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The Search for Life On Habitable Exoplanets
New submitter Benzainload895 writes "The Verge has an article about why life on other worlds would be far stranger than we might expect. They also interview some astronomers who are trying to narrow down the most likely locations for life. Quoting: 'As it turns out, the small planets with long orbits that Kepler was finding were the ones it was least disposed to find. [After estimating how often red dwarf stars have planets and taking into account their expanded habitable zones, they] came up with an estimate Cowan says is "starting to get really close to a hundred percent, where for every [red dwarf] out there you should expect there to be a habitable rocky planet." Furthermore, research exploring these planets suggests weirdness — and lots of it — in what life they might harbor. For instance, the dim light coming from a red dwarf may not be enough for plant photosynthesis like on Earth. This may lead plants to be black instead of green in order to absorb more available light. Even weirder, these planets likely don't spin as they orbit. Since red dwarfs are smaller and cooler than the sun, planets circle them at close range, creating greater tidal forces than on our planet. While the tidal force on Earth moves the ocean up and down a few meters, that force on a red dwarf planet would be so strong it'd gradually slow down the rotation of planet completely. The result? One side of the planet would face its star in a permanently sunny day, while the other side would face the stars in an endless night."
Higher life form evolved from cats.... as any BBC viewer of Red Dwarf knows.
Part of the questions we were posing to the grad student from UC Santa Cruz: many of the planets they're identifying are about White Dwarfs - which means planets which have survived the exit of main sequence and a expelling of gas, at high velocity it could strip atmosphere and perhaps scour water from the surface - these are likely to be dead worlds, if not mostly frozen.
Those in the Goldilocks are still very hard to detect, which is why so few have been. There's a couple hundred thousand candidates which Kepler identified, and these are still being evaluated and processed - no small task. Exciting times.
Obligatory XKCD
A feeling of having made the same mistake before: Deja Foobar
You know, someone asks more or less this exact question every time this topic comes up -- "why not look for other forms of life unlike our own?".
And the answer is always the same -- how do you look for something you don't know the first thing about? What do you look for? How do you look for a lifeform which has completely different biology from us? How will you know if you've found it?
If you're physically there, you can look and see. If you're doing inference from spectroscopy and the like, what, exactly, do you look for to find a bit of life which is so alien from our own that we don't have any idea of what to look for or what processes would be involved?
You can't just take random chemicals and decide that they do, or do not, suggest a lifeform we can't even imagine.
It's simply not possible to look for signs of something when you have no basis on which to even speculate what those signs would be -- because you could look at anything and say "gee, maybe that's alien life".
But you'll never know, and can never make any hypotheses or predictions. At which point, you're well outside of what can be called Science, and straight back to speculative fiction. There's really no point in trying to look for life built around other building blocks, because we don't know anything about what that hypothetical lifeform would look like or how to spot it.
I'm not saying it couldn't exist. I'm saying that until we know about it and how it works, there's no basis to look for it.
Lost at C:>. Found at C.
Always looking for water looking for life, or where the 6 building blocks for life as we know it could form.
I'll summarize the standard reply to this: we're looking for these signs because that's all that we know enough to look for. Every life form we've encountered is carbon-based and requires liquid water and a certain temperature range. We also know that O2 in the atmosphere indicates photosynthetic activity. Now, it's theoretically possible that somewhere, there exist silicon-based, chlorine-breathing lifeforms. But since we've never encountered these, we have absolutely no idea what constitutes habitable conditions, or what chemical signatures to search for. So, rather than guess wildly and look for something we can't identify, we focus on the environments that are most conducive to known forms of life, because we have some confidence that we could detect something interesting. Is this really that difficult to grasp?
Actually, it is more like spinning with a periodicity of one year
Carl Sagan took a look at what an alien spacecraft could sense as it approached our Solar System, to see at what distance life could be deduced. His conclusion was that as soon as the spacecraft could detect molecular oxygen and methane in the same atmosphere (an inherently unstable and unmaintainable combination) it would know that something unusual was happening on the third planet out from the Sun. Detecting light on what should be the dark side of the planet would be the confirmation.
"Think about how stupid the average person is. Now, realise that half of them are dumber than that." - George Carlin
No, Sagan wasn't looking at oxygen as a product of life, he was looking at molecular atmospheric oxygen as something that was inherently unstable, especially in the presence of methane, and very especially in the concentrations that we breathe. That meant something unusual was happening. An atmosphere rich in helium and xenon would attract attention as well, and prompt investigation. The default hypothesis would be complex radioactive processes, just like the default hypothesis for atmospheric O2 would be complex chemical processes. The discovery of artificially concentrated radioactive elements (for example) would be analogous to artificial light sources on Earth. We don't have to know what kind of things life produces, we just need to have a handle on what typical planetary evolution produces and look for variances from this norm. We'll probably end up with situations where investigators ask, "Is that life, or just an obscenely complex self-maintaining chemical process?"
"Think about how stupid the average person is. Now, realise that half of them are dumber than that." - George Carlin
If the planet is tide-locked, there might also be limitations on core circulation. No circulation, no magnet field. No magnet field, atmosphere gets stripped by solar wind and the planet surface gets blasted with protons. Therefore, No life.
You know, someone asks more or less this exact question every time this topic comes up -- "why not look for other forms of life unlike our own?".... There's really no point in trying to look for life built around other building blocks, because we don't know anything about what that hypothetical lifeform would look like or how to spot it.
I'm not saying it couldn't exist. I'm saying that until we know about it and how it works, there's no basis to look for it.
Look around, human. There are currently around 8.7 million different kinds of life on Earth. Only a handful of them look like YOU, and yet they are as alive as you are. Some of them are in your gut right now ensuring you can digest the dinner you will have tonight.
Out there in the vast universe, the odds are whatever life is there almost certainly looks even less like you than the 8.7 million kinds that are actually from the same planet. And yet there is this persistence to look only for life we know. We should be looking for what we do not know, which is oddly enough what most of science is supposed to be about. Except this one niche, where they only want to find what they know. Makes no sense to me.
It may be all we are capable of looking for, but then we should say that and understand our lack of ability to recognize life IS probably going to screw up any results we might get.
Sig for hire.