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'Mirage Earth' Exoplanets May Have Burned Away Chances For Life
vinces99 writes: Planets orbiting close to low-mass stars — easily the most common stars in the universe — are prime targets in the search for extraterrestrial life. But new research led by an astronomy graduate student at the University of Washington indicates some such planets may have long since lost their chance at hosting life because of intense heat during their formative years. Low-mass stars, also called M dwarfs, are smaller than the sun, and also much less luminous, so their habitable zone tends to be fairly close in. The habitable zone is that swath of space that is just right to allow liquid water on an orbiting planet's surface, thus giving life a chance. [Researchers found] through computer simulations that some planets close to low-mass stars likely had their water and atmospheres burned away when they were still forming because they were exposed to high temperatures from their parent stars.
Umm, it seems you're not aware that the prevailing theory is that those volcanic vents were the birthplace of life on Earth, and probably its primary residence for hundreds of millions of years thereafter? And that it's believed that the first light-sensitive molecules were probably used by microorganisms to flee the lethal ultraviolet sunlight penetrating the upper layers of the oceans? Until photosynthesis evolved sunlight had nothing to offer life: the energy gradients around volcanic vents were far more easily harnessed.
Even today it's believed that the vast mass of life on Earth are chemovores living deep underground, whose ancestors may have never seen sunlight in the entire history of the planet.
Even multicellular life thrives around those undersea vents, and quite possibly deep underground as well. The upper reaches of the ocean, to say nothing of the land, were barren energy-poor wastelands likely only colonized by those poor saps who couldn't compete for the more desirable locations.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Ok, I understand that, but isn't it possible for an ice bearing comet (or several) to impact the planet at some later time when the sun was cooler? Surely those planetary systems have their own equivalent of oort clouds?
The whole reason that a red dwarf is so dangerous to live around is its low gravity. It can hurl flares from its surface that ascend far out into space and reach its tight little "habitable zone", and its planets will occasionally orbit through a flare and get zapped. The flares are channeled and accelerated by electromagnetic turbulence that originates from deep inside the star. Even after the surface temperature of its photosphere finally declines, the star will continue to flare until it shrinks down to a white dwarf (which has no habitable zone at all, since its starlight is extreme ultraviolet radiation that can easily blast water molecules apart). Since M-class stars typically have expected lifetimes of trillions of years, you'd have to wait a long time to see it happen.