Microbial life on Mars, the fascination of researchers for decades, may be thriving just below the planet’s surface, according to a new study released this week. Researchers put together a model for the existence of brine – or very salty water – just below the Martian surface, which in some regions of the planet could face conditions that allow for the dissolution of oxygen into the water. The findings build on other recent discoveries and could potentially help to guide future expeditions in the search for life.
The study, published in Monday’s Nature Geoscience, went so far as to identify what geographic regions of the red planet, based on weather and other factors, are most likely to produce the conditions necessary for such brine deposits beneath the surface. Identifying these regions could in theory help to inform where the next generation of Martian rovers are sent to explore.
“Nobody thought of Mars as a place where aerobic respiration would work because there is so little oxygen in the atmosphere,” said the lead researcher, Vlada Stamenkovic, an environmental scientist at the NASA Jet Propulsion Laboratory. “What we’re saying is that it is possible that this planet that is so different from Earth could have given aerobic life a chance.”
The study begins with the Mars rover Curiosity’s discovery of manganese oxide compounds, the production of which requires large amounts of oxygen. Based on this, the scientists developed two models: one to show how oxygen dissolves in brine at temperatures below freezing, the other to chart the changes in the Martian climate over the course of the last 20 million years and to predict future changes. Together, the two models helped the researchers hypothesize which regions of Mars are most likely to contain such deposits.
“Our results do not imply that there is life on Mars,” said Stamenkovic. “But they show that the Martian habitability is affected by the potential of dissolved oxygen.”
After multiple tests, the researchers found that even in their “worst case” scenario such deposits would have enough oxygen to support basic life. In their best case scenario, they would be able to support more complex life like sea sponges. “We were absolutely flabbergasted,” said Stamenkovic. “I went back to recalculate everything like five different times to make sure it’s a real thing.”
The new study itself is speculative, but builds on another recent report on a radar map of one of the Martian poles – a map that suggests the existence of a large underground reservoir full of this sort of oxygen-rich liquid water. The authors of this week’s study theorize the existence of such deposits closer to the Martian surface but suggest also that their findings further support the idea of one or more of these vast mile-deep reservoirs with enough oxygen to support life. “Our study focused on near-surface environments,” wrote Stamenkovic and his coauthors. “Recent results have indicated the potential existence of…subsurface brines at…a depth of 1.5 km [about a mile]. Our results imply that the O2 solubility in such a reservoir would be high.”
The next step, so to speak, for exploring Mars and testing these results on the surface is not precisely clear, but will most likely involve trying to access these brine deposits (depending on how deep they are). When the radar mapping study came out, scientists estimated that we could still be decades from attempting to access such reservoirs because of how deep below the surface they are. The possibility of brine deposits closer to the surface, however, might make reaching them in the near future more feasible.
“The question of extant life is something that we might solve if we had the right tools on Mars,” said Stamenkovic. “Looking for liquid water and brines on the Martian subsurface would be the first step; drilling would be another critical step.” Stamenkovic says that he and his group of researchers are in the process of developing a sensor, TH2OR, to search for water on the surface of Mars without digging below it. As the scientists wait for future missions to develop and test their results, their new study adds to a growing, and increasingly positive, body of research on the likelihood of life on Mars.