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The results of the analysis of meteorite samples, carried out by John Bridges and Hitesh Changela (University of Leicester, Department of Physics and Astronomy) that show how asteroid impacts
on Mars could have caused water to flow on the surface, have just been published in the journal Meteoritics and Planetary Science.
The meteorites analysed are a very rare class called Nakhlites, that have their origin in violent impacts on Mars, capable of ejecting significant quantities of debris into space, some of which fell to Earth as meteorites. The class takes its name from the location of the first example found in 1911 in the Egyptian village of El-Nakhla, and now in the Natural History Museum in London. Other classes of Martian meteorites are the Shergottites and Chassignites.
Bridges and Changela used an electron microscope to study extremely thin sections (0.1 micron) of five different Nakhlites, and found structures (see photo) caused by the high temperatures and pressures associated with an impact capable of making a crater 1-10 km in diameter. Such an impact would have melted large quantities of sub-surface ice, causing liquid water to flow on the surface and allowing the formation of the clays and carbonates found in the meteorite samples.
The Nakhlites studied also show a series of sinuous veins whose mineral makeup suggest they formed in processes that also produce methane. The presence of this gas in the Martian atmosphere can also be attributed to asteroid impacts.
It will be the task of the Trace Gas Orbiter mission (2016) to detect traces of methane in the atmosphere, and distinguish between this method of production and another possibility, that is, the anaerobic decomposition of living organisms.
The results on Nakhlites should allow a model to be constructed that will explain the role of water in the formation of certain minerals, taking into account the influence of temperature, acidity and duration of the hydrothermal action resulting from asteroid impacts. |
