NASA on Friday released the first pictures ever taken of an eclipse as seen from the surface of another planet, snapped by the Opportunity rover a day earlier. The thumbnail-size pictures showed the moon Deimos passing like a tiny speck over the sun's disk.
Deimos is the smaller of Mars' two moons. Over the next few days, the rover's panoramic camera could catch the larger moon, Phobos, as it makes a similar transit, said Cornell University astronomer Jim Bell, who heads the science team for the camera.
"While Deimos would produce just a small speck traveling across the surface of the sun, we expect Phobos, because it's much closer to the surface (of Mars), to blot out half or more of the sun," he said during Friday's news conference at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It's a very quick event — it happens in 30 or 40 seconds or so."
The observations would require close coordination with the engineering team outside the rover's prime hours of operation, he said.
Eclipses are far more common on Mars than on Earth, but far less spectacular. Earth's moon is sized exactly right to cover the full disk of the sun during a total eclipse — something that's not possible for Phobos and Deimos. The two moons ("Fear" and "Panic" in Greek) are named after the sons of Ares (equivalent to the Roman god Mars) in Greek mythology.
The main mission for Opportunity and its twin on the other side of Mars, the Spirit rover, is to look for geologic traces left behind by liquid water — traces that could help scientists determine how likely it was that life could have developed there. On Tuesday , the rover science team declared that the Opportunity landing site, within a small crater in Meridiani Planum, was once drenched with enough water to make the area habitable.
On Friday, the team said Spirit found the geological signature of ancient water around its landing site as well, but not to the same extent . The water may have been mixed with magma that welled up during the volcanic eruptions that shaped the area, said Ray Arvidson of the Washington University in St. Louis, the science team's deputy principal investigator. The findings were based on pictures of a rock nicknamed Humphrey, snapped by Spirit's microscopic imager.
Amid the geological experiments, the rovers have been taking other pictures such as the eclipse snapshots and views of a Martian sunset .
Scientists plan to make astronomical observations from the Martian surface as well, aimed at determining how clear the atmosphere gets at night.
Another experiment is aimed at studying Mars' magnetic dust. Cameras are checking magnets mounted on the rovers to see how grains of varying sizes build up on the instruments. "Particles arriving on the magnets interact with each other," said a member of the rover science team, Morten Madsen of the Danish Center for Planetary Science.
Both of the rovers are "just doing extremely well," said mission manager Matt Wallace. Opportunity is wrapping up its work in the crater where it landed, and soon will be heading off across the surrounding plain toward a larger crater called Endurance. Spirit, meanwhile, is continuing its trek toward a crater named Bonneville.
The $820 million twin-rover mission was designed to run for at least 90 Martian days, or sols, but scientists say the rovers could last far longer than 90 days each. Wallace added together Spirit's 60 sols and Opportunity's 40 sols to proclaim "we've had a terrific hundred days on Mars."
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