Filtering starlight to probe new worlds

[Rick]

European star gazers have been filtering stellar light through the atmospheres of the three inner planets to find out what they are made of.

The technique, known as stellar occultation, involves watching a star as it drops behind a planet, and measuring its light before it drops below the horizon. It can give scientists a profile of the molecules present in the atmosphere, by allowing a comparison between the unfiltered and filtered starlight.

More: http://www.theregister.co.uk/2007/11/11/starlight_planet/