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Phoenix finds dry Martian soil, ice underneath |
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Written by Derek Kessler on
Sunday, 20 July 2008
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 (From July 16, 2008) So, Phoenix has been busy in the past month. First up is that sticking dirt that got stuck on top of the grate leading into one of the lander’s oven. Having gotten that soil finally into the oven, heating it up revealed no signs of water. The gasses given off by the 175° C (350° F) soil were sent into the Thermal and Evolved-Gas Analyzer (TEGA). With no water vapor detected, the sample was then heated to a scorching 1000° C (1800° F) to vaporize any water-formed minerals in the soil. Nada.
Even so, Phoenix did see water. As part of its soil collection, the lander’s shovel scraped against a hard surface several centimeters below the surface, chipping off a few bits of white material. While none of the substance was delivered into the lander’s laboratories, camera imaging showed that after just a few days the material had disappeared. Scientists said there was only one explanation: it was ice, and it had evaporated.
The ice bits underwent sublimination: the transformation from a solid direction to a gas. This resulted from the lower atmospheric pressure on the surface of Mars, forgoing any melting into water. Water itself is nearly impossible to find in a liquid form in the frigid Martian arctic where Phoenix landed.
From there, Phoenix hit another roadblock. Confident that the hard surface below the surface was ice of some sort, scientists at the University of Arizona decided to dig into it. They discovered that Phoenix was futilely scraping away at the ice, creating only small piles of shavings which it could not collect with its shovel. Richard Volpe, a scientist with NASA’s Jet Propulsion Lab likened it to “trying to pick up dust with a dustpan, but without a broom.”
Frustrated with the progress of the failed digging, mission controllers turned the shovel over and used a powered rasp on its back to scrape up enough material to scoop. The rasp use was a test of the system’s viability as a collection technique and scientists were satisfied with the results. Additionally, images of the collected material showed that in a span of mere hours the sample size decreased, most likely due to sublimination. In the coming days, mission controllers will again turn the rasp on the icy sub-surface to collect a larger sample for the TEGA.
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