I watched an interesting TED talk by Freeman Dyson about where life might be in our solar system outside of Earth.
He had an interesting idea that life might have started on Europa, because it probably has an ocean under a few miles of ice. He said it's possible (though none of this is probable) that life there evolved to be able to live on the surface. The sun's 25 times weaker there, so any plants would need lenses or reflectors to collect the faint sunlight to stay warm and get energy. He then suggested that these lenses and reflectors would make them relatively easy to see, so we should look for them.
You can see this talk here:
Seems to me though that another possibility is that the plants would reflect as little light as possible back into space. Wouldn't they be black?
It also got me thinking that we should see this reflector/lens strategy being used by life in the more hostile climates on Earth. As far as I know it has not. Is this because it's biologically impractical, or because it just has not happened yet? Will we be able to genetically engineering life to be able to do this? Dyson thinks so.