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Sky falls above the moon !

"Every day, more than a metric ton of meteoroids hits the Moon," says Bill Cooke of the Marshall Space Flight Center's Meteoroid Environment Office. They literally fall out of the sky, in all shapes and sizes, from specks of comet dust to full-blown asteroids, traveling up to a hundred thousand mph. And when they hit, they do not disintegrate harmlessly in the atmosphere as most would on Earth. On the airless Moon, meteoroids hit the ground.

Clues to how often and how hard the Moon is hit lie in data from four seismometers placed on the Moon by the Apollo 12, 14, 15, and 16 missions during 1969-72. They operated until NASA turned them off in 1977. For years, the seismometers recorded all manner of tremors and jolts, including almost 3000 moonquakes, 1700 meteoroid strikes, and 9 spacecraft deliberately crashed into the Moon. All these data were transmitted to Earth for analysis.

Cooke and Diekmann are now loading the old seismic data into machines at the MSFC where they can perform digital calculations at speeds impossible 30 years ago, rapidly trying new algorithms to find previously unrecognized impacts.

Critical to the analysis are nine man-made impacts. "NASA deliberately crashed some spacecraft into the Moon while the seismometers were operating," he explains. "They were the empty ascent stages of four lunar modules (Apollo 12, 14, 15 and 17) and the SIV-B stages of five Saturn rockets (Apollo 13, 14, 15, 16 and 17)." Their seismic waveforms tell researchers what an impact should look like.


According to the Standard Model, such meteoroids hit the Moon approximately 400 times a year—more than once a day. (Picture a map of Africa stuck with 400 pushpins.) The Apollo seismic dataset can test that prediction and many others.

The analysis is just beginning. "We hope to find many impacts," he says. Regardless of the final numbers, however, their work will have value. "We're developing new algorithms to find meteoroid impacts in seismic data." Eventually, Cooke believes, next-generation seismometers will be placed on the Moon and Mars to monitor quakes and impacts, and when the data start pouring in, "we'll be ready."

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NASA spacecraft hits moon - a search for water

NASA today announced that a small spacecraft, to be developed by a team at NASA Ames, has been selected to travel to the moon to look for precious water ice at the lunar south pole.

The name of the mission is LCROSS, short for Lunar CRater Observation and Sensing Satellite. LCROSS is a secondary payload: It will hitch a ride to the moon onboard the same rocket as the Lunar Reconnaissance Orbiter (LRO) satellite due to launch from the Kennedy Space Center in October 2008.



Left: LCROSS approaches the moon...
Daniel Andrews's team proposed LCROSS. He says , "We think we have assembled a very creative, highly innovative mission." LCROSS will hunt for water by hitting the moon--twice--throwing up plumes that may contain signs of H2O.

It works like this: After launch, the LCROSS spacecraft will arrive in the moon's vicinity independent of Lunar Reconnaissance Orbiter. On the way to the moon, the LCROSS spacecraft's two main parts, the Shepherding Spacecraft (S-S/C) and the Earth Departure Upper Stage (EDUS), will remain coupled. As the pair approach the moon's south pole, the upper stage will separate, and then hit a crater in the south pole area. A plume from the upper stage crash will develop as the Shepherding Spacecraft heads in toward the moon. The Shepherding Spacecraft will fly through the plume using its instruments to analyze the cloud for signs of water and other compounds. Additional space and Earth-based instruments also will study the 2.2-million-pound (1000-metric-ton) plume.


Left: ...and hits. Pictured is the first of two impacts delivered by the split craft.

Lunar Reconnaissance Orbiter and LCROSS are the first of many robotic missions NASA will conduct between 2008 and 2016 to study, map, and learn about the lunar surface to prepare for the return of astronauts to the moon. These early missions will help determine lunar landing sites and whether resources, such as oxygen, hydrogen, and metals, are available for use in NASA's long-term lunar exploration objectives.

NASA NEWS RELEASE

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Planets around Dead Stars

NASA's Spitzer Space Telescope has uncovered new evidence that planets might rise up out of a dead star's ashes.

The infrared telescope surveyed the scene around a pulsar, the remnant of an exploded star, and found a surrounding disk made up of debris shot out during the star's death throes. The dusty rubble in this disk might ultimately stick together to form planets.

This is the first time scientists have detected planet-building materials around a star that died in a fiery blast.



Pic : An artist's concept of a planet-forming disk around pulsar 4U 0142+61. [Movie]

The paper on the Spitzer finding appears in the April 6 issue of Nature. Other authors of the paper are lead author Zhongxiang Wang and co-author David Kaplan, both of the Massachusetts Institute of Technology.

"We're amazed that the planet-formation process seems to be so universal," says Deepto Chakrabarty of the Massachusetts Institute of Technology, principal investigator of the new research. "Pulsars emit a tremendous amount of high energy radiation, yet within this harsh environment we have a disk that looks a lot like those around young stars where planets are being born."


The finding represents the missing piece in a puzzle that arose in 1992, when Aleksander Wolszczan of Pennsylvania State University found three planets circling a pulsar called PSR B1257+12. Those pulsar planets, two the size of Earth, were the first planets of any type ever discovered outside our solar system. Astronomers have since found indirect evidence the pulsar planets were born out of a dusty debris disk, but nobody had directly detected this kind of disk until now.

The pulsar observed by Spitzer, named 4U 0142+61, is 13,000 light-years away in the constellation Cassiopeia. It was once a large, bright star with a mass between 10 and 20 times that of our sun. The star probably survived for about 10 million years, until it collapsed under its own weight about 100,000 years ago and blasted apart in a supernova explosion.

Some of the debris, or "fallback," from that explosion eventually settled into a disk orbiting the shrunken remains of the star, or pulsar. Spitzer was able to spot the warm glow of the dusty disk with its heat-seeking infrared "eyes." The disk orbits at a distance of about 1 million miles and probably contains about 10 Earth-masses of material.

see captionPulsars are a class of supernova remnants, called neutron stars, which are incredibly dense. They have masses about 1.4 times that of the sun squeezed into bodies only 10 miles wide. One teaspoon of a neutron star would weigh about 2 billion tons. Pulsar 4U 0142+61 is an X-ray pulsar, meaning that it spins and pulses with X-ray radiation.

Any planets around the stars that gave rise to pulsars would have been incinerated when the stars blew up. The pulsar disk discovered by Spitzer might represent the first step in the formation of a new, more exotic type of planetary system, similar to the one found by Wolszczan in 1992.

"I find it very exciting to see direct evidence that the debris around a pulsar is capable of forming itself into a disk. This might be the beginning of a second generation of planets," Wolszczan says.

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