How small the planet Mars was judged to be uninhabitable

The history of Mars itself may contain a basic fact about the habitability of planets And why today is a desert of rocks and dirt without visible signs of life.

Thanks to the observations of the probes orbiting Mars today and advanced robotic scanners And real laboratories on wheels, like roving vehicles Curiosity and perseverance from NASA, Scientists You know that in the ancient past, liquid water would have flowed across the surface of Mars.

Thus, the The Red Planet once had lakes, rivers, streams, and perhaps even a huge ocean covering much of the Northern Hemisphere.. But Mars does not have liquid water on its surface today. That surface water practically disappeared about 3.5 billion years ago, lost to space along with a large part of the Martian atmosphere.

new Investigation from Washington University in St. Louis One rationale: Mars may be too small to hold large amounts of water. Scientists believe that the dramatic climate change that the Red Planet underwent began when that world lost its global magnetic field, which had been protecting Martian air from being swept away by charged particles streaming in from the sun. But that immediate cause was based on a more fundamental motive, according to the new study: Mars is too small to hold surface water in the long term.

“The fate of Mars was decided from the beginning“, She said kun wang, assistant professor of earth and planetary sciences in the arts and sciences and lead author of the study. “There is likely to be a threshold in the size requirements of rocky planets to hold enough water to allow habitability and plate tectonics, with a mass greater than that of Mars.”

To carry out this revealing study, Wang and his collaborators used stable isotopes of potassium (K) to estimate the presence, distribution, and abundance of volatile elements in different planetary bodies. Potassium is a moderately volatile element, but scientists decided to use it as a kind of tracer for more volatile elements and compounds, such as water. This is a relatively new method that differs from previous attempts to use ratios of potassium to thorium (Th) collected by remote sensing and chemical analysis to quantify the amount of volatiles that Mars once had. In previous research, members of the research group used the potassium tracing method to Study of the composition of the moon.

Wang and his team measured the potassium isotope compositions of 20 previously confirmed Martian meteorites, It was chosen to be representative of the bulk silicate composition of the red planet. Using this approach, the researchers decided that Mars lost more potassium and other volatiles than Earth during its formation, but retained more of these volatiles than the moon and asteroid 4-Vesta., two bodies much smaller and drier than Earth and Mars. Thus, the researchers found a well-defined relationship between body size and the composition of potassium isotopes.

“Why there is a much lower abundance of volatile elements and their compounds in dissimilar planets than in undifferentiated primitive meteorites has been a longstanding question.Co-author Katarina Luders, associate professor of Earth and Planetary Sciences Research at the University of Washington, said in the same statement. statment. (The term “differentiated” refers to a cosmic body whose interior has been separated into different layers, such as the crust, mantle, and core.) “The discovery that K isotopic compositions correlate with planet gravity is a new finding that has important quantitative implications for when and how dissimilar planets received and lost their volatiles,” Lauders added.

The New study, which – which Published online in the Proceedings of the National Academy of Sciences, and previous work together suggests that small size is a double whammy of livability. Young planets lose a lot of water during formation, and their global magnetic fields turn off relatively early, thinning the atmosphere. The new work could also have applications outside our cosmic backyard, Team members said.

“Martian meteorites are the only samples we have to study the chemical composition of the mass of Mars. These Martian meteorites range in age from several hundred million to 4 billion years and have recorded the history of the fluctuating evolution of Mars. By measuring isotopes of moderately volatile elements, such as potassium, we can infer the degree of volatile depletion of planets in large quantities and make comparisons between different bodies in the solar system, Wang said. To be liquid water on Mars, but it is difficult to quantify the amount of water in total Mars through only probe and remote sensing studies. There are many models for the greater water content of Mars. In some of them, the first planet Mars was wetter than Earth. We don’t think that’s the case.”

“This study confirms that there is a very limited size range for planets to have enough water but not too much to develop a habitable surface environment.Co-author Klaus Mezger, of the Center for Space and Habitat at the University of Bern in Switzerland, said in the same statement. He continued, “These findings will guide astronomers in their search for habitable exoplanets in other solar systems.”

The “surface environment” disclaimer is important in any discussion of habitability. Scientists believe that modern Mars still harbors aquifers that could support life, for example. Moons such as Jupiter’s Europa and Saturn’s Enceladus host huge oceans that potentially support life beneath their ice-covered surfaces. Wang now thinks, For planets within habitable zones, perhaps the size of the planets should be emphasized even more and routinely taken into account when considering whether an exoplanet could support life..

“The size of an exoplanet is one of the easiest parameters to determine. Based on size and mass, we now know whether an exoplanet is a candidate for life, because the first-order limiting factor for volatiles retention is size,” the experts concluded.

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