New evidence about the early atmosphere of Mars suggests that

September 21, 2022, Mountain View, California – A new research has been published in Earth and Planetary Science Letters It indicates that Mars was born wet, with a dense atmosphere that allows warm to warm oceans for millions of years. To reach this conclusion, the researchers developed the first model of Martian atmospheric evolution that links the high temperatures associated with the formation of Mars in a molten state through the formation of the first oceans and atmospheres. This model shows that, as on modern Earth, water vapor in the Martian atmosphere is concentrated in the lower atmosphere and that the upper atmosphere of Mars was “dry” because the water vapor would condense as clouds at lower levels in the atmosphere. Molecular hydrogen (H2), in contrast, did not condense and was carried into the upper atmosphere of Mars, where it was lost to space. This finding – that water vapor condensed and held on early Mars while molecular hydrogen neither condensed nor escaped – allows the model to relate directly to measurements made by spacecraft, specifically the Mars Science Laboratory rover. Curiosity of.

“We think we modeled a neglected class in Mars’ earliest history in the time immediately following the planet’s formation. To explain the data, the primordial Mars atmosphere must have been very dense (about 1,000 times as dense as the modern atmosphere) and composed primarily of molecular hydrogen ( H2), said Kaveh Pahlivan, a research scientist at the SETI Institute. “This finding is significant because H.2 It is known to be a potent greenhouse gas in dense environments. This dense atmosphere would have produced a strong greenhouse effect, allowing very early warm-to-hot water oceans to settle on Mars for millions of years until H2 gradually into space. For this reason, we conclude that—sometime before the Earth itself was formed—Mars was born wet.”

The data constraining the model is the ratio of deuterium to hydrogen (D/H) (deuterium is the heavy isotope of hydrogen) of various Martian samples, including Martian meteorites and those analyzed by Curiosity of. Meteorites from Mars are mostly igneous rocks – formed when the interior of Mars melted, and magma rose towards the surface. The dissolved water in these inner igneous samples (derived from the mantle) has a similar deuterium to hydrogen ratio to that of Earth’s oceans, indicating that the planets started with similar D/H ratios and that their water came from the same source in the early Solar System. On the contrary, Curiosity of He measured the D/H ratio of 3 billion year old clay on Mars and found this value to be about 3 times the value of Earth’s oceans. Apparently, by the time these ancient clays formed, the surface water reservoir on Mars – the hydrosphere – had largely concentrated deuterium relative to hydrogen. The only process known to produce this level of deuterium concentration (or “enrichment”) is the preferential loss of the lighter H isotope to space.

The model further shows that if the Martian atmosphere is H.2Rich at the time of its formation (and more than 1,000 times as dense as today), the surface waters would then be naturally enriched in deuterium by a factor of 2-3x relative to the interior, which would reproduce the observations. Deuterium prefers to split into a water molecule relative to molecular hydrogen (H .).2), which preferentially absorbs ordinary hydrogen and escapes from the upper atmosphere.

“This is the first published model that naturally reproduces this data, which gives us some confidence that the atmospheric evolution scenario we describe is consistent with early events on Mars,” Pahelvan said.

Aside from curiosity about early environments on planets, H2Rich atmospheres are important to SETI’s search for extraterrestrial life. Experiments dating back to the mid-20th century show that prebiotic molecules implicated in the origin of life readily form in H2Rich ambiance but not so easy in H.2Poor atmosphere (or more “oxidizing”). The implication is that early Mars was a warm version of modern Titan and at least as promising a site for the origin of life as the early Earth was, if not more promising.

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About SETI Institute
Founded in 1984, the SETI Institute is a not-for-profit, interdisciplinary research and educational organization whose mission is to lead humanity’s quest to understand the origins and spread of life and intelligence in the universe and to share that knowledge with the world. Our research spans the physical and biological sciences and leverages data analytics, machine learning, and advanced signal detection techniques. The SETI Institute is a distinguished research partner for industry, academia, and government agencies, including NASA and the National Science Foundation.

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