Dead Spacecraft on Mars Lives on in New Study

Datacollected by NASA's Phoenix Mars Lander before it went silent for good on theRed Planet is providing valuable insight for a new study on the interactions betweenthe Martian dirt and atmosphere.

NASA'sPhoenix lander has been sitting idle in the Martian arctic since November 2008,when engineers lost the ability to contact the craft after its solar powersupplies were depleted by the Martian winter. Photographsof the Phoenix lander from spacecraft orbiting Mars showedextensive damage to its solar arrays.

Butnow, Phoenix has a chance to contribute again thanks to a new study thatdraws on the data the probe gathered before it died. [Photosof Phoenix on Mars]

VincentChevrier, a research professor at the Arkansas Center for Space and PlanetarySciences at the University of Arkansas in Fayetteville, has received fundingfrom NASA to study measurements made previously by the now-defunct Phoenix mission. Chevrier hopes to develop a better understanding ofhow dirt on Mars interacts with the planet's atmosphere, as well as whetherthese interactions ever produce liquid water.

Phoenixdata's new life

Phoenixlanded on Mars in May 2008, and conducted a successful mission, outlasting itsplanned three-month tenure. It carried equipment to take samples of the Martiandirt to search for signs that the environment could be habitable to microbiallife.

Chevrierwill analyze Phoenix data on Mars dirt's temperature, humidity, electricalconductivity, heat parameters and permittivity, which is the measure of amaterial's ability to transmit an electric field.

Thesetens of thousands of measurements, which were collected over the course ofabout six months, couldreveal how the dirt affects the stability of ice and the formation of liquidbrine solutions, which contain liquid water.

"Ourgroup has shown that it is thermodynamically possible to have a stable liquidin the soil for a few hours a day under certain conditions," Chevriersaid. "The effect of the regolith, or soil, on the water cycle is poorlyunderstood and the Phoenix data provide a unique insight into theseprocesses."

Ifthere is liquidwater on Mars, it might cause certain changes in some of theelectrical data from the Phoenix lander, Chevrier said. However,those changes could be extremely subtle, or even nonexistent.

"Youneed a continuous layer of fluid in order to detect changes in theseparameters," Chevrier said. "A drop of water won't do it."

SaltyMars dirt

Chevrier'sstudy will also examine the nature and composition of the salts in the Marsdirt at the Phoenix site, including perchlorates, a type of charged compoundcontaining hydrogen, chlorine and oxygen.

ThePhoenix mission originally determined the presence of perchlorates on the surface of Mars. These compounds attractwater, which means that they may help control humidity in the soil andatmosphere, said Chevrier.

Currentmeteorological models for Mars are somewhat basic. While they work well forpredicting where a Mars explorer should land, they fail to accurately describethe complex atmosphere on the planet, Chevrier said.

Theresearchers will examine how the soil on Mars interacts with the atmosphere bystudying the exchange of water vapor between salts, as well as the speed ofabsorption where water molecules collect around grains in the soil. Then, theywill examine the ice layer under the top layer of soil,looking for signs of sublimation, in which the ice becomes gas and is dispersedthrough the soil.

HuntingMars water

Afterstudying the Martian dirt, Chevrier's team will focus on liquid water.

"Ifthe salts can exchange, maybe they will form a brine solution," Chevriersaid.

Thiswill require a detailed examination of the data, since Chevrier's previous studyshowed that liquid water might be stable for a mere two or three hours on agiven day.

Chevrierwill also reinvestigate the chemical data to detect the possible presence ofchlorate, another compound. Currently, Phoenix's measurements do not fit with scientists'understanding of the chemical composition of the Martian soil.

Chevrierand his team of researchers believe the discrepancy may be explained by thepresence of chlorates as well as perchlorate. These two molecules appearsimilar to the instruments on Phoenix, and have approximately the samestability.

• Gallery - Mars: A Spacecraft Graveyard
• Images: Phoenix on Mars! 
• NASA Declares Phoenix Mars Lander Broken and Dead