Marsbugs: The Electronic Astrobiology NewsletterVolume 12, Number 12, 7 April 2005

Editor/Publisher: David J. Thomas, Ph.D., Science Division, Lyon College, Batesville, Arkansas 72503-2317, USA. dthomas@lyon.edu

Marsbugs is published on a weekly to monthly basis as warranted by the number of articles and announcements. Copyright of this compilation exists with the editor, but individual authors retain the copyright of specific articles. Opinions expressed in this newsletter are those of the authors, and are not necessarily endorsed by the editor or by Lyon College. E-mail subscriptions are free, and may be obtained by contacting the editor. Information concerning the scope of this newsletter, subscription formats and availability of back-issues is available at http://www.lyon.edu/projects/marsbugs. The editor does not condone "spamming" of subscribers. Readers would appreciate it if others would not send unsolicited e-mail using the Marsbugs mailing lists. Persons who have information that may be of interest to subscribers of Marsbugs should send that information to the editor.

Articles and News

Page 1 HELP WANTED: SPACE COLONISTS NEED TO BE MORE THAN ASTRONAUTS By G. B. Leatherwood

Page 1 CENSORING SCIENCE: IMAX AND EVOLUTIONBy Edna DeVore

Page 1 FIVE OUT OF FIVE RESEARCHERS AGREE: EARTH'S SOLAR SYSTEM SPECIALBy Sara Goudarzi

Page 2 FIRST CONFIRMED PICTURE OF A PLANET BEYOND THE SOLAR SYSTEMBy Robert Roy Britt

Page 2 CHEMICAL GUIDEBOOK MAY HELP MARS ROVER TRACK EXTRATERRESTRIAL LIFEBy Regina Nuzzo

Page 3 "EARTHS" GALORE AWAIT DISCOVERYRoyal Astronomical Society release

Page 4 LEGO BIOLOGYBy Chris McKay

Page 4 EXPLOSIONS IN SPACE MAY HAVE INITIATED ANCIENT EXTINCTION ON EARTHNASA release 05-094

Announcements

Page 6 ASTROBIOLOGY RESEARCHERS MEET TO SHARE NEW FINDINGSNASA/ARC advisory 05-20AR

Page 6 APRIL 15TH MANUSCRIPT DEADLINE FOR EARLY MARS SPECIAL SECTION OF JGR PLANETS Lunar and Planetary Institute release

Mission Reports

Page 7 CASSINI UPDATESNASA/JPL releases

Page 9 DURABLE MARS ROVERS SENT INTO THIRD OVERTIME PERIODNASA/JPL release 2005-055

Page 10 MARS GLOBAL SURVEYOR IMAGESNASA/JPL/MSSS release

Page 10 MARS ODYSSEY THEMIS IMAGESNASA/JPL/ASU release

HELP WANTED: SPACE COLONISTS NEED TO BE MORE THAN ASTRONAUTS By G. B. LeatherwoodFrom Ad Astra and Space.com30 March 2005

Had trouble finding an electrician, a carpenter, a bricklayer, or any one of a number of other skilled craftspeople for that little project you just can't handle yourself? Probably—we often read about the scarcity of those we used to call "trades people". (Well, we really used to call them "trades men," but that's neither proper nor accurate any more.) The trade unions were strong and had extensive apprentice programs so young people could learn the trade from the experts—people who usually had rough hands, sometimes used less than perfect grammar, but sure knew how to build and repair things. Their tools weren't computers and word processors, but they sure knew how to measure and cut, nail and solder, wire and paint. They knew about hammers and saws, pliers and wrenches, blowtorches and soldering irons. What's that got to do with space?

Read the full article at http://www.space.com/adastra/adastra_tradesmen_050330.html.

CENSORING SCIENCE: IMAX AND EVOLUTIONBy Edna DeVoreFrom Space.com31 March 2005

This week, I'm headed to Dallas, Texas, for the National Science Teachers Association national meeting. Science educators from across the nation meet each spring to share resources, lessons, meet publishers, and generally advance science teaching for the nation. As a part of the NSTA events, there's

an afternoon field trip to the Fort Worth Museum of Science and History. Teachers are promised a great experience. To quote the program, "Extraordinary Learning Environments at the Fort Worth Museum of Science and History: Spend a high-energy afternoon in the extraordinary learning environments at the Fort Worth Museum of Science and History. Tailor the afternoon to meet your own professional development interests and needs. Options include observing science learning with the youngest visitors in Museum School; visiting the stellar Noble Planetarium; experiencing the incredible Omni Theatre; exploring visual perception, force and motion, waves, and pendulums in Explorazone; and reliving the past in Kid Stuff: Great Toys from Our Childhood. You'll also want to visit the Museum's permanent exhibit collection. Pick up lots of teacher resource materials in the Center." Sounds great. But something is missing here. The IMAX theater won't be showing films that involve evolution.

Read the full article at http://www.space.com/searchforlife/seti_censorship_050331.html.

FIVE OUT OF FIVE RESEARCHERS AGREE: EARTH'S SOLAR SYSTEM SPECIALBy Sara GoudarziFrom Space.com31 March 2005

Though researchers find more and more distant planets revolving around alien suns, the discoveries highlight that Earth and its solar system may be an exceptionally rare place indeed. That was the consensus here Wednesday evening among five planetary science experts who spoke at the 5th annual Isaac Asimov Memorial Panel Debate held at the American Museum of Natural History.

Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 12, 7 April 2005

Neil DeGrasse Tyson, the Frederick P. Rose Director of the Hayden Planetarium, moderated the informal discussion. At issue was whether our solar system is special, why it looks the way it does, and how others thus far detected differ. The debate took place between theoretical and observational scientists on the different aspects of detecting and categorizing alien solar systems. About 700 people attended the event.

Read the full article at http://www.space.com/scienceastronomy/050331_asimov_debate.html.

FIRST CONFIRMED PICTURE OF A PLANET BEYOND THE SOLAR SYSTEMBy Robert Roy BrittFrom Space.com1 April 2005

After a few close calls, astronomers have finally obtained the first photograph of a planet beyond our solar system, SPACE.com has learned. And this time they say they're sure. Though some doubt lingers about the mass of the object. The planet is thought to be one to two times as massive as Jupiter, according to the scientists who imaged it. It orbits a star similar to a young version of our Sun. The star, GQ Lupi, has been observed by a team of European astronomers since 1999. They have made three images using the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in Chile. The Hubble Space Telescope and the Japanese Subaru Telescope each contributed an image, too. The work was led by Ralph Neuhaeuser of the Astrophysical Institute & University Observatory (AIU).

The young star GQ Lupi and its fainter planetary companion. Image credit: ESO/VLT.

Read the full article at http://www.space.com/scienceastronomy/050401_first_extrasolarplanet_pic.html.

CHEMICAL GUIDEBOOK MAY HELP MARS ROVER TRACK EXTRATERRESTRIAL LIFEBy Regina NuzzoIdaho National Laboratory release4 April 2005

To help a NASA rover eventually hunt for life on Mars, scientists are writing a chemical guidebook to aid the search for extraterrestrial life. Using new imaging tools and earthly parallels of ancient Mars environments, they're recording the types of subtle chemical changes that martian microbes may have left on the planet's rocks. The researchers hope someday to arm a Mars rover with a suite of tools—a guidebook, precise chemical imagers, and human-like reasoning ability—and let it search for signs of alien life on its own.

Postdoctoral research associate Dr. Beizhan Yan inserts a sample into the Laser and Optical Chemical Imager. Image credit: INL.

Scientists from the U.S. Department of Energy's Idaho National Laboratory, University of Idaho, and University of Montana are developing the chemical guidebook as part of what they hope will be a definitive method to determine whether extraterrestrial rocks have ever harbored life. The group, supported by a $900,000 grant from the NASA Astrobiology Program, will be using chemical imaging technology that was previously developed at the INL and awarded a patent in November 2004. The technology will be discussed during the 15th Annual Goldschmidt Conference, "A Voyage of Discovery," the premier annual meeting in geochemistry and mineralogy. The conference will be in Moscow, Idaho, May 20-25, and will mark the 50th anniversary of the Geochemical Society.

In 1996, a group of scientists reported they had found evidence of life on a martian meteorite. But the claims are still controversial, said Daphne Stoner, project leader and chemistry research professor at the University of Idaho in Idaho Falls. The debates highlight the need for clear methods that will distinguish so-called "biosignatures" from look-alike signs of life.

"This project will help build a good gold standard for the unequivocal determination of life on extraterrestrial materials," Stoner said.

Stoner is collaborating with chemist Jill Scott at INL, geologist Nancy Hinman at University of Montana in Missoula, post-doctoral geochemist Beizhan Yan at the University of Idaho, and geology graduate student J. Michelle Kotler at the University of Montana. The team is using a specialized mass spectrometer to take chemical images of microbes and rocks under conditions close to what might be found on Mars, as well as developing a fuzzy logic computer program to decipher those spectral pictures. The researchers will take advantage of local exotic microbes to test the system's ability to identify signs of microbial life in minerals here on Earth.

The key to finding signs of unfamiliar life is recognizing that all organisms must change their environment somehow as they breathe and eat, Scott said, even if they don't breathe or eat the same chemicals that we're used to.

Stoner compares the idea to how even careful humans will still leave behind traces of their presence when camping. "You can notice a backcountry campsite," Stoner said. "It looks different from the forest around it."

So the researchers want to scour martian rocks in search of the unexpected. With luck, they'll stumble across the remnants of a microbe. If not, they could still glean useful information from surprises in the rock's composition.

"We can ask, 'Is there something extra there, something not common? Or is there something that's missing—some minerals leached away?'" Stoner explained.

Some chemical changes, for instance, would arise as organisms use raw material in their environment for food and deposit other chemicals as waste. These clues may remain even after the organism itself has moved on or died and decayed beyond detection, Stoner said. The researchers expect these environmental anomalies to show up in detailed chemical images, called spectra, taken from samples of the planet's rocky surface.

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Recent discoveries indicate significant amounts of water might still exist beneath the barren surface of Mars—an intriguing prospect for scientists seeking to determine if life forms once existed—or still exist—on the red planet. Image credit: NASA.

Before scientists teach a rover to analyze these clues on Mars, though, they need to train it on easier things on Earth, Hinman said. First, the team will work in the lab with basic biomolecules, such as amino acids or DNA fragments, sprayed onto a background of minerals commonly found on Mars, such as iron-rich basalt. Then the researchers will move on to living microbes and see how they might affect various rocky environments, Scott said.

Lastly, the team will leave the lab and train their system, using exotic microbes found on Earth called extremophiles. These bacteria thrive in extreme environments such as high-heat, low-oxygen geothermal pools. Because they rely on sulfur and iron for energy sources—rather than the plant-based food that humans prefer—extremophiles are good examples of the type of adaptable microbes that might survive on Mars.

Two sophisticated research tools will aid in building the chemical guidebook. The recently-patented Laser and Optical Chemical Imager (LOCI) combines a laser positioning system with a device known as a Fourier-transform mass spectrometer. The LOCI's laser can blast a rock's surface and lift off a very thin top layer of material as a small gas cloud. Sensors then create spectral images of the cloud, and scientists can decide what the surface layers were made of—minerals such as iron, say, with a sprinkling of microbial waste products.

A LOCI-type instrument would be well suited for the sorts of tricky situations Mars is likely to pose, Scott said. For instance, it could do tests on the spot, freeing the rover up to haul less cargo back to Earth. "Rock samples from Mars are going to be precious," Scott said. "We want to bring back the ones with the best chance of showing signs of life."

To help make these decisions, a fuzzy logic computer program called the Spectral IDentification Inference Engine (SIDIE) would supply the Mars rover with some extra brains. The SIDIE, developed at the INL, uses an open-ended reasoning approach that mimics a human's decision-making abilities and learning. "Fuzzy logic is a very powerful technique," Scott said.

The program can analyze spectral images very quickly, report the level of uncertainty in its conclusions, build on information from neighboring rocks, and even learn from past experiences—all of which will speed along the human analyst's job.

"The other nice thing is that it's easy for a user to understand the decision-making process," Scott said.

Read the original news release at http://www.inl.gov/featurestories/2005-04-04.shtml.

An additional article on this subject is available at http://www.spacedaily.com/news/mars-life-05g.html.

"EARTHS" GALORE AWAIT DISCOVERYRoyal Astronomical Society release5 April 2005

How many planets like the Earth are there among the 130 or so known planetary systems beyond our own? How many of these "Earths" could be habitable? Recent theoretical work by Barrie Jones, Nick Sleep, and David Underwood at the Open University in Milton Keynes indicates that as many as half of the known systems could be harboring habitable "Earths" today. Unfortunately, existing telescopes are not powerful enough to see these relatively small, distant "Earths". Orbiting close to a much brighter star, these very faint worlds resemble glow-worms hidden in the glare of a searchlight.

All of the planets that have been detected so far are giants the mass of Neptune or larger. Even so, they cannot be directly seen with ground-based instruments. Almost all of the known exoplanets have been found through the "wobbling" motion they induce in their star as they orbit it, like a twirling dumb-bell in which the mass at one end (the star) is much greater than the mass at the other end (the giant planet).

An artist's conception of an Earth-like exoplanet. Image credit: Julian Baum, Take 27, Ltd.

Speaking today at the RAS National Astronomy Meeting in Birmingham, Professor Jones explained how his team used computer models to see if "Earths" could be present in any of the currently known exoplanetary systems, and whether the gravitational buffeting from one or more giant planets in those systems would have torn them out of their orbits.

"We were particularly interested in the possible survival of 'Earths' in the habitable zone," said Professor Jones. "This is often called the 'Goldilocks zone', where the temperature of an 'Earth' is just right for water to be liquid at its surface. If liquid water can exist, so could life as we know it."

The Open University team created a mathematical model of a known exoplanetary system, with its star and giant planet(s), then launched an Earth-sized planet at some distance from the star to see if it survived. By detailed study of a few representative exoplanetary systems, they found that each giant planet is accompanied by two 'disaster zones' - one exterior to the giant, and one interior. Within these zones, the giant's gravity will cause a catastrophic change in the Earth-like planet's orbit. The dramatic outcome is a collision with either the giant planet or the star, or ejection into the cold outer reaches of the system.

The team found that the locations of these disaster zones depend not only on the mass of the giant planet (a well known result) but also on the eccentricity of its orbit. They thus established rules for determining the extent of the disaster zone. Having found the rules, they applied them to all of the known exoplanetary systems—a much quicker method than studying each system in detail. The range of distances from the star covered by its habitable zone was

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compared to the locations of the disaster zones to see if there was a full or partial safe haven for an Earth-like planet.

They discovered that about half of the known exoplanetary systems offer a safe haven for a period extending from the present into the past that is at least long enough for life to have developed on any such planets. This assumes that "Earths" could have formed in the first place, which seems quite likely. However, the situation is complicated by the fact that the habitable zone migrates outwards as the star ages, and in some cases this changes the potential for life to evolve. Thus, in some cases a safe haven might have been available only in the past, while in other cases it might exist only in the future. These scenarios of past extinction and future birth increase to about two-thirds the proportion of the known exoplanetary systems that are potentially habitable at some time during the main-sequence lifetime of their central star.

Additional information A paper by Barrie W. Jones, David R. Underwood, and P. Nick Sleep, entitled "Prospects for habitable 'Earths'", is scheduled to appear in the 1 April 2005 issue of the Astrophysical Journal.  Artist's impression of an Earth-like planet, courtesy of Julian Baum/Take 27 Ltd., https://physics.open.ac.uk/graphics/Exo_Earth+caption.jpg Exoplanetary systemshttp://www.obspm.fr/encycl/encycl.html Contact:Professor Barrie JonesOpen UniversityMilton KeynesPhone: +44 (0)1908-653229Mobile: +44 (0)7740-871273E-mail: b.w.jones@open.ac.uk

Read the original news release at http://www.ras.org.uk/html/press/pn0510ras.html.

Additional articles on this subject are available at:http://www.astrobio.net/news/article1511.htmlhttp://www.space.com/scienceastronomy/050405_earth_like.htmlhttp://www.spacedaily.com/news/extrasolar-05p.htmlhttp://spaceflightnow.com/news/n0504/04planets/http://www.universetoday.com/am/publish/how_many_habitable_planets.html

LEGO BIOLOGYBy Chris McKayFrom Astrobiology Magazine6 April 2005

Chris McKay, a planetary scientist at the Ames Research Center, has long been investigating the coldest and driest places on Earth. These harsh environments—and the ability of life to adapt there—could point the way to finding life on Mars. McKay presented this lecture, entitled "Drilling in Permafrost on Mars to Search for a Second Genesis of Life," at a NASA Astrobiology Institute Director's Seminar on November 29, 2004.

In this part of his lecture, McKay defines one of the most interesting topics to astrobiology: how would one know an organic relic when it appears?

The martian surface as imaged by one of the Viking landers. Image credit: NASA.

How would we decide if any relic organics were ever alive? We know the solar system is full of organic material—lots of gooey brown stuff—but it was never alive. If it is like us, we can put it in a PCR and amplify the DNA. But

if it is alien, we may not be able to detect DNA. Here we need some standard methods to detect alien life. The first standard method is to use a tricorder, of course. The second method is just, "We'll know it when we see it." Neither of these is going to work very well. We don't have any tricorders, obviously, and we don't have any guesses as to how one might work.

Clouds and frost cover on the north martian pole from Mars Orbital Camera. Image credit: NASA/ JPL/MSSS.

I have a suggestion, which I call the LEGO principle. Biology is built from a small number of components, just like LEGOS. Biology is going to pick a few common building blocks—some amino acids, sugars, etc.—but not the whole spectrum of available biomolecules. Different life forms could have a different LEGO kits. As a kid, I used Lincoln Logs. You could build anything that you could with LEGOS, but you couldn't mix the two kits. They won't work together, but they can each be used to build equivalent construction projects.

Will alien life be that different? At the very least, when we go to Mars, we're not going to be surprised if life depends on carbon and water. At a higher level, we are also okay. Darwinian evolution is going to apply. Big fish are going to eat little fish. There will be photosynthetic organisms capable of using sunlight. So at the ecological level, life will be similar. At the chemical level, it will be similar. These will converge. It is the middle level, the level of the biomolecules, where life might be different. At DNA, at ATP, etc., it might diverge.

Left: Mars polar water-ice and frozen carbon dioxide. Image credit: GSFC/NASA. Right: Concept artwork shows the Active Thermal Probe (Mars Cryobot) melting down through the northern ice cap on Mars. Image credit: NASA JPL.

To test the LEGO principle, we plot distributions of the types of molecules. If non-organic, for instance, we will see equal mixtures of right- and left-handed biomolecules. But if the distribution is biological, it will be unusual. It will be a series of delta-functions, spikes of right- and left-handed molecular types. So in principle, if we could get a complete molecular picture from the subsurface, we should be able to see this biological signature. Even if martian life is different from Earth's, it still may have a biological distribution.

We may not know now how to do this analysis, but if you had a sample in the lab, you would probably do a gas chromatography/mass spectrometer study. It is not entirely satisfactory, because GCMS is destructive. Think of it as characterizing a building by blowing it up, rather than going into it. What you would rather do is not just see structures, but also functions.

Read the original article at http://www.astrobio.net/news/article1513.html.

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EXPLOSIONS IN SPACE MAY HAVE INITIATED ANCIENT EXTINCTION ON EARTHNASA release 05-0946 April 2005

Scientists at NASA and the University of Kansas say that a mass extinction on Earth hundreds of millions of years ago could have been triggered by a star explosion called a gamma-ray burst. The scientists do not have direct evidence that such a burst activated the ancient extinction. The strength of their work is their atmospheric modeling—essentially a "what if" scenario. The scientists calculated that gamma-ray radiation from a relatively nearby star explosion, hitting the Earth for only ten seconds, could deplete up to half of the atmosphere's protective ozone layer. Recovery could take at least five years. With the ozone layer damaged, ultraviolet radiation from the Sun could kill much of the life on land and near the surface of oceans and lakes, and disrupt the food chain.

Scientists say that a ten-second burst of gamma rays from a massive star explosion within 6,000 light years from Earth could have triggered a mass extinction hundreds of millions of years ago. In this artist's conception we see the gamma rays hitting the Earth's atmosphere. (The expanding shell is pictured as blue, but gamma rays are actually invisible.) The gamma rays initiate changes in the atmosphere that deplete ozone and create a brown smog of NO2. With the ozone layer damaged for up to five years, harmful ultraviolet radiation from the Sun would kill smaller life-forms and disrupt the food chain. Scientists say that a gamma-ray burst might have caused the Ordovician extinction 450 million years ago, some 200 million years before dinosaurs. Image credit: NASA.

Gamma-ray bursts in our Milky Way galaxy are indeed rare, but the scientists estimate that at least one nearby likely hit the Earth in the past billion years. Life on Earth is thought to have appeared at least 3.5 billion years ago. This research, supported by a NASA astrobiology grant, represents a thorough analysis of the "mass extinction" hypothesis first announced by members of this science team in September 2003.

Gamma-ray bursts are the most powerful explosions known in the Universe, and most originate in distant galaxies. A large percentage of bursts likely arise from the explosion of stars over 15 times more massive than our Sun. Scientists say burst from a nearby star could cause severe damage to the Earth’s protective ozone layer. In this artists conception we see the gamma rays hitting the Earth's atmosphere. (The expanding shell is pictured as blue, but gamma rays are actually invisible.) Image credit: NASA.

"A gamma-ray burst originating within 6,000 light years from Earth would have a devastating effect on life," said Dr. Adrian Melott of the Department of Physics and Astronomy at the University of Kansas, Lawrence. "We don't know exactly when one came, but we're rather sure it did come—and left its mark. What's most surprising is that just a 10-second burst can cause years of devastating ozone damage," Melott added.

A scientific paper describing this finding appears in Astrophysical Journal Letters. The lead author is Brian Thomas, a Ph.D. candidate at University of Kansas.

This simulation depicts the regions of the planet most susceptible to DNA damage (shown in red) if a large gamma ray burst were to occur close to Earth. Though there is no direct evidence, scientists say a nearby gamma-ray burst may have caused the great extinction of the late Ordovician period 450 million years ago, which killed 60 percent of all marine invertebrates. Image credit: NASA/U. of Kansas.

Gamma-ray bursts are the most powerful explosions known. Most originate in distant galaxies, and a large percentage likely arise from explosions of stars over 15 times more massive than our Sun. A burst creates two oppositely-directed beams of gamma rays that race off into space. Thomas says that a gamma-ray burst may have caused the Ordovician extinction 450 million years ago, killing 60 percent of all marine invertebrates. Life was largely confined to the sea, although there is evidence of primitive land plants during this period.

In the new work, the team used detailed computer models to calculate the effects of a nearby gamma-ray burst on the atmosphere and the consequences

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for life. Thomas, with Dr. Charles Jackman of NASA's Goddard Space Flight Center in Greenbelt, MD, calculated the effect of a nearby gamma-ray burst on the Earth's atmosphere. Gamma- rays, a high-energy form of light, can break molecular nitrogen (N2) into nitrogen atoms, which react with molecular oxygen (O2) to form nitric oxide (NO). NO will destroy ozone (O3) and produce nitrogen dioxide (NO2). NO2 will then react with atomic oxygen to reform NO. More NO means more ozone destruction. Computer models show that up to half the ozone layer is destroyed within weeks. Five years on, at least 10 percent is still destroyed.

Next, researchers calculated the effect of ultraviolet radiation on life. Deep-sea creatures living several feet below water would be protected. Surface-dwelling plankton and other life near the surface, however, would not survive. Plankton is the foundation of the marine food chain.

Dr. Bruce Lieberman, a paleontologist at the University of Kansas, originated the idea that a gamma-ray burst specifically could have caused the great Ordovician extinction, 200 million years before the dinosaurs. An ice age is thought to have caused this extinction. However, gamma-ray burst could have caused a fast die-out early on and also could have triggered the significant drop in surface temperature on Earth.

"One unknown variable is the rate of local gamma-ray bursts," Thomas said. "The bursts we detect today originated far away billions of years ago, before the Earth formed. Among the billions of stars in our Galaxy, there's a good chance that a massive one relatively nearby exploded and sent gamma rays our way," he added.

Swift is a first-of-its-kind multi-wavelength observatory dedicated to the study of gamma ray burst (GRB) science. Its three instruments will work together to observe GRBs and afterglows in the gamma ray, X-ray, ultraviolet, and optical wavebands. Swift is designed to solve the 35-year-old mystery of the origin of gamma-ray bursts. Scientists believe GRB are the birth cries of black holes. Image credit: NASA.

The Swift mission, launched in November 2004, will help determine recent burst rates.

For images, movies, and more information via the Internet, visit http://www.nasa.gov/vision/universe/starsgalaxies/gammaray_extinction.html.

Journal reference:B. C. Thomas et al., 2005. Terrestrial ozone depletion due to a Milky Way gamma-ray burst. Astrophysical Journal Letters, 622(2):L153-156. http://www.journals.uchicago.edu/ApJ/journal/issues/ApJL/v622n2/19056/brief/19056.abstract.html

Contacts:Dolores Beasley/Gretchen Cook-AndersonNASA Headquarters, Washington, DCPhone: 202-358-1753/0836

Susan HendrixNASA Goddard Space Flight Center, Greenbelt, MDPhone: 301-286-7745

ASTROBIOLOGY RESEARCHERS MEET TO SHARE NEW FINDINGSNASA/ARC advisory 05-20AR31 March 2005

News media representatives are invited to hear NASA scientists discuss key aspects of astrobiology research and technology development for the study of the origins, evolution and distribution of life in the universe. The NASA Astrobiology Institute (NAI) will hold its biennial meeting April 10-14, 2005, at the Millennium Harvest House Hotel, Boulder, CO. During the meeting, the members of NAI and its five international partners will participate in presentations, poster sessions, focus group discussions and informal meetings.

"Every two years, the institute meets as a community, and it is always an exciting event. Leading scientists in many different disciplines come together to strengthen existing collaborations and forge new partnerships," said NAI Deputy Director Dr. Rosalind Grymes. "NAI members are focused on more than facts and findings. We are interested in understanding our work in context. That context includes the formation of stars and their planetary systems, life's emergence on habitable worlds, and our own abilities to question, seek and reason about our origins, evolution and future," she said.

"Astrobiology is an integral part of the Vision for Space Exploration. The results and directions discussed at this meeting will influence NASA's future approaches to Earth and space sciences," explained NAI Director Dr. Bruce Runnegar.

The meeting will be hosted by the University of Colorado at Boulder (CU). No prior registration or admission is required by the news media. Reporters should follow the signs at the entrance to a press check-in point to obtain a press badge. If interested in scheduling an interview in advance, please contact Emily CoBabe-Ammann of the CU Education and Public Outreach at ecobabe@lasp.colorado.edu.

For more information about astrobiology research and NAI's meeting, visit http://nai.nasa.gov/nai2005/.

Contact:Victoria Steiner NASA Ames Research Center, Moffett Field, CAPhone: 650-604-0176E-mail: Victoria.L.Steiner@nasa.gov

APRIL 15TH MANUSCRIPT DEADLINE FOR EARLY MARS SPECIAL SECTION OF JGR PLANETS Lunar and Planetary Institute release4 April 2005

This is a final reminder that manuscripts for the JGR-Planets Special Section on "Early Mars: Geologic, Hydrologic, and Climatic Evolution and the Implications for Life" are due Friday, April 15, 2005 at 5:00 PM EST. Manuscripts submitted after this date will only be considered for inclusion in the special issue if, during the review process, they are able to catch up with the papers that were submitted by the April 15th deadline.

Submitted manuscripts should have a substantial Early Mars focus, but may also address terrestrial analogs and processes where there is a clear and demonstrated relevance to Mars. Papers may address any relevant aspect of Early Mars research, including: physical & chemical properties, geology, hydrology, climate, and life. Papers must be of a scientific (i.e., involving data analysis, or the presentation of new theories and interpretations, etc.), rather than engineering nature. JGR-Planets generally does not publish papers describing instrument designs or concepts, or any paper that might be seen as advocating a particular mission that is not yet approved. Where a question exists regarding the potential acceptability of a topic, authors should contact the editor.

All manuscripts will go through the standard review process, and there is no guarantee that a given manuscript will be accepted for publication. Cover letters should reference the 2nd Early Mars Conference special section. Please feel free to suggest possible reviewers for your paper. All manuscript submittal information can be found at http://www.agu.org/journals/je/.

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CASSINI UPDATESNASA/JPL releases

Cassini Significant Events for 24-30 March 2005NASA/JPL release, 1 April 2005

The most recent spacecraft telemetry was acquired today from the Goldstonetracking station. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm.

Science activities this week continued with the acquisition of Ultraviolet Imaging Spectrograph mosaics of Saturn's inner magnetosphere, Imaging Science Subsystem (ISS) observations of Iapetus limb topography and geodesy, and a magnetospheric boundary campaign performed by the Magnetospheric and Plasma Science instruments.

Saturn's small, irregularly-shaped moon Epimetheus orbits against the backdrop of the planet's rings, which are nearly edge-on in this view. Some of the moon's larger geological features can be seen here. Epimetheus is 116 kilometers (72 miles) across. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on February 18, 2005, at a distance of approximately 990,000 kilometers (615,000 miles) from Epimetheus and at a Sun-Epimetheus-spacecraft, or phase, angle of 99 degrees. Resolution in the original image was 6 kilometers (4 miles) per pixel. The image has been contrast-enhanced and magnified by a factor of two to aid visibility. Image credit: NASA/JPL/Space Science Institute.

Thursday, March 24:

Ion and Neutral Mass Spectrometer flight software normalization was performed last week on the Solid State Recorder (SSR). The SSR has room for two different versions of flight software for each instrument, as well as for

the software for the engineering computers. Normalization means that both versions are equivalent. This is actually the first time in flight that all instrument and engineering flight software copies are equivalent.

Last week, a Conference on Quality in the Space and Defense Industries (CQSDI) featured a session on mission success at JPL, and how mission operations assurance contributes to project reliability.  The talk beganwith a short session illustrating success highlights from 2004 and followed with a 90-minute panel breakout presentation on Cassini. The presentation illustrated the Cassini mission operations assurance process and described how the Cassini flight team prepared for the critical mission events last year of Saturn orbit insertion and the Huygens Probe release and relay. Results from the Huygens mission were also shared along with lessons learned. Attendees were encouraged to learn from the Cassini-Huygens experiences with respect to integrating mission operations assurance to increase reliability.

Systems Engineering gave a presentation on the Radio Science Subsystem (RSS) Inertial Vector Definition (IVD) process at today's Cassini Design Team meeting. Instrument Operations delivered version 2 of the Spacecraft, Planet, Instruments, C-matrix, and Events Kernel Generation Program, along with required documentation.

At a Program Change Control Board meeting it was decided to defer thedelivery of Mission Sequence Subsystem version D11 for about two weeks from the current date of May 25 to allow for another re-delivery of the Inertial Vector Propagator (IVP) tool to fix an error that impacts RSSIVDfunctionality. The first operational use of D11 was identified as S14Science and Sequence Update Process, which begins on June 20, so the delayhas no impact on operations use of the software.

Friday, March 25:

An image related to Huygens's discovery of Luna Saturni (Titan) was Astronomy Picture of the Day today.

The Tethys Tweak Assessment/Approval Meeting was held today. This is arather complex issue with multiple options. Before a decision could bemade, more information was deemed useful for deciding on the possiblescience trades affecting data collection for both Tethys and Saturn. Astime was still available before a final decision must be made, ProjectManagement agreed to wait until next Tuesday's Mission Planning Forum toenable the team to continue studying options.

Pandora is seen in this dramatic view, orbiting just beyond the outer edge of Saturn's F ring. Several bright areas are visible within the F ring. In the main rings, the Keeler gap and the Encke gap, with a bright ringlet, are also visible. Pandora is 84 kilometers (52 miles) across. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on February 18, 2005, at a distance of approximately 1.2 million kilometers (746,000 miles) from Pandora and at a Sun-Pandora-spacecraft, or phase, angle of 108 degrees. The image scale is 7 kilometers (4 miles) per pixel. Image credit: NASA/JPL/Space Science Institute.

Sequence Development continues for S11. The Preliminary Sequence Integration and Validation 1 cycle one initial merged sequence products were

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published to the project file repository and are now available for review.Today Navigation delivered the final orbit determination solution for Orbit Trim Maneuver (OTM) #19. After that, evaluation files were published, reviewed, and cancellation of the Easter weekend maneuver was approved. Just a few short weeks ago on March 5, OTM #16 was cancelled. The Significant Events report for that week discusses why cancellation iscarefully considered, and last week's report goes into some detail on theprocess for cancellation.

Monday, March 28:

Official port 2 occurred today for the S12 Science Planning update process. The team sequence files were merged and delivered to ACS for end-to-end pointing validation.

Tuesday, March 29:

A Cassini image of the crescents of Titan and Dione was Astronomy Picture of the Day today. Events today included an Enceladus non-targeted flyby, Saturn periapsis, main engine cover close, a ring plane crossing, and a Cosmic Dust Analyzer (CDA) rocking downlink activity.

Downlinked data was lost over Madrid's station DSS-63 today when stationtransmitter problems occurred. CDA reported a loss of considerable data for the rocking downlink activity on day of year 88. They did succeed, however, in partially reconstructing the impact rate based on the impact counters transmitted via housekeeping data.

At the Mission Planning Forum, the decision was made to proceed with thetrajectory adjustment that will reduce the non-targeted Tethys flybyaltitude from about 32,000 km to 1500 km, and to reduce the targetedHyperion altitude from 1000 km to 500 km. There were pros and cons for thescience that could be obtained with and without the change, but theconsensus was that there was an overall improvement with the change. Thecost for making the change is around 7 to 8 m/sec.

The Multi-Mission Image Processing Laboratory converted operations toversion D33 software. This date was picked to minimize the impact uponoptical navigation deliveries and scheduled processing requests. Theswitch-over involved bringing down the automated processes, making database updates, changing pointers to the new D33 software set and restarting the processes. The transition was successful and went very smoothly.

Wednesday March 30:

Though much farther away from Cassini when the spacecraft acquired this image, Saturn's second-largest moon Rhea still dwarfs the brightest icy moon Enceladus in this scene. Rhea is 1,528 kilometers (949 miles) across. Enceladus is 505 kilometers (314 miles) across. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on February 21, 2005, at a distance of approximately 2 million kilometers (1.3 million miles) from Enceladus and 2.5 million kilometers (1.6 million miles) from Rhea. The image scale is 12 kilometers (7 miles) per pixel on Enceladus, and 15 kilometers (9 miles) per pixel on Rhea. Image credit: NASA/JPL/ Space Science Institute.

A Planetary Data System (PDS) peer review was held for a sample ISS teamarchive volume. No major liens were identified. The ISS team's goal was to produce a usable, well-documented data set. They met that goal extremely

well. PDS is currently organizing a review for a recently received CDA peer review volume.

Today's on-board activities included RSS Titan gravity science, a Radio and Plasma Wave Science high frequency receiver calibration, and a reaction wheel biasing activity.

A Software Requirements and Certification Review for CDA flight software (FSW) version 10.0.0 was held today. The FSW was approved pending support documentation modifications. The new software will be uplinked to the spacecraft and a checkout performed in May of this year. The purpose ofthis delivery was to implement updated parameters and algorithms foron-board data processing and data evaluation based on results of the earlyinner-Saturnian measurements. This will calibrate the instrument based onto-date results, allowing for enhanced science return. Cassini Mission Status ReportNASA/JPL release 2005-056, 6 April 2005

Although the Huygens probe has now pierced the murky skies of Titan and landed on its surface, much of the moon remains for the Cassini spacecraft to explore. Titan continues to present exciting puzzles. This view of Titan uncovers new territory not previously seen at this resolution by Cassini's cameras. The view is a composite of four nearly identical wide-angle camera images, all taken using a filter sensitive to wavelengths of infrared light centered at 939 nanometers. The individual images have been combined and contrast-enhanced in such a way as to sharpen surface features and enhance overall brightness variations. The images for this composite view were taken with the Cassini spacecraft on March 31, 2005, at distances ranging from approximately 146,000 to 130,000 kilometers (91,000 to 81,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of about 57 degrees. The image scale is 8 kilometers (5 miles) per pixel. Previous observations indicate that, due to Titan's thick, hazy atmosphere, the sizes of surface features that can be resolved are a few times larger than the actual pixel scale. Image credit: NASA/JPL/Space Science Institute.

NASA's Cassini spacecraft successfully flew by Saturn's moon Titan at a distance of 2,402 kilometers (1,493 miles) on Thursday, March 31. Cassini's multiple instruments are providing new views of the haze-enshrouded world. On this recent flyby, Titan's haze was the focus of ultraviolet observations. By mapping the haze, scientists hope to learn about particle size and properties. Titan's transient clouds were also studied during the flyby. Titan's northern hemisphere was previously imaged with Cassini's radar instrument in October 2004 and February 2005. This time, Cassini's optical cameras got

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their best view of the same area, as did the visual and infrared mapping spectrometer.

Titan is a prime target of the Cassini-Huygens mission because it is the only moon in our solar system with a thick, smoggy atmosphere. Cassini was launched over seven years ago and has traveled 3.55 billion kilometers (2.2 billion miles). All 12 of Cassini's instruments have been returning data, including tantalizing images. Recently, scientists noticed episodic interferences on the composite infrared spectrometer that were traced back to the time of orbit insertion. A mirror on the spectrometer is showing some signs of jitter. The movement may be associated with the use of the spacecraft reaction wheels, used for spacecraft pointing control. A motor on one of three sensors on the magnetospheric imaging instrument and another motor on the plasma spectrometer are also not working properly. However, a workaround has been identified for the latter. All three instruments continue to function, although with some reduced level of science data collection. "We are working to understand why the instruments are not performing properly but it is likely to be a few weeks before we have definitive answers," said Robert T. Mitchell, Cassini program manager at NASA's Jet Propulsion Laboratory, Pasadena, CA. "When running a mission for this long, you expect to have a few glitches. Cassini has been working remarkably well considering the duration and complexity of the mission." Cassini's next encounter is with Titan on April 16 at an altitude of 1,025 kilometers (637 miles). This will be Cassini's closest flyby of Titan yet. The latest images from this flyby are available at http://saturn.jpl.nasa.gov  and http://www.nasa.gov/cassini.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, DC. JPL designed, developed and assembled the Cassini orbiter.

Contact:Carolina Martinez Jet Propulsion Laboratory, Pasadena, CAPhone: 818-354-9382

Additional articles on this subject are available at:http://www.spacedaily.com/news/saturn-titan-05u.htmlhttp://spaceflightnow.com/cassini/050330prometheus.htmlhttp://spaceflightnow.com/cassini/050405titan.htmlhttp://www.universetoday.com/am/publish/ultraviolet_mimas.htmlhttp://www.universetoday.com/am/publish/ring_pandora.htmlhttp://www.universetoday.com/am/publish/cassini_titan_flyby_4.html

DURABLE MARS ROVERS SENT INTO THIRD OVERTIME PERIODNASA/JPL release 2005-0555 April 2005 NASA has approved up to 18 more months of operations for Spirit and Opportunity, the twin Mars rovers that have already surprised engineers and scientists by continuing active exploration for more than 14 months.

"The rovers have proven their value with major discoveries about ancient watery environments on Mars that might have harbored life," said Dr. Ghassem Asrar, deputy associate administrator for NASA's Science Mission Directorate. "We are extending their mission through September 2006 to take advantage of having such capable resources still healthy and in an excellent position to continue their adventures."

The rovers have already completed 11 months of extensions on top of their successful three-month prime missions. "We now have to make long-term plans for the vehicles because they may be around for quite a while," said Jim Erickson, rover project manager at NASA's Jet Propulsion Laboratory, Pasadena, CA.

Erickson cautioned though, "Either mission could end tomorrow with a random part failure. With the rovers already performing well beyond their original design lifetimes, having a part wear out and disable a rover is a distinct possibility at any time. But right now, both rovers are in amazingly

good shape. We're going to work them hard to get as much benefit from them as we can, for as long as they are capable of producing worthwhile science results."

"Spirit and Opportunity are approaching targets that a year ago seemed well out of reach," said Doug McCuistion, director of NASA's Mars Exploration Program. "Their successes strengthen NASA's commitment to a vision with the ambitious targets of returning samples from Mars and sending human explorers to Mars."

Opportunity is within a few football fields' length of a region called "Etched Terrain," where scientists hope to find rocks exposed by gentle wind erosion rather than by disruptive cratering impacts, and rocks from a different time in Mars' history than any examined so far. "This is a journey into the unknown, to something completely new," said Dr. Steve Squyres of Cornell University, Ithaca, NY, principal investigator for the rovers' science instruments. To reach the Etched Terrain, rover planners have been pushing the rover fast. Opportunity has overtaken Spirit in total distance driven. It has rolled more than 4.9 kilometers (3 miles)—eight times the original goal. On March 20, Opportunity also set a new martian record of 220 meters (722 feet) in a single day's drive. Drive-distance estimates can vary by a few percent. The long drives take advantage of crossing a plain so smooth it's "like an East Coast beach," said JPL's Jeff Favretto, mission manager on the Opportunity shift in recent weeks. Also, Opportunity's solar panels, though now dustier than Spirit's, still generate enough power to allow driving for more than three hours on some days. Spirit is in much rougher terrain than Opportunity, climbing a rocky slope toward the top of "Husband Hill." However, with a boost in power from wind cleaning its solar panels on March 9 and with its formerly balky right-front wheel now working normally, Spirit made some longer one-day drives last week than it had for months. "We've doubled our power," said JPL's Emily Eelkema, mission manager. "It has given us extra hours of operations every day, so we can drive longer and we've used more time for observations." The jump in power output has taken some urgency out of Spirit's southward climb. With Mars now beginning southern-hemisphere spring, the Sun is farther south in the sky each day. If not for panel-cleaning, Spirit might be facing the prospect of becoming critically short of power if still on the north-facing slope by early June.

As of the Mars Exploration Rover Opportunity's 413th martian day, or sol, (March 23, 2005), the robot had driven a total of 4.62 kilometers (2.87 miles) since landing. The rover has been making rapid progress southward since it finished examining its jettisoned heat shield on sol 357 (January 24, 2005, one year after landing). Scientists are eager for Opportunity to reach an area to the south called the "Etched Terrain," which appears mottled in the map's base images and might offer access to different layers of bedrock than what the rover has seen so far. This traverse map is overlaid on a mosaic of images from NASA's Mars Global Surveyor and Mars Odyssey orbiters and from Opportunity's descent camera. The scale bar at lower left is 2 kilometers (1.24 miles) long. Image credit: NASA/JPL/OSU/MSSS. "We still want to get to the summit of Husband Hill and then head down into the 'Inner Basin' on the other side," Squyres said. "But now we have more

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flexibility in how we carry out the plan. Before, it was climb or die." Cresting the hill is now not as crucial for solar energy, but it still offers allures of potential exposures of rock layers not yet examined, plus a vista of surrounding terrain. In orbital images, the Inner Basin farther south appears to have terracing that hints of layered rock.

Both rovers do have some signs of wear and exposure. Spirit's rock abrasion tool shows indications that its grinding teeth might be worn away after exposing the interiors of five times more rock targets than its design goal of three rocks. Researchers probably won't know the extent of wear until Spirit's next rock-grinding attempt, which may be weeks away. Also, troubleshooting continues for determining whether Opportunity's miniature thermal emission spectrometer is still usable despite tests indicating a problem last month. All other instruments on both rovers are still working normally. JPL, a division of the California Institute of Technology in Pasadena, has managed NASA's Mars Exploration Rover project since it began in 2000. Images and additional information about the rovers and their discoveries are available on the Internet at http://www.nasa.gov/vision/universe/solarsystem/mer_main.html and http://marsrovers.jpl.nasa.gov.

Contacts:Guy WebsterJet Propulsion Laboratory, Pasadena, CAPhone: 818-354-6278

Dolores BeasleyNASA Headquarters, Washington, DCPhone: 202-358-1753

Additional articles on this subject are available at:http://www.astrobio.net/news/article1512.htmlhttp://www.spacedaily.com/news/mars-mers-05zf.htmlhttp://www.spacedaily.com/news/mars-mers-05zg.htmlhttp://www.spacedaily.com/news/mars-mers-05zh.htmlhttp://spaceflightnow.com/news/n0504/05mera/http://www.universetoday.com/am/publish/rover_3rd_extension.html

MARS GLOBAL SURVEYOR IMAGESNASA/JPL/MSSS release24-30 March 2005

The following new images taken by the Mars Orbiter Camera (MOC) onthe Mars Global Surveyor spacecraft are now available.

Becquerel Dunes and Layers (Released 24 March 2005)http://www.msss.com/mars_images/moc/2005/03/24/

Chasma Boreale (Released 25 March 2005)http://www.msss.com/mars_images/moc/2005/03/25/

Herschel Dunes (Released 26 March 2005)http://www.msss.com/mars_images/moc/2005/03/26/

North Polar Layers (Released 27 March 2005)http://www.msss.com/mars_images/moc/2005/03/27/

Ejecta Boulders (Released 28 March 2005)http://www.msss.com/mars_images/moc/2005/03/28/

Mars at Ls 176 Degrees (Released 29 March 2005)http://www.msss.com/mars_images/moc/2005/03/29/

Dunes of the North (Released 30 March 2005)http://www.msss.com/mars_images/moc/2005/03/30/

All of the Mars Global Surveyor images are archived at http://www.msss.com/mars_images/moc/index.html.

Mars Global Surveyor was launched in November 1996 and has beenin Mars orbit since September 1997. It began its primary mapping mission on March 8, 1999. Mars Global Surveyor is the first mission in a long-term program of Mars exploration known as the Mars Surveyor Program that is managed by JPL for NASA's Office of Space Science, Washington, DC. Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

MARS ODYSSEY THEMIS IMAGESNASA/JPL/ASU release28 March - 1 April 2005

Valles Marineris Graben (Released 28 March 2005)http://themis.la.asu.edu/zoom-20050328a.html

Alba Patera Graben (Released 29 March 2005)http://themis.la.asu.edu/zoom-20050329a.html

Old and New Graben (Released 30 March 2005)http://themis.la.asu.edu/zoom-20050330a.html

Compounded Fractures (Released 31 March 2005) http://themis.la.asu.edu/zoom-20050331a.html

Relative Dating via Fractures (Released 1 April 2005)http://themis.la.asu.edu/zoom-20050401a.html

All of the THEMIS images are archived at http://themis.la.asu.edu/latest.html.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, DC. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

End Marsbugs, Volume 12, Number 12.

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