Abstract
A flowing ice mass has a predictable shape, and therefore the shape of an ice surface can be informative about the history of ice flow. While present-day ice flow is insignificant on Mars, the shape of the present-day ice-surface topography over at least a portion of the Martian North Polar Layered Deposits can be well-reproduced using an ice-flow model; this is strong evidence for a past era of significant ice flow on Mars. For any ice mass, the ice-flow rate depends on the mass-balance rate and on the near-basal ice temperature and any flow enhancement due to impurities in the ice or variations in the physical properties of the ice. We use the shape of the relict Martian ice-surface topography to infer characteristics of past ice temperatures, or past climate conditions, in which ice-flow rates on Mars would have been more significant than today. In addition, radar-observed internal layers contain detailed information about the history of the Martian polar layered deposits. We show that for a given ice-flow history, the internal-layer shapes can be informative about the mass-balance history.