Newly Discovered Carbon may Yield Clues to Ancient Mars

NASA’s rover landed on Mars on Aug. 6, 2012, and since then has roamed Gale Crater, taking samples and sending the results back home for researchers to interpret. Analysis of Carbon isotopes in sediment samples taken from half a dozen exposed locations, including an exposed cliff, leave researchers with three plausible explanations for the origin: cosmic dust, ultraviolet degradation of dioxide, or ultraviolet degradation of biologically produced methane.

The researchers note today in Proceedings of the National Academy of Sciences that all three of these scenarios are unconventional, unlike processes common on Earth. Carbon has two stable isotopes, 12 and 13. By looking at the amounts of each in a substance, researchers can determine specifics about the cycle that occurred, even if it happened a very long time ago.

Christopher H. House, professor of geosciences, said that the amounts of Carbon 12 and 13 in our solar system are the amounts that existed at the solar system’s formation. Both live in everything, but because Carbon 12 reacts more quickly than 13, the relative amounts of each in samples can reveal the cycle.The team led by NASA’s Jet Propulsion Laboratory in Southern California, has spent the last nine years exploring an area of Gale Crater that has exposed layers of ancient rock. The rover drilled into the surface of these layers and recovered samples from buried sedimentary layers.

Curiosity heated the samples in the absence of oxygen to separate any chemicals. Analysis of a portion of the reduced produced by this pyrolysis showed a wide range of Carbon 12 and 13 amounts depending on where or when the original sample formed. Some was exceptionally depleted in 13, while other samples were enriched.