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慢速英语2004-07-12
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发布时间：2006-05-23
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| New Images Reveal Details of Saturn's Rings ...Solar Storms May Have Torn Away Mars Water: NASA ... | |
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 NASA has released ultraviolet images of Saturn's rings which may offer astronomers clues about the origin of the planet's shimmering halos of ice and debris.
The images taken by the international Cassini spacecraft show more ice toward the outer part of the rings, possibly providing hints about how the rings have changed over time.
Scientists say the images show the rings vary in composition. They are mostly ice but also contain other "dirty" material that astronomers want to investigate.
Cassini, a project of NASA and the European and Italian space agencies, entered orbit around Saturn last week after a seven-year, 2.2 billion-mile journey to the outer solar system.
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NASA scientists say solar storms might have torn away the water that used to cover parts of Mars.
They monitored the after-effects of a monster solar storm that hit Earth in last October and November.
They think repeated battering by this kind of space weather could have ripped away Mars' water veil.
According to observations by the Mars rovers Spirit and Opportunity, astronomers believe Mars once had enough surface water to support life, but they have not determined where that water went some 3.5 billion years ago.
Scientists think the solar radiation events could have affected the surface of Mars because the planet has so little protection.
Unlike Earth, only isolated zones of Mars has a protective magnetosphere that guards the planet against bombardment by high-energy particles during a solar storm. | |
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