Experiments prompted by a 2008 surprise from NASA's Phoenix Mars Lander suggest that soil examined by NASA's Viking Mars landers in 1976 may have contained carbon-based chemical building blocks of life.

"This doesn't say anything about the question of whether or not life has existed on Mars, but it could make a big difference in how we look for evidence to answer that question," said Chris McKay of NASA's Ames Research Center, Moffett Field, Calif. McKay coauthored a study published online by the Journal of Geophysical Research - Planets, reanalyzing results of Viking's tests for organic chemicals in Martian soil.

NASA's Phoenix Mars Lander has ended operations after repeated attempts to contact the spacecraft were unsuccessful. A new image transmitted by NASA's Mars Reconnaissance Orbiter shows signs of severe ice damage to the lander's solar panels.

"The Phoenix spacecraft succeeded in its investigations and exceeded its planned lifetime," said Fuk Li, manager of the Mars Exploration Program at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Although its work is finished, analysis of information from Phoenix's science activities will continue for some time to come."

NASA's Mars Odyssey orbiter heard no signal from the Phoenix Mars Lander when it listened from orbit while passing over Phoenix 60 times last week.

Odyssey had also listened for a signal from Phoenix during periods in January and February. During the third campaign, April 5 through April 9, the sun stayed above the horizon continuously at the arctic site where Phoenix completed its mission in 2008.

NASA's Phoenix Mars Lander showed no sign during February that it has revived itself after the northern Mars winter. NASA's Mars Odyssey orbiter will check again in early April.

The solar-powered Phoenix lander operated for two months longer than its planned three-month mission in the Martian arctic in 2008. It was not designed to withstand winter conditions.

Mars Odyssey began a second campaign Monday to check on whether the Phoenix Mars Lander has revived itself after the northern Martian winter. The orbiter received no signal from the lander during the first 10 overflights of this campaign.

Odyssey will listen for Phoenix during 50 additional overflights, through Feb. 26, during the current campaign.

NASA's Mars Odyssey orbiter has completed 11 overflights, listening for the Phoenix Mars Lander on Jan. 19 and 20, without hearing anything from the lander. Nineteen more listening overflights are planned this week, and additional attempts in February and March.

The attempts are being made because of the unlikely scenario that Phoenix has survived Martian arctic winter conditions the spacecraft was never designed to withstand.

Beginning Jan. 18, NASA's Mars Odyssey orbiter will listen for possible, though improbable, radio transmissions from the Phoenix Mars Lander, which completed five months of studying an arctic Martian site in November 2008.

The solar-powered lander operated two months longer than its three-month prime mission during summer on northern Mars before the seasonal ebb of sunshine ended its work. Since then, Phoenix's landing site has gone through autumn, winter and part of spring. The lander's hardware was not designed to survive the temperature extremes and ice-coating load of an arctic Martian winter.

The High Resolution Imaging Science Experiment, or HiRISE, run from the University of Arizona, is releasing two views of the Phoenix Mars Lander, the 2008 NASA mission also run from the UA, which show the lander shrouded in dry-ice frost on Mars.

The HiRISE camera aboard NASA's Mars Reconnaissance Orbiter captured one image of the Phoenix lander on July 30, 2009, and the other on Aug. 22, 2009. That's when the sun began rising over the northern polar plains at the end of the northern hemisphere winter, the imaging team said.

Wind speeds and directions were measured for the first time in the Mars polar region using the Phoenix lander's Telltale instrument. Astronomers recorded Easterly winds of approximately 15-20 kilometres per hour during the martian mid-summer.

When autumn approached, the winds increased and switched round to come predominantly from the West. While these winds appeared to be dominated by turbulence, the highest wind speeds recorded of up to nearly 60 kilometres per hour coincided with the passing of weather systems, when also the number of dust devils increased by an order of magnitude.

Mars gets as far as 250 million miles away, but many parts of it closely resemble places on Earth, including its landscape, history of water, soil and even its weather, says a Texas A&M University researcher in the current issue of Science magazine.

Mark Lemmon, a professor of atmospheric sciences who has been involved with Mars missions for years, says last year's Phoenix Mars Lander mission keeps revealing secrets about the planet, answering some questions but raising other big ones. He is one of several authors detailing the Phoenix discoveries.

Four papers in the journal Science this week offer new details about the history of water on Mars, gleaned from the 2008 NASA Phoenix Mars Mission that was operated from The University of Arizona.

Peter H. Smith, a scientist with the UA Lunar and Planetary Laboratory and the mission's principal investigator, is the first author of "H2O at the Phoenix Landing Site" in Science. There are 35 co-authors from six countries on the paper. Smith and his group of scientists and students used the lander to investigate the role of water and ice on Mars, as well as the changing weather patterns.

Researchers at the University of Arkansas have shown that salts formed from perchlorates discovered at the Phoenix landing site have the potential to be found in liquid solution under the temperature and pressure conditions on present-day Mars.

Research professor Vincent F. Chevrier and graduate students Jennifer Hanley and Travis S. Altheide report their findings in the current issue of Geophysical Research Letters. Their work provides the first demonstration of a potential stable liquid on present-day Mars in the immediate environment of the lander.

Summer turned to autumn for the Phoenix Mars Lander on December 26, 2008. This image, taken on December 21 by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, shows the lander during the last waning days of northern hemisphere summer.

The image was acquired at 15:31 Local Mars Time when the sun was 14-degrees above the horizon. The image is false color, but appears bluish due to atmospheric haze. Frost is not yet apparent here during the middle afternoon.

The Martian arctic soil that NASA's Phoenix Mars Lander dug into this year is very cold and very dry. However, when long-term climate cycles make the site warmer, the soil may get moist enough to modify the chemistry, producing effects that persist through the colder times.

Phoenix found clues increasing scientists' confidence in predictive models about water vapor moving through the soil between the atmosphere and subsurface water-ice. The models predict the vapor flow can wet the soil when the tilt of Mars' axis, the obliquity, is greater than it is now.

After nearly a month of daily checks to determine whether Martian NASA's Phoenix Mars Lander would be able to communicate again, the agency has stopped using its Mars orbiters to hail the lander and listen for its beep. As expected, reduced daily sunshine eventually left the solar-powered Phoenix craft without enough energy to keep its batteries charged.

The final communication from Phoenix remains a brief signal received via NASA's Mars Odyssey orbiter on Nov. 2. The Phoenix lander operated for two overtime months after achieving its science goals during its original three-month mission. It landed on a Martian arctic plain on May 25.