| Daily Updates - February 28, 2004 Scratch and Sniff Opportunity remains healthy and active. During its 34th sol on Mars, which ended at 5:34 a.m. Saturday, PST, the rover used its rock abrasion tool for the second time. It ground the surface off a patch of rock at a site called "Guadalupe" in the outcrop the rover has been examining. The rover looked at the patch with its microscope both before and after the grinding session. Then it placed its Moessbauer spectrometer against the newly exposed interior material of the rock for a long reading of data that scientists use to identify what iron-containing minerals are present in the target. Opportunity also used its miniature thermal emission spectrometer during the sol to assess the composition of an outcrop feature dubbed "Shoemaker Wall." It took images of "Guadalupe" with its panoramic camera before and after the use of the rock abrasion tool. Wake-up music played in the mission support area at JPL for sol 34 was "Dig In," by Lenny Kravitz. For sol 35, ending at 6:15 a.m. Sunday, PST, plans call for continuing use of tools on the robotic arm to examine the rock interior exposed by the "Guadalupe" grind. Spotlight: Spirit Science Advances on Multiple Levels Just past the halfway point of its three-month prime mission, NASA's Mars Exploration Rover Spirit has achieved several scientific firsts, but may still have its best "Eureka!" moments in front of it. The mobile robotic geologist has yet to identify any sign of ancient lakebed material that scientists suspect may lie beneath the surface where it has been driving. The rover is, however, approaching a stadium-sized crater that could provide access to older, lower layers. "We need to use nature's drills, which are craters," said Dr. Ray Arvidson of Washington University in St. Louis, deputy principal investigator for Spirit and its twin rover, Opportunity. Scientists estimate that the meteorite impact that excavated the nearby crater threw rocks out onto the surrounding surface from as deep as 10 to 15 meters (33 to 49 feet), and may have exposed rock layers to that depth inside the bowl.
Gusev's Appeal
Spirit's prime mission was planned for three months of operations on Mars' surface. The rover is in such good health, engineers are optimistic it will be able to run considerably longer than that with an extended mission. Just hours after it landed on Jan. 4 (Universal Time), Spirit looked around and showed its eager science team a broad plain with scattered rocks. A few hills and crater rims punctuated the horizon. Spirit has surveyed the surface materials in its neighborhood with versatile cameras and a rock-identifying infrared sensor. It has inspected them up close with experiments such as the first microscopic examinations of soil and rock on a foreign planet and composition analysis of the first rock interior ever exposed by cutting into a stone on a foreign planet. Preliminary assessments of those surface materials are in. "The caprock on the plains is volcanic basalt," Arvidson said. "It has been broken up by impact cratering, and then wind-blown materials have accumulated into a mantle of soil." Sticking Together One trait of particular interest in Spirit's findings so far is how soil grains stick together, forming a crust in some areas examined. Soil cohesiveness made Spirit's trenching at a site called "Laguna Hollow" take longer for a shallower hole than when Opportunity dug into looser soil for a deeper hole at that rover's landing site halfway around Mars. Sulfur and chlorine identified in the soil may contribute to this trait. "Some process is cementing things together," Arvidson said.
In general, soil is an indicator of more recent environmental conditions than rocks are. Spirit is on the lookout for unusual rocks as it progresses toward the rim of the crater informally named "Bonneville." The crater is roughly 150 meters (about 500 feet) across, and Spirit is more than halfway from its now-empty lander to the crater rim. "When we get to the rim and look inside, it may very well be a new mission," Arvidson predicted. |
