Slashdot Mirror
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."
NASA has finally proved that planet Earth is (still, at least) habitable! We knew that all that investment will bring us new knowledge some day.
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.
Table-ized A.I.
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.
http://michaelsmith.id.au
This technique only works on light that passes through the planet's atmosphere. In this case, during a lunar eclipse, they pointing a telescope at the part of the moon that was reflecting the light that had traveled through the Earth's atmosphere. They found that the moon had absorption lines resulting from interactions with Earth's atmosphere.
The technique would work if the Earth occulted the Sun from Cassini's viewpoint, but such occultations are rare.
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.
"A search for life on Earth from the Galileo spacecraft", Nature, 1993 C. Sagan et al., http://www.nature.com/nature/journal/v365/n6448/abs/365715a0.html
I for one welcome our new Earth overl-...... wait a second.....HEY, that's me!
soylentnews.org Go there to enjoy the people!
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.
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 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.