Bad Moon Rising
Summary (Mar 06, 2004): The Opportunity rover captured an image of a solar eclipse from the surface of Mars. While not a rare event on the red planet, capturing the image of one of Mars' two moons as thet pass in front of the Sun can tell atmospheric scientists much about what lies between the rover and the upper air layer.
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Bad Moon Rising
by Astrobiology Magazine staffwriter  |
| Shadow cast on cratered martian surface near western Xanthe Terra on August 26, 1999, about 2 p.m. local time, by moon Phobos. Compared to surface missions returning 10,000 or so images, the orbiters continue to provide over ten times that many. Credit: NASA JPL/MSSS/MOC |
Opportunity was able to photograph this brief eclipse of the Sun by the small Martian moon Deimos, as shown in the banner. Mars has two natural satellites, or moons, called Phobos ( Greek for "Fear") and Deimos ("Terror"). The inset right in the banner image shows the non-spherical shape of Deimos. Probably like its sister moon, it is also a captured asteroid. Deimos orbits Mars every 30 hours. The natural moon is 10 by 7.5 miles (16 by 12 kilometers) in size. Opportunity awoke Thursday morning to "Bad Moon Rising" by Creedence Clearwater Revival in honor of the eclipse.
Mission scientists hope to be able to catch a similar eclipse with the larger moon Phobos - which could blot out half the sun or more - in the near future. Somewhere near the martian equator, Phobos eclipses the sun nearly every day.
Viking images of Phobos proved very valuable in determining the opacity of the night sky. Color and infrared reflectance values of the integrated disc were clues to the satellite's chemical composition. The spectral data best fit that of carbonaceous chondrite, a carbon-rich variety of meteorite believed to represent primitive solar system material.
Phobos and the smaller, more distant satellite, Deimos, were discovered in 1877 by Asaph Hall, an astronomer at the United States Naval Observatory in Washington, D.C. Hall had been hunting for martian satellites for some time, and was about to abandon the search when he was encouraged by his wife to continue. In honor of her role in the discovery, the largest crater on Phobos was named Stickney, her maiden name. In a strange case of prescience, author Jonathan Swift wrote a century and a half earlier in his Gulliver's Travels (1726) that " [The astronomers]..have likewise discovered two lesser stars, or satellites, which revolve about Mars."
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Saturday, March 06, 2004
