Posted on by Fraser Cain

Bounce Rock’s Mystery Ends

Image credit: NASA/JPL
Steve Squyres, the principal investigator for the Mars Exploration Rover, wrote in his science journal for April 16 that “Well, the Battle of Bounce Rock is over.”

Squyres was referring not only to the odd rock that rests alone on the otherwise flat, rockless Meridiani plains, but also what battles had to be waged even to consider it a rock at all.

“Not everybody on the team was even convinced that it was a rock at first,” noted Squyres. “There was some speculation that it might actually have been one of the airbag covers, shaken off during the landing by a particularly sharp jolt. Before we got to it we had a little guessing game going, with the votes about evenly split between ‘Mars rock’ and ‘flight hardware’, along with a few brave souls who thought it might be a meteorite.” Flight hardware has presented a number of fantastic images in the landscape, from objects like airbag threads and parachutes to tiny paper bits.

“There was only one object anywhere outside Eagle crater that looked even remotely like a decent-sized rock. We named it ‘Bounce Rock’ because we could see that the airbags had bounced right on top of it as the landing took place,” wrote Squyres. “It figures that if there was only one rock for what seems like miles in every direction, we’d find a way to hit it!”

“It was fun, and it sure was interesting, but it was a bit of a struggle,” described Squyres. “What had us going for awhile there was a very nice Mini-TES spectrum that seemed to show a lot of hematite in the rock. We knew there was hematite in the soil at Meridiani, but this was the first time we’d gotten a hematite signal from rock… so it looked very interesting. We rolled up to it, whipped out the Moessbauer Spectrometer, took some good data, and to our surprise we found no hematite in the rock at all. In fact, the only mineral that the Moessbauer detected was pyroxene, which made this rock look very different from anything we’d ever seen, at either landing site. We put a hole in it with the RAT, looked again, and saw the same thing — lots of pyroxene and no hematite.”

“So what was going on?”, asked Squyres. “Turns out we’d been faked out on the Mini-TES data. We had been pretty far away from the rock when we had first looked it, and the Mini-TES field of view had also included a particularly hematite-rich patch of soil immediately behind the rock. Once we got close enough to see the rock better with Mini-TES, the Mini-TES data confirmed the absence of hematite, confirmed the pyroxene, and also showed some plagioclase, another mineral, in the rock. So the story was coming together.”

“Then came the most interesting part of all, the APXS data.” Squyres referred to the alpha proton spectrometer, an instrument to determine chemical composition. “The APXS measures elemental chemistry, and what we found was that, chemically, Bounce Rock is almost a dead ringer for a rock called EETA 79001-B. Odd name for a rock; 79001 actually is a rock from Mars that was found in Antarctica back in 1979. It was knocked off of Mars long ago, orbited the sun for awhile, and eventually hit the Earth in Antarctica, where it was found many years later by an expedition sent there to collect meteorites. There are more than a dozen such rocks that are believed to be from Mars on Earth. But until Bounce Rock, nobody had ever found a rock that was actually on Mars and that matched the chemistry of one of these rocks. Now we have.”

“We’re not quite sure where on Mars Bounce Rock came from, but we suspect that it might have been thrown out of a big impact crater that’s about 50 kilometers southwest of our landing site,” concluded Squyres. “So it’s not a meteorite, but it probably did fall from the sky. And it turned out to be a very interesting stop on our drive across Meridiani Planum.”

The rover team has two hills on the horizon, each approaching closer everyday, as Spirit drives towards the Columbia Hills and Opportunity motors towards Endurance Crater with a slightly raised lip that otherwise stands out as the closest thing to a hill on the flat plains.

On its way to the Columbia Hills, Spirit acquired new microscopic imager views of its capture magnet on sol 92 (April 6, 2004). Both Spirit and Opportunity are equipped with a number of magnets. The capture magnet, as seen right, has a stronger charge than its sidekick, the filter magnet. The lower-powered filter magnet captures only the most magnetic airborne dust with the strongest charges, while the capture magnet picks up all magnetic airborne dust.

The magnets’ primary purpose is to collect the martian magnetic dust so that scientists can analyze it with the rovers’ Moessbauer spectrometers. While there is plenty of dust on the surface of Mars, it is difficult to confirm where it came from, and when it was last airborne. Because scientists are interested in learning about the properties of the dust in the atmosphere, they devised this dust-collection experiment.

The capture magnet is about 4.5 centimeters (1.8 inches) in diameter and is constructed with a central cylinder and three rings, each with alternating orientations of magnetization. Scientists have been monitoring the continual accumulation of dust since the beginning of the mission with panoramic camera and microscopic imager images. They had to wait until enough dust accumulated before they could get a Moessbauer spectrometer analysis. The results of that analysis, performed on sol 92, have not been sent back to Earth yet.

The plains appear to be uniform in character from the rover’s current position all the way to Endurance Crater. Granules of various sizes blanket the plains. Spherical granules fancifully called blueberries are present – some intact and some broken. Larger granules pave the surface, while smaller grains, including broken blueberries, form small dunes. Randomly distributed 1-centimeter (0.4 inch) sized pebbles (as seen just left of center in the foreground of the image) make up a third type of feature on the plains. The pebbles’ composition remains to be determined. Scientists plan to examine these in the coming sols.

Examination of this part of Mars by NASA’s Mars Global Surveyor orbiter revealed the presence of hematite, which led NASA to choose Meridiani Planum as Opportunity’s landing site. The rover science conducted on the plains of Meridiani Planum serves to integrate what the rovers are seeing on the ground with what orbital data have shown. Opportunity will make stop at a small crater called “Fram” (seen in the upper left, with relatively large rocks nearby) before heading to the rim of Endurance Crater.

Original Source: NASA Astrobiology Magazine

Posted on by Fraser Cain

Two Space Celebrations this Week

It’s time to celebrate the skies and reflect on ways to improve our stargazing experience. There are two events going on right now that you should consider; both running from April 19 to the 25th.

The first is Astronomy Week. Astronomical societies around the world are planning events all this week, so this should be a great time to meet other space enthusiasts and take a look through a telescope. Astronomy Day is on April 24th, with even more events happening that day.

The second is National Dark-Sky Week, which hopes to raise awareness about light pollution. It asks people to turn off unnecessary outdoor lights and consider low-glare alternatives to try and keep the skies as dark as possible.

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

A Movie of Titan’s Hazy Atmosphere

Image credit: Keck
As the Cassini-Huygens spacecraft approaches a July encounter with Saturn and its moon Titan, a team of University of California, Berkeley, astronomers has produced a detailed look at the moon’s cloud cover and what the Huygens probe will see as it dives through the atmosphere of Titan to land on the surface.

Astronomer Imke de Pater and her UC Berkeley colleagues used adaptive optics on the Keck Telescope in Hawaii to image the hydrocarbon haze that envelops the moon, taking snapshots at various altitudes from 150-200 kilometers down to the surface. They assembled the pictures into a movie that shows what Huygens will encounter when it descends to the surface in January 2005, six months after the Cassini spacecraft enters orbit around Saturn.

“Before, we could see each component of the haze but didn’t know where exactly it was in the stratosphere or the troposphere. These are the first detailed pictures of the distribution of haze with altitude,” said atmospheric chemist Mate Adamkovics, a graduate student in UC Berkeley’s College of Chemistry. “It’s the difference between an X-ray of the atmosphere and an MRI.”

“This shows what can be done with the new instruments on the Keck Telescope,” added de Pater, referring to the Near Infrared Spectrometer (NIRSPEC) mounted with the adaptive optics system. “This is the first time a movie has been made, which can help us understand the meteorology on Titan.”

Adamkovics and de Pater note than even after Cassini reaches Saturn this year, ground-based observations can provide important information on how Titan’s atmosphere changes with time, and how circulation couples with the atmospheric chemistry to create aerosols in Titan’s atmosphere. This will become even easier next year when OSIRIS (OH-Suppressing Infra-Red Imaging Spectrograph) comes on-line at the Keck telescopes, de Pater said. OSIRIS is a near-infrared integral field spectrograph designed for the Keck’s adaptive optics system that can sample a small rectangular patch of sky, unlike NIRSPEC, which samples a slit and must scan a patch of sky.

De Pater will present the results and the movie on Thursday, April 15, at an international conference in The Netherlands on the occasion of the 375th birthday of the Dutch scientist Christiaan Huygens. Huygens was the first “scientific director” of the Acad?mie Fran?aise and the discoverer of Titan, Saturn’s largest moon, in 1655. The four-day conference, which started April 13, is taking place at the European Space & Technology Centre in Noordwijk.

The Cassini-Huygens mission is an international collaboration between three space agencies – the National Aeronautics and Space Administration, the European Space Agency and the Italian Space agency – involving contributions from 17 nations. It was launched from Kennedy Space Center on Oct. 15, 1997. The spacecraft will arrive at Saturn in July, with the Cassini orbiter expected to send back data on the planet and its moons for at least four years. The orbiter also will relay data from the Huygens probe as it plunges through Titan’s atmosphere and after it lands on the surface next year.

What makes Titan so interesting is its seeming resemblance to a young Earth, an age when life presumably arose and before oxygen changed our planet’s chemistry. The atmospheres of both Titan and the early Earth were dominated by nearly the same amount of nitrogen.

The atmosphere of Titan has a significant amount of methane gas, which is chemically altered by ultraviolet light in the upper atmosphere, or stratosphere, to form long-chain hydrocarbons, which condense into particulates that create a dense haze. These hydrocarbons, which could be like oil or gasoline, eventually settle to the surface. Radar observations indicate flat areas on the moon’s surface that could be pools or lakes of propane or butane, Adamkovics said.

Astronomers have been able to pierce the hydrocarbon haze to look at the surface using ground-based telescopes with adaptive optics or speckle interferometry, and with the Hubble Space Telescope, always with filters that allow the telescopes to see through “windows” in the haze where methane doesn’t absorb.

Imaging the haze itself hasn’t been as easy, primarily because people have had to observe at different wavelengths to see it at specific altitudes.

“Until now, what we knew about the distribution of haze came from separate groups using different techniques, different filters,” Adamkovics said. “We get all that in one go: the 3-D distribution of haze on Titan, how much at each place on the planet and how high in the atmosphere, in one observation.”

The NIRSPEC instrument on the Keck telescope measures the intensity of a band of near-infrared wavelengths at once as it scans about 10 slices along Titan’s surface. This technique allows reconstruction of haze versus altitude because specific wavelengths must come from specific altitudes or they wouldn’t be visible at all because of absorption.

The movie Adamkovics and de Pater put together shows a haze distribution similar to what had been observed before, but more complete and assembled in a more user-friendly way. For example, haze in the atmosphere over the South Pole is very evident, at an altitude of between 30 and 50 kilometers. This haze is known to form seasonally and dissipate during the Titan “year,” which is about 29 1/2 Earth years.

Stratospheric haze at about 150 kilometers is visible over a large area in the northern hemisphere but not the southern hemisphere, an asymmetry observed previously.

At the southern hemisphere’s tropopause, the border between the lower atmosphere and the stratosphere at about 42 kilometers altitude, cirrus haze is visible, analogous to cirrus haze on Earth.

The observations were made on Feb. 19, 20 and 22, 2001, by de Pater and colleague Henry G. Roe of the California Institute of Technology, and analyzed by Adamkovics using models made by Caitlin A. Griffith of the University of Arizona, with co-author S. G. Gibbard of Lawrence Livermore National Laboratory.

The work was sponsored in part by the National Science Foundation and the Technology Center for Adaptive Optics.

Original Source: UC Berkeley News Release

Posted on by Fraser Cain

Meteorite Matches Rock on Mars

NASA’s Opportunity rover has examined an odd volcanic rock on the plains of Mars’ Meridiani Planum region with a composition unlike anything seen on Mars before, but scientists have found similarities to meteorites that fell to Earth.

“We think we have a rock similar to something found on Earth,” said Dr. Benton Clark of Lockheed Martin Space Systems, Denver, science-team member for the Opportunity and Spirit rovers on Mars. The similarity seen in data from Opportunity’s alpha particle X-ray spectrometer “gives us a way of understanding ‘Bounce Rock’ better,” he said. Bounce Rock is the name given to the odd, football-sized rock because Opportunity struck it while bouncing to a stop inside protective airbags on landing day.

The resemblance helps resolve a paradox about the meteorites, too. Bubbles of gas trapped in them match the recipe of martian atmosphere so closely that scientists have been confident for years that these rocks originated from Mars. But examination of rocks on Mars with orbiters and surface missions had never found anything like them, until now.

“There is a striking similarity in spectra,” said Christian Schroeder, a rover science-team collaborator from the University of Mainz, Germany, which supplied both Mars rovers’ Moessbauer spectrometer instruments for identifying iron-bearing minerals.

Mars Exploration Rover scientists described two such meteorites in particular during a Mars Exploration Rover news conference at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. One rock, named Shergotty, was found in India in 1865 and it gave its name to a class of meteorites called shergottites. A shergottite named EETA79001 was found in Antarctica in 1979 and has an elemental composition even closer to Bounce Rock’s. Those two and nearly 30 other meteorites found on Earth are believed to have been ejected from Mars by the impacts of large asteroids or comets hitting Mars.

Opportunity’s miniature thermal emission spectrometer indicates that the main ingredient in Bounce Rock is a volcanic mineral called pyroxene, said science-team collaborator Deanne Rogers of Arizona State University, Tempe. The Moessbauer spectrometer also identified pyroxene in the rock. The high proportion of pyroxene makes it unlike not only any other rock studied by Opportunity or Spirit, but also unlike the volcanic deposits mapped extensively around Mars by a similar spectrometer on NASA’s Mars Global Surveyor orbiter, Rogers said.

Thermal infrared imaging by another orbiter, Mars Odyssey, suggests a possible origin for Bounce Rock. An impact crater about 25 kilometers wide (16 miles wide) lies about 50 kilometers (31 miles) southwest of Opportunity. The images show that some rocks thrown outward by the impact that formed that crater flew as far as the distance to the rover. “Some of us think Bounce Rock could have been ejected from this crater,” Rogers said.

Opportunity is driving eastward, toward a crater dubbed “Endurance” that might offer access to thicker exposures of bedrock than the rover has been able to examine so far. With new software to improve mobility performance, the rover may reach Endurance within two weeks, said JPL’s Jan Chodas, flight software manager for both Mars Exploration Rovers.

Mission controllers at JPL successfully sent new versions of flight software to both rovers. Spirit switched to the new version successfully on Monday, and Opportunity did late Tuesday.

A parting look at the small crater in which Opportunity landed is part of a full 360-degree color panorama released at the news conference. The view combines about 600 individual frames from the rover’s panoramic camera, said science-team collaborator Jason Soderblom of Cornell University, Ithaca, N.Y. It is called the Lion King panorama because it was taken from a high-ground viewpoint at the edge of the crater, like the high-ground viewpoint used by animal characters in the Lion King story.

The panorama gives a good sense of how wind has uncovered the outcrop at the upwind side of the crater and deposited sand in the downwind side of the crater and bright martian dust in the wind shadow of the crater, Soderblom commented. On the wide plain outside the crater lies Bounce Rock.

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

Posted on by Fraser Cain

Gravitational Lens Reveals Distant Planet

Image credit: NASA/JPL
Like Sherlock Holmes holding a magnifying glass to unveil hidden clues, modern day astronomers used cosmic magnifying effects to reveal a planet orbiting a distant star.

This marks the first discovery of a planet around a star beyond Earth’s solar system using gravitational microlensing. A star or planet can act as a cosmic lens to magnify and brighten a more distant star lined up behind it. The gravitational field of the foreground star bends and focuses light, like a glass lens bending and focusing starlight in a telescope. Albert Einstein predicted this effect in his theory of general relativity and confirmed it with our Sun.

“The real strength of microlensing is its ability to detect low-mass planets,” said Dr. Ian Bond of the Institute for Astronomy in Edinburgh, Scotland, lead author of a paper appearing in the May 10 Astrophysical Journal Letters. The discovery was made possible through cooperation between two international research teams: Microlensing Observations in Astrophysics (Moa) and Optical Gravitational Lensing Experiment (Ogle). Well-equipped amateur astronomers might use this technique to follow up future discoveries and help confirm planets around other stars.

The newly discovered star-planet system is 17,000 light years away, in the constellation Sagittarius. The planet, orbiting a red dwarf parent star, is most likely one-and-a-half times bigger than Jupiter. The planet and star are three times farther apart than Earth and the Sun. Together, they magnify a farther, background star some 24,000 light years away, near the Milky Way center.

In most prior microlensing observations, scientists saw a typical brightening pattern, or light curve, indicating a star’s gravitational pull was affecting light from an object behind it. The latest observations revealed extra spikes of brightness, indicating the existence of two massive objects. By analyzing the precise shape of the light curve, Bond and his team determined one smaller object is only 0.4 percent the mass of a second, larger object. They concluded the smaller object must be a planet orbiting its parent star.

Dr. Bohdan Paczynski of Princeton University, Princeton, N.J., an OGLE team member, first proposed using gravitational microlensing to detect dark matter in 1986. In 1991, Paczynski and his student, Shude Mao, proposed using microlensing to detect extrasolar planets. Two years later, three groups reported the first detection of gravitational microlensing by stars. Earlier claims of planet discoveries with microlensing are not regarded as definitive, since they had too few observations of the apparent planetary brightness variations.

“I’m thrilled to see the prediction come true with this first definite planet detection through gravitational microlensing,” Paczynski said. He and his colleagues believe observations over the next few years may lead to the discovery of Neptune-sized, and even Earth-sized planets around distant stars.

Microlensing can easily detect extrasolar planets, because a planet dramatically affects the brightness of a background star. Because the effect works only in rare instances, when two stars are perfectly aligned, millions of stars must be monitored. Recent advances in cameras and image analysis have made this task manageable. Such developments include the new large field-of-view Ogle-III camera, the Moa-II 1.8 meter (70.8 inch) telescope, being built, and cooperation between microlensing teams.

“It’s time-critical to catch stars while they are aligned, so we must share our data as quickly as possible,” said Ogle team-leader Dr. Andrzej Udalski of Poland’s Warsaw University Observatory. Udalski in Poland and Paczynski in the U.S lead the Polish/American project. It operates at Las Campanas Observatory in Chile, run by the Carnegie Institution of Washington, and includes the world’s largest microlensing survey on the 1.3 meter (51-inch) Warsaw Telescope.

NASA and the National Science Foundation fund the Optical Gravitational Lensing Experiment in the U.S. The Polish State Committee for Scientific Research and Foundation for Polish Science funds it in Poland. Microlensing Observations in Astrophysics is primarily a New Zealand/Japanese group, with collaborators in the United Kingdom and U.S. New Zealand’s Marsden Fund, NASA and National Science Foundation, Japan’s Ministry of Education, Culture, Sports, Science, and Technology, and the Japan Society for the Promotion of Science support it.

Images and information about the latest research are available on the Internet at http://www.jpl.nasa.gov/releases/2004/103a.cfm. More information on NASA’s planet-hunting efforts is at http://planetquest.jpl.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Atlas Launches Superbird-6

Image credit: Boeing
The Superbird-6 satellite is in orbit tonight thanks to a successful launch on an Atlas IIAS rocket provided by International Launch Services (ILS).

Liftoff of the Atlas vehicle, built by Lockheed Martin (NYSE:LMT), was at 8:45 p.m. EDT (00:45 April 16 GMT). The rocket released the satellite into its target transfer orbit 30 minutes later.

This was the fourth launch conducted this year by ILS, a Lockheed Martin joint venture. It also was ILS? second launch for Space Communications Corp. of Tokyo. Both Superbird spacecraft are 601 model satellites from Boeing Satellite Systems (BSS) of Los Angeles.

?We appreciate that SCC again placed its confidence in ILS and Atlas,? said ILS President Mark Albrecht. ?And we?re delighted to have a role in inaugurating new telecommunications services in the Western Pacific region.?

Albrecht added: ?Tonight?s launch marks the 80th mission since the start of the commercial Atlas program. I want to acknowledge BSS and the team that builds the 601 model ? 26 of these satellites have flown on Atlas rockets of various configurations over the last 11 years. So this launch is a reunion of a winning trio of companies.?

The vehicle flown tonight was the 28th in the Atlas IIAS configuration. Two more flights of this model are scheduled in the next two months. This mission also was the second in two months carrying a satellite for Japan. On March 13, another Atlas rocket carried the MBSAT satellite for Mobile Broadcasting Corp. of Japan, in which SCC is an investor.

The Atlas launch vehicle line has proven its operational reliability over 71 consecutive successful flights since 1993. The current generation of vehicles has a wide performance range for payloads ranging from approximately 3 metric tons to 10 metric tons, with either a 4-meter or 5-meter diameter fairing.

ILS is a joint venture of Lockheed Martin and Russian rocket builder Khrunichev State Research and Production Space Center. ILS markets and manages the missions on the Atlas rocket in the United States at both Cape Canaveral and at Vandenberg Air Force Base, Calif.; and on the Proton rocket at the Baikonur Cosmodrome, Kazakhstan. Together ILS Atlas and Proton vehicles have launched more than 30 satellite payloads for commercial services in the Asia-Pacific Rim.

ILS was formed in 1995, and is based in McLean, Va., a suburb of Washington, D.C.

The Atlas rockets and their Centaur upper stages are built by Lockheed Martin Space Systems Company in Denver, Colo.; Harlingen, Texas; and San Diego, Calif.

Original Source: ILS News Release

Posted on by Fraser Cain

Scientists Analyze Meteor Fragments

Image credit: University of Chicago
The meteorites that punched through roofs in Park Forest, Ill., on the evening of March 26, 2003, came from a larger mass that weighed no less than 1,980 pounds before it hit the atmosphere, according to scientific analyses led by the University of Chicago?s Steven Simon, who himself also happens to live in Park Forest.

Simon, a Senior Research Associate in Geophysical Sciences at the University of Chicago, and seven co-authors will publish these and other findings in the April issue of the journal Meteoritics and Planetary Science. Simon holds a unique distinction among scientists: his home sits in the middle of the strewnfield, the area from which the meteorites were recovered.

?I don?t know of any other time when a meteoriticist was in the middle of a strewnfield,? said Lawrence Grossman, Professor in Geophysical Sciences at the University of Chicago and one of Simon?s co-authors.

In fact, Simon actually saw the flash the meteorite created. He had the drapes closed when the rock entered the sky over Illinois, but ?the whole sky lit up,? he said.

Grossman, who lives in Flossmoor, not far from Park Forest, also experienced the meteorite?s arrival firsthand. He was awakened by the sound of the meteorite entering the atmosphere that night. ?I heard a detonation,? Grossman said. ?It was sharp enough to wake me up.?

The team calculated the projectile?s size range based on measurements of the galactic cosmic rays that it absorbed. Measurements of a radioactive form of cobalt provided the projectile?s minimum size. ?If the object is too small the cosmic rays will just pass through and not make 60cobalt,? Simon explained.

Simon and Grossman classify the meteorite as an L5 chondrite, a type of stony meteorite, one low in iron that was heated for a long period of time inside its parent body, probably an asteroid. ?It?s a fairly common type of meteorite,? Simon said.

The Park Forest meteorite also showed signs that it had been highly shocked, probably when it was part of a rock that was broken from a much larger asteroid following a collision. The evidence for shock includes shocked feldspar. Apollo astronauts recovered shocked specimens of the mineral from the moon, as well, Simon said. Impact shock was common in the early history of the solar system because of the large quantity of interplanetary debris then in existence.

Witnesses in Michigan, Illinois, Indiana and Missouri reported seeing the fireball that the meteorite produced as it broke up in the atmosphere, Simon and his colleagues reported. Local residents collected hundreds of meteorite fragments totaling approximately 65 pounds from an area extending from Crete in the south to the southern end of Olympia Fields in the north. Located in Chicago?s south suburbs, ?this is the most densely populated region to be hit by a meteorite shower in modern times,? the authors write.

One meteorite narrowly missed striking a sleeping Park Forest resident after it burst through the ceiling of a bedroom. The meteorite sliced through some window blinds, cratered the windowsill, then bounced across the room and broke a mirror before coming to rest.

The meteorites were recovered from a track that trends southeast to northwest. Satellite data analyzed by Peter Brown of the University of Western Ontario indicates that the meteorite traveled from southwest to northeast, however.

?The meteorite broke up in the atmosphere, and the fragments encountered strong westerly winds as they fell,? the authors write. ?The smallest pieces were deflected the furthest eastward from the trajectory, and the largest pieces, carrying more momentum, were deflected the least.?

Contributing to the paper in addition to Simon and Grossman were the University of Chicago?s Robert Clayton and the late Toshiko Mayeda; Jim Schwade of the Planetary Studies Foundation in Crystal Lake, Ill.; Paul Sipiera of Harper College in Palatine, Ill.; John Wacker of Pacific Northwest National Laboratory in Richland, Wash.; and Meenakshi Wadhwa of the Field Museum of Natural History in Chicago.

Their research was supported by grants from the National Aeronautics and Space Administration, the National Science Foundation, and the Planetary Studies Foundation.

Original Source: University of Chicago News Release

Posted on by Fraser Cain

Cassini Sees Shepherding Moons

Image credit: NASA/JPL/Space Science Institute
Cassini has sighted Prometheus and Pandora, the two F-ring-shepherding moons whose unpredictable orbits both fascinate scientists and wreak havoc on the F ring.

Prometheus (102 kilometers, or 63 miles across) is visible left of center in the image, inside the F ring. Pandora (84 kilometers, or 52 miles across) appears above center, outside the ring. The dark shadow cast by the planet stretches more than halfway across the A ring, the outermost main ring. The mottled pattern appearing in the dark regions of the image is ‘noise’ in the signal recorded by the camera system, which has subsequently been magnified by the image processing.

The F ring is a narrow, ribbon-like structure, with a width seen in this geometry equivalent to a few kilometers. The two small, irregularly shaped moons exert a gravitational influence on particles that make up the F ring, confining it and possibly leading to the formation of clumps, strands and other structures observed there. Pandora prevents the F ring from spreading outward and Prometheus prevents it from spreading inward. However, their interaction with the ring is complex and not fully understood. The shepherds are also known to be responsible for many of the observed structures in Saturn’s A ring.

The moons, which were discovered in images returned by the Voyager 1 spacecraft in 1980, are in chaotic orbits–their orbits can change unpredictably when the moons get very close to each other. This strange behavior was first noticed in ground-based and Hubble Space Telescope observations in 1995, when the rings were seen nearly edge-on from Earth and the usual glare of the rings was reduced, making the satellites more readily visible than usual. The positions of both satellites at that time were different than expected based on Voyager data.

One of the goals for the Cassini-Huygens mission is to derive more precise orbits for Prometheus and Pandora. Seeing how their orbits change over the duration of the mission will help to determine their masses, which in turn will help constrain models of their interiors and provide a more complete understanding of their effect on the rings.

This narrow angle camera image was snapped through the broadband green spectral filter, centered at 568 nanometers, on March 10, 2004, when the spacecraft was 55.5 million kilometers (34.5 million miles) from the planet. Image scale is approximately 333 kilometers (207 miles) per pixel. Contrast has been greatly enhanced, and the image has been magnified to aid visibility of the moons as well as structure in the rings.

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 Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: CICLOPS News Release

Posted on by Fraser Cain

New Planet Hunter Gets to Work

Image credit: SuperWasp
A consortium of astronomers is tomorrow (April 16th) celebrating the commissioning of the SuperWASP facility at the astronomical observatory on the island of La Palma in the Canary Islands, designed to detect thousands of planets outside of our own solar system.

Only about a hundred extra-solar planets are currently known, and many questions about their formation and evolution remain unanswered due to the lack of observational data. This situation is expected to improve dramatically as SuperWASP produces scientific results.

The SuperWASP facility is now entering its operational phase. Construction of the instrument began in May 2003, and in autumn last year the first test data was obtained which showed the instrument’s performance to exceed initial expectations.

SuperWASP is the most ambitious project of its kind anywhere in the world. Its extremely wide field of view combined with its ability to measure brightness very precisely allows it to view large areas of the sky and accurately monitor the brightnesses of hundreds of thousands of stars.

If any of these have nearby Jupiter-sized planets then they may move across the face of their parent star, as viewed from the Earth. While no telescope could actually see the planet directly, its passage or transit, blocks out a small proportion of the parent star’s light i.e. we see the star get slightly fainter for a few hours. In our own solar system a similar phenomenon will occur on 8th June 2004 when Venus will transit the Sun’s disk.

One nights’ observing with SuperWASP will generate a vast amount of data, up to 60 GB – about the size of a typical modern computer hard disk (or 42000 floppy disks). This data is then processed using sophisticated software and stored in a public database within the Leicester Database and Archive Service of the University of Leicester.

The Principal Investigator for the Project, Dr Don Pollacco (Queens University Belfast), said “While the construction and initial commissioning phases of the facility have been only 9 months long, SuperWASP represents the culmination of many years work from astronomers within the WASP consortium. Data from SuperWASP will lead to exciting progress in many areas of astronomy, ranging from the discovery of planets around nearby stars to the early detection of other classes of variable objects such as supernovae in distant galaxies”.

Dr Ren? Rutten (Director of the Isaac Newton Group of Telescopes) said “SuperWASP is a very nice example of how clever ideas to exploit the latest technology can open new windows to explore the universe around us, and shows that important scientific programmes can be done at very modest cost.”

The history of the project over the last ten years including the exciting discovery of the Sodium Tail of Comet Hale-Bopp in 1997 can be found at http://www.superwasp.org/history.html and enclosed web links.

The SuperWASP facility is operated by the WASP consortium involving

astronomers from the following institutes: Queen’s University Belfast, University of Cambridge, Instituto de Astrof?sica de Canarias, Isaac Newton Group of Telescopes (La Palma), University of Keele, University of Leicester, Open University and University of St Andrews.

The SuperWASP instrument has cost approximately ?400K, and was funded by major financial contributions from Queen’s University Belfast, the Particle Physics and Astronomy Research Council and the Open University. SuperWASP is located in the Spanish Roque de Los Muchachos Observatory on La Palma, Canary Islands which is operated by the Instituto de Astrof?sica de Canarias (IAC).

Pictures of the SuperWASP facility and some of its astronomical first-light images are available at http://www.superwasp.org/firstlight.html

Original Source: PPARC News Release

Posted on by Fraser Cain

Magnesium Could Be a Source of Fuel on Mars

Image credit: UMich
One of the big problems with space travel is that one cannot over pack.

Suppose astronauts reach Mars. How do they explore the planet if they cannot weigh down the vessel with fuel for excursions?

A team of undergraduate aerospace engineering students at the University of Michigan is doing research to help astronauts make fuel once they get to Mars, and the results could bring scientists one step closer to manned or extended rover trips to the planet.

Their research proposal won the five-student team a highly competitive trip to NASA’s Johnson Space Center in Houston to participate in the Reduced Gravity Student Flight Opportunities Program.

In Houston, the students conducted zero-gravity experiments using iodine as a catalyst to burn magnesium. Magnesium is a metal found on Mars that can be harvested for fuel?fossil fuels don’t burn on Mars because of the planet’s carbon dioxide (CO2) atmosphere, but metals do burn in a CO2 atmosphere.

The idea for the students’ experiments evolved from previous research done by Margaret Wooldridge, an associate professor in mechanical engineering and the team’s adviser. Wooldridge’s research showed that while magnesium is a promising fuel source, burning magnesium alone?without a catalyst such as iodine?has several challenges. Preliminary results from the student experiments showed that using iodine as a catalyst helped make the magnesium burn better, said Arianne Liepa, aerospace engineering undergrad and team member.

The experiments also showed that using the iodine, magnesium, CO2 system worked even better in a microgravity environment. “That bodes well for a power source on Mars where the gravity is approximately one-third that of Earth,” Wooldridge said.

The students?Greg Hukill, Arianne Liepa, Travis Palmer, Carlos Perez and Christy Schroeder?who conducted the experiments over a nine-day period in March, flew on a specially modified Boeing KC 135A turbojet transport. The plane flies parabolic arcs to produce weightless periods of 20 to 25 seconds at the apex of the arc.

Original Source: University of Michigan News Release