Earth As an Extrasolar Planet

sciencehabit writes "Astronomers have a theory that they can detect whether a planet light years away will be habitable by just looking at how its sun is reflected in its atmosphere. To test the idea, they pretended that they were observing Earth from a distant object — in this case, the moon. And sure enough, they picked up critical components for life in Earth's atmosphere: ozone, oxygen, sodium, and nitrogen."

Comments

Re:Why not point Cassini back at us?

[Tablizer]

Cassini is probably not designed to be sensitive to those signatures. It's built for Saturn and co. It cost a lot to add & launch extra's outside of mission objective.

Not NASA

[pigeon768]

Astrophysicist Alfred Vidal-Madjar and colleagues at the Institut d'Astrophysique de Paris decided to test the idea...

Granted, NASA does have the firepower and crack soldiering skills necessary to invade and occupy Paris, but they haven't done it. (yet)

Re:Narrow-minded folks

[MichaelSmith]

People are chucking around the idea of life on Titan, with Hydrogen taking the place of Oxygen. The thing you have to look for is an environment out of balance. Plant life on Earth turns sunlight and carbon dioxide into oxygen. Our free oxygen gives the game away and would be obvious to a good telescope many light years away. I think we would look first for free oxygen, but other combinations would raise alarm bells too.

Re:Narrow-minded folks

[cheesecake23]

wHo says that life needs oxygen? Even on our planet are living beings who do not need oxygen at all. Black smoker bacterias for example. Life develops according to outer circumstances. Darwin. Read it. it's just plain stupid to believe extra-terrestial life can only develop on Earth 2.

Thank God we have enlightened ACs teaching scientists how to do things! I'm sure they never considered the points you raised.

To address your point: they do NOT assume that life needs oxygen. However, the presence of significant amounts of oxygen in a planetary atmosphere is a strong indicator of life. This is because the gas is so reactive that it gets removed from the atmosphere very quickly. The only reason we have oxygen in our air is because it is continuously put there by photosynthesis.

Re:Narrow-minded folks

[chichilalescu]

they're not saying life can only develop this way. but if they find an earth-like planet, there's a pretty good chance it might have life. by the way, they're looking for habitable planets, not life.
the science of a class of systems "X" is always hard when you have just one example; there's no need to call them stupid.

You're very shortsighted

[dreamchaser]

They are testing techniques for detecting elements that may signal the existence of life as we know it. You have to learn to walk before you learn to run.

If everyone had your attitude we'd still be living in caves and worshiping the spirits all around us.

Re:You're very shortsighted

[snowgirl]

You have to learn to walk before you learn to run.

Right, but learning to walk is not the first steps towards crossing an ocean.

This test is trivial at best, because the data present themselves so readily. We can't even isolate extrasolar planets from their sun. Could we even detect this stuff from a more reasonable distance away. If this detects elements in the atmosphere, then we can use it on Venus, too, right? Which would be a lot more meaningful since it is relatively faint from the Earth surface, and LEO.

Not like much of this really means jack anyways, we already knew that elements absorb light in specific frequencies.

So, now to apply this to an extrasolar planet, we have to have the planet reflect the light of its sun back at the Earth, which means that their sun is already between them and us (counting "between" as being able to project the vector from here to their sun upon the vector from here to the extrasolar planet, and result in a vector of lesser magnitude than the vector from here to the extrasolar planet). And we're supposed to be able to isolate any of the light from that planet apart from its sun?

Most of the planets we can't even detect directly yet anyways.

So, yay! Someone tests a theory that will be completely non-applicable for at least decades. It's like having internal combustion engine before the wheel... mostly useless. (Yeah, I know the ICE uses wheel-type devices in it, leave me alone, it's supposed to be a lame analogy.)

Re:Only works on eclipsed light.

[pigeon768]

So... the light went through the Earth's atmosphere, into a reflector on the moon, which reflected it back... to the Earth's surface? Like... THROUGH the atmosphere that they were trying to detect anyways?

Yes. Part of calibrating a spectroscope involves adjusting for the fact that every result you'll ever get ever will have passed through Earth's atmosphere, and will demonstrate roughly the same absorption lines as a result. This is mitigated partially by the fact that spectroscopic analysis is usually performed somewhere at an observatory on the top of a mountain in some dry region with relatively stable weather, but considerations must still be made. Otherwise, every single star in the sky demonstrates molecular nitrogen and oxygen absorption lines - which would be surprising, to say the least.

This is usefulish science - one day, we may be in a situation where an Earth-like mass planet with an Earth-like orbit around a Sun-like star will occult. We have more information about what we need to do then.

Re:Only works on eclipsed light.

[Jarik C-Bol]

yes of course, lets worry deeply about detecting (from light years upon light years away) a form of life that has only be theorized to be possible, and if exists is most likely in an environment that is totally incompatible with ours, thus making any contact with such life forms extremely difficult at best..

or you know, we could figure out how to detect life forms similar to our own, then try and branch out from that knowledge base once we accomplish that.