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Phoenix Probes Martian Soil--No Ice Yet but Lots of Resolution

NASA set to turn up the heat in Phoenix Mars Lander's soil-sniffing ovens
Martian soil



NASA/JPL-Caltech/University of Arizona

NASA announced today that the first soil sample baked in the Phoenix Mars Lander shows no signs of water. No surprise, considering that the crusty sample sat stubbornly on a protective screen for several days before slipping into the oven below, giving whatever ice the dirt might have contained plenty of time to sublimate away.

In the first run of the Thermal and Evolved-Gas Analyzer (TEGA), described in a press conference, Phoenix heated a soil sample to 95 degrees Fahrenheit (35 degrees C) and then to 350 degrees F (175 degrees C). "We will be going up to 1,800 degrees Fahrenheit, or about 1,000 degrees C, in the next soil test happening over the next few days," says William Boynton, a geochemist at the University of Arizona in Tucson Lunar and Planetary Laboratory and a TEGA co-investigator.

Boynton says there are quite a few minerals which, if present in the Martian dirt, would release water, carbon dioxide and possibly sulfur dioxide. "The temperatures at which these certain gases are released," he says, "give us a fingerprint for the mineral." And identifying the minerals is key to understanding whether water ever played over them.

Some chunks of white material, believed to be ice or salt, had made it into the scoopful that only reluctantly passed through a sifter above the oven. But it's not clear if that material—the source of some excitement among mission scientists—had actually made it into TEGA. Researchers say it's possible the white bits did not break up enough to fall through the screen.
 
Phoenix scientists also announced today that the lander will soon abandon its initial dig site, nicknamed "Dodo–Goldilocks," and instructed its robotic arm to dig a new trench, "Wonderland," in the next few weeks. Along with the change of venue, researchers plan to try out one of Phoenix's yet-to-be-deployed toys—a thermal and electrical conductivity probe, which consists of three spikes attached to the robotic arm's "knuckle." This probe is expected to provide a basic measure of the soil's salt and water content.

"That robotic arm is sweet," says Ray Arvidson, a Phoenix co-investigator at Washington University in Saint Louis. "Power is plentiful, and it goes exactly where we tell it to go."

Researchers hope that data from the probe's multiple instruments will allow them to gradually piece together the details of the soil around the Phoenix landing site. Late last week, the lander's optical microscope obtained the most magnified view of Martian soil ever, resolved down to less than one tenth the diameter of a human hair.

This high-resolution shows particles in a range of different sizes: from bigger, black, glassy particles thought to have been forged in ancient volcanoes down to finer, more iron-rich grains that may have resulted from the glassy pieces grinding together.


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