Posted on by Fraser Cain

Satellites Show How the Earth is Warming Up

Image credit: NASA
Like thermometers in space, satellites are taking the temperature of the Earth’s surface or skin. According to scientists, the satellite data confirm the Earth has had an increasing “fever” for decades.

For the first time, satellites have been used to develop an 18- year record (1981-1998) of global land surface temperatures. The record provides additional proof that Earth’s snow-free land surfaces have, on average, warmed during this time period, according to a NASA study appearing in the March issue of the Bulletin of the American Meteorological Society. The satellite record is more detailed and comprehensive than previously available ground measurements. The satellite data will be necessary to improve climate analyses and computer modeling.

Menglin Jin, the lead author, is a visiting scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md., and a researcher with the University of Maryland, College Park, Md. Jin commented until now global land surface temperatures used in climate change studies were derived from thousands of on-the- ground World Meteorological Organization (WMO) stations located around the world, a relatively sparse set of readings given Earth’s size. These stations actually measure surface air temperature at two to three meters above land, instead of skin temperatures. The satellite skin temperature dataset is a good complement to the traditional ways of measuring temperatures.

A long-term skin temperature data set will be essential to illustrate global as well as regional climate variations. Together with other satellite measurements, such as land cover, cloud, precipitation, and sea surface temperature measurements, researchers can further study the mechanisms responsible for land surface warming.

Furthermore, satellite skin temperatures have global coverage at high resolutions, and are not limited by political boundaries. The study uses Advanced Very High Resolution Radiometer Land Pathfinder data, jointly created by NASA and the National Oceanic and Atmospheric Administration (NOAA) through NASA’s Earth Observing System Program Office. It also uses recently available NASA Moderate Resolution Imaging Spectroradiometer skin temperature measurements, as well as NOAA TIROS Operational Vertical Sounder (TOVS) data for validation purposes. All these data are archived at NASA’s Distributed Active Archive Center.

Inter-annually, the 18-year Pathfinder data in this study showed global average temperature increases of 0.43 Celsius (C) (0.77 Fahrenheit (F)) per decade. By comparison, ground station data (2 meter surface air temperatures) showed a rise of 0.34 C (0.61 F) per decade, and a National Center for Environmental Prediction reanalysis of land surface skin temperature showed a similar trend of increasing temperatures, in this case 0.28 C (0.5 F) per decade. Skin temperatures from TOVS also prove an increasing trend in global land surface temperatures. Regional trends show more temperature variations.

“Although an increasing trend has been observed from the global average, the regional changes can be very different,” Jin said. “While many regions were warming, central continental regions in North America and Asia were actually cooling.”

One issue with the dataset is that it cannot detect surface temperatures over snow. In winter, most of the land areas in the mid to upper latitudes of the Northern Hemisphere are covered by snow. Of Earth’s land area, 90 percent of it is snow free in July, compared to only 65 percent in January. For this reason, the study only focused on snow free areas. Still, in mountainous areas that are hard to monitor, like Tibet, satellites can detect the extent of snow coverage and its variations.

The satellite dataset allows researchers to also look at daily trends on global and regional scales. The largest daily variation was above 35.0 C (63 F) at tropical and sub-tropical desert areas for a July 1988 sample, with decreasing daily ranges towards the poles, in general. Daily changes were also closely related to vegetation cover. The daily skin temperature range showed a decreasing global mean trend over the 18-year period, resulting from greater temperature increases at night compared to daytime.

Things like clouds, volcanic eruptions, and other factors gave false readings of land temperatures, but scientists factored those out to make the skin temperature data more accurate. Scientists are considering extending this 18-year satellite- derived skin temperature record up to 2003. The mission of NASA’s Earth Science Enterprise is to develop a scientific understanding of the Earth system and its response to natural or human-induced changes to enable improved prediction capability for climate, weather, and natural hazards. NASA funded the study.

Original Source: NASA News Release

Posted on by Fraser Cain

Gravity Probe B Launches

Image credit: NASA
The NASA space vehicle designed to test two important predictions of Albert Einstein’s Theory of General Relativity launched today from Vandenberg Air Force Base, Calif., aboard a Boeing Delta II expendable launch vehicle.

The spacecraft is being inserted into an almost perfect circular polar orbit around the Earth at an altitude of 400 statute miles. “The solar arrays are deployed, and we have received initial data that indicates all systems are operating smoothly. We are very pleased,” said Gravity Probe B (GP-B) program manager Rex Geveden of NASA’s Marshall Space Flight Center (MSFC), Huntsville, Ala. “The Gravity Probe B space vehicle houses one of the most challenging science instruments ever devised and seeks to answer some of the most important questions about the structure of our universe,” he said.

The GP-B mission will use four ultra-precise gyroscopes to test Einstein’s theory that space and time are distorted by the presence of massive objects. To accomplish this, the mission will measure two factors, how space and time are very slightly warped by the presence of the Earth, and how the Earth’s rotation very slightly drags space-time around with it.

“This is a great moment and a great responsibility, the outcome of a unique collaboration of physicists and engineers to develop this near-perfect instrument to test Einstein’s theory of gravity,” said the experiment’s principal investigator Dr. Francis Everitt of Stanford University in Stanford, Calif. “We are very grateful for all the support we have received at NASA and elsewhere for this exacting effort, truly a new venture in fundamental physics.”

In-orbit checkout and calibration is scheduled to last 60 days, followed by a 12-month science-data acquisition period and a two-month post-science period for calibrations.

During the mission, data from GP-B will be received a minimum of twice daily. Either Earth-based ground stations or NASA’s data relay satellites can receive the information. Controllers will be able to communicate with the orbiting space vehicle 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 pointing. By 2005 the GP-B mission will be complete. A one-year period is planned for scientific analysis of the data.

MSFC 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 space vehicle and some of its major payload components. NASA’s Kennedy Space Center and Boeing Expendable Launch Systems were responsible for the pre-launch preparations, countdown and launch of the Delta II.

For information about NASA and agency missions on the Internet, visit:

http://www.nasa.gov/

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

Posted on by Fraser Cain

Chandra Reveals a Supernova’s Power

Image credit: Chandra
The NASA Chandra X-ray Observatory image of SNR 0540-69.3 clearly shows two aspects of the enormous power released when a massive star explodes. An implosion crushed material into an extremely dense (10 miles in diameter) neutron star, triggering an explosion that sent a shock wave rumbling through space at speeds in excess of 5 million mph.

The image reveals a central intense white blaze of high-energy particles about 3 light years across created by the rapidly rotating neutron star, or pulsar. Surrounding the white blaze is a shell of hot gas 40 light years in diameter that marks the outward progress of the supernova shock wave.

Whirling around 20 times a second, the pulsar is generating power at a rate equivalent to 30,000 Suns. This pulsar is remarkably similar to the famous Crab Nebula pulsar, although they are seen at vastly different distances, 160,000 light years versus 6,000 light years. Both SNR 0540-69.3 and the Crab pulsar rotating rapidly, and are about a thousand years old. Both pulsars are pumping out enormous amounts of X-radiation and high-energy particles, and both are immersed in magnetized clouds of high-energy particles that are a few light years in diameter. Both clouds are luminous X-ray sources, and in both cases the high-energy clouds are surrounded by a filamentary web of cool gas that shows up at optical wavelengths.

However, the extensive outer shell of 50 million degree Celsius gas in SNR 0540-69.3 has no counterpart in the Crab Nebula. This difference is thought to be due to environmental factors. The massive star that exploded to create SNR 0540-69.3 was evidently in a region where there was an appreciable amount of gas. The supernova shock wave swept up and heated the surrounding gas and created the extensive hot X-ray shell. A similar shock wave presumably exists around the Crab Nebula, but the amount of available gas is apparently too small to produce a detectable amount of X-radiation.

Original Source: Chandra News Release

Posted on by Fraser Cain

NASA Turns Down Year Long Stays in the Station

NASA has rejected a Russian proposal to lengthen missions on board the International Space Station up to a year. By extending the mission times, cash-starved Russia could enable more tourists to visit the station, and help cover its costs – without the shuttle, Russian has shouldered the burden of sending people to and from the station. NASA didn’t reject the concept outright, but said that this wasn’t the best time to extend the stay, giving the Russians room for further negotiations.

Posted on by Fraser Cain

Martian Dust Devils Could Be Charged Up

Image credit: NASA
Scientists have found clues that dust devils on Mars might have high-voltage electric fields, based on observations of their terrestrial counterpart. This research supports NASA’s Vision for Space Exploration by helping to understand what challenges the Martian environment presents to explorers, both robotic and eventually human.

NASA and university researchers discovered that dust devils on Earth have unexpectedly large electric fields, in excess of 4,000 volts per meter (yard), and can generate magnetic fields as well. Like detectives chasing down a suspect, the scientists attached instruments to a truck and raced across deserts in Nevada (2000) and Arizona (2001), driving through dust devils to get their measurements as part of the Martian Atmosphere and Dust in the Optical and Radio (MATADOR) activity. The Arizona observations also included a fixed base camp with a full suite of meteorological instruments (refer to Item 2 for a picture of the Arizona campaign).

Dust devils are like miniature tornadoes, about 10 to 100 meters wide with 20- to 60-mile-per-hour (32- to 96-km/hr) winds swirling around a hot column of rising air. “Dust devils are common on Mars, and NASA is interested in them as well as other phenomena as a possible nuisance or hazard to future human explorers,” said Dr. William Farrell of NASA’s Goddard Space Flight Center in Greenbelt, Md. “If Martian dust devils are highly electrified, as our research suggests, they might give rise to increased discharging or arcing in the low-pressure Martian atmosphere, increased dust adhesion to space suits and equipment, and interference with radio communications.” NASA’s Mars Testbed missions in the coming decade may be able to investigate whether such is the case. Farrell is lead author of a paper on this research published in the Journal of Geophysical Research April 20.

“Complex tracks, generated by the large Martian dust devils, are commonly found in many regions of Mars, and several dust devils have been photographed in the act of scouring the surface,” said MATADOR Principal Investigator Dr. Peter Smith of the University of Arizona (Tucson). “These Martian dust devils dwarf the 5- to 10-meter terrestrial ones and can be greater than 500 meters in diameter and several thousand meters high. The track patterns are known to change from season to season, so these huge dust pipes must be a large factor in transporting dust and could be responsible for eroding landforms.”

“Two ingredients, present on both Earth and Mars, are necessary for a dust devil to form: rising air and a source of rotation,” said Dr. Nilton Renno of the University of Michigan, a member of the research team who is an expert in the fluid dynamics of dust devils. “Wind shear, such as a change in wind direction and speed with altitude, is the source for rotation. Stronger updrafts have the potential to produce stronger dust devils, and larger wind shear produces larger dust devils.”

Dust particles become electrified in dust devils when they rub against each other as they are carried by the winds, transferring positive and negative electric charge in the same way you build up static electricity if you shuffle across a carpet. Scientists thought there would not be a high-voltage, large-scale electric field in dust devils because negatively charged particles would be evenly mixed with positively charged particles, so the overall electric charge in the dust devil would be in balance.

However, the team’s observations indicate that smaller particles become negatively charged, while larger particles become positively charged. Dust devil winds carry the small, negatively charged particles high into the air, while the heavier, positively charged particles remain near the base of the dust devil. This separation of charges produces the large-scale electric field, like the positive and negative terminals on a battery. Since the electrified particles are in motion, and a magnetic field is just the result of moving electric charges, the dust devil generates a magnetic field also.

If Martian dust grains have a variety of sizes and compositions, dust devils on Mars should become electrified in the same way as their particles rub against each other, according to the team (refer to Item 1 for an artist’s concept of an electrified Martian dust devil). We experience more static electricity on dry days because water molecules draw charge from electrified objects. Since the Martian atmosphere is extremely dry, the charging is expected to be strong, as there will be few atmospheric water molecules to steal charge from the dust grains. However, since the density of the Martian atmosphere is much lower than Earth’s, the near-surface electrical conductivity of the Martian atmosphere is expected to be 100 times higher. A Martian dust devil will therefore take longer to fully charge, since the increased atmospheric conductivity draws charge away from Martian dust grains.

To date, none of the robotic Mars landers and rovers that have operated on the Martian surface have experienced any consequences of this phenomena, including the rovers Spirit and Opportunity. However, more complex landed laboratories, such as the Mars Science Laboratory (MSL), slated to launch in 2009, may be far more sensitive to electrical disturbances than previous missions. As such, this research is a key stepping stone to more advanced robotic and human exploration of Mars.

Martian dust storms, which can cover the entire planet, are also expected to be strong generators of electric fields (Item 3 shows dust suspended in the Martian atmosphere as a result of Martian dust devil and dust storm activity). The team hopes to measure a large dust storm on Earth and have instruments to detect atmospheric electric and magnetic fields on future Mars landers.

The team includes researchers from NASA Goddard, NASA Glenn (Cleveland, Ohio), NASA Jet Propulsion Laboratory (Pasadena, Calif.), University of Arizona (Tucson), University of California (Berkeley), SETI Institute (Mountain View, Calif.), University of Washington (Seattle), University of Michigan (Ann Arbor), and Duke University (Durham, N.C.). This research was sponsored in part by the NASA Mars Fundamental Research Program, which is operated out of NASA Headquarters in Washington, DC.

Original Source: NASA News Release

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