Rocky planets resembling Venus, Mars and the Earth may be as common in our galaxy as any Star Trek fan could hope, according to University of Arizona astronomer Michael Meyer, who announced a new finding from NASA’s Spitzer space telescope at a AAAS press conference today on planetary discovery.

The new Spitzer data, from a survey of 309 very young, sun-like stars in our immediate galactic neighborhood, suggest that rocky planets form around 20% to 60% of them, said Meyer—a very large fraction. True, he said, the evidence is indirect. Instead of seeing actual planets, Spitzer detected the infrared warmth of fine dust grains that orbit the stars at Earth-like distances. But astronomers believe that such dust grains are the byproduct of constant collisions among larger, asteroid-sized chunks—the ongoing process of cosmic bump-‘em cars by which the chunks coalesce into full-scale planets. And soon, Meyer added, we should have even better evidence from NASA’s Kepler mission. Due for launch in February 2009, Kepler will be the first observatory able to detect Earth-sized (and smaller) extrasolar planets directly.

Meanwhile, as NASA science chief Alan Stern described in the same press conference, NASA is already planning for an even more capable planet-finding mission to be launched in about 2015. This mission is mired in controversy at the moment, because the US Congress recently gave NASA a mandate to pursue one specific technical approach, known as the Space Interferometry Mission (SIM) (See Nature, 15 January 2008) But Stern insisted that that issue is far from settled. The final design of the new mission should and will be made in close collaboration with the scientific community, he said—probably in the 2010 time frame, after the astronomers have had a chance to analyze the early results from Kepler.

Rocky planets resembling Venus, Mars and the Earth may be as common in our galaxy as any Star Trek fan could hope, according to University of Arizona astronomer Michael Meyer, who announced a new finding from NASA’s Spitzer space telescope at a AAAS press conference today on planetary discovery.

The new Spitzer data, from a survey of 309 very young, sun-like stars in our immediate galactic neighborhood, suggest that rocky planets form around 20% to 60% of them, said Meyer—a very large fraction. True, he said, the evidence is indirect. Instead of seeing actual planets, Spitzer detected the infrared warmth of fine dust grains that orbit the stars at Earth-like distances. But astronomers believe that such dust grains are the byproduct of constant collisions among larger, asteroid-sized chunks—the ongoing process of cosmic bump-‘em cars by which the chunks coalesce into full-scale planets. And soon, Meyer added, we should have even better evidence from NASA’s Kepler mission. Due for launch in February 2009, Kepler will be the first observatory able to detect Earth-sized (and smaller) extrasolar planets directly.

Meanwhile, as NASA science chief Alan Stern described in the same press conference, NASA is already planning for an even more capable planet-finding mission to be launched in about 2015. This mission is mired in controversy at the moment, because the US Congress recently gave NASA a mandate to pursue one specific technical approach, known as the Space Interferometry Mission (SIM) (See Nature, 15 January 2008) But Stern insisted that that issue is far from settled. The final design of the new mission should and will be made in close collaboration with the scientific community, he said—probably in the 2010 time frame, after the astronomers have had a chance to analyze the early results from Kepler.