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:Only works on eclipsed light.

[snowgirl]

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.

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?

If it simply needed to pass through the atmosphere, I could do that in my back yard, why reflect it off the moon? Why involve anything other than a sensor on the Earth's surface? If "zomg, we have to be all mythbusters sciencey on this", then why not just a LEO satellite... each one, I'm sure receives more than enough light passing through the earth's atmosphere... I think it's like 16 sunsets a day, or something like that.

Seriously... cool science, cool results, but essentially just mast stroking...