earth is one special planet.
it has liquid water, plate tectonics, and an atmosphere that shelters it from the worst of the sun's rays. but many scientists agree our planet's most special feature might just be us.
"it? s the only planet we know of that has life," said alan boss, a planet formation theorist at the carnegie institution of washington in washington, d.c.
though other bodies in our solar system, such as saturn's moon titan, seem like they could have once been hospitable to some form of life, and scientists still have hope of eventually digging up microbes beneath the surface of mars, earth is still the only world known to support life.
"so far, we haven't found it anywhere else," said alex wolszczan of pennsylvania state university, who co-discovered the first planets beyond our solar system. he agreed that life was earth's single most impressive characteristic.
none of this is a revelation, but understanding what's special about earth is crucial for finding other planets out there and predicting what they might be like.
the fact that earth hosts not just life, but intelligent life, makes it doubly unique. and the planet's intelligent life (humanity) has even developed rockets that enable travel beyond the planet, said gregory laughlin, astrophysicist and planet hunter at the university of california, santa cruz.
"during the last half century, the planet earth has fashioned together tiny pieces of the metal in its crust, and has flung these delicately constructed objects to all of the other planets in the solar system," laughlin said, adding that these achievements should be counted as an exemplary trait of our planet.
"from our anthropocentric viewpoint, we naturally separate ourselves from the planet that we live on, but if one adopts the point of view of an external observer, it is the 'planet' (taken as a whole) that has done these remarkable things," he told space.com.