Wednesday, August 13, 2008

Mysteries of alien dirt

We've all been following the day-to-day stories from the Phoenix Mars Lander but Richard Kerr, science writer with Science, put together a broader view in this week's issue of the journal.

He noted that the icy soil is so "interesting that team members spent the middle third of the mission trying in vain to get an ice-rich sample into one of the lander's two prime analytical instruments. Now Phoenix has moved on to less challenging, less icy samples while team members try to sort out the mysteries of alien dirt."

The Lander team members admit they don't fully understand what's going on with the Martian soil. The clumpiness "might reflect either a buildup of electrostatic charge on the finest particles, a mechanical interlocking at particle edges, or the dampening effect of salts." [right, soil sample from a trench informally called 'Rosy Red' after being delivered to a gap between partially opened doors on the lander's Thermal and Evolved-Gas Analyzer, or TEGA. NASA/JPL-Caltech/University of Arizona/Texas A&M University]

The team spent 30 days, one-third of the planned mission, practicing "how best to scrape, rasp, and scoop up ice chips and deliver the sample to TEGA." However, the "least-likely" problem of getting the soil sample out of the robotic scoop has stymied the group.

A growing suspicions centers around pulling a very cold sample out with a relatively warmer scoop into a relatively warmer atmosphere, possibly leading to melting and refreezing of the sample in the scoop, so that it becomes so frozen to the instrument that it cannot be readily dislodged.

"It's unfortunate we spent 30 [days] working on delivering ice," said team member Ray Arvidson. The group was concerned about enough time to analyze six more samples with each taking 7 days to analyze but the 30 day extension of the mission has lessened those fears.

The team is working on dry soil tests while they try to figure out the icy-soil problem.

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