Free Astronomy Magazine September-October 2018

SEPTEMBER-OCTOBER 2018 E xoMars Trace Gas Orbiter captured this view of part of the south polar ice cap on Mars on 13 May 2018. The poles of Mars have huge ice caps that are similar to Earth’s polar caps in Greenland and Antarctica. These caps are composed primarily of water ice and were deposited in layers that contain varying amounts of dust. They are referred to as the martian Polar Layered Deposits (PLD). Thanks to massive canyons that dissect the layered deposits, orbiting spacecraft can view the layered internal structure. The ExoMars orbiter’s Colour and Stereo Surface Imaging System, CaSSIS, viewed this 7 x 38 km segment of icy layered deposits near the margin of the South PLD, which extend as far north as 73ºS. Here, CaSSIS has imaged remnant deposits within a crater at this margin. The beautiful variations in colour and brightness of the layers are visible through the camera’s colour filters. It highlights the bright ice and the redder sandy deposits to- ward the top of the image. The ExoMars pro- gramme is a joint endeavour between ESA and Roscosmos. [ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO] but are also a testament to the abilities of re- searchers and their equipment to be flexible when new approaches are needed − even when technicians must be creative from tens or hundreds of millions of kilometers away. The temperature of this liquid body cannot be directly measured without knowledge of its actual composition, but the estimated temperature for the ice/rock interface at the polar caps is as low as -68°C. The measure-