how to test if a planet is 'livable'?

indianroads

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It's useful to remember that Earth has an oxygen-rich atmosphere ONLY because it has organic photosynthetic life forms that produce the oxygen. Oxygen is chemically very reactive, and would disappear very quickly from the atmosphere if photosynthesis ceased. Detection of free diatomic oxygen in a planet's atmosphere is a strong signal that some form of organic life already exists there.

caw

I can't remember (my head is like a sieve sometimes) - but wasn't oxygen detected on one of the planets around Trappist-1?
 

Twick

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Lol -- hey, I have a cool shake flashlight that says the beam can be seen really far....



A human outpost where that'd make someplace outside the Milky Way more plausible though? I know it's sci-fi but still. At warp 10, we're talking 250,000 years away.

I don't think science fiction should be limited by anything so trivial as our current state of knowledge.
 

P.K. Torrens

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I don't think science fiction should be limited by anything so trivial as our current state of knowledge.

This is off-topic from the OP's initial question but tech limitation in SF *almost* defines sub-genre. If you include FTL travel, you are *almost* always writing space-opera. I guess what I am saying is that SF, as a genre, isn't defined by our current state of knowledge - it never was, really - but sub-genre is.

Also, if you have inter-galactic travel in your story, IMO, figuring out if a world is "livable" is next to inconsequential in terms of the tech required. Mobile labs in robot-form are being used now (look at the stuff we have on Mars). Running remote DNA amplification and pathogenic tests would be a piece of piss compared to popping into a parallel universe and then popping back into ours exactly where you want.

indianroads - I suspect you can get away with pretty much anything you want if you've got FTL travel.
 

ipsbishop

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In today's real world a spectrographic analysis would be the tool to use in the beginning. You could easily acquire a lot of information about a planet remotely from a vessel in orbit such as what gases by percentage are in the atmosphere, life signatures such as methane, clues about it's biosphere, temperatures, observable minerals....
 

the.real.gwen.simon

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Guys, focus, this isn't about how they got there.

You can determine the chemical components of the air/water/soil from samples (Not my field, but I think it would be a mass spectrometer.). I have no idea how one tests for gravity other than dropping something and seeing how long it takes to get to the ground, but I'm sure if you asked physics people there's an equation for how much gravity a thing of particular size has. (I asked Dr. Google, who says it's Gravitational force = (G * mass1 * mass2) ÷ (distance^2), where G is Newton's gravitational constant. For most texts G = 6.673×10-11 N m2 kg-2.)

When you get to the 'But what about Horrible Unknown Alien Disease, personally, I'd go with frogs. Their skins are incredibly porous, which is why frogs are often the first symptom of pollution here on earth. Plus, some species of frog can just be frozen and then thawed out and be fine. (How remains a super cool science mystery, which is probably not relative to what you're doing.) Of course, sometimes what causes cancer in rats only causes cancer in rats, or never causes cancer in rats but always causes cancer in Capuchins. In the end, the only way to be 100% is not one person being potentially sacrificed, but many, many people being potentially sacrificed. Different things affect different people differently based on factors of sex, race, overall health, and in certain memorable cases, a random genetic quirk that doesn't seem to really do anything except mean you won't get AIDS.

If none of this is lighting your candle, though, you could always go the Star Trek route of having the Scientist!character wave a Doohickey around and loudly declare that everything is fine, and everyone can take their helmets off. It's light on sci and heavy on fi, but it's an answer if you don't have a better one.
 

the.real.gwen.simon

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Oooh, I almost forgot: the oxygen content in the air determines the size of the organisms there, which is why prehistoric plants are SO HUGE, because apparently there used to be more oxygen laying around for them to use. Pretty sure it works that way for bugs, too, not sure about vertebrates.
 

Twick

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It would be unlikely that there'd be a virus or bacteria specifically adapted for a host that doesn't exist on the planet (despite War of the Worlds.)

If it's important to get the characters out into the environment quickly, air and soil sampling, with computer analysis set to look for chemical patterns that can replicate in human cells. That would look out for very small viruses and prions. Larger microfauna could be cultured in media that replicate human tissue and monitored for chemical output.

If your computer system can navigate you light-years away, it should be able to look at a chemical structure and say, "any way this could interact with human cells in a harmful way?"