Thursday, 13 June 2013

Possible ancient volcanoes on Arabia Terra, Mars.

Much of the surface of Mars is covered by volcanic rocks, and sedimentary rocks which appear to be derived directly from volcanic sources. However the planet lacks a clear source for this material, with the few large, well-known volcanoes not being sufficient to explain the large volumes of material.

In a paper presented at the 44th Lunar and Planetary Science Conference in March 2013, Joseph Michalski of the Planetary Science Institute in Tucson, Arizona, and the Department of Earth Sciences at the Natural History Museum in London, Jacob Bleacher of the NASA Goddard Spaceflight Center and Shawn Wright of the Department of Geology and Geography at Auburn University, discuss a number of structures on the Arabia Terra uplands of the Martian Northern Hemisphere.

These are deep depressions superficially resembling impact craters, but without ejecta, a raised rim, inverted topography, a central peak, or nearly circular geometry, and associated with dine grained sediments and ridged plains lavas. Michalski et al. conclude that these are in fact collapsed caldera structures. They are too large to be explained by the melting of subsurface ice, but could potentially have been caused by the withdrawal or migration of magma at depth, and explosive eruptions.

Michalski et al. suggest that volcanism could have occurred on Arabia Terra due to crustal thinning associated with extensional activity or thermal erosion. On Earth explosive eruptions are associated with evolved magmas (magmas that have remained in chambers close to the surface for long enough to divide into lighter and heavier fractions), but on Mars, with its lighter gravity and thin atmosphere, gas rich basaltic magma could potentially erupt explosively as shallow depths within the crust.

Topographic map of Eden Patera, one of the proposed volcanic calderas of Arabia Terra. Michalski et al. (2013).

Arabia Tera with potential volcanic calderas labeled. Michalski et al. (2013).

Hubble image of Mars with major geographical features, including Arabia Terra, shown. Astrobiology Magazine.

See also India plans mission to MarsCuriosity about to set down on MarsDutch team plan colony on MarsMartian Dust Devils and Ubehebe Crater; a seventh potentially active volcano in California.

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