Martian Soil Sample Clogs Phoenix Probe's Oven

The researchers have not yet determined why none of the sample appears to have gotten past the screen, but they have begun proposing possibilities.

"I think it's the cloddiness of the soil and not having enough fine granular material," said Ray Arvidson of Washington University in St. Louis, the digging czar for the $420 million Phoenix mission.

The Phoenix lander touched down on the red planet on May 25 to begin a planned three-month mission to hunt for buried water ice in the northern polar region of Mars. It is equipped with a scoop-tipped robotic arm, weather station, wet chemistry lab and eight ovens to study samples of Martian terrain and determine if the region could have once supported primitive life.

TEGA?s screen is designed to let through particles up to 0.04 inch (1 millimeter) across while keeping out larger particles, in order to prevent clogging a funnel pathway to a tiny oven inside.

Mission scientists said they planned to send new commands to Phoenix to try to shake the sample into the oven as early as Monday. They'll spend Sunday developing the plan for the following Martian day.

The small vibration tool can shake the oven screen across a variety of frequencies, ranging from a light tapping to moderate shake, mission managers said.

?The soil that we're looking at is probably sandy and it has a lot of fine grains and dust, but it is also a little bit cohesive,? Arvidson said. ?I'm pretty confident that if we shake this stuff, we'll get some in.?

For future samples, they may use the robotic arm to prepare a site by poking and prodding the Martian surface to break up clumps and clods. They may also collect smaller scoops of material to pour directly into the oven.

While this is the first oven they've tried to pour samples into, it is designated Oven 4 of eight. Despite the overflow of soil across the other oven doors, mission managers are confident the extra stuff won't hinder the opening of other instruments.

The TEGA ovens have an opening just 2 mm wide and are designed to collect about 30 milligrams of material for baking.

Phoenix's planned activities for Saturday include horizontally extending a trench, dubbed ?Dodo,? where the lander dug two practice scoops earlier this week, and taking additional images of a small pile of soil that was scooped up and dropped onto the surface during the second of those practice digs.

"We are hoping to learn more about the soil's physical properties at this site," Arvidson said. "It may be more cohesive than what we have seen at earlier Mars landing sites."

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