Phoenix has collected a sample of Martian soil, after it made its first dig. The sample will be delivered for analysis to the instrument called the Thermal and Evolved-Gas Analyzer, or TEGA.

Peter Smith, Phoenix principal investigator at the University of Arizona, Tucson, the analysis will take somewhere between few days and a whole week.

The Thermal and Evolved-Gas Analyzer will study substances that are converted to gases by heating samples delivered to the instrument by the robotic arm. It provides two types of information. One of its tools, called a differential scanning calorimeter, monitors how much power is required to increase the temperature of the sample at a constant rate. This reveals which temperatures are the transition points from solid to liquid to gas for ingredients in the sample. The gases that are released, or “evolved,” by this heating then go to a mass spectrometer, a tool that can identify the chemicals and measure their composition.

The mass spectrometer will determine whether the samples of soil and ice contain any organic compounds. It would be used to identify the types and amounts if any are present. Finding any would be an important result for interpreting the habitability of the site.

The instrument will also give information about water and carbon dioxide present as ices or bound to minerals. The amount of heat needed to drive off water or carbon dioxide that is bound to minerals is characteristically different for different minerals. The calorimeter’s information from that process can help identify minerals in the soil, including carbonates if they are present.

The mass spectrometer will measure the ratios of different isotopes of carbon, oxygen, hydrogen,argon and some other elements in the Martian samples. Isotopes are alternate forms of the same element with different atomic weights due to different numbers of neutrons. Ratios can be changed by the effects of long-term processes that act preferentially on lighter or heavier isotopes of the same element. For example, some of Mars’ original water was lost from the planet by processes at the top of the atmosphere, favoring the removal of lighter isotopes of hydrogen and oxygen and leaving modern Mars water with a raised ratio of heavier isotopes.

The sample was collected the top 2 to 4 centimeters (0.8 to 1.6 inches) of surface material at a site informally named "Baby Bear" on the north side of the lander. In the past week, engineers had used the arm to collect two practice scoops adjacent to Baby Bear and dump those scoopfuls back onto the surface. The move was calculated to get enough material to be sure to get some delivered into the TEGA without inundating the instrument with unnecessary extra soil.

"We are particularly interested in minerals that are formed or altered by the action of liquid water in the soil," Smith said.

The Thermal and Evolved-Gas Analyzer was built by teams at the University of Arizona, led by William Boynton (science lead) and Heather Enos (project manager), and at the University of Texas, Dallas, led by John Hoffman. It is adapted from a similar instrument with the same name that flew on the Mars Polar Lander mission in 1999.

The team has developed commands for the spacecraft to use cameras and the Robotic Arm on Saturday to study how strongly the soil from the top layer of the surface clings together into clumps.

The researchers are trying to figure out why the sample has not been delivered to the Thermal and Evolved-Gas Analyzer. Ray Arvidson of Washington University in St. Louis said that a probable cause is the cloddiness of the soil and not having enough fine granular material.

One of the strategies under consideration is to use mechanical shakers inside the TEGA instrument differently than the five minutes of shaking that was part of the sample-receiving process on Friday.

Meanwhile, the researchers are preparing Phoenix for its other activities that should take place on Saturday.