Nature2014-06-26 5:24 PM

行星Ceres上的水蒸气 Localized sources of water vapour on the dwarf planet (1) Ceres

论文摘要 

Ceres(太阳系主小行星带中的最大天体)表面上水合矿物的存在表明,那里也可能有水。现在,由欧洲航天局的Herschel Space Observatory获得的红外光谱提供的明确证据证明,在Ceres的表面上或其表面附近存在水冰。水蒸气以至少每秒1026个分子的速度从Ceres上局限于中纬度地区的水源排放出。水的蒸发可能是由于类似彗星的升华作用或冷火山作用(在其中火山喷发的是水等挥发物而不是熔岩)。这一发现支持提出以下观点的模型:彗星等冰质体可能是从我们想象中的将早期太阳系分成“干”的内层区域和“冰质”外层区域的“雪线”之外迁移到小行星带内的。

Abstract 

The ‘snowline’ conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Models suggest that some of the icy bodies may have migrated into the asteroid belt. Recent observations indicate the presence of water ice on the surface of some asteroids, with sublimation5 a potential reason for the dust activity observed on others. Hydrated minerals have been found on the surface of the largest object in the asteroid belt, the dwarf planet (1) Ceres, which is thought to be differentiated into a silicate core with an icy mantle. The presence of water vapour around Ceres was suggested by a marginal detection of the photodissociation product of water, hydroxyl (ref. 12), but could not be confirmed by later, more sensitive observations. Here we report the detection of water vapour around Ceres, with at least 1026 molecules being produced per second, originating from localized sources that seem to be linked to mid-latitude regions on the surface. The water evaporation could be due to comet-like sublimation or to cryo-volcanism, in which volcanoes erupt volatiles such as water instead of molten rocks.

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