The Rovers that Never Die

This near-true-color image from Spirit's panoramic camera shows a peak atop West Spur, which lies at the base of the Columbia Hills. Rocks throughout the hills are surprisingly diverse.
Courtesy NASA / JPL / Cornell University.
Move over Energizer Bunny! After more than a year on the red planet, the Mars Exploration Rovers Spirit and Opportunity continue to keep going and going and going. This week at the Lunar and Planetary Science Conference in Houston, Texas, the rover team updated participants on the mission's latest science findings.

Wednesday marked Martian day (sol) 427 of Spirit's scheduled 90-sol mission. Having traversed several kilometers across Gusev Crater, the rover began its long ascent up the Columbia Hills. It's current goal is to scale Husband Hill, named for the Space Shuttle Columbia's commander, astronaut Rick D. Husband. While it's keeping busy rock climbing, the rover has uncovered a wide variety of rock types. "There's a bewildering diversity of composition in the Columbia Hills," says mission principal investigator Steve Squyres (Cornell University). He estimates that Spirit will reach the summit around sol 500 (about June 1st).

Spirit's panoramic camera took this near-true-color image of a patch of unsually white dust known as Paso Robles. Spectral analysis shows that Paso Robles is rich in salts, which is often a 'smoking gun' for material left behind when water evaporates.
Courtesy NASA / JPL / Cornell University.

As of Wednesday, the rover was parked next to one of the most fascinating rock outcrops seen in the entire mission. During a driving maneuver, Spirit accidentally churned up a bright-white patch of soil buried only a few centimeters under the surface. Upon closer analysis, the feature, dubbed Paso Robles, was determined to be the saltiest spot ever seen on the red planet, with a composition more than 50 percent salt.

Halfway around the planet, Opportunity is driving south as fast as it can. Having thoroughly examined the blueberry-littered terrain of Meridiani Planum and two craters, MER team members are now driving the rover to a large crater about 5 kilometers away called Victoria. Orbiter images show that while en route, Opportunity will cross a large patch of white terrain, which the team is anxious to examine. But the scientists' ultimate goal is to examine the layers and stratigraphy carved out in Victoria. "We're going to drive like crazy," says Ray Arvidson (Washington University in St. Louis).

Driving fast might not be a problem. After team members uploaded an upgrade to Opportunity's driving software, the rover set out on a record driving run, traversing nearly 390 meters (a quarter mile) across the flat, hematite-rich plains in just three days. That said, the rover's driving speed depends on the road conditions. "We're not sure how fast we'll be able to drive on the white terrain," said project scientist Joy A. Crisp (NASA/Jet Propulsion Laboratory).

The Columbia Hills Complex, seen here in this enhanced-color image, overlook the plains of Gusev Crater.
Courtesy NASA / JPL / Cornell University.
Despite a balky front wheel, Spirit had nothing but good news to report, thanks to a dust devil that cleaned off the dust that had been accumulating on its solar panels, blocking sunlight needed to power the craft. With more power available for the mission's instruments, "It's like being back at sol 30," says Harry Y. McSween, Jr. (University of Tennessee). On the other side of Mars, Opportunity's news wasn't so fortunate. Over the past week, its thermal emission spectrometer (Mini-TES) started acting up. Diagnostic tests conducted in the coming days and weeks will determine whether the instrument can be saved.

Many other MER science results were announced as well. Among them:

  • Spectroscopic observations of Mars's dust from both Meridiani Planum and Gusev Crater are strikingly similar. It seems, as one might assume from Mars's episodic global dust storms, that the dust on one side of the planet looks the same as the dust in the other hemisphere.

  • Atmospheric dust significantly impacts rock observations. The same target observed spectroscopically on a clear day will look different if observed on a dusty day because atmospheric dust will mask the rock's spectral signature.

  • Tiny magnets on the rovers reveal that more than 90 percent of Mars's dust is magnetic, and that some dust grains are more magnetic than others. The mineral primarily responsible is magnetite.

  • Scientists are using the MER's Rock Abrasion Tool (RAT) as a way to assess a given rock's relative hardness and strength. Furthermore, team members are observing the dust left behind when the RAT is done grinding a rock. The powder, it seems, acts as a windsock that measures wind direction.

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