Imagine a hot volcanic spring. Mineral-laden acidic water streams through sulfur-rich rocks. A strange scent hangs in the air. For human beings it’s a horrible environment, best appreciated through only the lens of a tourist’s camera. But for strong thermophilic microorganisms this is lovely stuff. And that could be problematic in the hunt for signs of life on Mars. This similar type of environment may have once existed on a young Red Planet, and might have assisted in an exceptional incubator for living things. Certainly, few of the places visited by NASA’s small fleet of rovers over the past years appears to be composed of the early leftovers of places that were once chemically tough and wet, like earthly hot springs. Findings like these have openly influenced the plans for exploration.
However, a recent study proposes that a mineral – termed as “jarosite”, an iron sulfate – that would form freely in these possibly life-supporting circumstances, might also confound the experiments being performed by tools like those on Curiosity rover to search for organic matter. In a paper published in the journalAstrobiology, Lewis and coworkers explain the outcomes of flash-heating jarosite mixed with organic matter, in the similar technique that Curiosity’s onboard lab cooks samples. This technique steps the temperature up to around 1000 Celsius while sniffing for exciting compounds as they’re released. But the jarosite breaks down above 500 Celsius, generating sulfur dioxide and oxygen, and in these hot circumstances the released oxygen reacts energetically with any organics (carbon-holding materials that could be deposited by biology).
The outcome is that both the jarosite and the organics are expected to be destroyed, and the experimenter might not directly record their presence. This worsens an already complicated state. Naturally existing perchlorates on Red Planet are known to confuse this type of ‘cooking’ test. The oxygen they create has an equally vicious reaction with organics – efficiently burning them up.
Jarosite impurity may or may not be identifiable, which is a big problem as it might be present in exactly the type of environments you’d also want to search for organics in – fossil remnants of hot springs.
It’s quite a difficulty, and jarosite has certainly been identified on Red Planet, so this is a very serious problem. To work around this problem it may be probable to install methods that have been applied to perchlorate impurity, which include reviewing the details of the carbon dioxide production in a sample that could specify organic matter is being destroyed. A similar method might work if jarosite is present.
It appears that the natural environment on Mars and our investigational selections might be collaborating to obscure what’s actually lurking on the surface. It might be time for a fundamental reconsideration of how we go about examining Martian soil.