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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