Christopher Crochett in Science News June 29, 2017 summarizes the possibilities and problems for life on planets near M dwarf stars, the “…darlings in the search for life.”
The planetary problems–early excessive heat, close orbits, sun flares, and difficultyholding onto water–all caused by their host M dwarf stars, are obvious, so I’ve summarized the good news here:
- So far, dozens of the 200 planets found near M dwarfs are in their suns’ habitable zones, where liquid water exists.
- Most M dwarfs are “cool and tiny,” many the size of Jupiter, about half as hot as our sun.
- M dwarfs live a long time (about 12 trillion years) since they burn their “nuclear fuel” slowly. This is plenty of time for life to find some way to appear, if it can.
- M dwarfs often have lots of small planets.
- Though M dwarfs’ planets suffer their sun’s intense early brightness and UV radiation that could strip away any water, oxygen, or nitrogen, Earth’s history provides some hope. Our oceans came back after the blast that whipped away our water and created our moon by venting water and gases from deep within the mantle.
- Even if a planet is locked so that one side faces the sun,
a) atmospheric carbon dioxide could “…help store heat and distribute it,”
b) or a permanent cloud bank could form facing the sun.
c) Simulations at the Laboratoire Meteorologic Dynamique in Paris have found that under a “range of conditions” a planet could “…hold onto some surface water.” As little as .001 percent of Earth’s oceans is enough.
When the Webb Telescope begins work in 2018, we can look forward to more signs of habitable planets near the M dwarfs. Atmospheric sniffs could add to the one indication we have of methane in the vicinity of an earth-sized planet.
Author of The Archives of Varok
The View Beyond Earth (Book 1.)
The Webs of Varok (Book 2.)
Nautilus Silver Award 2013 YA
ForeWord IBPA finalist 2012 adult SF
The Alien Effect (Book 3.)
An Alien’s Quest (Book 4. Released Nov.21, 2016)
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