Phoenix Takes First Martian Soil Sample
This image taken on June 5, 2008 shows the Robotic Arm scoop containing a soil sample poised over the partially open door of the Thermal and Evolved-Gas Analyzer's number four cell, or oven. Light-colored clods of material on the scoop's lower edge may be part of the crusted surface material seen previously near the foot of the lander.
Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University

NASA's Phoenix Mars Lander successfully scooped up a sample of Martian soil with its robotic arm, mission scientists said on Friday.

The scoop is poised and ready to deliver the sample to an instrument on the spacecraft that will analyze the soil.

"This is really an important occasion for us, to be poised to make a measurement for the first time of the Martian arctic soil," said Phoenix principal investigator Peter Smith of the University of Arizona.

The $420 million mission aims to dig down through the soil to the layers of water ice thought to lie underneath the surface, and to analyze soil samples to determine their composition and see if the ice might once have been liquid water, potentially creating a habitable zone for microbial life at some point in the past.

Phoenix retrieved its sample Thursday from a site dubbed Baby Bear, which lies just to the right of the trench the lander dug out in its practice digs. The practice digging locale is called Dodo. ?After scooping up the sample, measuring about 1 cup in volume, Phoenix used its robotic arm camera to photograph the sample so that scientists could make sure they had enough to deliver to the Thermal and Evolved-Gas Analyzer (TEGA) instrument aboard the lander.

"This looks like a really good sample for us," Smith said.

Mission controllers will send instructions to the lander to dump the sample into one of the TEGA ovens tonight. The TEGA ovens, which are about an inch long and the diameter of a pencil lead, will heat up the soil samples and use a mass spectrometer to detect the gases that come off the samples, which will shed light on some of the materials in the soil, specifically those formed by the process of liquid water.

"The TEGA system is particularly sensitive to water in its oven ? water is the first thing that's cooked out," Smith said.

Mission scientists must be careful when delivering the sample not to overload the instrument and contaminate other ovens. Once the sample is delivered on Friday, Phoenix will image TEGA to make sure the sample has been delivered and that the oven door is shut. The instrument is will then begin its four-day analysis (which may not occur in four consecutive days); the team will report each day's results as they become available. Any water present in the sample should be the first thing to vaporize from the soil, Smith said.

The sample also contains some of the white material seen in the scoop after Phoenix's first practice "dig and dump," which scientists think could be ice or a type of salt mineral.

Of course, they can't be sure that any of the white material will make it through the oven's entry screen. "We're hoping that some of this goes in and that we get a hint of what it is," Smith said.

Some science team members think that the whitish material can't be ice because it has been too easy to scrape up ? the ice layers under the soil will likely be difficult to scrap because ice is so hard at the brutally frigid temperatures on Mars (which have so far reached a high of only -22 degrees Fahrenheit (-30 Celsius) since Phoenix landed).

"Some people think that it's too easy to get this material and that it can't be ice," Smith said. But he added that if the white material turns out to be some kind of salt, "that would be a very nice discovery" because salts are what is left when water reacts with soil.

After TEGA begins its analysis, the lander will start digging up samples for its microscopes and its wet chemistry lab. The microscope samples will likely be taken from the same Baby Bear site as the TEGA samples, because they will she further light on TEGA's results. The wet chemistry samples will be taken from an adjacent site just to the right of Baby Bear, dubbed Mama Bear.

"If we have a really good week [next week], we could have each of those delivered by the end of the week," Smith said.