2025年7月6日
The Spiral North Pole of Mars
Image Credit: ESA/DLR/FU Berlin; NASA MGS MOLA Science Team
Explanation: Why is there a spiral around the North Pole of Mars? Each winter this pole develops a new outer layer about one meter thick composed of carbon dioxide frozen out of the thin Martian atmosphere. This fresh layer is deposited on a water-ice layer that exists year round. Strong winds blow down from above the cap’s center and swirl due to the spin of the red planet — contributing to Planum Boreum‘s spiral structure. The featured image is a perspective mosaic generated in 2017 from numerous images taken by ESA’s Mars Express and elevations extracted from the laser altimeter aboard NASA’s Mars Global Surveyor mission.
Tomorrow’s picture: alien comet
火星的北极螺旋
影像提供: ESA/DLR/FU Berlin; NASA MGS MOLA Science Team
说明: 为何火星的北极会有螺旋结构？在每年的冬天，火星北极都会覆盖大约1米厚、从稀薄大气冻结出来的二氧化碳冰（干冰）层 ，而这个新覆层会叠在经年常在的水冰层之上。然后，强风从冰冠的中心上方向下吹袭，因火星自转而成为涡旋气流，造就了北极高原（Planum Boreum）的螺旋结构。这张侧视的主题影像，组合自欧洲航天局火星快车号拍摄的影像数据，而高度资讯，则来自美国航空航天局火星全球探勘者号的激光高度计之数据。
明日的图片: alien comet
