The Mars Global Surveyor and Odyssey spacecraft reveal evidence that Mars may have experienced significant climate change in the recent past (105-106 Myr ago). Examples include gullies , cold-based tropical glaciers , paleolakes , and youthful near-surface ice . Except for the gullies, the evidence for recent climate change requires ice and/or liquid water at low latitudes. An obvious question, therefore, is how is it possible for ice and/or liquid water to exist at low latitudes which is not possible in the present climate system? There are several mechanisms to consider. An episode of intense volcanic activity could alter the mean composition of the atmosphere and, therefore, the climate system. Impacts, depending on the size, composition, and velocity of the impactor are another way to dramatically alter the climate system. Polar wander and solar variability are also possibilities. However, the most promising way to change the climate is through changes in orbital properties. Mars, because of its proximity to Jupiter and lack of a large stabilizing moon, experiences much greater changes in its orbit properties than the Earth.
Meteorology and Climatology
Lunar and Planetary Science XXXV: Special Session: Mars Climate Change; LPI-Contrib-1197