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The possibility of a life on Mars can not be referred to the distant past. New research suggests that our neighboring world could hide enough oxygen in salty water near its surface to support microbial life, opening up a multitude of potentially habitable regions all over the planet. Although the results do not directly measure the oxygen content of known brines on the Red Planet, they are an important step in determining where life might exist today.
Aerobic breathing, which is based on oxygen, is a key element of life on Earth today. In this process, the cells absorb oxygen and decompose it to produce the energy needed for metabolism. The very low levels of atmospheric oxygen in Mars have led many scientists to rule out the possibility of aerobic respiration in this country, but new research puts this possibility at stake. The study appears in the October 22 edition of Nature Geoscience.
"Our work calls for a complete overhaul of our vision of the potential life on Mars and the work that oxygen can do, which implies that if life had existed on Mars, it might have breathed some air. 39, oxygen, "says Vlada Stamenkovi, lead author of the study. , researcher at NASA's Jet Propulsion Laboratory in California. "We now have the potential to understand the current livability."
Although Mars is now a freeze-dried desert, it has abundant underground water ice reserves, as well as some liquid water in the form of brine. The high salt content of the brine lowers the temperature at which it freezes, allowing it to remain liquid even on the icy surface of Mars. In their new study, Stamenkovi and his colleagues associated a model of the dissolution of oxygen in brines to a model of the Martian climate. Their results revealed that puddles of salty liquid on the surface or just below the surface could capture the meager amounts of oxygen in the red planet's atmosphere, creating a reservoir that microbes could use metabolically. According to research, Martian brines today may contain higher oxygen concentrations than those found on the Early Earth – which, about 2.4 billion years ago, contained only traces of the gas in his air.
The study analyzed how a slow evolution of Mars's inclination to the sun (a well-studied phenomenon that continues today) would alter the average temperature of the planet, examining a time span of 20 million from years to 10 million in the past. future. This analysis showed that the associated temperature changes over these long periods of time could allow the brines to absorb and retain oxygen from the Martian air.
And while the model-based results may seem rather speculative, they align with otherwise mysterious in situ discoveries on Mars. NASA's Curiosity robot identified rocks rich in manganese, which probably required a significant amount of oxygen to form. "Manganese deposits on Earth are closely associated with life, both indirectly and directly," said Nina Lanza, a global geologist at the Los Alamos National Research Laboratory in New Mexico. However, this does not mean that Martian life has created the manganese deposits; instead, it may simply be that Mars has had much more atmospheric oxygen in the past than it does today – which is corroborated by several other independent sources of data.
In turn, an old oxygen-rich Mars would require a thicker atmosphere, perhaps thick enough to allow oceans of water to accumulate on the surface. This is the Martian story that most researchers are currently embracing, based on a multitude of observations from multiple missions.
But Stamenkovi says that an ocean, an oxygen-rich atmosphere or a warmer climate might not be needed to create the deposits. It is also possible that brines interacting with rocks for millions of years could have formed manganese-rich rocks and could still create them today, thus eliminating the need for Mars to have had oceans and an atmosphere similar to the Earth. Lanza agrees that manganese-rich rocks could have formed on a Mars planet without an ocean, but notes that further study is needed.
Steve Clifford, an expert in marine hydrology from the Planetary Science Institute in Arizona who was not part of the project, is not ready to count the role of the oceans in the formation of Mars brines. "You need the presence of water to have these brines," he says. Clifford points out that regardless of the water that remains on Mars today – and researchers think there is enough to cover the entire surface with at least half a kilometer or even one kilometer deep – it would take more in the past, essentially ensuring The past of the planet is a little watery.
Whatever the origin of the Mars brines, their existence and possible oxygenation suggest a powerful planetary niche and then neglected for past and even present life. "The question of existing life is an issue we could solve if we had the right tools on Mars," says Stamenkovi. "Looking for liquid water and brines in the Martian basement would be the first step. drilling would be another critical step. "
But the simple fact that brines retain oxygen does not necessarily mean that they provide a refuge for any Martian microbe, which spreads all over the planet. First, Stamenkovi and his colleagues have not yet modeled the actual formation or stability of brines over time; Instead, they simply looked for areas where salty liquid could exist, based on the atmospheric pressures measured by Martian and an estimated average annual temperature range. According to the study, the brines would require more salty conditions at the equator, which would require them to absorb less oxygen and become less suitable habitats – but the polar brines would be able to absorb enough oxygen to support a wider variety of life forms.
However, according to Edgard Rivera-Valentin, it would be difficult for the near-surface salts to absorb moisture from the Mars atmosphere to produce brine, a process called decay. Rivera-Valentin, a global scientist from the Lunar and Planetary Institute in Texas, who was not part of the study, says that decay is a challenge even at the poles of the planet. The water vapor is more abundant than at the equator, thanks to the presence of ice caps, but it is rare in the atmosphere because of the frost.
According to Rivera-Valentin, equatorial brines are more likely to form when groundwater comes into contact with minerals rich in salt rather than with salts interacting with atmospheric water vapor. According to Clifford, water-rock interactions across the planet are more likely to occur in depth, where groundwater can dissolve rocks that surround it while remaining isolated from the atmosphere for billions of years. "In areas close to the surface, it's a bit harder to anticipate brine composition or saturation," Clifford said. Rivera-Valentin also expressed concern that the brines are too salty for life. "The types of brine that would form on Mars would kill him," he says. "Life as we know it on Earth could not survive these brines – too salty and too cold."
Woodward Fischer, a geobiologist at the California Institute of Technology and co-author of the newspaper, says that to know the salt limit of life, one should know the energy budget of a cell. "We hardly know that in some very specific laboratory cases [microbes] on Earth, and we have no idea [about it] on any other planet, "he says. Fischer thinks that scientists should avoid too rigid constraints to imagine how extraterrestrial extraterrestrial life could emerge and evolve.
While biologically-friendly salmon oases dot the red planet, they could paradoxically be bad news for future life-hunting missions, potentially making vast expanses of the planet habitable – and thus forbidden to in-situ exploration, based on interpretations of international law. Planetary protection protocols require rigorous decontamination methods for spacecraft landing near "special areas" that may contain the conditions necessary for life, namely the presence of a usable energy source and liquid water . These protocols aim to prevent the accidental extinction or contamination of Martian life by the invasion of microorganisms of the Earth. They also aim to protect our planet from any Martian insect likely to end up on Earth sometime in future return sample missions. Presumably, if most of the Martian surface and subsoil were suddenly to be considered a "special region", exploration could still be done via robots somehow completely stripped of all traces potentially contaminating terrestrial biology.
These strict requirements would increase the already high cost of Martian exploration, but Stamenkovi remains optimistic. "I think there's a great place where we can be curious and be explorers and not ruin everything," he says. "We have to go."
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