Mars's ice-covered north pole
Mars's ice-covered north pole
It has been known since the 17th century that Earth's outer neighbour, Mars, is permanently covered by water-ice at its north pole. The ice sheet here is approximately 1000 kilometres in diameter and up to three kilometres thick, and its load depresses the rocky crust beneath. For the first time, it has been possible to determine the speed of this process – which occurs at a rate of up to 0.13 millimetres per year. This implies that the mantle below Mars's crust is highly viscous, approximately 10 to 100 times more viscous than Earth's mantle. The processes that led to the cap's several-hundred-metre-deep valleys between the spiral-shaped ice formations are not yet clear, but may be related to prevailing wind patterns in this region.
Credit:
ESA/DLR/FU Berlin, NASA MGS MOLA Science Team