A hint: it has varying shades of a color known as "blue." A
NASA-sponsored team of scientists looking back at Earth with the Deep
Impact/EPOXI mission have developed a totally intuitive method to
pinpoint whether Earth-like alien worlds beyond our solar system have
oceans. The Daily Show could have fun with this.
Seen from dozens of light years away, an Earth-like exoplanet will
appear in telescopes as little more than a "pale blue dot," the term
coined by the late astronomer Carl Sagan to describe how Earth appeared
in a 1990 photograph taken by the Voyager spacecraft from near the edge
of the solar system.
But, using instruments aboard the Deep Impact spacecraft, a team of
astronomers and astrobiologists has devised a technique to tell whether
such a planet harbors liquid water, which in turn could tell whether it
might be able to support life.