Photo of the Week:

Image of martian meteorite Miller Range 03346, showing large clinopyroxene grains at five times magnification. These minerals grow in magma chambers in the upper crust of Mars, and contain certain forms of sulfur that give clues to the composition of the martian atmosphere.

As rovers dispatched from Earth cross the surface of Mars in search of water and other materials, martian meteorites that struck Earth millions of years ago are giving clues as to whether there ever could have been life on Mars. Researchers, including Scripps Institution of Oceanography, UC San Diego geochemist James Day, studied the isotopic composition of sulfur in 40 martian meteorite samples and discovered that Mars has had a substantially different atmosphere from Earth’s for at least 4 billion years. The results are published today in the journal Nature.

The NASA-led study analyzed meteorites comprised of magma that would have come into contact with Mars’s atmosphere, changing the composition of the magma in the process. Researchers concluded that Mars’s atmosphere was likely thinner with lower concentrations of greenhouse gases such as sulfur dioxide.

The researchers worked with samples determined to be of martian origin found in Antarctica’s Miller Range. The types of oxygen isotopes found in the meteorites, the presence of certain noble gases that match those currently found on Mars, and other physical characteristics indicates that the Antarctic rocks came from Mars originally.

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