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New Maps Detail Solar System Objects

New Maps Detail Solar System Objects
A NASA image of asteroid Eros (left) and Robert Gaskell's shape model of the asteroid (right). (Image credit: NASA/JPL/PSI/Robert Gaskell)

Galactic hitchhikers visiting our solar system, if theyexist, would probably love to get their hands on a new guide that puts GPS toshame.

A planetary scientist has made the most detailed maps of ourlocal planets, moons and asteroids yet by combining hundreds of spacecraftimages to chart all the nooks and crannies of numerous surfaces, including theasteroids Phobos, Itokawa and Eros. Upcoming targets for mapping include theplanet Mercury and eight of Saturn's moons, such as frozenEnceladus with its icy geysers, as well as Earth's moon.

"I have three computers crunching away right now,"said Robert Gaskell, a planetary scientist based in Altadena, Calif., who worksat the Planetary Science Institute. "One's working on the moon, one'sworking on Eros, and another's working on Mercury."

?Gaskell uses many images from different angles andilluminations to figure out the slopes and heights of alien terrains, whether arocky asteroid or icy moon. His method of stereo-photo-clinometry (SPC) createssquare "maplets" on a computer model of the target, and smallersquares get added as the model receives more detailed data.

A major project involves creating highly accurate maps ofthe entire surface of Mercury — the closest planet to the sun — based on anexpected stream of images from NASA's MESSENGERspacecraft. The probe still needs to swoop past Earth and Venus beforesettling into a Mercury orbit in 2011.

"Doing the larger bodies like the moon and Mercury,you've got to make an awful lot of maplets," Gaskell told added that Mercury alone would probably involve 500,000 maplets of varyingsize.

Gaskell has already begun combining images from an initialMESSENGER flybyof Mercury in January with older Mariner 10 images taken in 1973. But thethree Mariner 10 flybys produced photos from the same sun angle, which meansGaskell only has two angles to work with at the moment.

"It won't be until we get overlapping data fromdifferent sun directions that it will really start making a lot of sense,"Gaskell said. "It does give a reasonable solution now, but I don'tcompletely trust it."

Other map work need not wait until MESSENGER settles intoits Mercury orbit in 2011. NASA also wants Gaskell to map eight of the moonsorbiting Saturn's ringed visage, including Enceladus.

Mission planners may use the maps as navigational tools forthe Cassini spacecraft to revisit Enceladus in October, where a fresh flyby mayprovide additional data on the moon'sgeysers.

The accurate map modeling could also help scientists studySaturn's moons for signs of frozen tidal stresses that might reflect thesatellites' orbital histories, when they gravitationally tugged at one anotherin more unpredictable ways.

Gaskell's earlier work has already garnered a NASAExceptional Achievement Medal. The award recognized the maps of the asteroidItokawa as "the highest resolution description of an asteroid,"at resolutions better than 15.75 inches (40 cm).

The scientist's computers continue working around the clock,but thousands of planetary and other bodies still remain in the solar system.

"So far, I've barely scratched the surface, if you'llpardon the expression," Gaskell said.

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