Monday, July 17, 2017

Life On Earth-Like Planets Is Extremely Resilient

Astrophysical events that kill off many species of life on Earth or another Earth-like planet do happen. We have had several on Earth in the last 4 billion years. 

But, astronomy events so severe that they would sterilize Earth or an Earth-like planet killing off all life of all kinds on it, are extremely rare according to a new study of the topic.
Much attention has been given in the literature to the effects of astrophysical events on human and land-based life. However, little has been discussed on the resilience of life itself. Here we instead explore the statistics of events that completely sterilise an Earth-like planet with planet radii in the range 0.5−1.5R Earth and temperatures of ∼300K, eradicating all forms of life. 
We consider the relative likelihood of complete global sterilisation events from three astrophysical sources -- supernovae, gamma-ray bursts, large asteroid impacts, and passing-by stars. To assess such probabilities we consider what cataclysmic event could lead to the annihilation of not just human life, but also extremophiles, through the boiling of all water in Earth's oceans. 
Surprisingly we find that although human life is somewhat fragile to nearby events, the resilience of Ecdysozoa such as Milnesium tardigradum renders global sterilisation an unlikely event.
David Sloan, Rafael Alves Batista and Abraham Leob, "The Resilience of Life to Astrophysical Events" (July 13, 2017).

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