The polar ice caps are the largest reservoir of water ice on Mars. The north polar ice cap is composed of the ice-rich north polar layered deposit (NPLD) and a lower-lying, silicate-rich basal unit (BU). Together, these units represent a record of Martian climate history throughout the Amazonian period. Here we place a bulk compositional constraint on the BU by modeling its gravity signature in both spatial and spectral domains using two independent approaches. We find the density of the BU to be ~1.5-m kg/m3, suggesting that it may contain 55 + 25% water ice. We estimate that the BU contains ~1.5-m global equivalent layer of water making it one of the largest reservoir of water-ice on Mars. Our compositional constraint suggests that the north pole of Mars was not only a cold trap for ices but also an aeolian trap for silicates during the Amazonian period.
All Science Journal Classification (ASJC) codes
- Earth and Planetary Sciences(all)