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Rover "Digs" the Dirt
Mars is like a candy store for scientists and researchers. With each new day comes another flavor of discovery, questions to be answered and successes to be savored.

The Mars Exploration Rover made its first close-up examination of a patch of soil after it drove off its lander on Jan. 15. "There are some puzzles and there are surprises," noted Dr. Steve Squyres, payload principal investigator for Spirit and its twin, Opportunity.Graph of Mars soil sample elements

This graph captured by the Möessbauer spectrometer shows the presence of three different iron-bearing minerals in the soil at the rover's landing site. One of these minerals has been identified as olivine, a shiny green rock commonly found in lava on Earth. The other two have yet to be pinned down. Click graph to view larger image.

The first unexpected finding was detection of a mineral called olivine, using the Möessbauer Spectrometer. Since olivine doesn't hold up well through weather, scientists speculate that the soil particles could be finely ground volcanic material.

The alpha particle X-ray spectrometer (AXPS), also located on Spirit's arm, takes X-ray radiation measurements of the Mars targets. Researchers hope to find the basic composition of the planet's soils and rocks. In the first soil patch, AXPS found mainly silicon and iron along with significant levels of chlorine and sulfur. The chlorine and sulfer levels were unlike any in soils on Earth. Squyres said, "The soil may not have even originated anywhere near Spirit's landing site, because Mars has dust storms that redistribute fine particles around the planet."

Scientists also were puzzled when they discovered how little the soil was disturbed when Spirit's arm pressed into the ground. Before and after pictures, taken by the Microscopic Imager, showed almost no indentation, which would happen in loose soils on Earth under the same circumstances. That raised a question: What's holding the grains together?

The next project for Spirit is investigation of the rocks on Mars. A rock the size of a football has been selected for investigation. The science team has named it Adirondack. Another rock, called Sashimi, was considered because it was a shorter distance and an easier drive for the rover. But its dusty outer layer made it a less attractive choice for observation. "Rocks are time capsules containing evidence of the environmental conditions of the past, and we needed to decide which of these time capsules to open," said Dr. Dave Des Marais, one of NASA's rover science team members. Spirit's arm reaches down to the Martian soil to investigate a rock.

Another handy device on Spirit's arm, the Rock Abrasion Tool (RAT), will be used to drill into Adirondack and other rocks. RAT can grind away a two-inch diameter area, exposing fresh rock for scientists to examine using other instruments.

Before a problem related to Spirit's computer memory began disrupting communications and operations on Jan. 22, the rover had surpassed NASA's expectations. Engineers are currently working at diagnosing and correcting the problem.

Spirit has transmitted incredible amounts of data in relay sessions through NASA's Mars Odyssey spacecraft. During Spirit's time on Mars, 75% of the rover's pictures and data have come to Earth through Odyssey. The rover can also communicate directly with Earth or use NASA's Mars Global Surveyor as a relay.

Opportunity, Spirit's twin Exploration Rover, arrived at Mars on Jan. 24, PST to begin its studies of the Martian surface. We wish the rovers good luck and look forward to more spectacular images, mysteries and surprises to fulfill our unquenchable desire for more "sweets" of discovery.

For further information, visit:

NASA's John F. Kennedy Space Center and Jet Propulsion Laboratory