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Friday, October 29, 2010

Space Radar Provides a Taste of Comet Hartley 2

Twelve radar images of the nucleus of comet Hartley 2 Twelve radar images of the nucleus of comet Hartley 2 were obtained by the Arecibo Observatory's planetary.

Trapped NASA Mars Rover finds more evidence of water on 'Red Planet'

The presence of water on Mars has become more evident, suggests a new NASA finding.

Scientists have revealed that the ground where NASA's Mars Exploration Rover Spirit became stuck last year holds evidence that water, perhaps as snow melt, trickled into the subsurface fairly recently and on a continuing basis.

Stratified soil layers with different compositions close to the surface led the rover science team to propose that thin films of water may have entered the ground from frost or snow.

The seepage could have happened during cyclical climate changes in periods when Mars tilted farther on its axis. The water may have moved down into the sand, carrying soluble minerals deeper than less soluble ones. Spin-axis tilt varies over timescales of hundreds of thousands of years.

The relatively insoluble minerals near the surface include what is thought to be hematite, silica and gypsum. Ferric sulphates, which are more soluble, appear to have been dissolved and carried down by water.

"The lack of exposures at the surface indicates the preferential dissolution of ferric sulphates must be a relatively recent and ongoing process since wind has been systematically stripping soil and altering landscapes in the region Spirit has been examining," said Ray Arvidson, investigator for the twin rovers Spirit and Opportunity.

The twin Mars rovers finished their three-month prime missions in April 2004, then kept exploring in bonus missions. One of Spirit's six wheels quit working in 2006.

Researchers took advantage of Spirit's months at Troy last year to examine in great detail soil layers the wheels had exposed, and also neighbouring surfaces.

"With insufficient solar energy during the winter, Spirit goes into a deep-sleep hibernation mode where all rover systems are turned off, including the radio and survival heaters," said John Callas, project manager for Spirit and Opportunity at NASA.

"All available solar array energy goes into charging the batteries and keeping the mission clock running," said Callas.

Spirit, Opportunity, and other NASA Mars missions have found evidence of wet Martian environments billions of years ago that were possibly favourable for life.

These newest Spirit findings contribute to an accumulating set of clues that Mars may still have small amounts of liquid water at some periods during ongoing climate cycles.

The findings were published in the Journal of Geophysical Research. (ANI)

Dead Spacecraft Walking

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A pair of NASA spacecraft that were supposed to be dead last year are instead flying to the Moon for a breakthrough mission in lunar orbit.

"Their real names are THEMIS P1 and P2, but I call them 'dead spacecraft walking,'" says Vassilis Angelopoulos of UCLA, principal investigator of the THEMIS mission. "Not long ago they appeared to be doomed, but now they are beginning an incredible new adventure."

The story begins in 2007 when NASA

launched a fleet of five spacecraft into Earth's magnetosphere to study the physics of geomagnetic storms. Collectively, they were called THEMIS, short for "Time History of Events and Macroscale Interactions during Substorms." P1 and P2 were the outermost members of the quintet.

Working together, the probes quickly discovered a cornucopia of previously unknown phenomena such as colliding auroras, magnetic spacequakes, and plasma bullets shooting up and down Earth's magnetic tail. This has allowed researchers to solve several longstanding mysteries of the Northern Lights.

The mission was going splendidly, except for one thing: Occasionally, P1 and P2 would pass through the shadow of Earth. The solar powered spacecraft were designed to go without sunlight for as much as three hours at a time, so a small amount of shadowing was no problem. But as the mission wore on, their orbits evolved and by 2009 the pair was spending as much as 8 hours a day in the dark.

"The two spacecraft were running out of power and freezing to death," says Angelopoulos. "We had to do something to save them."

The team brainstormed a solution. Because the mission had gone so well, the spacecraft still had an ample supply of fuel--enough to go to the Moon. "We could do some great science from orbit," he says. NASA approved the trip and in late 2009, P1 and P2 headed away from the shadows of Earth.

With a new destination, the mission needed a new name. The team selected ARTEMIS, the Greek goddess of the Moon. It also stands for "Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun."

The first big events of the ARTEMIS mission are underway now. On August 25, 2010, ARTEMIS-P1 reached the L2 Lagrange point on the far side of the Moon. Following close behind, ARTEMIS-P2 entered the opposite L1 Lagrange point on Oct. 22nd. Lagrange points are places where the gravity of Earth and Moon balance, creating a sort of gravitational parking spot for spacecraft.

"We're exploring the Earth-Moon Lagrange points for the first time," says Manfred Bester, Mission Operations Manager from the University of California at Berkeley, where the mission is operated. "No other spacecraft have orbited there."

Because they lie just outside Earth's magnetosphere, Lagrange points are excellent places to study the solar wind. Sensors onboard the ARTEMIS probes will have in situ access to solar wind streams and storm clouds as they approach our planet-a possible boon to space weather forecasters. Moreover, working from opposite Lagrange points, the two spacecraft will be able to measure solar wind turbulence on scales never sampled by previous missions.

"ARTEMIS is going to give us a fundamental new understanding of the solar wind," predicts David Sibeck, ARTEMIS project scientist at the Goddard Space Flight Center. "And that's just for starters."

ARTEMIS will also explore the Moon's plasma wake-a turbulent cavity carved out of the solar wind by the Moon itself, akin to the wake just behind a speedboat. Sibeck says "this is a giant natural laboratory filled with a whole zoo of waves waiting to be discovered and studied."

Another target of the ARTEMIS mission is Earth's magnetotail. Like a wind sock at a breezy airport, Earth's magnetic field is elongated by the action of the solar wind, forming a tail that stretches to the orbit of the Moon and beyond. Once a month around the time of the full Moon, the ARTEMIS probes will follow the Moon through the magnetotail for in situ observations.

"We are particularly hoping to catch some magnetic reconnection events," says Sibeck. "These are explosions in Earth's magnetotail that mimic solar flares--albeit on a much smaller scale." ARTEMIS might even see giant 'plasmoids' accelerated by the explosions hitting the Moon during magnetic

These far-out explorations may have down-to-Earth applications. Plasma waves and reconnection events pop up on Earth, e.g., in experimental fusion chambers. Fundamental discoveries by ARTEMIS could help advance research in the area of clean .

After six months at the Lagrange points, ARTEMIS will move in closer to the Moon-at first only 100 km from the surface and eventually even less than that. From point-blank range, the spacecraft will look to see what the solar wind does to a rocky world when there's no magnetic field to protect it.

"Earth is protected from solar wind by the planetary magnetic field," explains Angelopolous. "The Moon, on the other hand, is utterly exposed. It has no global magnetism."

Studying how the solar wind electrifies, alters and erodes the Moon's surface could reveal valuable information for future explorers and give planetary scientists a hint of what's happening on other unmagnetized worlds around the solar system.

Orbiting the Moon is notoriously tricky, however, because of irregularities in the lunar gravitational field. Enormous concentrations of mass (mascons) hiding just below the surface tug on spacecraft in unexpected ways, causing them over time to veer out of orbit. ARTEMIS will mitigate this problem using highly elongated orbits ranging from tens of km to 18,000 km.

"We'll only be near the lunar surface for a brief time each orbit (accumulating a sizable dataset over the years)," explains Angelopoulos. "Most of the time we'll linger 18,000 km away where we can continue our studies of the solar wind at a safe distance."

The Dead Spacecraft Walking may have a long life ahead, after all.

NASA recycles two small satellites for lunar mission

Having finished their primary mission investigating the formation of auroral light displays at Earth's poles, two diminutive NASA satellites have been dispatched to the moon for bonus science.

Artist's concept of an ARTEMIS spacecraft near the moon. Credit: NASA

Packed with magnetometers and electrical instruments specially designed to probe shocking solar storms, the two are now positioned to study the mysterious interaction between the solar wind and the moon.

Scientists call the new mission ARTEMIS, or Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun.

"Using two repurposed satellites for the ARTEMIS mission highlights NASA's efficient use of the nation's space assets," said Dick Fisher, director of the heliophysics division in NASA's science directorate.

The two satellites were part of a fleet of five platforms launched in February 2007 to fly through Earth's magnetosphere, a nearly invisible bubble that protects the planet from radiation and charged particles originating from the sun and the cosmos.

Called the THEMIS mission, the five satellites discovered the natural mechanism that triggers geomagnetic storms, which manifest themselves as spectacular light shows known as aurora, or the Northern and Southern Lights.

With the primary mission completed, NASA moved two of the satellites from their unique, high-altitude orbit around Earth to never-before-explored regions at gravitationally stable points less than 40,000 miles from the moon.

Three remaining THEMIS satellites are still circling Earth in an extended mission observing the Northern Lights.

Using a series of novel thruster firings and taking advantage of lunar gravity, engineers guided the two highest THEMIS satellites to Lagrange points averaging about 37,000 miles from the near and far sides of the moon. The Lagrange points are sites where the gravity of two celestial bodies, the Earth and moon in this case, balance to create a stable home for scientific spacecraft.

One of the box-shaped spacecraft reached its Lagrange point Aug. 25, and the other arrived Oct. 22, according to NASA.

The newly-christened ARTEMIS probes are in stable orbits around each Lagrange point. The satellites are already collecting data, according to NASA.

More complex maneuvers are planned to place the satellites in elliptical orbits around the moon by May 2011. The probes will fluctuate between about 60 miles and 12,000 miles above the lunar surface.

NASA has approved ARTEMIS for a two-year mission. The mission is also named for Artemis, the Greek goddess of hunting and the wilderness often linked to lunar mythology.

A drawing depicting three THEMIS satellites in Earth orbit and two ARTEMIS probes near the moon. Credit: NASA

"ARTEMIS will provide a unique two-point view of the moon's under-explored space environment," said Vassilis Angelopoulos, THEMIS principal investigator at the University of California, Los Angeles. "These two spacecraft are headed for an incredible new adventure."

Five instruments on each satellite will measure the electric and magnetic fields, ions and electrons around the spacecraft, uncovering unprecedented details on the space environment close to the moon.

The moon does have a robust magnetosphere like Earth, leaving the lunar surface exposed to erosion from the solar wind, a stream of ionized particles flowing from the sun into the solar system.

ARTEMIS observations began this week to measure how the solar wind charges, alters and erodes the lunar surface, according to a NASA press release.

Scientists say ARTEMIS will be the most extensive study of the space environment around a planetary body without a magnetosphere.

Results from ARTEMIS will be crucial for characterizing the lunar radiation environment before possible long-term human voyages or robotic exploration.

Nasa uncovers new 'life on Mars' evidence after rover got stuck in the mud

Nasa uncovers new 'life on Mars' evidence after rover got stuck in the mud

This mosaic of images shows the soil in front of NASA's Mars Exploration Rover Spirit Photo: REUTERS

Researchers at the American space agency made the discovery after the Mars Exploration Rover Spirit became stuck in wet ground on the red planet earlier this year.

Astronomers have become excited by the latest discovery, which they say proves that water favourable for life formed on the red planet more recently than previously thought.

Scientists had always believed water formed more than a billion years ago but the latest discovery is the first sign of liquid forming in the past few hundred thousands years.

Nasa’s latest study, reported in the Journal of Geophysical Research, concluded the liquid likely formed from melting snow, which then trickled into the subsurface and dissolved.

It contained several minerals including hematite, silica and gypsum while ferric sulphates, which are more soluble, also were carried down by the water.

None of these minerals are exposed at the surface, which is covered by windblown sand and dust.

“On Earth … hydrothermal systems provide the environmental conditions, water, nutrients and energy sources needed to sustain robust microbial communities,” concluded the Nasa team, who are based at Nasa’s Jet Propulsion Laboratory, Pasadena, California.

“It seems likely the region (on Mars) … may have likewise supported a habitable environment.”

According to Nasa, the Mars explorer became stuck in April last year when its left wheels broke through the surface’s crust called “Troy” and fell into soft sand below.

The soil exposed by Spirit’s spinning wheels carries clues that Mars may still be wet.

The seepage could have happened during cyclical climate changes in periods when Mars tilted farther on its axis.

"Liquid water and life kind of go together," said Ray Arvidson, of Washington University in St. Louis, who was involved in the project.

Nasa abandoned plans to extract the rover earlier this year.