First results from Phoenix bakery
BY DR EMILY BALDWIN
ASTRONOMY NOW
Posted: June 17, 2008

After a difficult time delivering soil samples to one of the ovens onboard Phoenix, the results are now in from the first round of baking: no water, yet.

Colour image of the “Dodo-Goldilocks” trench. White material, possibly ice, is located in the upper portion of the trench only. Image: NASA/JPL-Caltech/University of Arizona/Texas A&M University.

But there is no reason to go home yet. The soil sample that finally made it into the oven had been sitting on the lander’s deck for several days while engineers figured out a way of getting the clumpy soil through the filters and into the ovens. During that time it is more than likely that any water ice contained within the soil would have sublimated into a gas because of the thin Martian atmosphere.

"If the material is ice, it should change with time. Frost may form on it, or it could slowly sublimate," says Robotic Arm lead scientist Ray Arvidson of the University of Washington.

The sample was heated to different temperatures during the experiment, first to 35 degrees Celsius, which would melt any water, and then to 175 degrees Celsius, which would reveal any water vapour, but scientists saw no water whatsoever coming off the soil. The next experiment will heat the sample to 1000 degrees Celsius, which will vapourise any minerals that might be chemically bound to water, carbon dioxide or sulphur dioxide, in order to determine the quantities of the vented gases.

Colour-coded elevation map of the “Dodo-Goldilocks” trench. The deepest areas are 7-8 centimetres and coloured in blue, and the highest areas are coloured in red and pink. Because the terrain is inclined at a 14 degree angle, the highest areas (pink) are about 20 centimetres above the lowest parts of the trench. Image: NASA/JPL-Caltech/University of Arizona/Texas A&M University/NASA Ames Research Centre.

Meanwhile, multi-tasking Phoenix has dug deeper into the two trenches informally known as “Dodo” and “Goldilocks” where white material, possibly ice, was previously identified. The digging has now created one large trench, nicknamed “Dod-Goldilocks”, which is 22 centimetres wide, 35 centimetres long and around 8 centimetres deep.

“We have continued to excavate in the Dodo-Goldilocks trench to expose more of the light-toned material, and we will monitor the site," says Arvidson.

The white material has only been seen in the shallowest part of the trench, farthest from the lander, indicating that it is not continuous throughout the excavated site. Scientists are speculating that the trench might be exposing a ledge or a small portion of a larger slab of white material.

The science team remain confident that future rounds of testing on soil that can be delivered immediately to the ovens will reveal evidence for the existence of water on Mars.

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