The search for signs of life on Mars is starting to pay off. Rock samples collected by the Curiosty rover appear to show signs of a key component of life as we know it.
This doesn’t mean Curiosity just stumbled across little green men on Mars (it would be bigger news), but scientists studying the rover’s samples measured the total organic carbon – a key component in the molecules of life – in Martian rocks for the first time.
“Total organic carbon is one of several measurements [or indices] that help us understand how much material is available as feedstock for prebiotic chemistry and potentially biology,” said Jennifer Stern of NASA’s Goddard Space Flight Center in a statement.
“We found at least 200 to 273 parts per million of organic carbon. This is comparable to or even more than the amount found in rocks in very low-life places on Earth, such as parts of the Atacama Desert in South America, and more than has been detected in Mars meteorites.”
Organic carbon is carbon bound to a hydrogen atom and is a prerequisite for organic molecules, which are created and used by all known life forms. However, it can also be created by non-living sources, like volcanoes, or come from meteorites, which Curiosity's Earthly counterparts suspect may be the culprit here.
As NASA points out, this isn’t the first time carbon has been found on Mars, but previous measurements just captured a portion of the carbon in the rocks. This new measurement captured the total amount of organic carbon found in the rocks, which provides insight into the amount of carbon in organic compounds.
The samples were collected from 3.5 billion-year-old mudstone rocks in the Yellowknife Bay formation in Gale Crater back in 2014. The rover has been exploring the crater since it arrived on Mars in 2012 as evidence points to it once hosting a great lake around 3.7 billion years ago, and life, as we know it on Earth, requires water.
The rover analyzed the samples by using oxygen and high heat to convert the organic carbon in the samples into carbon dioxide (CO2). From the amount of CO2 detected, the tool can work out not just how much organic carbon was in the sample but the exact isotope ratio, which helps the scientists back home understand the source of the carbon. They published their analysis this week in the Proceedings of the National Academy of Sciences.
“In this case, the isotopic composition can really only tell us what portion of the total carbon is organic carbon and what portion is mineral carbon,” explained Stern.
“While biology cannot be completely ruled out, isotopes cannot really be used to support a biological origin for this carbon, either, because the range overlaps with igneous (volcanic) carbon and meteoritic organic material, which are most likely to be the source of this organic carbon.”
That doesn't mean Curiosity is going to stop looking for life. Gale Crater is still one of our best bets. Aside from the liquid water and organic carbon we now know it has, it has other elements essential for biology, including sulfur, nitrogen, and oxygen.
“Basically, this location would have offered a habitable environment for life, if it ever was present,” Stern said.