'Mirage Earth' Exoplanets May Have Burned Away Chances For Life 62
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.
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It was the FSM who fed beans to the volcanoes!
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Re:How's that different from Earth? (Score:5, Interesting)
Or they evaporated and the gravity of the planet is strong enough to hold onto H2. Unlike Mars for instance.
Most likely it was a combination of heat and weaker gravity. The hotter the planet, the more gravity needed to hold onto an atmosphere, because the molecules move faster. The Earth's collision with Theia [wikipedia.org] is believed to have generated enough heat to liquify the entire mass of the resulting combined planet. This would have been hot enough to drive off any water vapor in the atmosphere. One reason we believe this is true is the absence of much neon on Earth. Neon is abundant in the universe, but very rare on Earth. If the Earth was too hot to hold on to neon (mw=20) then it wouldn't have been able to hold onto water (mw=18) either.
Re:How's that different from Earth? (Score:5, Interesting)
Our water and atmosphere were burned away when the Earth was still forming. We got them back from comet impact.
Not only that, but shallow Earth-like oceans are likely better for life than deep Europa-like oceans. Although we may think of Earth as a watery planet, water is far more rare on Earth than in the rest of the Universe, making up only 0.02% of Earth's mass. If our oceans were as deep as Europa's, the continents would be completely submerged, there would be no upwelling, and all the nutrients would settle at the bottom, 100km below the surface. Without nutrients, the sunlit surface would be nearly lifeless. There might be some life around volcanic vents, but those are too rare to provide much scope for evolution. Mostly likely, if there was life at all, it would never even become multi-cellular. Having your oceans boiled away is a good thing!
Re:How's that different from Earth? (Score:5, Informative)
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.
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Yeah, I can't help but think that there's a lot more to creating a life bearing planet than simply forming from more or less the right components at the right distance from the sun.
I've long held that there's a good chance that the impact that created our moon, even the presence of our freaky-huge moon* was essential for the development of life, or at least complex multicellular life.
If to get life you need:
1. right distance from sun
2. The right mix of materials - CO2**, hydrocarbons, just the right amoun
One step forward, two steps back (Score:3)
It seems every week that we get a story about habitability of planets - one saying that life could be in more places than we thought, two saying it's unlikely in areas we previously thought it was.
I'm just sad because the equations seem to be shaping up to quite a distance* between intelligent complex tool using species.
*If you assume they're more or less randomly scattered, the lower the odds per solar system, the longer the median distance between such races/civilizations.
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Still go back and do the math.
say .1% of stars in the galaxy are like our own, and .1% of those stars have planets in just the right configuration, and .1% of those planets have plant life, and .1% of those worlds have intelligent life.
Then in this galaxy alone there are 100,000's of different sentient species. Even if they are separated over 100 million years of time odds are we are not alone right now.
Re:One step forward, two steps back (Score:5, Insightful)
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Still go back and do the math.
What part of 'the math' did I screw up? I don't recall ever calling the presence of additional 'intelligent complex tool using species' in question. I stated that, assuming a random distribution, the lower the odds of such a species the further apart they will be, on average.
Then I said that that makes me sad. I forgot to mention that it makes me sad because the further apart we are, the more difficult finding and talking to each other are.
You also forgot a few steps. of the .1% with intelligent life, .
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Then I said that that makes me sad. I forgot to mention that it makes me sad because the further apart we are, the more difficult finding and talking to each other are.
On the bright side, if we did find intelligent life out there, we would immediately launch into action doing something nasty to them. They're better off not knowing us, and if they're like us, we're probably better off not knowing them too. Good fences make good neighbors.
A nice dream (Score:2, Insightful)
Assuming there is life elsewhere in the universe, and there's a good chance, it takes many right circumstances to happen.
What's more, to be relevant to us it must also coincide with our time frame. We've only been capable over interacting with extra-terrestrials for about 150 years of 2+B years of the Earth's existence. Another civilization would have to be both advanced (more than we are) and at the right time for us to meet.
Re:A nice dream (Score:5, Insightful)
Earth has been advertising itself for more like a half-billion years. An atmosphere with free oxygen is rare, at least we haven't found one yet out of the explanets we've discovered. To be sure, we haven't studied the atmosphere on very many, but at the very least we know how to do so, at least for some.
There has been some suggestion of merely chemical processes that can give rise to free oxygen in the atmosphere, but I don't know how likely (or un) those processes are, and whether they cause the levels the Earth has, especially with traces of methane present at the same time.
We know our atmosphere has been biosculpted, and that would be something others could have seen for half a billion years.
One must assume that any alien civilization capable of interstellar travel would know at least as much as we do about the relevant technologies. That would include something Keplar-like, only better. You don't want to take your first interstellar steps to a place with no relevant planets.
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we will likely send our first interstellar probe to Alpha Centauri system (with three stars) whether it has "relevant" planets or not.
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Possibly true, but only because it's much closer than the alternatives, and offers three different star systems to explore for (roughly) the price of one. I rather doubt the Centaurians would send probes here unless they already had some reason to believe there was something interesting to see.
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If age of A or B 7 billion years as some studies say then perhaps they did just that a couple billion years ago, found algae and fungus, and wrote the place off as totally boring.
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Perhaps, though unless life is extremely common in the universe even algae and fungus would likely make us incredibly interesting, even if they only check back every few hundred million years or so to see if the slime as done anything interesting yet.
Then again maybe they dropped by 4 billion years ago and discovered only lifeless rocks, and we all evolved from the stuff they flushed from their bilge tanks as they restocked.
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My personal belief is that life is common in the galaxy, but complex multicellular life rare. We've had 3 billion years of the simple, then only half a billion of the complex.
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I'm inclined to agree. But be careful - don't conflate muticellular with complex, we know quite well that at least some modern unicellular life is astoundingly complex. Hell, we share something like 20% of our genome with single-celled yeast. It may well be that complexity was increasing steadily, and it just took three billion years for unicellular life to become complex enough that it could really exploit the advantages of forming larger colonies. After all, it doesn't do you much good to form large c
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Are you so sure of that? Almost all life on Earth, including virtually everything that's substantially dangerous to us, are unicellular (or non-cellular). I'm not sure how much easier it would actually be to colonize a "slime world" than a world with non-sapient complex life.
Unless it's just the sapience you were considering, in which case yeah, less competition on that front would make thing easier, but also a lot less interesting.
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Assuming there is life elsewhere in the universe, and there's a good chance, it takes many right circumstances to happen.
What's more, to be relevant to us it must also coincide with our time frame. We've only been capable over interacting with extra-terrestrials for about 150 years of 2+B years of the Earth's existence. Another civilization would have to be both advanced (more than we are) and at the right time for us to meet.
Well we know other civs either go silent or don't exist because we don't hear them. But a silent civ isn't necessarily an irrelevant one. If relativity holds they probably haven't even heard of us yet, they might have probes that noticed stone age humans roaming around but they didn't know if we'd developed. And even if they have noticed us they may not be ready to contact us yet. Maybe they want to give us a million years or so to play around on our own first.
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Well we know other civs either go silent or don't exist because we don't hear them.
Just because we can't hear them doesn't necessarily mean they're silent or don't exist. Due to the inverse square law, most of our signals are indistinguishable from background noise by the time they hit Alpha Centauri. A couple years ago we pumped a lot of energy into a directed Arecibo transmission toward the Wow! signal [wikipedia.org], but even that will get lost in the noise a couple hundred light years away. This is not to mention that we transmit on and listen to a certain band of frequencies. My understanding i
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Nah, if that sort of wildly speculative nonsense could happen there'd be water on Earth today, instead of the dry barren moonscape left after the existing water was boiled off by the planet-liquefying collision with Theia.
Initial conditions (Score:3)
[Researchers found] through computer simulations that some planets close to low-mass stars likely had their water and atmospheres burned away
That's a large assumption they had any atmosphere or water in the first place.
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nitrogen oxygen and hydrogen are pretty common throughout the universe. It would be reasonable to assume many planets had water at least at some point in their existence.
Um yea no... (Score:4, Insightful)
Given that we have a sample size of one: The earth
I think it's a tad ridiculous that we assume we have any idea what kind of environment can support life at all. There is no environment that we've explored that we can rule out the existence of life on. Yes, I understand that's because we haven't really explored any of them... but that's kind of the point.
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I knew there was going to be one of these.
There always is.
Each time, someone has to explain that the point of looking for life like us is because we know what we're looking for.
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Well, we have a somewhat decent understanding of the terrestrial requirements for "life as we know it". "Life as we don't know it" is a fascinating topic, but without any data points on which to rest an argument it's just not one worth seriously discussing outside of synthetic biochemistry labs. At least not unless an until we have reason to believe we may have discovered some.
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Yes, but there's clearly a huge amount of life, even on this planet, that we don't understand at all. And even some of the life we know about on this planet has been proven to be able to live in environments very similar to what we see on planets we're assuming are uninhabitable. Doesn't that seem a tad foolish?
It seems like these stories we keep hearing about aren't about finding a planet that has life... they're more about finding a planet we could live on. While that's definitely a noble goal, I think th
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"Life as we know it" aka intelligent life requires an enormous amount of energy. We can't measure the output of a pool of bacteria on other planets, only of full ecosystems. To sustain full ecosystems as we know it, we need water. It makes sense because hydrogen is a very common product in space as is carbon. Water has some very specific properties that sustain life (frozen water rises, if it didn't, our oceans would be a frozen wasteland) Although evolution without hydrogen and carbon is probably possible,
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Generally speaking "life as we know it" is a lot less specific than that. Like, say, based on DNA. Or at least amino acids. Perhaps cellular. Carbon-based. Water-based.
We share 20% of our genome with baker's yeast, along with most of the environmental requirements for survival. *That* is life as we know it. Life almost identical to us. There's no reason to assume "life as we don't know it" would share *any* of those qualities. Silicon-based crystalline life forms? Sentient standing waves of energy?
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My point was that all that stuff we are made out of is abundant in the Universe. Silicon isn't nearly as abundant therefore the likelihood of stuff happening with it is less likely. How would we even know what to look for with "standing waves of energy"? If what we are has happened elsewhere in the Universe, it would've happened a lot. Perhaps with silicon, perhaps with energy but it's more likely to have happened with carbon and hydrogen.
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In fairness, for now the kinds of planet we could live on are the only ones we're certain any life could survive on. And it's not like we're ignoring the rest, I have no doubt that will be listening, and eventually (once it's possible) be sending interstellar signals to every planet showing evidence of possessing complex chemistry. Just in case. In the mean time, well, Earthlike worlds have a romantic quality that sells headlines. There's something deep in our genetic imperative that tells us to seek out
What if we're the oddballs . . . ? (Score:2)
comets? (Score:2)
Caveat, I'm not an astrophysicist or anyone who would know anything about this. I couldn't even play one on TV. However:
> 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.
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 eq
Flare stars (Score:4, Informative)
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.
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Ok. So it's not just that water has been boiled off during the star's hot stage, it's that low mass stars go through multiple stages, none of which are conducive to life, for different reasons. Thanks, I get it.
So, there's not just a goldilocks zone, there are goldilocks stars. Too small is not good, and too big is probably not good for other reasons.
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Missing Asterisk (Score:1)
There's a missing asterisk right next to every mention of the word "life" to qualify it as "earth like". Who knows what other life forms might exist without requiring water?!
Unless they migrated (Score:2)
We really don't have much idea how much migration goes on in early planetary systems, but it looks like there is a lot. So, a "mirage Earth" won't be a mirage if it sent its formative years further out from its star.
Did they forget planetary migration? (Score:2)
Planets move (Score:4, Interesting)
Presumptuous maybe, but TFA is flawed as hell; planets move after they have formed, and generally inwards. They make no mention of this fact anywhere.
In our case, we had the Jupiter - Saturn duo that stabilized things, and prevented Jupiter from crashing into the Sun, taking the inner 4 planets with it.
It's entirely plausible that decent planets with atmospheres exist within the habitable zones of small stars, with crazy shit like 50 day years, and the dark side of the moon melts a little when it swings close to the sun. Heh.
But, a planet that formed close in to a star early on, and has remained there the whole time the system has cooled down, is likely to be a barren rock. Agreed. And a bit obvious...
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Even an outer planet of a class M star that had an atmosphere at some point and drifted into what would be the goldilocks zone for water would not retain its atmosphere (and water) for long. As other posters have mentioned, class M stars are relatively low mass and there for have huge solar flares that would bombard said planet, thus blowing away the atmosphere. Even if such a planet was lucky enough to survive that, by the time that activity has declined, the star has cooled significantly and said planet w
Earth size planets with moons (Score:1)
It seems that earth size planets with moons formed by impact have nil chance to support life due to boiling of the atmosphere and water as a result of the impact by a Mars size object
oh well, another promising candidate off the list
a simulation? (Score:2)
> [Researchers found] through computer simulations
Simulations are not science. I could produce my own simulation that would show exactly the opposite of what his simulation showed. It's all a matter of your assumptions. No simulation can sufficiently mimic the complexity of the real world. This is guessing and nothing more. That simulations have somehow become 'science' is just sad. Simulations, if anything, are the opposite of science.
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> [Researchers found] through computer simulations
Simulations are not science. I could produce my own simulation that would show exactly the opposite of what his simulation showed. It's all a matter of your assumptions. No simulation can sufficiently mimic the complexity of the real world. This is guessing and nothing more. That simulations have somehow become 'science' is just sad. Simulations, if anything, are the opposite of science.
Simulations have always been part of science. They are called mathematical models and they usually exist until a better, more refined model comes about.
This assumes ... (Score:2)
We consider how improbable life on Earth is given the odds of multiple