The UA-led Phoenix Mars Lander scooped up a soil sample from an intermediate depth between the ground surface and a subsurface icy layer the other day. The sample was delivered it to a laboratory oven on the spacecraft to look for oxygen release that indicates perchlorate. The discovery of perchlorate last month triggered rumors and speculation about its impact on the potential for life on Mars. [right, soil was delivered through cell #7 on the left of the Thermal and Evolved-Gas Analyzer - TEGA]
The samples are going through a 3-stage heating process. The low temperature heating is to look for ice in the sample. The next step is a middle temperature process to thoroughly dry the sample. The last heating takes the sample to 1000 degrees Celsius (1832 degrees Fahrenheit) to drive off gases that can help determine soil properties.