火星上融化的沙丘

2019 September 24

Sand Dunes Thawing on Mars
Image Credit & License: ESA, Roscosmos, CaSSIS

Explanation: What are these strange shapes on Mars? Defrosting sand dunes. As spring dawned on the Northern Hemisphere of Mars, dunes of sand near the pole, as pictured here in late May by ESA’s ExoMars Trace Gas Orbiter, began to thaw. The carbon dioxide and water ice actually sublime in the thin atmosphere directly to gas. Thinner regions of ice typically defrost first revealing sand whose darkness soaks in sunlight and accelerates the thaw. The process might even involve sandy jets exploding through the thinning ice. By summer, spots will expand to encompass the entire dunes. The Martian North Pole is ringed by many similar fields of barchan sand dunes, whose strange, smooth arcs are shaped by persistent Martian winds.

火星上融化的沙丘
影像提供与授权: ESA, Roscosmos, CaSSIS

说明：火星上这些奇怪的形状是什么？它们是正在融化的沙丘。随着火星北半球春天的来临，如这幅在5月下旬由欧洲航天局外火星跟踪气体轨道器所拍摄的影像，北极附近的沙丘开始融化。实际上，二氧化碳和水冰会直接升华成气体，飘浮在稀薄的大气中。冰层较薄的区域通常会最先解冻，露出沙子，而这些黑色的沙子吸收阳光，加速了冰层的融化。这个过程甚至可能有沙质喷流在稀薄的冰层中爆炸。到了夏天，这些点将扩大到整个沙丘。火星北极被许多类似的新月形沙丘环绕，这些平滑的奇怪弧形结构是由持续不断的火星风造成的。