Titan: Hubble's view of the surface | PIA01465 | ||
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Four
global projections of the HST Titan data, separated in longitude by 90 degrees.
Upper left: hemisphere facing Saturn. Upper right: leading hemisphere (brightest
region). Lower left: the hemisphere which never faces Saturn. Lower right:
trailing hemisphere. Not that these assignments assume that the rotation is synchronous. The imaging team says its data strongly support this assumption -- a longer time baseline is needed for proof. The surface near the poles is never visible to an observer in Titan's equatorial plane because of the large optical path. |
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Image Credit: Peter H. Smith and Mark Lemmon of the UA Lunar and Planetary Laboratory, and NASA | |||
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Scientists
for the first time have made images of the surface of Saturn's giant, haze-shrouded
moon, Titan. They mapped light and dark features over the surface of the
satellite during nearly a complete 16-day rotation. One prominent bright
area they discovered is a surface feature 2,500 miles across, about the
size of the continent of Australia. Titan, larger than Mercury and slightly smaller than Mars, is the only body in the solar system, other than Earth, that may have oceans and rainfall on its surface, albeit oceans and rain of ethane- methane rather than water. Scientists suspect that Titan's present environment -- although colder than minus 289 degrees Fahrenheit, so cold that water ice would be as hard as granite -- might be similar to that on Earth billions of years ago, before life began pumping oxygen into the atmosphere. Titan's atmosphere, about four times as dense as Earth's atmosphere, is primarily nitrogen laced with such poisonous substances as methane and ethane. This thick, orange, hydrocarbon haze was impenetrable to cameras aboard the Pioneer and Voyager spacecraft that flew by the Saturn system in the late 1970s and early 1980s. The haze is formed as methane in the atmosphere is destoyed by sunlight. The hydrocarbons produced by this methane destruction form a smog similar to that found over large cities, but is much thicker. |
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Titan
makes one complete orbit around Saturn in 16 days, roughly the duration
of the imaging project. Scientists have suspected that Titan's rotation
also takes 16 days, so that the same hemisphere of Titan always faces Saturn,
just as the same hemisphere of the Earth's moon always faces the Earth.
It's too soon to conclude much about what the dark and bright areas in the Hubble Space Telescope images are -- continents, oceans, impact craters or other features. Scientists have long suspected that Titan's surface was covered with a global ehtane-methane ocean. The new images show that there is at least some solid surface. The images are important information for the Cassini mission, which launched a robotic spacecraft on a 7-year journey to Saturn in October 1997. About three weeks before Cassini's first flyby of Titan, the spacecraft is to release the European Space Agency's Huygens Probe to parachute to Titan's surface. Images of Titan can be used to identify choice landing spots - - and help engineers and scientists understand how Titan's winds will blow the parachute through the satellite's atmosphere. |
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