Friday, June 06, 2003
Is there another Earth out there?
Is there another Earth out there? Scientists say new space probes might find another Earthlike planet -- one that could support life -- in the next decade
Within 10 years, an Earth-size planet -- the size that scientists consider the most likely to contain oceans and therefore life -- is expected to turn up in searches by two scheduled NASA probes. Astronomers hope to be able to detect life, or rule it out, in such places within 20 years.
''We know for certain there are a hell of a lot of planets out there,'' easily 10 billion in our galaxy alone, says astronomer Steve Vogt of the UCO/Lick Observatory at the University of California-Santa Cruz. Current data suggest at least 12% of nearby stars have Jupiter-size planets, he says, and 3% might have Earth-size ones.
Finding solar systems like our own, where a Jupiter-size planet on a stately circular orbit screens smaller inner planets from space junk, is the focus of his team's efforts in the next five years.
''I expect we'll find many planets like Earth,'' says Louis Friedman, head of the Planetary Society, a space activism group based in Pasadena, Calif. Most likely, they will come as a series of scientific ''hints,'' he says, first a planet of the right size but the wrong orbit, then the right orbit but seemingly no atmosphere, and then one giving signs of a water-rich atmosphere like Earth's.
A number of planned space missions are aimed squarely at detecting Earth-size planets:
* Kepler. Named after Johannes Kepler, the 16th-century astronomer who divined the laws of orbital motion, this NASA mission in 2006 is expected to find about 30 Earth-size planets in Earthlike orbits. It will detect ''transits,'' the slight dimming of a star's light that occurs when a planet passes in front of it.
* Space Interferometry Mission (SIM). A NASA mission in 2009 expected to detect one or two Earthlike planets from a survey of 200 nearby stars. It will measure side-to-side gravitational wobbles that planets produce on their stars via gravitational pull.
* Terrestrial Planet Finder (TPF). Scientists are still deciding what instruments to install in this NASA search for life in 2014 on an Earthlike planet. ''The goal is a picture of an Earthlike planet to run in every newspaper, above the fold,'' says Traub, a member of one TPF development team.
* Darwin. The European Space Agency plans to launch this flotilla of small telescopes in 2015. By combining the light from telescopes to make a powerful ''interferometer'' device, the mission should be capable of detecting chemical composition of atmospheres on Earthlike planets discovered by SIM or other missions.
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