a relatively local test bed for studying intense star formation processes that are usually hard to observe in detail because of their great distance from us.

The new view was captured by the European Southern Observatory's Very Large Telescope in the Atacama desert of Chile. The cosmic panorama displays the rich texture of the surrounding clouds of gas and dust in the area, with many of the hot newborn stars dotting the scene with blue light.

This nebula is also home to the most massive star ever to be "weighed" so far. This behemoth, part of a binary system called A1, is estimated to be roughly 116 times the mass of the sun.

NGC 3603 owes its shape to the intense light and winds coming from the young, massive stars that push out against the curtains of gas and clouds. The central cluster of stars inside the nebula harbors thousands of stars of all sorts: the majority have masses similar to or less than that of our sun, but most spectacular are several of the very massive stars that are close to the end of their lives.

Several blue supergiant stars crowd into a volume of less than a cubic light-year, along with three so-called Wolf-Rayet stars — extremely bright and massive stars that are ejecting vast amounts of material before finishing off in glorious explosions known as supernovae.

Star Birth in Living Color

A dramatic new image from the Gemini North telescope, on Mauna Kea in Hawaii, illustrates the dynamic and sometimes violent process of star birth. It also demonstrates the capabilities of new filters available to researchers using the Gemini Multi-Object Spectrograph (GMOS).

The hourglass-shaped (bipolar) nebula in the new Gemini image, known as Sharpless 2-106 (Sh2-106), is a stellar nursery made up of glowing gas and light-scattering dust. The material shrouds a natal high-mass star thought to be mostly responsible for the hourglass shape of the nebula due to high-speed winds blowing more than 200 kilometers/second, ejecting material from deep within the forming star. Research also indicates that many sub-stellar objects are forming within the cloud, which may someday create a cluster of 50 to 150 stars.

The nebula lies about 2,000 light-years away in the direction of the constellation Cygnus. It measures about 2 light-years long by 0.5 light-year across. It is thought that its central star could be up to 15 times the mass of our Sun. The star's formation likely began no more than 100,000 years ago, and eventually its light will break free of the enveloping cloud as it begins the relatively short life of a massive star.

The new filters provide valuable insights by transmitting very specific colors of visible light emitted by excited hydrogen, helium, oxygen, and sulfur, as radiation from hot young birthing stars energize clouds of gas and dust. The filters are also used to study planetary nebulae and excited gas in other galaxies.

For this image four colors were combined as follows: Violet — helium II filter; Blue — sulfur II filter; Green — oxygen III filter; and Red — hydrogen-alpha filter. Each filter was integrated for a total of 900 seconds. The seeing was 0.4 arcsecond RMS. The rotation of the image is 125° CCW from north up, east to the left and the field of view is 3.87 arcminutes on each side.

The image was obtained using the Gemini Multi-Object Spectrograph on the Gemini North telescope. An identical instrument and filter set is available at the Gemini South telescope in Chile for parallel capabilities on the southern sk

Why Is The Sun's Atmosphere So Hot?

New imagery of the sun is revealing the complex dynamics of its surface and corona. Here, an image of the solar chromosphere showing a "hedgerow" of spicules, or jets of dense plasma that shoot up from the chromosphere. Scientists think that certain types of spicules may help explain why the Sun's atmosphere is too hot. Credit: Scott McIntosh, Bart De Pontieu, Viggo Hansteen and Karel Schrijver/UCAR


The 2006 launch of the multinational Hinode satellite changed the picture of the Sun for astrophysicists. For two astrophysicists in particular, the resulting imagery offered a voyage of discovery and the thrill of unraveling a long-held solar mystery.

Earth's atmosphere can obscure the view of unaided ground-based telescopes, but, unimpeded by this problem, the high-resolution telescope flying on Hinode captures images of the Sun in unparalleled detail.

It is in these new images that Scott McIntosh, Bart De Pontieu, Viggo Hansteen and Karel Schrijver found the first tantalizing clues that led them to a new way of considering why the solar corona is millions of degrees hotter than the Sun's visible surface.

Intuitively, the Sun's atmosphere should get cooler with distance from the Sun's surface, but reality doesn't match supposition. Using Hinode imagery, De Pontieu, a scientist at Lockheed Martin's Solar and Astrophysics Laboratory, McIntosh, and colleagues discovered in the Hinode imagery a new type of spicule.

"Classic" Type-I spicules are jets of dense plasma that shoot up from the chromosphere and, more often than not, return along the same path, said McIntosh. The "Type-II" spicules, which McIntosh and De Pontieu have recently dubbed "radices," are hotter, shorter lived and faster moving than their Type-I brethren.

"In the Hinode imagery," added McIntosh, "the radices appeared to shoot upward and disappear, often moving at speeds in excess of 100 kilometers per second. These jets likely contain plasma that ranges in temperature from 10,000 to several million degrees Celsius, and have a life span of no more than 10 to 100 seconds. While astrophysicists, including NCAR founder, Walter Orr Roberts, have long studied Type I spicules, it is known that the material in them does not reach typical coronal temperatures — about 1 million degrees — eliminating a connection to coronal heating."

But it was only during a 2008 scientific meeting about Hinode — when a colleague discussed seeing a subtle 100-plus kilometer per second upward velocity component in a coronal region with a strong magnetic field — that De Pontieu and McIntosh caught each other's eye, thinking exactly the same thing: were they possibly seeing evidence of radices reaching coronal temperatures?

Together, they searched for the "ideal" Hinode data set, one in which they were able to trace the columns of plasma ejected from the chromosphere into the corona. Upon identifying the data, each approached the task from a different perspective.

In comparing their results, they realized that the locations of the radices and the upward velocity signatures seen in the corona were the same. They also found that the velocities of the chromospheric jets and those of the coronal events matched extremely well.

"This evidence indicates that radices may play an important role in supplying and replenishing the hot mass of the solar corona and wind, explaining the temperature differential between corona and photosphere," McIntosh said. "Our calculations indicate that radices can fill the corona with hot plasma even if only one to five percent of the radices reach coronal temperatures."

US Large Hydron Smashes Gold to Create "Quark Soup"

Computer simulations of the lab work, clockwise from top left: Gluons and quarks; gold ions about to collide; just after the collision; the resulting perfect liquid. Credit: RHIC
WASHINGTON – By smashing gold particles together at super-fast speeds, physicists have basically melted protons, creating a kind of "quark soup" of matter that is about 250,000 times hotter than the center of the sun and similar to conditions just after the birth of the universe.Scientists reported in 2005 that they suspected they had created this unique state of matter, but for the first time they have verified that the extreme temperatures necessary have been reached.

"This is the hottest matter ever created in the laboratory," Steven Vigdor, associate laboratory director for nuclear and particle physics at the U.S. Department of Energy (DOE)'s Brookhaven National Laboratory in Upton, N.Y., said Monday at a meeting of the American Physical Society in Washington, D.C. "The temperature is hot enough to melt protons and neutrons."

The gold particles used in the experiment were only the nuclei — the positively-charged part of the atom made of protons and neutrons. Two sprays of gold nuclei were accelerated in opposite directions along a circular track in an underground "atom smasher" called the Relativistic Heavy Ion Collider (RHIC) Brookhaven.


These scorching conditions are enough to melt the protons and neutrons into their constituent parts — namely fundamental particles called quarks and gluons.

This soup of quarks and gluons is thought to have filled the universe a few microseconds after the Big Bang that may have created it about 13.7 billion years ago. After that point, the matter would have cooled and condensed to form the protons and neutrons that make up the matter we see today.

"This research offers significant insight into the fundamental structure of matter and the early universe, highlighting the merits of long-term investment in large-scale, basic research programs at our national laboratories," said Dr. William F. Brinkman, director of the DOE Office of Science. "I commend the careful approach RHIC scientists have used to gather detailed evidence for their claim of creating a truly remarkable new form of matter."

The soupy cauldron of fundamental particles lasted less than a billionth of a trillionth of a second. But that was enough time for physicists to measure its properties and temperature using a detector built around the collision site.

The temperature measurements came via photons, or bits of light, that were emitted shortly after the nuclei crashed into each other.

"This was an extraordinarily challenging measurement," said Barbara Jacak, a professor of physics at Stony Brook University in Stony Brook, N.Y. and spokesperson for the PHENIX collaboration, one of RHIC's four experiments.

Somewhat surprisingly, the strange state of matter behaves like a liquid, though earlier predictions suggested it would act more like a gas.

"We know that this is a liquid, but we need to find out why it's a liquid, and what role did its free-flowing nature play in the early universe?" Jacak said.

Physicists may have a chance to study an even hotter state of matter once the world's largest particle accelerator, the Large Hadron Collider near Geneva, Switzerland, starts operating at full speed. Collisions in that machine could produce temperatures two or three times hotter than the recent experiment, Jacak said.