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Volume 46 | Issue 2 | March 2004

Research Roundup

photo: Mars terrain

Scientists around the globe are excited about compelling evidence in rock formations on the martian surface that strongly suggests the presence of water activity.
NASA Photo / Courtesy JPL

Rovers find evidence of water

By Sarah Merlin
X-Press Assistant Editor

More than halfway through their 90-day mission on the Red Planet, Mars rovers Spirit and Opportunity continue bringing home the bacon for Jet Propulsion Laboratory scientists busy back on Earth analyzing all the data being transmitted about martian geology.

Since touching down in January, the twin robotic explorers have been functioning almost flawlessly, looking for evidence of past water activity, grinding into rocks and soil and photographing Mars' moons and sunsets as they amble around the planet's surface. Thus far, scientists at the JPL in Pasadena have received more than 11,000 images and 9.1 gigabytes of data from the pair.

In February, Spirit dug a trench in an area called "Laguna Hollow" in the Gusev crater that served as Spirit's Jan. 3 landing site, using its instruments to study the rock and soil lining the trench for clues to their make-up. Meanwhile, Opportunity dug away on the opposite side of the planet, in the area surrounding its Meridiani Planum landing site, exposing a rock outcropping and using a spectrometer to examine soil content. Scientists are hoping to find conclusive evidence that life-sustaining water once was present on Mars and believe the rovers' findings thus far strongly suggest that it did. In addition to the theory of water activity, researchers are weighing such other theories as volcanic eruptions or windblown dust or sediments as possible explanations for how the planet's rocks were formed.

Among other duties, Opportunity also has used its panoramic camera - or "pancam" - to gaze around the martian landscape and send photos back to mission control in Pasadena. The rover captured a blue-tinted sunset as it dipped on the martian horizon, leading scientists to speculate that the tint and rapid dimming of the sun as seen in the photos were caused by dust in the Red Planet's atmosphere - similar to a smog-filled sunset in Los Angeles. Opportunity's photos evidenced more than twice as much atmospheric dust as an earlier rover, Pathfinder, found on its 1997 visit.

photo: research

This photo is among more than 11,000 images to date sent back to Earth by the Mars rovers Spirit and Opportunity.
NASA Photo / Courtesy JPL

With the rock band Creedence Clearwater Revival's hit "Bad Moon Rising" blaring back in mission control, Opportunity next turned its sights skyward to photograph the martian moons Deimos and Phobos (in Greek, "terror" and "fear," respectively), capturing the smaller of the two moons, Deimos, as it eclipsed the sun. Opportunity also took sky photos in collaboration with the European Space Agency orbiter Mars Express.

Technical malfunctions have been minor throughout the mission and have not inhibited the rovers' ability to do their work.

In late February, a small glitch in Opportunity's communications system compelled scientists to direct the rover to reduce its daily transmissions and take more powered-down "naps" to conserve electricity. A switch that operates an onboard heater had been stuck in the "on" position since shortly after the rover's Jan. 24 landing, causing a constant drain on the vehicle's solar-powered batteries. Compounding the problem was a reduction in the amount of sunlight necessary to feed the solar panels as Mars heads into its winter season. Mission controllers addressed the problem by reloading some of Opportunity's system software.

A software reload also will be used to remedy a "bug" that kept Spirit's rock abrasion tool - dubbed the "rat" - from performing properly.

Both six-wheeled rovers were launched from Cape Canaveral Air Force Station, Fla., Spirit on June 10, 2003, and Opportunity shortly afterward, on July 7. The two are identically structured and instrumented, but landed at different sites on Mars and are exploring regions on opposite sides of the planet. Each is similar to the earlier Pathfinder rover but is larger, more mobile and equipped with more sophisticated instruments.

The rovers are part of NASA's Mars Exploration program, a long-term effort that focuses on robotic exploration of the Red Planet. The program was designed so as to take advantage of each opportunity to launch a craft to Mars when planetary alignment offered the most favorable conditions - about every 26 months. Earth was closer to Mars when the rovers were launched last year than it had been in 60,000 years, giving scientists their best shot at getting weighty aircraft all the way to Earth's neighbor with the limited fuel capacity of current launch technology. Cost of the two rovers is about $820 million. Their names were selected through a student essay contest that drew nearly 10,000 entries.