Researchers based at the University of Vienna and the Space Research Institute of the ÖAW in Graz have calculated for the first time how rapidly an Earth-like atmosphere would be lost from a planet orbiting a very active young star. Their calculations have shown that extreme hydrodynamic losses of the atmosphere would take place, leading to an Earth-like atmosphere being entirely lost in less that one million years, which for the evolution of a planet is almost instantaneous.
These results have significant implications for the early evolution of the Earth and for the possibility of Earth-like atmospheres forming around M-dwarfs. For the Earth, the most likely explanation for why the atmosphere was not lost is that the early atmosphere was dominated by carbon dioxide, which cools the upper atmosphere by emitting infrared radiation to space, thereby protecting it from the heating by the early Sun’s high activity. The Earth’s atmosphere could not have become Nitrogen dominated, as it is today, until after several hundred million years when the Sun’s activity decrease to much lower levels.
More dramatically, the results of this study imply that for planets orbiting M-dwarf, the planets can only form Earth-like atmospheres and surfaces after the activity levels of the stars decrease, which can take up to several billion years. More likely is that many of the planets orbiting M-dwarf stars to have very thin or possible no atmospheres. In both cases, life forming in such systems appears less likely than previously believed. Paper. (open access) – C. P. Johnstone, M. L. Khodachenko, T. Lüftinger, K. G. Kislyakova, H. Lammer, M. Güdel. Extreme hydrodynamic losses of Earth-like atmospheres in the habitable zones of very active stars. Astronomy & Astrophysics, 2019; 624: L10 DOI: 10.1051/0004-6361/201935279 More.
Is finding life elsewhere “inevitable” because that’s how it happens in science fiction?
How to put this gently?: In science fiction, “They’re out there” because that is the premise of the story. It may or may not work as directed in real life.
See also: Researcher: Why finding extraterrestrial life “now seems inevitable,” maybe soon. He ends with, “The ancient question ‘Are we alone?’ has graduated from being a philosophical musing to a testable hypothesis. We should be prepared for an answer.” It’s worth asking another question: What if, after decades of research, no answer comes? What would that change?
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