National Aeronautics and Space Administration scientists said the spacecraft's Thermal and Evolved-Gas Analyzer, or TEGA, has eight tiny ovens to bake the soil to assess its volatile ingredients, such as water.
The lander's robotic arm delivered a partial scoopful of clumpy soil to the number 4 oven on TEGA last Friday -- 12 days after the spacecraft landed.
A screen covers each of TEGA's eight ovens to prevent larger bits of soil from clogging the narrow port to each oven. The oven was shaken Friday, Sunday and Monday to allow small particles into it.
"There's something very unusual about this soil, from a place on Mars we've never been before," said Phoenix Principal Investigator Peter Smith of the University of Arizona-Tucson. "We're interested in learning what sort of chemical and mineral activity has caused the particles to clump and stick together."
The NASA team plans to sprinkle Martian soil onto the delivery port for the spacecraft's Optical Microscope, as well as analyze additional portions of a high-resolution color panorama of the lander's surroundings.