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

This just in

[gmuslera]

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.

Only works on eclipsed light.

[pigeon768]

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.

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.

The Galileo probe already did this

[De_Boswachter]

"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

Re:The Galileo probe already did this

[interactive_civilian]

For those without access to Nature, a Google Scholar search turns up a freely downloadable PDF of the full article.

PDF Link

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. :)

WTF?

[mcneely.mike]

I for one welcome our new Earth overl-...... wait a second.....HEY, that's me!