Here’s a daily news story that has a singular reason to exist. A writer decided to go to a meeting. He found no other press there. He learned something very interesting – at least, to the community of readers who avidly follow every twist and turn of the hunt for alien Earths, including Super Earths, and the long grind toward the day we might be able to analyze them for signs of life (or its signals, saying hello). And he got it into the journalism section of a major journal.
- NatureNews – Richard (Rick) Lovett: Tidal heating shrinks the ‘goldilocks’ zone ;
For that crowd who follows such news as this, what is the first thing, quick, that the moon Io evokes? I bet it’s volcanoes. That mini-world is the most volcanic thing in the solar system. Its orbit of Jupiter is not quite circular, so it cannot match its rotation rate with its orbital period except on average. Sometimes it’s a little fast, sometimes a little slow, nodding its face at Jove while the latter’s tidal forces regularly squeeze the thing out-of-round on a shifting axis. The friction keeps its melt zone hopping and bubbling.
Lovett, at a little specialty astrodynamics meeting in Oregon, heard a University of Washington astrobiologist describe how similar processes could be heating to unliveable levels a large share of a recently-speculated huge repository for Earthlike planets: the billions of tiny red dwarf stars in the Milky Way and probably nearly every other galaxy. He and colleagues calculate that to be warm enough to be in the zone where liquid water can exist requires a world be close to a red dwarf. There, tidal forces are fairly high. It takes only slight ellipticity for a planet, even a tidally-locked one, to undergo the kind of kneading that Io feels. Ergo, gushers of lava everywhere.
This is no reason to despair about SETI finding paydirt near an M-dwarf. But it may cut chances by half or more. But with, as we say, billions of them out there it would seem some ought to be potential habitats anyway. Or, as Lovett puts things gracefully, there may yet be, around red dwarfs, “a menagerie of previously undreamt-of planets.” And for stars with greater than about one fourth the mass of our Sun, the tidal, volcanic hell effect fades away from the habitable zone.
Looking around I found a recent story on the general topic that came oh-so-close to describing the problem:
- Space.com – Nola Taylor Redd (April 27): Odds of Finding Alien Life Boosted by Billions of Habitable Worlds ; The story explicitly mentions tidal locking. But Redd’s sources addressed only one difficulty for life on a world with one face toward its star: near side very hot, far side very cold. Those sources tell her perhaps winds or other factors might spread the heat around in a comfy manner. Nobody, apparently, thought of Io’s object lesson.
*UPDATE (Dept of no scoop like an old scoop) See comments, or looky here:
- Astrobiology Magazine (Feb 9) Charles Q. Choi: Tidal Forces Could Squeeze Out Planetary Water ;
– Charlie Petit
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