Penn State University: Newly discovered carbon may yield clues to ancient Mars

NASA’s Curiosity 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 carbon’s origin — cosmic dust, ultraviolet degradation of carbon dioxide, or ultraviolet degradation of biologically produced methane.

The researchers note today (Jan.17) 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 carbon cycle that occurred, even if it happened a very long time ago.

“The amounts of carbon 12 and carbon 13 in our solar system are the amounts that existed at the formation of the solar system,” said Christopher H. House, professor of geosciences, Penn State. “Both exist in everything, but because carbon 12 reacts more quickly than carbon 13, looking at the relative amounts of each in samples can reveal the carbon cycle.”

Curiosity, which is 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. Spectrographic analysis of a portion of the reduced carbon produced by this pyrolysis showed a wide range of carbon 12 and carbon 13 amounts depending on where or when the original sample formed. Some carbon was exceptionally depleted in carbon 13 while other carbon samples where enriched.

“The samples extremely depleted in carbon 13 are a little like samples from Australia taken from sediment that was 2.7 billion years old,” said House. “Those samples were caused by biological activity when methane was consumed by ancient microbial mats, but we can’t necessarily say that on Mars because it’s a planet that may have formed out of different materials and processes than Earth.”

Comments are closed.