The first heroes of the Earth were microbes. 2.7 billion years ago, the atmosphere began to accumulate oxygen produced by cyanobacteria that lived in the oceans and were capable of photosynthesis. Oxygen was fundamental for the appearance of more complex life, including the first animals, and today sustains the most common type of metabolism on the planet.
Now, a new study suggests that in areas of Mars There may also be enough oxygen to sustain some terrestrial living beings. Vlada Stamenkovic, a researcher at NASA and colleagues at the Technological Institute of California have developed a model that calculates the amount of oxygen that could have dissolved in salty waters that may exist in some areas of the planet. The salts present in these brines allow the water to remain liquid at temperatures below zero degrees. According to the study, posted today in Nature Geoscience, around 6.5% of the entire planet can hold quantities of oxygen on the surface or a few centimeters below it similar to those that on Earth are enough to sustain some microbes and sponges.
Recent studies suggest that the first ancestors of the current animals were sponges and that these living beings can proliferate at very low oxygen concentrations. Areas with possible oxygen are above 50 degrees of latitude around the poles. Among the Martian exploration missions that the study analyzes, there is only one that has explored these areas: the Phoenix, which landed on what could be water ice on the red planet in 2008.
This same year a possible large lake of salt water hidden under the ice of the south pole was discovered on Mars. The new study speculates that the oxygen concentration inside it could be "high" if there is temporary contact with the surface or if there is enough radiation to separate oxygen and hydrogen. Those responsible for the work believe that these theoretical results can explain the oxidation state of some Martian rocks and imply "that there are opportunities for life based on oxygen on current Mars or other planetary bodies thanks to oxygen sources that are alternatives to photosynthesis" .
Víctor Parro, researcher at the Center for Astrobiology (CAB-CSIC), points out that until now the presence of oxygen on Mars has been "neglected" due to the low concentrations. Although this is a theoretical study that would have to be confirmed with real measurements, the scientist emphasizes that "these models highlight the role that dissolved O₂ can play even currently for both the respiration of microorganisms and the oxidation of metals."
"Microorganisms do not need O₂ to breathe," he explains, "but molecular oxygen allows for greater energy in breathing processes, and their presence on Mars at adequate concentrations increases the chances of new and more efficient metabolisms. "For example, it would allow the existence of bacteria like those found in Rio Tinto [Huelva] that oxidize iron in pyrite to obtain energy. And, something that abounds on Mars, is iron, "he says.
"The authors choose the group of terrestrial organisms that are capable of living at lower concentrations of dissolved oxygen in water, which are basically certain types of bacteria and sponges, and conclude that the concentrations of oxygen that they calculate may exist in the brines. Martians would be enough for these organisms to thrive on Mars today, "explains Alberto González Fairén, a researcher at the CAB and Cornell University. "Of course, it's just a graphical comparison to highlight the high levels of dissolved oxygen in these brines and the authors do not imply that sponges can exist in liquid pockets hidden in the ice of Mars. The possible inhabitants of the brines would not only depend on the oxygen available to breathe: the very low temperatures, the high concentration of salts and the radiation do not allow the existence of life similar to the terrestrial one near the surface of Mars today, "he adds.
Another one of the unanswered questions that the work leaves is if there really are brines of liquid water on the surface of Mars, since the evidence accumulated so far They are not conclusive.