Evidence for Water Ice Near the Martian Equator

When one looks for water on Mars, the most obvious targets are the ice-capped polar regions. However, Shean finds what appears to be buried water ice or an ice-debris mix within 38 craters in the Sinus Sabaeus region near the Martian equator. 

Sinus Sabaeus region

Credit: NASA


While previous research has suggested that water was historically present near the equator, Mars's current climate is supposed to be inhospitable to equatorial water ice. Using satellite imagery, the author finds material at the bottom of equatorial craters that is visually similar to material thought to be buried ice found elsewhere on Mars, especially in midlatitude craters (30°to 60°N/S). He also finds 30 additional craters where this material has been partially or completely removed, leaving traces that suggest it is composed of buried ice.


The findings corroborate the idea that Mars experiences dramatic climate change when the planet's axial tilt shifts. Earth's axial tilt undergoes small wobbles but tends to stay within a few degrees of its current position of 23.4°. Mars's tilt, which currently sits at 25.2°, is thought to oscillate between about 0° and 60°. 


General circulation models of the red planet's atmosphere suggest that the Sinus Sabaeus region would see increases in ice stability and preferential increases in water ice precipitation when the axial tilt exceeds 35°to 40°. This configuration has occurred multiple times in the past 10 million years, and the ice has apparently survived in the modern Martian climate due to its burial under debris or other low-permeability material.


Title: Candidate ice-rich material within equatorial craters on Mars
Authors: David E. Shean: Malin Space Science Systems, San Diego, California, USA.
Source: Geophysical Research Letters, doi:10.1029/2010GL045181, 2010
http://dx.doi.org/10.1029/2010GL045181