HiRISE Science Theme: Climate Change

By Candy Hansen


Explanation of the theme.

            Mars has experienced climate change on many different timescales over its 4.5 billion year history.  Cycles in its orbital eccentricity, obliquity and season of perihelion determine the solar insolation that affects where reservoirs of water and carbon dioxide will be stable (north pole vs. south pole vs. atmosphere vs. subsurface).  This theme is focused on looking for current evidence of ongoing climate change.  Past climates are addressed by the polar geology, fluvial processes and stratigraphy themes.  Current climate change is detected by finding evidence that Mars' volatiles (H2O and CO2) are moving from one reservoir to another.  Mars Observer Camera (MOC) data show this process underway for example in the "Swiss Cheese" terrain at Mars' south pole (see Figure 1).  More CO2 is being eroded than is being replaced from year to year, which indicates that the CO2 reservoir at the south pole is not in equilibrium with Mars' current climate.  MOC has been monitoring this change since 1999 by taking images of the same terrain every year.  HiRISE will extend the MOC coverage into the future.


Major science questions for this theme.

Is Mars experiencing global climate change right now?


Relationship to other science themes.

            This theme is closely related to the seasonal processes and polar geology themes.  Polar geology is primarily focused on the permanent polar cap and the past climate record conserved in the polar layered deposits.  Climate change is an extension of seasonal processes in which we look for long-term trends that surpass seasonal variability.


Features of interest potentially visible at HiRISE scale.

            One indicator that Mars may be currently experiencing global change is the evolution of the swiss cheese terrain.  Other indicators such as formation of new gullies are covered by the fluvial processes theme.


Figure 1.  The "swiss cheese" terrain on the residual south polar ice cap has been observed to retreat 1 to 3 m in one Mars year. 




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