SOHO Has Seen 750 Comets

Image credit: ESA
On 22 March 2004, the ESA/NASA SOHO solar observatory spacecraft discovered its 750th comet since its launch in December 1995.

SOHO comet 750 was discovered by the German amateur astronomer Sebastian H?nig, one of the most successful SOHO comet-hunters. It was a part of the Kreutz family of ‘sungrazing’ comets, which usually evaporate in the hot solar atmosphere.

The LASCO coronagraph on SOHO, designed for seeing outbursts from the Sun, uses a mask to block the bright rays from the visible surface. It monitors a large volume of surrounding space and, as a result, has become the most prolific ‘discoverer’ of comets in the history of astronomy. Its images are displayed on the internet.

More than 75% of the discoveries have come from amateur comet hunters around the world, watching these freely available SOHO images on the internet. So, anyone with internet access can take part in the hunt for new comets and be a ‘comet discoverer’! Click here for information about how to search for your own comet.

SOHO is a mission of international co-operation between ESA and NASA, launched in December 1995. Every day SOHO sends thrilling images from which research scientists learn about the Sun’s nature and behaviour. Experts around the world use SOHO images and data to help them predict ‘space weather’ events affecting our planet.

Original Source: ESA News Release

Chandra Sees Titan’s X-Ray Shadow

Image credit: Chandra
A rare celestial event was captured by NASA’s Chandra X-ray Observatory as Titan ? Saturn’s largest moon and the only moon in the Solar System with a thick atmosphere ? crossed in front of the X-ray bright Crab Nebula. The X-ray shadow cast by Titan allowed astronomers to make the first X-ray measurement of the extent of its atmosphere.

On January 5, 2003, Titan transited the Crab Nebula, the remnant of a supernova explosion that was observed to occur in the year 1054. Although Saturn and Titan pass within a few degrees of the Crab Nebula every 30 years, they rarely pass directly in front of it.

“This may have been the first transit of the Crab Nebula by Titan since the birth of the Crab Nebula,” said Koji Mori of Pennsylvania State University in University Park, and lead author on an Astrophysical Journal paper describing these results. “The next similar conjunction will take place in the year 2267, so this was truly a once in a lifetime event.”

Chandra’s observation revealed that the diameter of the X-ray shadow cast by Titan was larger than the diameter of its solid surface. The difference in diameters gives a measurement of about 550 miles (880 kilometers) for the height of the X-ray absorbing region of Titan’s atmosphere. The extent of the upper atmosphere is consistent with, or slightly (10-15%) larger, than that implied by Voyager I observations made at radio, infrared, and ultraviolet wavelengths in 1980.

“Saturn was about 5% closer to the Sun in 2003, so increased solar heating of Titan may account for some of this atmospheric expansion,” said Hiroshi Tsunemi of Osaka University in Japan, one of the coauthors on the paper.

The X-ray brightness and extent of the Crab Nebula made it possible to study the tiny X-ray shadow cast by Titan during its transit. By using Chandra to precisely track Titan’s position, astronomers were able to measure a shadow one arcsecond in diameter, which corresponds to the size of a dime as viewed from about two and a half miles.

Unlike almost all of Chandra’s images which are made by focusing X-ray emission from cosmic sources, Titan’s X-ray shadow image was produced in a manner similar to a medical X-ray. That is, an X-ray source (the Crab Nebula) is used to make a shadow image (Titan and its atmosphere) that is recorded on film (Chandra’s ACIS detector).

Titan’s atmosphere, which is about 95% nitrogen and 5% methane, has a pressure near the surface that is one and a half times the Earth’s sea level pressure. Voyager I spacecraft measured the structure of Titan’s atmosphere at heights below about 300 miles (500 kilometers), and above 600 miles (1000 kilometers). Until the Chandra observations, however, no measurements existed at heights in the range between 300 and 600 miles.

Understanding the extent of Titan’s atmosphere is important for the planners of the Cassini-Huygens mission. The Cassini-Huygens spacecraft will reach Saturn in July of this year to begin a four-year tour of Saturn, its rings and its moons. The tour will include close flybys of Titan that will take Cassini as close as 600 miles, and the launching of the Huygens probe that will land on Titan’s surface.

“If Titan’s atmosphere has really expanded, the trajectory may have to be changed,” said Tsunemi.

The paper on these results has been accepted and is expected to appear in a June 2004 issue of The Astrophysical Journal. Other members of the research team were Haroyoski Katayama (Osaka University), David Burrows and Gordon Garmine (Penn State University), and Albert Metzger (JPL). Chandra observed Titan from 9:04 to 18:46 UT on January 5, 2003, using its Advanced CCD Imaging Spectrometer instrument.

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Additional information and images are available at:

http://chandra.harvard.edu/ and http://chandra.nasa.gov/

Original Source: Chandra News Release

Is There Life on Europa?

Image credit: NASA
Christopher Chyba is the principal investigator for the SETI Institute lead team of the NASA Astrobiology Institute (NAI). Chyba formerly headed the SETI Institute’s Center for the Study of Life in the Universe. His NAI team is pursuing a wide range of research activities, looking at both life’s beginnings on Earth and the possibility of life on other worlds. Several of his team’s research projects will examine the potential for life – and how one might go about detecting it – on Jupiter’s moon Europa. Astrobiology Magazine’s managing editor Henry Bortman recently spoke with Chyba about this work.

Astrobiology Magazine: One of the areas of focus of your personal research has been the possibility of life on Jupiter’s moon Europa. Several of the projects funded by your NAI grant deal with this ice-covered world.

Christopher Chyba: Right. We’re interested in interactions of life and planetary evolution. There are three worlds that are most interesting from that point of view: Earth, Mars and Europa. And we have a handful of projects going that are relevant to Europa. Cynthia Phillips is the leader of one of those projects; my grad student here at Stanford, Kevin Hand, heads up another one; and Max Bernstein, who’s a SETI Institute P.I., is a leader on the third.

There are two components to Cynthia’s projects. One that I think is really exciting is what she calls “change comparison.” That goes back to her days of being a graduate associate on the Galileo imaging team, where she did comparisons to look for surface changes on another of Jupiter’s moons, Io, and was able to extend her comparisons to include older Voyager images of Io.

We have Galileo images of Io, taken in the late 1990s, and we have Voyager images of Io, taken in 1979. So there are two decades between the two. If you can do a faithful comparison of the images, then you can learn about what’s changed in the interim, get some sense of how geologically active the world is. Cynthia did this comparison for Io, then did it for the much more subtle features of Europa.

That may sound like a trivial task. And for really gross features I suppose it is. You just look at the images and see if something’s changed. But since the Voyager camera was so different, since its images were taken at different lighting angles than Galileo images, since the spectral filters were different, there are all sorts of things that, once you get beyond the biggest scale of examination, make that much more difficult than it sounds. Cynthia takes the old Voyager images and, if you will, transforms them as closely as one can into Galileo-type images. Then she overlays the images, so to speak, and does a computer check for geological changes.

When she did this with Europa as part of her Ph.D. thesis, she found that there were no observable changes in 20 years on those parts of Europa that we have images for from both spacecraft. At least not at the resolution of the Voyager spacecraft – you’re stuck with the lowest resolution, say about two kilometers per pixel.

Over the duration of the Galileo mission, you’ve got at best five and a half years. Cynthia’s idea is that you’re more likely to detect change in smaller features, in a Galileo-to-Galileo comparison, at the much higher resolution that Galileo gives you, than you were working with images that were taken 20 years apart but that require you to work at two kilometers per pixel. So she’s going to do the Galileo-to-Galileo comparison.

The reason this is interesting from an astrobiological perspective is that any sign of geological activity on Europa might give us some clues about how the ocean and the surface interact. The other component of Cynthia’s project is to better understand the suite of processes involved in those interactions and what their astrobiological implications might be.

AM: You and Kevin Hand are working together to study some of the chemical interactions believed to be taking place on Europa. What specifically will you be looking at?

There are a number of components of the work I’m doing with Kevin. One component stems from a paper that Kevin and I had in Science in 2001, which has to do with the simultaneous production of electron donors and electron acceptors. Life as we know it, if it doesn’t use sunlight, makes its living by combining electron donors and acceptors and harvesting the liberated energy.

For example, we humans, like other animals, combine our electron donor, which is reduced carbon, with oxygen, which is our electron acceptor. Microbes, depending on the microbe, may use one, or several, of many possible different pairings of electron donors and electron acceptors. Kevin and I were finding abiotic ways that these pairings could be produced on Europa, using what we understand about Europa now. Many of these are produced through the action of radiation. We’re going to continue that work in much more detailed simulations.

We’re also going to look at the survival potential of biomarkers at Europa’s surface. That is to say, if you’re trying to look for biomarkers from an orbiter, without getting down to the surface and digging, what sort of molecules would you look for and what are your prospects for actually seeing them, given that there’s an intense radiation environment at the surface that should slowly degrade them? Maybe it won’t even be that slow. That’s part of what we want to understand. How long can you expect certain biomarkers that would be revelatory about biology to survive on the surface? Is it so short that looking from orbit doesn’t make any sense at all, or is it long enough that it might be useful?

That has to be folded into an understanding of turnover, or so-called “impact gardening” on the surface, which is another component of my work with Cynthia Phillips’, by the way. Kevin will be getting at that by looking at terrestrial analogs.

AM: How do you determine which biomarkers to study?

CC: There are certain chemical compounds that are commonly used as biomarkers in rocks that go back billions of years in the terrestrial past. Hopanes, for example, are viewed as biomarkers in the case of cyanobacteria. These biomarkers withstood whatever background radiation was present in those rocks from the decay of incorporated uranium, potassium, and so on, for over two billion years. That gives us a kind of empirical baseline for survivability of certain kinds of biomarkers. We want to understand how that compares to the radiation and oxidation environment on the surface of Europa, which is going to be much harsher.

Both Kevin and Max Bernstein are going to get after that question by doing laboratory simulations. Max is going to be irradiating nitrogen-containing biomarkers at very low temperatures in his laboratory apparatus, trying to understand the survivability of the biomarkers and how radiation changes them.

AM: Because even if the biomarkers don’t survive in their original form they might get transformed into another form that a spacecraft could detect?

CC: That’s potentially the case. Or they might get converted into something that is indistinguishable from meteoritic background. The point is to do the experiment and find out. And to get a good sense of the time scale.

That’s going to be important for another reason as well. The kind of terrestrial comparison I just mentioned, while I think it’s something we should know, potentially has limits because any organic molecule on the surface of Europa is in a highly oxidizing environment, where the oxygen’s getting produced by the radiation reacting with the ice. Europa’s surface is probably more oxidizing than the environment organic molecules would experience trapped in a rock on the Earth. Since Max will be doing these radiation experiments in ice, he will be able to give us a good simulation of the surface environment on Europa.

Original Source: Astrobiology Magazine

Two Directions for Sample Return Mission

Image credit: EADS
Following award of the ?600k study contract by ESA, EADS Space has made significant progress in completing the first definition of a European Mars Sample Return (MSR) mission. While EADS Astrium is defining the overall mission and the spacecraft, EADS Space Transportation is responsible for the re-entry systems and a ‘Mars Ascent Vehicle’ – a small rocket to carry the precious sample up through the Martian atmosphere.

The team at EADS Astrium, Stevenage is currently preparing for the Mid Term Review where two very different designs will have to be reduced to one.

In the first concept the launch vehicle lifts the sample from the surface of Mars and docks with the Earth Return Vehicle. In the second concept the launch vehicle releases the sample container into a low Mars orbit and the Earth Return Vehicle uses a capture mechanism to perform the rendezvous. The selection of the rendezvous concept has a significant impact on the overall mass, cost and complexity of the mission.

Marie-Claire Perkinson, Senior Systems Engineer at EADS Astrium, Stevenage, leading the study said. “Our industrial team, which includes EADS Space in France; Galileo Avionica in Italy, Sener in Spain and Utopia Consultancies in Germany has done a great job so far in proposing the two exciting concepts. We now have to select the best solution and then, once ESA has raised the appropriate support and funds for the implementation of the mission, launch could be as early as 2011.”

European astronauts may land on Mars one day, but getting them there and safely returning them to Earth will involve many steps and numerous technical challenges in propulsion, structures, computers and software. It will require sophisticated spacecraft to escape from Earth’s orbit; fly to Mars, survive atmospheric entry and landing; operate on the surface; take-off; return to Earth and then finally get the crew back on terra firma. Long before this can be accomplished some key technologies must be demonstrated. The best way to do this is to fly a robotic mission with a scaled-down version of the eventual manned mission.

This is exactly the goal of Mars Sample Return, the second flagship mission of the European Space Agency’s Aurora planetary exploration initiative and one of the most eagerly awaited future space missions for the planetary scientists.

Because Martian winds have transported dust across the planet’s surface over millions of years, the MSR sample could include particles from many different sources, representing a wide variety of rock types and ages, like grains of sand on a beach. Each granule could offer completely different insights into the rich geologic past of the Red Planet. Scientists could now “look at the sample as if each grain were a rock,” said Professor Colin Pillinger of the Open University. This would build on the decades of research already carried out on lunar rock samples.

EADS Space has used its unique heritage in building launch vehicles, planetary spacecraft and re-entry systems, combined with a deep understanding of the science goals to win the ESA mission study. ESA’s Aurora Project Manager Bruno Gardini said “The Mars Sample Return mission is one of the most challenging missions ever considered by ESA. Not only does it include many new technologies and four or five different spacecraft, but it is also a mission of tremendous scientific importance and the first robotic mission with a similar profile to a possible human expedition to Mars.”

Original Source: RAS News Release

SpaceDev Wins Its Largest Satellite Contract

Image credit: SpaceDev
SpaceDev (OTCBB: SPDV) announced that it has been awarded a five-year $43 million cost-plus-fixed fee indefinite delivery/indefinite quantity contract by the Missile Defense Agency (MDA) to conduct a micro satellite distributed sensing experiment, an option for a laser communications experiment, and other micro satellite studies and experiments as required in support of the Advanced System Deputate. The first of four phases is expected to be completed this year and will result in detailed mission and microsat designs. The milestone-based, multiyear, multiphase contract has an effective start date of March 1, 2004.

?This contract is our largest award to-date, and the successful completion of each contract phase would result in significantly accelerated growth in sales and revenues for us over the next few years,? said SpaceDev founding chairman and chief executive, Jim Benson. ?This award is the result of working collaboratively with the MDA team for two years, and our successful and revolutionary Internet-based CHIPSat microsatellite launched in January 2003.

SpaceDev?s new high precision microsats for MDA will build on and improve proprietary SpaceDev-developed CHIPSat technology, such as SpaceDev?s high performance, Miniature Flight Computer?, SpaceDev?s general purpose Micro Space Vehicle Operating System?, SpaceDev?s Internet-based Mission Control and Operations Software? that permits SpaceDev satellites to be controlled from anywhere in the world from a laptop computer. For the new low earth orbit MDA satellites, SpaceDev will increase pointing and tracking precision, increase the processing power of its flight computer to achieve more difficult real-time problem solving on-orbit, add autonomous satellite commissioning, and will introduce other innovative techniques and technologies.

?The SpaceDev engineering team continues its transformational thinking by developing and delivering fast turnaround, high performance, responsive space systems at affordable prices,? said Benson. ?With CHIPSat, our hybrid-based Streaker? small launch vehicle under development for the Air Force, and our hybrid rocket motors for safe government and private sector human space flight, we feel that SpaceDev is in a position to achieve more firsts in space technology and operations. We believe that SpaceDev is becoming a global leader for responsive and innovative small satellites and hybrid rocket propulsion systems.?

Original Source: Spacedev News Release

Astronauts Hear Mystery Sound Again

The crew on board the International Space Station heard a strange sound again on Friday; the second time in four months. Alexander Kaleri was speaking with flight controllers when he heard a loud, drumlike sound coming from an instrument panel. Kaleri and Michael Foale searched for the source of the sound last time, but they weren’t able to locate it. A spacewalk outside the station was called short because of a suit malfunction before the astronauts were able to see if there was a problem on the outside of the station. Kaleri and Foale are expected to return to Earth in just a few more weeks.

Andromeda’s Carnage

Image credit: RAS
An international team of astronomers has used the UK’s 2.5-m Isaac Newton Telescope on La Palma in the Canary Islands to map the Andromeda Galaxy (otherwise known as M31) and a large area of sky all around it. Their work over the last few years has created the most detailed image of a large spiral galaxy that currently exists. Dr Mike Irwin of the University of Cambridge, one of the team leaders, reports on some of the latest findings on Wednesday 31 March, when he will tell the RAS National Astronomy Meeting at the Open University about the first clear evidence that M31 is pulling one of its bright satellite galaxies apart, and the discovery of 14 previously unknown globular clusters orbiting far from the centre of M31 which could have been left behind when Andromeda devoured their parent galaxies.

Located around 2.5 million light years away, the Andromeda Galaxy is the most distant object visible to the naked eye, and is considered to be the sister galaxy of our own Milky Way. By studying this galactic neighbour, astronomers hope to understand more about the formation and evolution of many of the billions of spiral galaxies in the universe, including the Milky Way.

For their survey, the team have taken 150 individual images with a sensitive electronic CCD camera, which reveal millions of individual stars. It extends over an area 100 times greater than all earlier studies combined. The reason for scanning such a large area is that. around bright galaxies. there is a tenuous “halo” of stars which are leftovers from the formation of the galaxy billions of years ago. Studying this “fossil” information reveals evidence for how the halo, and hence the rest of the galaxy, has built up over cosmic history.

Traditionally, galaxy halos were thought to be relatively smooth and devoid of substructure. In fact the new survey shows that Andromeda’s halo is the exact opposite: it has a wealth of structure, indicating that it has ripped apart smaller galaxies that came too close and that the halo is built up from their remains. “Given that the disk of Andromeda appears so pristine, we were shocked to discover that its halo shows so much evidence for a history of interactions with other galaxies,” says Mike Irwin.

At this year’s National Astronomy Meeting, the Andromeda team report the discovery of a large stream of stars which appears to have been pulled out of one of Andromeda’s well-known satellite galaxies, NGC205. The visible part of the apparent stream extends nearly 50,000 light years from the main body of this small elliptical galaxy and was previously unknown despite the fact that NGC 205 has been well-studied.

“This is the first clear indication that one of Andromeda’s companion galaxies is being ripped apart as we watch,” commented team member Alan McConnachie, a doctoral student at Cambridge.

The 14 globular clusters the team has found orbiting far out from M31 may be evidence of Andromeda’s past cannibalism. Globular clusters are ancient systems of hundreds of thousands of stars, which are seen around many galaxies, and provide many clues to their evolutionary history. “Since the most distant of these globular clusters is some 250,000 light years from the centre of M31, our work shows that M31’s halo extends far beyond the edge of the bright part of the galaxy disk,” said Avon Huxor of the University of Hertfordshire.

“Both these discoveries will greatly aid in understanding the evolution of these nearby galaxies and should shed light on how our own Galaxy became what it is today,” commented Nial Tanvir, another team member from the University of Hertfordshire.

Original Source: RAS News Release

Milky Way’s Centre Measured

Image credit: NRAO
Thirty years after astronomers discovered the mysterious object at the exact center of our Milky Way Galaxy, an international team of scientists has finally succeeded in directly measuring the size of that object, which surrounds a black hole nearly four million times more massive than the Sun. This is the closest telescopic approach to a black hole so far and puts a major frontier of astrophysics within reach of future observations. The scientists used the National Science Foundation’s Very Long Baseline Array (VLBA) radio telescope to make the breakthrough.

“This is a big step forward,” said Geoffrey Bower, of the University of California-Berkeley. “This is something that people have wanted to do for 30 years,” since the Galactic center object, called Sagittarius A* (pronounced “A-star”), was discovered in 1974. The astronomers reported their research in the April 1 edition of Science Express.

“Now we have a size for the object, but the mystery about its exact nature still remains,” Bower added. The next step, he explained, is to learn its shape, “so we can tell if it is jets, a thin disk, or a spherical cloud.”

The Milky Way’s center, 26,000 light-years from Earth, is obscured by dust, so visible-light telescopes cannot study the object. While radio waves from the Galaxy’s central region can penetrate the dust, they are scattered by turbulent charged plasma in the space along the line of sight to Earth. This scattering had frustrated earlier attempts to measure the size of the central object, just as fog blurs the glare of distant lighthouses.

“After 30 years, radio telescopes finally have lifted the fog and we can see what is going on,” said Heino Falcke, of the Westerbork Radio Observatory in the Netherlands, another member of the research team.

The bright, radio-emitting object would fit neatly just inside the path of the Earth’s orbit around the Sun, the astronomers said. The black hole itself, they calculate, is about 14 million miles across, and would fit easily inside the orbit of Mercury. Black holes are concentrations of matter so dense that not even light can escape their powerful gravity.

The new VLBA observations provided astronomers their best look yet at a black hole system. “We are much closer to seeing the effects of a black hole on its environment here than anywhere else,” Bower said.

The Milky Way’s central black hole, like its more-massive cousins in more-active galactic nuclei, is believed to be drawing in material from its surroundings, and in the process powering the emission of the radio waves. While the new VLBA observations have not provided a final answer on the nature of this process, they have helped rule out some theories, Bower said. Based on the latest work, he explained, the top remaining theories for the nature of the radio- emitting object are jets of subatomic particles, similar to those seen in radio galaxies; and some theories involving matter being accelerated near the edge of the black hole.

As the astronomers studied Sagittarius A* at higher and higher radio frequencies, the apparent size of the object became smaller. This fact, too, Bower said, helped rule out some ideas of the object’s nature. The decrease in observed size with increasing frequency, or shorter wavelength, also gives the astronomers a tantalizing target.

“We think we can eventually observe at short enough wavelengths that we will see a cutoff when we reach the size of the black hole itself,” Bower said. In addition, he said, “in future observations, we hope to see a ‘shadow’ cast by a gravitational lensing effect of the very strong gravity of the black hole.”

In 2000, Falcke and his colleagues proposed such an observation on theoretical grounds, and it now seems feasible. “Imaging the shadow of the black hole’s event horizon is now within our reach, if we work hard enough in the coming years,” Falcke added.

Another conclusion the scientists reached is that “the total mass of the black hole is very concentrated,” according to Bower. The new VLBA observations provide, he said, the “most precise localization of the mass of a supermassive black hole ever.” The precision of these observations allows the scientists to say that a mass of at least 40,000 Suns has to reside in a space corresponding to the size of the Earth’s orbit. However, that figure represents only a lower limit on the mass. Most likely, the scientists believe, all the black hole’s mass — equal to four million Suns — is concentrated well inside the area engulfed by the radio-emitting object.

To make their measurement, the astronomers had to go to painstaking lengths to circumvent the scattering effect of the plasma “fog” between Sagittarius A* and Earth. “We had to push our technique really hard,” Bower said.

Bower likened the task to “trying to see your yellow rubber duckie through the frosted glass of the shower stall.” By making many observations, only keeping the highest-quality data, and mathematically removing the scattering effect of the plasma, the scientists succeeded in making the first-ever measurement of Sagittarius A*’s size.

In addition to Bower and Falcke, the research team includes Robin Herrnstein of Columbia University, Jun-Hui Zhao of the Harvard-Smithsonian Center for Astrophysics, Miller Goss of the National Radio Astronomy Observatory, and Donald Backer of the University of California-Berkeley. Falcke also is an adjunct professor at the University of Nijmegen and a visiting scientist at the Max-Planck Institute for Radioastronomy in Bonn, Germany.

Sagittarius A* was discovered in February of 1974 by Bruce Balick, now at the University of Washington, and Robert Brown, now director of the National Astronomy and Ionospheric Center at Cornell University. It has been shown conclusively to be the center of the Milky Way, around which the rest of the Galaxy rotates. In 1999, Mark Reid of the Harvard-Smithsonian Center for Astrophysics and his colleagues used VLBA observations of Sagittarius A* to detect the Earth’s motion in orbit around the Galaxy’s center and determined that our Solar System takes 226 million years to make one circuit around the Galaxy.

In March 2004, 55 astronomers gathered at the National Radio Astronomy Observatory facility in Green Bank, West Virginia, for a scientific conference celebrating the discovery of Sagittarius A* at Green Bank 30 years ago. At this conference, the scientists unveiled a commemorative plaque on one of the discovery telescopes.

The Very Long Baseline Array, part of the National Radio Astronomy Observatory, is a continent-wide radio-telescope system, with 10, 240-ton dish antennas ranging from Hawaii to the Caribbean. It provides the greatest resolving power, or ability to see fine detail, of any telescope in astronomy, on Earth or in space.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Original Source: NRAO News Release

Spirit Finds Hints of Past Martian Water

Image credit: NASA/JPL
Clues from a wind-scalloped volcanic rock on Mars investigated by NASA’s Spirit rover suggest repeated possible exposures to water inside Gusev Crater, scientists said Thursday.

Gusev is halfway around the planet from the Meridiani region where Spirit’s twin, Opportunity, recently found evidence that water used to flow across the surface.

“This is not water that sloshed around on the surface like what appears to have happened at Meridiani. We’re talking about small amounts of water, perhaps underground,” said Dr. Hap McSween, a rover science team member from the University of Tennessee, Knoxville.

“The evidence is in the form of multiple coatings on the rock, as well as fractures that are filled with alteration material and perhaps little patches of alteration material,” McSween said during a press conference at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The rock, called “Mazatzal” after mountains in Arizona, lies partially buried near the rim of the crater informally named “Bonneville” inside the much larger Gusev Crater. Its light- toned appearance grabbed scientists’ attention. After Spirit’s rock abrasion tool brushed two patches on the surface with wire bristles, a gray, darker layer could be seen under the tan topcoat. The rock abrasion tool ground into the surface with diamond cutting teeth on March 26. Then, after an examination of the newly exposed material, it ground deeper into the rock two days later. A lighter-gray interior lies under the darker layer, and a bright stripe cuts across both.

Dr. Jeff Johnson, a science team member from the U.S. Geological Survey’s Astrogeology Team, Flagstaff, Ariz., said the stripe “seems to be a fracture that water has flowed through, potentially with minerals precipitating from that fluid and lining the walls of the crack.”

He and other scientists stressed that the interpretations are preliminary. “The team is, as always, trying to find time to digest these observations while also preparing for the next day’s operations,” Johnson said.

Spirit’s alpha particle X-ray spectrometer checked what chemical elements were close to the surface of untreated, brushed, once-drilled and twice-drilled patches. “Miracles, miracles, miracles. We have a lot of work to do,” the instrument’s lead scientist, Dr. Rudi Rieder of the Max Planck Institute, Mainz, Germany, exclaimed about the results. For example, the ratio of bromine to chlorine seen inside the rock is unusually high and possibly a clue to alteration by water.

The final experiment on Mazatzal was to scrub the surface with the rock abrasion tool in a pattern of five circles arranged in a ring, with a sixth circle in the center. Besides creating a rock-art daisy, this task by the engineers of New York-based Honeybee Robotics, as well as JPL, produced a brushed patch big enough to fill the field of view of Spirit’s miniature thermal emission spectrometer, said Dr. Steve Ruff of Arizona State University, Tempe. The tan outer surface appears to have a strikingly different mineral composition than the dark gray coating exposed by the brushing, but more time is needed to complete the analysis, he said.

McSween proposed that the light outer coat, dark inner coat and bright veins could have resulted from three different periods of the rock being buried, altered by fluids and unburied.

While scientists await transmission of additional data Spirit has collected about Mazatzal, the rover will be making its way toward the “Columbia Hills” about 2.3 kilometers (1.3 miles) away. Spirit left the rock and drove 36.5 meters (120 feet) early Thursday.

Opportunity set a one-day driving record on Mars on March 27 by covering 48.9 meters (160 feet) toward a rock called “Bounce Rock” because airbag bounce marks show that the spacecraft hit it on landing day two months ago. “We’re looking to break that record again very soon with longer and longer drives,” said JPL’s Chris Lewicki, flight director.

Before moving on across the plains of Meridiani, though, Opportunity will complete an investigation it has begun of Bounce Rock. The rock is unlike any seen on Mars before, said Dr. Jim Bell, lead scientist for the rovers’ panoramic cameras. “There are some shiny surfaces on this rock,” he said, describing them as “almost mirrorlike.”

The two rovers’ 18 cameras have now taken more than 20,000 images. JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C.

Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu .

Original Source: NASA/JPL News Release

Gravity Probe B Launch in Two Weeks

Image credit: Stanford
A NASA spacecraft designed to test two important predictions of Albert Einstein’s general theory of relativity is set to launch from Vandenberg Air Force Base, Calif., at 1 p.m. EDT, April 17.

NASA’s Gravity Probe B mission, also known as GP-B, will use four ultra-precise gyroscopes, orbiting the Earth in a unique satellite, to experimentally test two extraordinary predictions of Einstein’s 1916 theory that space and time are distorted by the presence of massive objects. The two effects being tested are: The geodetic effect, the amount by which the Earth warps local spacetime in which it resides, and the frame-dragging effect, the amount by which the Earth drags local spacetime around with it as it rotates.

“Gravity Probe-B has the potential to uncover fundamental properties of the invisible universe, a universe which seems very bizarre and alien to our everyday perceptions yet one that Einstein tried to show us almost a century ago,” said Dr. Anne Kinney, director of the Astronomy and Physics Division in NASA’s Office of Space Science, Washington. “Testing the key aspects of Einstein’s theory, such as GP-B will do, will provide crucial information to science just as it has already helped America by pushing technological progress in developing the tools needed for these ultra-precise measurements,” she added

Once placed in its polar orbit of 640 kilometers (400 miles) above Earth, GP-B will circle the globe every 97.5 minutes, crossing over both poles. In-orbit checkout and calibration is scheduled to last 40-60 days, followed by a 13-month science-data acquisition period and a two-month post-science period for calibrations.

To test the general theory of relativity, GP-B will monitor any drift in the gyroscopes’ spin axis alignment in relation to its guide star, IM Pegasi (HR 8703). Over the course of a year, the anticipated spin axis drift for the geodetic effect is a minuscule angle of 6,614.4 milliarcseconds, and the anticipated spin axis drift for the frame-dragging effect is even smaller, only 40.9 milliarcseconds. To illustrate the size of the angles, if you climbed a slope of 40.9 milliarcseconds for 100 miles, you would rise only one inch in altitude.

During the mission, data from GP-B will be received a minimum of two times each day. Earth-based ground stations or NASA’s data relay satellites can receive the information. Controllers will be able to communicate with GP-B from the Mission Operations Center at Stanford University.

Data will include space vehicle and instrument performance, as well as the very precise measurements of the gyroscopes’ spin-axis orientation. By 2005 the GP-B mission will be complete, and a one-year period is planned for scientific analysis of the data.

“Developing GP-B has been a supreme challenge requiring the skillful integration of an extraordinary range of new technologies,” said Professor Francis Everitt of Stanford University, and the GP-B principal investigator. “It is hard to see how it could have been done without the kind of unique long-term collaboration that we have had between Stanford, Lockheed Martin, and NASA. It is wonderful to be ready for launch,” he said.

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the GP-B program. NASA’s prime contractor for the mission, Stanford University, conceived the experiment and is responsible for the design and integration of the science instrument, as well as for mission operations and data analysis. Lockheed Martin, a major subcontractor, designed, integrated and tested the spacecraft and some of its major payload components. NASA’s Kennedy Space Center, Fla., and Boeing Expendable Launch Systems, Huntington Beach, Calif., are responsible for the countdown and launch of the Delta II.

The launch from Vandenberg will be broadcast live on NASA Television on the AMC-9 satellite, transponder 9C, located at 85 degrees West longitude, vertical polarization, frequency 3880.megahertz, audio 6.8 megahertz. Information about launch events and video will be carried on a NASA website called the Virtual Launch Control Center at:

http://www.ksc.nasa.gov/elvnew/gpb/vlcc.htm
For information about the GP-B mission on the Internet, visit:

http://einstein.stanford.edu/

and

http://www.gravityprobeb.com

Original Source: NASA News Release