Alien planets without big, climate-stabilizing moons like the one that orbits Earth may still be capable of supporting life, a new study reports.
Previous modeling work had suggested that Earth's axial tilt, or obliquity, would vary wildly over long time spans without the moon's steadying gravitational influence, creating huge climate swings that would make it tough for life to get a foothold on our planet.
But that's not necessarily the case, said Jack Lissauer of NASA's Ames Research Center in Moffett Field, Calif. [The Moon: 10 Surprising Facts]
"If the Earth did not have a moon, its obliquity — and, therefore, its climate — would vary, indeed, substantially more than it does at present," Lissauer said during a presentation in December at the American Geophysical Union's annual fall meeting in San Francisco. "But it's nowhere near as bad as was predicted based on previous models."
An abnormally large moon
Most researchers think the moon formed from material blasted into space when a mysterious planet-size body slammed into Earth nearly 4.5 billion years ago.
The moon is 27 percent as wide as Earth and 1 percent as massive, making it a celestial oddball. No other non-dwarf planet in the solar system harbors a moon so large relative to itself, and such enormous satellites appear to be rare farther afield as well, Lissauer said.
"If giant moons were common around exoplanets, then Kepler would've found one by now," he said, referring to NASA's planet-hunting Kepler space telescope.