The Sunnara Arkive Year Beta

What About 288P Hubble: It's a System of Two Things Orbiting Each Other

Image: ESA:NASA:Hubble

 

|| September 20: 2017 || ά. With the help of the NASA:ESA Hubble Space Telescope, a German-led group of astronomers have observed the intriguing characteristics of an unusual type of object in the asteroid belt between Mars and Jupiter: two asteroids orbiting each other and exhibiting comet-like features, including, a bright coma and a long tail. This is the first known binary asteroid, also, classified as a comet. The research is presented in a paper published in the journal Nature this week. In September 2016, just before the asteroid 288P made its closest approach to the Sun, it was close enough to Earth to allow astronomers a detailed look at it using the NASA:ESA Hubble Space Telescope.

The images of 288P, which is located in the asteroid belt between Mars and Jupiter, showed that it was, actually, not a single object, but two asteroids of almost the same mass and size, orbiting each other at a distance of about 100 kilometres. That discovery was in itself, an important find; because they orbit each other, the masses of the objects in such systems can be measured. But the observations, also, found ongoing activity in the binary system. “We detected strong indications of the sublimation of water ice due to the increased solar heating, similar to how the tail of a comet is created.” explains Ms Jessica Agarwal, Max Planck Institute for Solar System Research, Germany, the Team Leader and main Author of the research paper.

This makes 288P the first known binary asteroid, that is, also, classified as a main-belt comet. Understanding the origin and evolution of main-belt comets, asteroids orbiting between Mars and Jupiter, that show comet-like activity, is a crucial element in our understanding of the formation and evolution of the whole Solar System. Among the questions main-belt comets can help to answer is how water came to Earth. Since only a few objects of this type are known, 288P presents itself as an extremely important system for future studies.

According to Ms Agarwall the various features of 288P, wide separation of the two components, near-equal component size, high eccentricity and comet-like activity, also, make it unique among the few known wide asteroid binaries in the Solar System. The observed activity of 288P shows information about its past. “Surface ice cannot survive in the asteroid belt for the age of the Solar System but can be protected for billions of years by a refractory dust mantle, only a few metres thick.”

From this, the research team concluded that 288P had existed as a binary system for only about 5,000 years. Ms Agarwal elaborates on the formation scenario, “The most probable formation scenario of 288P is a breakup due to fast rotation. After that, the two fragments, may have been, moved further apart by sublimation torques.”

The fact that 288P is so different from all other known binary asteroids raises some questions about whether it is not just a coincidence that it presents such unique properties. As finding 288P included a lot of luck, it is likely to remain the only example of its kind for a long time. “We need more theoretical and observational work, as well as, more objects similar to 288P, to find an answer to this question.” concludes Ms Agarwal.

The international team of astronomers in this study consists of MsJessica Agarwal: Max Planck Institute for Solar System Research, Göttingen, Germany, Mr David Jewitt: Department of Earth, Planetary and Space Sciences and Department of Physics and Astronomy, University of California at Los Angeles, USA, Mr Max Mutchler: Space Telescope Science Institute, Baltimore, USA, Mr Harold Weaver: The Johns Hopkins University Applied Physics Laboratory, Maryland, USA and Mr Stephen Larson: Lunar and Planetary Laboratory, University of Arizona, Tucson, USA.

The results were released in the paper, A binary main belt comet, to be published in Nature. ω.

Contacts
Jessica Agarwal: Max Planck Institute for Solar-System Research: Göttingen, Germany: Tel: +49 551 384 979 438: email: agarwal at mps.mpg.de
Lauren Fuge: ESA:Hubble, Public Information Officer: Garching bei München, Germany: email: lfuge at partner.eso.org

Whatever Your Field of Work and Wherever in the World You are, Please, Make a Choice to Do All You Can to Seek and Demand the End of Death Penalty For It is Your Business What is Done in Your Name. The Law That Makes Humans Take Part in Taking Human Lives and That Permits and Kills Human Lives is No Law. It is the Rule of the Jungle Where Law Does Not Exist. The Humanion

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Hello Again and Good Bye: Cassini's Terminal Descent Ending Its 13-Year Odyssey of Saturn

Image: ESA:NASA:JPL:University of Arizona

 

|| September 11: 2017 || ά. Until the arrival of the international Cassini–Huygens Mission at Saturn in 2004, much about the gas giant, its intricate ring system and enigmatic moons was a mystery. On January 14, 2005, the mystery as to what lay beneath the thick atmosphere of Saturn’s largest moon Titan was to be revealed as ESA’s Huygens probe made the first successful landing on a world in the outer Solar System. During the two anda half hour descent under parachute, features, that looked remarkably like shore lines and river systems on Earth, appeared from the haze. But rather than water, with surface temperatures of around -180ºC, the fluid involved here is methane, a simple organic compound.

One set of images taken by Huygens is pictured here showing the view from two km altitude. It is in Mercator projection, so the N–S:E-W directions cross at right angles but surface areas appear distorted. Huygens touched down on a frozen surface littered with rounded pebbles and continued to transmit to its mothership for 72 minutes before Cassini dropped below the horizon. The stream of data returned from the surface provided a unique treasure trove of in situ measurements, that scientists are still mining today. In its 13-year Odyssey of the Saturn system Cassini made 127 close flybys of Titan, including, radar-mapping its surface, even, before Huygens’ descent and finding numerous hydrocarbon lakes and seas, evidence for a global ocean of water beneath its thick crust and an atmosphere teeming with pre-biotic chemicals.

Titan’s atmosphere is thought to be similar to early Earth’s before life developed and thus can be seen as a planet-scale laboratory to understand the chemical reactions, that, may have, led to life on Earth.

Cassini, also, watched Titan’s seasons change over time, including, the development of a swirling vortex and clouds of methane rain, that precipitate onto the surface. Titan has, also, acted as a gravitational slingshot for Cassini throughout its mission, setting it on course for exploration of the Saturn system.

Tonight, at 19:04 GMT, Cassini will make its last, distant, flyby of Titan, dubbed the ‘goodbye kiss’ by mission planners, taking it 119049 km from its surface.

The flyby seals Cassini’s fate, causing the spacecraft to slow down slightly in its orbit around Saturn and lowering its altitude over the planet. Thus, it will plunge into the atmosphere, disposing of the spacecraft in the safest way possible to avoid an unplanned impact into a pristine icy satellite, such as, ocean-bearing Enceladus.

The Cassini–Huygens mission is a co-operative project between NASA, ESA and Italy’s ASI Space Agency. ω.

Whatever Your Field of Work and Wherever in the World You are, Please, Make a Choice to Do All You Can to Seek and Demand the End of Death Penalty For It is Your Business What is Done in Your Name. The Law That Makes Humans Take Part in Taking Human Lives and That Permits and Kills Human Lives is No Law. It is the Rule of the Jungle Where Law Does Not Exist. The Humanion

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The Tiny Little Moon Blocks the Giant Giant Sun: This is What Must Be Called the Cosmic Proportional Precision Positioning of Variables: This is Seen in Wyoming in the US   || August 23: 2017 || ά. The total solar eclipse seen from Casper, Wyoming, US, by a team of ESA astronomers on August 21. The image shows the moment of totality, when the Moon passed directly in front of the Sun, blocking its light and revealing the details of the Sun’s atmosphere, its corona. Image: ESA:M.P. Ayucar, CC BY-SA 3.0 IGO: ω. Whatever Your Field of Work and Wherever in the World You are, Please, Make a Choice to Do All You Can to Seek and Demand the End of Death Penalty For It is Your Business What is Done in Your Name. The Law That Makes Humans Take Part in Taking Human Lives and That Permits and Kills Human Lives is No Law. It is the Rule of the Jungle Where Law Does Not Exist. The Humanion || Readmore || ‽: 230817 || Up ||

Surface of Mars Poses Danger to Earthly-Life-Forms

|| July 11: 2017: University of Edinburgh News || ά. The environment on Mars, may be, more harmful to Earth-based life forms than previously thought, experiments by Edinburgh scientists have shown. Researchers investigated the behaviour of chemical compounds, called, perchlorates, which are found on the surface of the red planet. They found that, when exposed to UV light whilst in environmental conditions mimicking those on Mars, the chemicals can kill bacteria, commonly carried by spacecraft.

Their findings could have implications for potential contamination from robotic and human exploration of Mars. The study suggested that the effect of perchlorates, can be, compounded by two other types of chemicals found on Mars’ surface, iron oxides and hydrogen peroxide. In experiments, in which all three were present, the combination led to a more than 10-fold increase in death of bacterial cells compared with perchlorates alone. Scientists have speculated on the influence that perchlorates, may have, on the habitability of the planet, since their discovery there several years ago.

Researchers in the UK Centre for Astrobiology and School of Physics and Astronomy investigated the potential reactivity of perchlorates and their effect on Bacillus subtilis, a bacterium found on spacecraft and common in soils and rocks. Their experiments showed that, when magnesium perchlorate was exposed to UV radiation similar to that on Mars, it became capable of killing bacteria much more effectively than UV light alone.

At concentrations of perchlorate similar to those found on the Martian surface, cells of B. subtilis quickly died. Although, the Martian surface has been suspected for some time to have toxic effects, the latest study suggests that it, may be, highly damaging to living cells.

This is owing to a toxic mix of oxidants, iron oxides, perchlorates and UV energy. Their study, funded by the Science and Technology Facilities Council, was published in Scientific Reports.

''Our findings have important implications for the possible contamination of Mars with bacteria and other materials from space missions. This should be taken into account in designing missions to Mars.'' says Ms Jennifer Wadsworth, UK Centre for Astrobiology and School of Physics and Astronomy. ω.

Thomas Pesquet Arrives Back Home From ISS

|| June 06: 2017 || ά. ESA astronaut Thomas Pesquet landed on the steppe of Kazakhstan with Russian commander Oleg Novitsky in their Soyuz MS-03 spacecraft on June 02 after six months in space. Touchdown was at 14:10 GMT after a four-hour flight from the International Space Station.

Thomas spent six months on the International Space Station as part of his Proxima mission. During Proxima, Thomas took part in 60 scientific experiments for ESA and France’s space agency CNES and the international Station partners.

The mission is part of ESA’s vision to use Earth-orbiting spacecraft as a place to live and work for the benefit of European society while using the experience to prepare for future voyages of exploration further into the Solar System. ω.

Isn't It About Time We Pay a Visit to the Solarian King Professor Parker

|| June 01: 2017: Geoff Brown Writing || ά. NASA has renamed the Solar Probe Plus spacecraft, humanity’s first mission to a star, which will launch in 2018, as the Parker Solar Probe in honour of astrophysicist Professor Eugene Parker. The announcement was made at a ceremony at the University of Chicago, where Parker serves as the S. Chandrasekhar Distinguished Service Professor Emeritus, Department of Astronomy and Astrophysics.

In 1958, Professor Parker, then a young professor at the university’s Enrico Fermi Institute, published an article in the Astrophysical Journal, titled, 'Dynamics of the interplanetary gas and magnetic fields'. Professor Parker believed that there was high speed matter and magnetism constantly escaping the sun and that it affected the planets and space throughout our solar system. This phenomenon, now known as the solar wind, has been proven to exist repeatedly through direct observation. Professor Parker’s work forms the basis for much of our understanding about how stars interact with the worlds that orbit them.

“This is the first time NASA has named a spacecraft for a living individual.” said Mr Thomas Zurbuchen, Associate Administrator for NASA’s Science Mission Directorate in Washington. “It’s a testament to the importance of his body of work, founding a new field of science that also inspired my own research and many important science questions NASA continues to study and further understand every day. I’m very excited to be personally involved honouring a great man and his unprecedented legacy.

''The solar probe is going to a region of space that has never been explored before.” said Professor Parker. “It’s very exciting that we’ll finally get a look. One would like to have some more detailed measurements of what’s going on in the solar wind. I’m sure that there will be some surprises. There always are.”

In the 1950s, Professor Parker proposed a number of concepts about how stars, including our sun, give off energy. He called this cascade of energy, the solar wind, and he described an entire complex system of plasmas, magnetic fields and energetic particles, that make up this phenomenon. He, also, theorised an explanation for the superheated solar atmosphere, the corona, which is, contrary to what was expected by physics laws, hotter than the surface of the sun itself. Many NASA missions have continued to focus on this complex space environment defined by our star, a field of research known as heliophysics.

“Parker Solar Probe is going to answer questions about solar physics, that we’ve puzzled over for more than six decades.” said Parker Solar Probe Project Scientist Ms Nicola Fox, of the Johns Hopkins University Applied Physics Laboratory. “It’s a spacecraft loaded with technological breakthroughs, that will solve many of the largest mysteries about our star, including finding out why the sun’s corona is so much hotter than its surface. And we’re very proud to be able to carry Gene’s name with us on this amazing voyage of discovery.”

NASA missions are most often renamed after launch and certification; in this case, given Professor Parker’s accomplishments within the field and how closely aligned this mission is with his research, the decision was made to honour him prior to launch, in order to draw attention to his important contributions to heliophysics and space science.

Born on June 10, 1927, in Michigan, Professor Eugene Newman Parker received a Bachelor of Science in physics from Michigan State University and a doctorate from Caltech. He then taught at the University of Utah and since 1955, Professor Parker has held faculty positions at the University of Chicago and at its Fermi Institute. He has received numerous awards for his research, including the George Ellery Hale Prize, the National Medal of Science, the Bruce Medal, the Gold Medal of the Royal Astronomical Society, the Kyoto Prize, and the James Clerk Maxwell Prize.

Parker Solar Probe is on track for launch during a 20-day window, that opens on July 31, 2018. The mission is part of NASA’s Living With a Star programme to explore aspects of the sun-Earth system, that directly affect life and society. LWS is managed by the agency’s Goddard Space Flight Centre in Greenbelt, Maryland, for NASA’s Science Mission Directorate in Washington, D.C. Johns Hopkins APL manages the mission for NASA and is designing and building and will operate the spacecraft.

Learn More nasa.gov/solarprobe.

Geoff Brown: Johns Hopkins University Applied Physics Laboratory

: Editor: Rob Garner: NASA: ω.

Mars: The Four Hundred Millions Years of Maarthitude

SSERVI_Mars Bombardment: Mars bears the scars of five giant impacts, including the ancient giant Borealis basin, top of globe, Hellas,
bottom right and Argyre, bottom left. A NASA-funded team at SwRI discovered that Mars experienced a 400-million-year
lull in impacts between the formation of Borealis and the younger basins. Image: University of Arizona:LPL:Southwest Research Institute
 

|| April 30: 2017 || ά.  Since the earliest days of our solar system’s history, asteroid impacts have shaped the planets and contributed to their evolution. New research, funded by NASA, shows that Mars experienced ten times fewer giant impacts than some previous estimates. The ancient surfaces of Mars, like those on the moon and Mercury, are covered with the scars of asteroid impacts. The largest and most ancient giant impact basin on Mars, called Borealis, is nearly 6,000 miles wide and encompasses most of the northern hemisphere of the Red Planet. A smaller giant basin, called, Hellas is 1,200 miles wide and five miles deep.

Scientists Bill Bottke, from the Southwest Research Institute:SwRI, and Jeff Andrews-Hanna, from the University of Arizona, have been investigating the early bombardment history of Mars and the timing of giant impacts. While past theories have suggested other reasons, the new findings indicate that the Borealis basin carved out the northern lowlands 04.5 billion years ago, followed by a lull of 400 million years, during which, no giant impacts occurred, culminating in a shower of impacts between 04.1 and 03.8 billion years ago, during which, four giant basins and countless smaller craters formed.

For a recently published paper in Nature Geoscience about the topic, Bottke and Andrews-Hanna collected data and ran models to support their findings, that the rim of Borealis was excavated by only one later giant basin, called, Isidis.

“This sets strong statistical limits on the number of giant basins that could have formed on Mars after Borealis.” said Bottke, Principal Investigator of the Institute for the Science of Exploring Targets:ISET, team with NASA’s Solar System Exploration Research Virtual Institute:SSERVI. “The number and timing of such giant impacts on early Mars has been debated, with estimates, ranging from four to 30 giant basins formed in the time since Borealis. Our work shows that the lower values are more likely.”

To fully understand the implications of this bombardment, the study, further, needed to constrain the timing of the impacts responsible for other giant basins, and compare their preservation state. The preservation state of the four youngest giant basins on Mars, Hellas, Isidis, Argyre and the now-buried, Utopia basins, are strikingly similar to the larger and older Borealis basin. The similar preservation of both Borealis and these younger basins indicates that any basins formed during this time interval should be similarly preserved.

Previous studies used superposed smaller craters, resulting from the occurrence of impacts close enough together over time for newer craters to form atop older ones, to estimate that the ages of Hellas, Isidis, and Argyre were 03.8-04.1 billion years old. The ages of minerals found within Mars rocks, that were blasted off the surface by impacts and came to Earth in the form of meteorites reveal the age of Borealis to be about 04.5 billion years old, nearly as old as Mars itself.

“The timing of these impacts requires two separate populations of objects striking Mars, one population, that was part of the formation of the inner planets, that died off early and a second population striking the surface at a later time.” said Bottke. “We refer to the lull as the doldrums, which was then followed by a period of more intense bombardment, commonly known as the Late Heavy Bombardment.” said Andrews-Hanna.

Bottke and Andrews-Hanna speculate that without giant impacts, release of gas from volcanoes, may have, built up a thicker atmosphere at this time and the more stable surface conditions may have even been more hospitable to life. Although much remains unknown about the earliest history of Mars, the results of the new study open a window into Mars’ tumultuous past.

The ISET is a research team managed by SSERVI. Located at NASA’s Ames Research Centre in California’s Silicon Valley, SSERVI is funded by the agency’s Science Mission Directorate and Human Exploration and Operations Mission Directorate, and manages national and international collaborative partnerships, designed to push the boundaries of science and exploration.

: Editor: Kimberly Williams: NASA: ω.

Maarth: In Meridiani Planum: The Victoria Crater

Victoria Crater in the Meridiani Planum: Image: NASA

|| October 14: 2016 || ά. This image from the High Resolution Imaging Science Experiment on NASA's Mars Reconnaissance Orbiter shows the Victoria Crater," an impact crater in Meridiani Planum, near the equator of Mars. The crater is approximately 800 meters, half a mile, in diameter. It has a distinctive scalloped shape to its rim, caused by erosion and downhill movement of crater wall material. Layered sedimentary rocks are exposed along the inner wall of the crater, and boulders that have fallen from the crater wall are visible on the crater floor. The floor of the crater is occupied by a striking field of sand dunes.

Since January 2004, the Mars Exploration Rover Opportunity has been operating at Meridiani Planum. Five days before this image was taken, Opportunity arrived at the rim of Victoria Crater, after a drive of more than nine kilometres, over five miles. The rover can be seen in this image, at roughly the "ten o'clock" position along the rim of the Crater.

Image: NASA:JPL:UA

Mars Reconnaissance Orbiter view of Victoria Crater This view is a portion of an image taken by the High Resolution Imaging Science Experiment:HiRISE camera onboard the Mars Reconnaissance Orbiter spacecraft on October 03, 2006. The complete image is centred at minus 07.8 degrees latitude, 279.5 degrees East longitude. The range to the target site was 297 kilometers, 185.6 miles. At this distance the image scale is 29.7 centimeters, 12 inches, per pixel, with 1 x 1 binning, so objects about 89 centimetres, 35 inches, across are resolved. The image shown here has been map-projected to 25 centimetres, 10 inches, per pixel and north is up. The image was taken at a local Mars time of 15:30 and the scene is illuminated from the west with a solar incidence angle of 59.7 degrees, thus the sun was about 30.3 degrees above the horizon. At a solar longitude of 113.6 degrees, the season on Mars is northern summer.

This is an enhanced-colour view generated from images acquired by the HiRISE camera using its red filter and blue-green filter.  JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace & Technologies Corporation and is operated by the University of Arizona. ω.

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Mawrth Vallis Martian Mosaic

Image Released on 26.09.2016 12:30: Image: ESA:DLR:FU Berlin, CC BY-SA 3.0 IGO

|| September 26: 2016 || ά. Sculpted by ancient water flowing on the surface, Mawrth Vallis is one of the most remarkable outflow channels on Mars. The valley, once a potentially habitable place, is one of the main features of a region at the boundary between the southern highlands and the northern lowlands.

Mawrth Vallis takes centre stage in this image, a bird’s eye view of a 330 000 sq km area surrounding the valley. With a length of 600 km and a depth of up to two km, it is one of the biggest valleys on Mars. Huge amounts of water once passed through it, from a higher elevation region, part of which is shown in the lower right of the image, into the northern plains, in the top left.

Among the remarkable features are the large exposures of light-toned phyllosilicates, weathered clay minerals, that lie along its course. Phyllosilicates on Mars are evidence of the past presence of liquid water and point to the possibility that habitable environments could have existed on the planet up until 03.6 billion years ago.

A dark cap rock, remains of ancient volcanic ash, covers many of the clays and could have protected traces of ancient microbes in the rocks from radiation and erosion. This makes Mawrth Vallis one of the most interesting regions for geologists and astrobiologists alike. It is one of the candidate landing sites for ExoMars 2020, a joint mission between ESA and Russia, with the primary goal of finding out if life once existed on Mars.

The name comes from the Welsh word for Mars, “Mawrth” and the Latin for valley, “Vallis”. This mosaic was created using nine individual images taken by the high-resolution stereo camera on ESA’s Mars Express spacecraft, which has been orbiting Mars since late 2003. It is one of a set of images of this region previously published on July 07, 2016 on the DLR website and the homepage of the Freie Universität Berlin. ω.

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The Cloud Impossible on Titan: Again

Image: NASA

|| September 24: 2016: Elizabeth Zubritsky Writing || ά. The puzzling appearance of an ice cloud seemingly out of thin air has prompted NASA scientists to suggest that a different process than previously thought, possibly similar to one seen over Earth's poles, could be forming clouds on Saturn's moon Titan. Located in Titan's stratosphere, the cloud is made of a compound of carbon and nitrogen known as dicyanoacetylene:C4N2, an ingredient in the chemical cocktail that colours the giant moon's hazy, brownish-orange atmosphere.

Decades ago, the infrared instrument on NASA's Voyager One spacecraft spotted an ice cloud just like this one on Titan. What has puzzled scientists ever since is this: they detected less than one percent of the dicyanoacetylene gas needed for the cloud to condense. Recent observations from NASA's Cassini mission yielded a similar result. Using Cassini's composite infrared spectrometer,  or CIRS, which can identify the spectral fingerprints of individual chemicals in the atmospheric brew, researchers found a large high-altitude cloud made of the same frozen chemical. Yet, just as Voyager found, when it comes to the vapour form of this chemical, CIRS reported that Titan's stratosphere is as dry as a desert.

"The appearance of this ice cloud goes against everything we know about the way clouds form on Titan," said Carrie Anderson, a CIRS co-investigator at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study. The typical process for forming clouds involves condensation. On Earth, we're familiar with the cycle of evaporation and condensation of water. The same kind of cycle takes place in Titan's troposphere -- the weather-forming layer of Titan's atmosphere, but with methane instead of water.

A different condensation process takes place in the stratosphere,  the region above the troposphere, at Titan's north and south winter poles. In this case, layers of clouds condense as the global circulation pattern forces warm gases downward at the pole. The gases then condense as they sink through cooler and cooler layers of the polar stratosphere. Either way, a cloud forms when the air temperature and pressure are favorable for the vapor to condense into ice. The vapor and the ice reach a balance point, an equilibrium, that is determined by the air temperature and pressure. Because of this equilibrium, scientists can calculate the amount of vapor where ice is present.

"For clouds that condense, this equilibrium is mandatory, like the law of gravity," said Robert Samuelson, an emeritus scientist at Goddard and a co-author of the paper. But the numbers don't compute for the cloud made from dicyanoacetylene. The scientists determined that they would need at least 100 times more vapor to form an ice cloud where the cloud top was observed by Cassini's CIRS.

One explanation suggested early on was that the vapor might be present, but Voyager's instrument wasn't sensitive enough in the critical wavelength range needed to detect it. But when CIRS also didn't find the vapor, Anderson and her Goddard and Caltech colleagues proposed an altogether different explanation. Instead of the cloud forming by condensation, they think the C4N2 ice forms because of reactions taking place on other kinds of ice particles. The researchers call this "solid-state chemistry," because the reactions involve the ice, or solid, form of the chemical.

The first step in the proposed process is the formation of ice particles made from the related chemical cyanoacetylene:HC3N. As these tiny bits of ice move downward through Titan's stratosphere, they get coated by hydrogen cyanide:HCN. At this stage, the ice particle has a core and a shell comprised of two different chemicals. Occasionally, a photon of ultraviolet light tunnels into the frozen shell and triggers a series of chemical reactions in the ice. These reactions could begin either in the core or within the shell. Both pathways can yield dicyanoacteylene ice and hydrogen as products.

The researchers got the idea of solid-state chemistry from the formation of clouds involved in ozone depletion high above Earth's poles. Although Earth's stratosphere has scant moisture, wispy nacreous clouds, also called polar stratospheric clouds, can form under the right conditions. In these clouds, chlorine-bearing chemicals that have entered the atmosphere as pollution stick to crystals of water ice, resulting in chemical reactions that release ozone-destroying chlorine molecules.

"It's very exciting to think that we may have found examples of similar solid-state chemical processes on both Titan and Earth," said Anderson. The researchers suggest that, on Titan, the reactions occur inside the ice particles, sequestered from the atmosphere. In that case, dicyanoacetylene ice wouldn't make direct contact with the atmosphere, which would explain why the ice and the vapor forms are not in the expected equilibrium.

"The compositions of the polar stratospheres of Titan and Earth could not differ more," said Michael Flasar, CIRS principal investigator at Goddard. "It is amazing to see how well the underlying physics of both atmospheres has led to analogous cloud chemistry." The findings are published in the journal Geophysical Research Letters.

The Cassini-Huygens mission is a cooperative project of NASA, European Space Agency:ESA and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter. The CIRS instrument was built by Goddard.

For more information about Cassini

Media Contact: Preston Dyches: Jet Propulsion Laboratory, Pasadena, Calif. 818-354-7013: preston.dyches at jpl.nasa.gov

:Editor: Karl Hille:NASA:ω.

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