User:Benhocking/Climate of Mars

Evidence for recent climatic change


In 1999 the Mars Global Surveyor photographed pits in the layer of frozen carbon dioxide at the Martian south pole. Because of their striking shape and orientation these pits have become known as swiss cheese features. In 2001 the craft photographed the same pits again and found that they had grown larger, retreating about 3 meters in one martian year.

These features are caused by the dry ice layer evaporating exposing the inert water ice layer.

More recent observations indicate that Mars' south pole is continuing to melt. "It's evaporating right now at a prodigious rate," says Michael Malin, principal investigator for the Mars Orbiter Camera (MOC). The pits in the ice continue to grow by about 3 meters per martian year. Malin states that conditions on Mars are not currently conductive to the formation of new ice. NASA has suggested in its releases on this phenomena that this continuing change indicates a "climate change in progress" on Mars.

Elsewhere on the planet, low latitude areas have more water ice that they should have given current climatic conditions. Mars Odyssey "is giving us indications of recent global climate change in Mars," said Jeffrey Plaut, project scientist for the mission at NASA's Jet Propulsion Laboratory. The observed trend so far is a warming one though nobody is asserting an airtight case has been established for any particular theory.

Assertions that the change is local
Colaprete et al. conducted calculations with the Mars General Circulation Model which show that the local climate around the Martian south pole may currently be in an unstable period. This computer calculated instability is rooted in the geography of the region, leading the authors to speculate that the melting of the polar ice is a local phenomenon rather than a global one. The researchers showed that even with a constant solar luminosity the poles were capable of jumping between states of depositing or losing ice - the trigger for a change of states could be either due to increased dust loading in the atmosphere or an albedo change due to a deposition of water ice on the polar cap. This theory is somewhat problematic due to the lack of ice depositation after the 2001 global dust storm Another issue is that the accuracy of the Mars General Circulation Model decreases as the scale of the phenomenon becomes more local. Model grid sizes are being reduced as more computing power becomes available but until recently, grid sizes of up to 300 kilometers in length were routinely used and 200 kilometer grid sizes were considered detailed. Today grid sizes of 45 kilometers are used by some researchers but this is a fairly recent development.

It has been argued that "observed regional changes in south polar ice cover are almost certainly due to a regional climate transition, not a global phenomenon, and are demonstrably unrelated to external forcing." Writing in a Nature news story, Chief News and Features Editor Oliver Morton said "The warming of other solar bodies has been seized upon by climate sceptics; but oh how wrong they are... On Mars, the warming seems to be down to dust blowing around and uncovering big patches of black basaltic rock that heat up in the day"

Indirect Solar Warming Hypothesis
Fill with Solanki's papers/theory (see talk page section), need 2 sources that apply it to Mars (need time to find them) not necessarily peer reviewed for enwiki but need to be reliable. This section is tough because Solanki is justifiably cautious of going much beyond the data available and so little empirical data is available on Mars. A globally warming Mars in sync with other planets would be a form of proof of Solanki's theories. Solanski studies the Sun and not Mars.

Orbital eccentricity theory
This theory was put forth in talk, why not put it up here. Even less evidence gathered so far on this one makes this section even more of a placeholder at this time. 

Assertion that solar irradiance is causing the change
K.I. Abdusamatov has asserted that the changes are due to increased levels of solar activity, saying that "parallel global warmings -- observed simultaneously on Mars and on Earth -- can only be a straightline consequence of the effect of the one same factor: a long-time change in solar irradiance." Abdusamatov's hypothesis has not been published in the peer-reviewed literature and has been dismissed by other scientists, who have stated that "the idea just isn't supported by the theory or by the observations" and that it "doesn't make physical sense." Furthermore, in recent decades solar activity has been relatively stable &mdash; 1978-2006 total solar irradiance (TSI) ranged from 1365 to 1368 W/m2. Other scientists have proposed that the observed variations are caused by irregularities in the orbit of Mars.

Evidence for recent local climatic change


There is no evidence for global climate change on Mars; indeed, there are no time series of martian temperature. There is some evidence for local changes around the south pole. In 1999 the Mars Global Surveyor photographed pits in the layer of frozen carbon dioxide at the Martian south pole. Because of their striking shape and orientation these pits have become known as swiss cheese features. In 2001 the craft photographed the same pits again and found that they had grown slightly larger, retreating about 3 meters in one martian year.

These features are caused by the dry ice layer evaporating exposing the inert water ice layer.

More recent observations indicate that Mars' south pole is continuing to melt. "It's evaporating right now at a prodigious rate," says Michael Malin, principal investigator for the Mars Orbiter Camera (MOC). The pits in the ice continue to grow by about 3 meters per martian year. Malin states that conditions on Mars are not currently conductive to the formation of new ice. NASA has suggested that this indicates a "climate change in progress" on Mars.

Causes of the local changes
Colaprete et al. conducted calculations with the Mars General Circulation Model which show that the local climate around the Martian south pole may currently be in an unstable period. This computer calculated instability is rooted in the geography of the region, leading the authors to speculate that the melting of the polar ice is a local phenomenon rather than a global one. The researchers showed that even with a constant solar luminosity the poles were capable of jumping between states of depositing or losing ice - the trigger for a change of states could be either due to increased dust loading in the atmosphere or an albedo change due to a deposition of water ice on the polar cap. This theory is somewhat problematic due to the lack of ice depositation after the 2001 global dust storm Another issue is that the more local the phenomena, the less likely the Mars General Circulation Model would measure and predict accurately. Grid sizes are being reduced as more computing power becomes available but until recently, grid sizes of up to 300 kilometers in length were routinely used and 200 kilometer grid sizes were considered detailed. Today grid sizes of 45 kilometers are used by some researchers but this is a very recent development.

It has been argued that "observed regional changes in south polar ice cover are almost certainly due to a regional climate transition, not a global phenomenon, and are demonstrably unrelated to external forcing." Writing in a Nature news story, Chief News and Features Editor Oliver Morton said "The warming of other solar bodies has been seized upon by climate sceptics; but oh how wrong they are... On Mars, the warming seems to be down to dust blowing around and uncovering big patches of black basaltic rock that heat up in the day"

Assertion that solar irradiance is causing the change
K.I. Abdusamatov has asserted that the changes are due to increased levels of solar activity, saying that "parallel global warmings -- observed simultaneously on Mars and on Earth -- can only be a straightline consequence of the effect of the one same factor: a long-time change in solar irradiance." Abdusamatov's hypothesis has not been published in the peer-reviewed literature and has been dismissed by other scientists, who have stated that "the idea just isn't supported by the theory or by the observations" and that it "doesn't make physical sense." Furthermore, in recent decades solar activity has been relatively stable &mdash; 1978-2006 total solar irradiance (TSI) ranged from 1365 to 1368 W/m2. Other scientists have proposed that the observed variations are caused by irregularities in the orbit of Mars.

Compromise Version
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