National Aeronautics and Space Administration scientists said results from that instrument, part of Phoenix's Microscopy, Electrochemistry and Conductivity Analyzer, are expected to provide the first measurement of the acidity or alkalinity of Martian soil. That will help researchers determine whether ice beneath the soil ever has melted, and whether the soil has other qualities favorable for life, NASA said.

The Phoenix team Thursday discussed what sample to deliver next to the lander's other analytical instrument, which bakes and sniffs soil to identify volatile ingredients. Engineers have identified possible problems in the operation of that instrument, the Thermal and Evolved-Gas Analyzer, or TEGA.

Scientists believe the first soil sample delivered to TEGA was so clumpy that soil particles clogged a screen over the opening. Four days of vibration succeeded at getting the soil through the screen, but engineers say the motor creating the vibration might also have caused a short circuit in wiring near that oven.

NASA says subsequent soil samples will be delivered using a method that will sprinkle soil into the instrument, avoiding vibration.