CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap
CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap
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DOI：
10.1038/nature04945
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发表时间：
2006-08-17
期刊：
影响因子：
64.8
通讯作者：
Titus, Timothy N.
中科院分区：
文献类型：
--
作者：
Kieffer, Hugh H.;Christensen, Philip R.;Titus, Timothy N.
火星极冠是火星上最具活力的区域之一，在冬季大量增长，因为大气的很大一部分以二氧化碳冰的形式冻结。不寻常的黑点，风扇和斑点的形式作为南极季节性二氧化碳冰帽撤退在春季和夏季。一旦冰消失，小的放射状通道网络通常与斑点的位置有关。这些斑点被认为只是裸露的、被侵蚀的地面（1-3）;通道的形成仍然不确定。在这里，我们报告了红外和可见光观测结果，这些观测结果表明，这些斑点和风扇在夏季仍然保持在二氧化碳冰的温度下，并且必须是已经被带到冰表面的颗粒状材料，需要一套复杂的过程才能将它们带到那里。我们认为，季节性冰盖形成了一个不可渗透的，半透明的CO2冰板，从底部升华，在板下建立高压气体。这种气体使冰漂浮起来，冰最终破裂，产生高速的二氧化碳喷口，喷出沙子大小的颗粒，形成斑点，侵蚀通道。这些过程与地球上观察到的任何过程都不同。
The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground(1-3); the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth.