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Raumfahrt - NASA-Raumsonde Dawn im Orbit von Zwergplaneten Ceres - Update-13

15.03.2018

Dwarf planet Ceres has a water cycle but it’s not like Earth’s

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uling crater on Ceres shows signs of a water cycle

IAPS - INAF

The dwarf planet Ceres, once thought to be a dead and static rock, may have water cycles. Observations from the Dawn spacecraft have shown a crater wall becoming icier as the sun’s position changed in the sky over the course of six months, indicating that subsurface ice particles may be lofted up into the air and land on the wall like dew.

On the steep wall of Juling crater in Ceres’s southern hemisphere, ice has been found to be increasing in the height of summer. During summer days on Ceres, sunlight hits the bottom of the crater but the wall remains mostly shrouded in cold shadows.

Carol Raymond at NASA’s Jet Propulsion Laboratory in Pasadena, California and her team examined infrared data from the Dawn spacecraft to figure out how the ice was changing in this crater as the warmest part of Ceres’s year began.

 

Decent exposure

In five sets of observations over the course of six months, they found that the amount of exposed ice on the Juling crater wall seemed to be increasing. 

Raymond says this could be due to a combination of two effects: small landslides revealing ice from behind a layer of dust, and ice in areas that aren’t usually sunlit getting heated up enough to sublimate into the air.

“It’s only getting a few degrees warmer than during other seasons,” says Raymond. “But it’s enough to sublimate some of this ice that’s just below the surface.”

The final Dawn

The sublimated ice would work a bit like dew, which evaporates in the heat of the day and then condenses on cool surfaces in the night. In Juling crater, the pool of sunlight at the crater’s bottom has a similar effect, turning ice into water vapour. That vapour then condenses on the cool, shadowed wall that Raymond and her colleagues observed.

“It is surprising,” says Raymond. “This kind of process is seen on comets, but we didn’t really expect to see a cycle of sublimation and condensation in action on Ceres.”

The team is planning to look at Juling crater one more time before the Dawn spacecraft runs out of fuel, which is expected to happen sometime this year. Raymond hopes that understanding this process may help us understand why some areas of Ceres have more ice than others.

Quelle: New Scientist

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Dwarf planet Ceres may store underground brine that still gushes up today

Waterlogged minerals and changing ice add to evidence that Ceres is geologically active

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FOLLOW THE ICE  A wall of ice in the shadows of Ceres’ Juling crater, shown here in an image taken by NASA’s Dawn spacecraft, grew by about 50 percent over the course of six months.

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