Earth As an Extrasolar Planet 83
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."
Re:Proving What (Score:4, Informative)
It looks like they focused on only measuring certain atmospheric things, but this proves nothing as far as extrasolar planets go.
Free oxygen on any planet tells you that something is making oxygen. In our case it is the plants which we treat so badly: turning them into newspapers, etc. Oxygen is so reactive that its presence tells you something must be going on. Mars used to have free oxygen but it combined with iron in the soil, turning it red: Iron Oxide.
Re:Only works on eclipsed light. (Score:1, Informative)
You miss the point, most sensors we have for detecting extrasolar planets are still placed within the atmosphere. What they simulated was detecting an earth-like planet placed two moon-distances away from earth trough the earth atmosphere.
Except for the distance beeing way too short by at least a factor of 10^10 this is something that could be useable.
The Galileo probe already did this (Score:4, Informative)
Re:Proving What (Score:4, Informative)
The Slashdot summary was really, really bad. They didn't pretend to be observing the earth from the moon, they analyzed the spectra of light passing through the earth's atmosphere and reflected off of the moon. The idea is that this is similar to analyzing the light passing through a planet's atmosphere as it transits in front of a star. So it's not as crazy as it sounds.
RTFA (Score:4, Informative)
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?
You misunderstand the experiment. For this idea to work, the planet has to be between us and the star. Exactly between - as in, the planet is eclipsing its sun, from our point of view. They're not detecting light that's been reflected off a planet, they're detecting light that's been filtered through a planet's atmosphere.
This is something we've already done [wikipedia.org] with large gas giant planets. The 'new' thing is that we did it with a planet the size of earth, with its significantly thinner atmosphere.
Re:The Galileo probe already did this (Score:5, Informative)
For those without access to Nature, a Google Scholar search turns up a freely downloadable PDF of the full article.
PDF Link [uiowa.edu]
I remember reading about this in Sagan's "The Pale Blue Dot", and thought it was such an awesome idea. I'm looking forward to reading the original paper. :)
Re:Only works on eclipsed light. (Score:1, Informative)
We're finding a few planets like that with the kepler mission. I'm sure we'll have some spectroscopy results published this decade.
Re:Earth is heaven... (Score:1, Informative)
1- We don't know how rare if at all for a planet like earth is to have a large moon, based in our solar system that may be the norm and Venus being the rarity.
2- Again, not true, mercury has one, earth has one, Mars had one, same with the non rocky planets, Venus being the exception.
3- by the actual sample of extrasolar planets it looks as if the goldie locks zone it is a good orbit for planets to form and as yourself mention our own solar system has two in that orbit
4-by the latest data it also looks as if single sol type stars are more numerous than expected, also nothing prevent much more stable stars e.g. red dwarfs to have planets
5-how rare is that, can you produce evidence that they are not common? and calling the solar system calm is also an overstatement with craters and impact marks all over the place and impacts happening even now.
7- again by the latest data it looks as if rocky planets are the norm rather than the exception.
8-those elements are as common as mug, we are detecting amino acids even in gas clouds.
9-Just like a few millions of stars around the periphery of our galaxy.
10-It did already happened several times on earth, we know of several extinction events, life seem to be very hardy once it takes hold and perhaps the earth may not be the best place for life after all, there may be better places elsewhere.
Re:Why not point Cassini back at us? (Score:3, Informative)
extras