Occasionally, asteroids and comets may stray close enough to a planetary body to be captured by its gravitational field, but won't get so close as to collide with it. In these rare cases, comets or asteroids may be captured in orbit for a short period of time.
As noted by the arXiv blog, this natural orbital insertion has been observed to occur around Jupiter, most notably when comet Oterma went into a two year orbit around the gas giant in 1936. The comet later drifted back into space after its celestial dance.
Are there any such objects that promise to place themselves into Earth orbit any time soon? After analyzing the orbits of 6,000 known Near-Earth objects (NEOs), Baoyin's team turned up none. But are there any NEOs that come close to the Earth, of low enough velocity, that could be captured by us?
"When such an NEO approaches Earth, it is possible to change its orbit energy to close up the zero velocity surface of the three-body system at point L1 and make the NEO become a small satellite of the Earth," says Baoyin.
A 10 meter-wide asteroid called 2008EA9 is one of those candidates that makes its closest approach to Earth in 2049. To enter terrestrial orbit, rather than fly by, 2008EA9 just needs to be sped up by 410 meters per second for it to attain an orbital distance twice that of the moon.
Could this be the future of asteroid capture techniques? Will there be orbital asteroid mining drive-thrus?
Strapping rockets to a few lazy NEOs shuffling close to Earth is one thing, but to convince the world that plonking millions of tons of (otherwise harmless) space rock into orbit is a good idea, is quite another.
Regardless, that's one Health and Safety Committee I'd love to sit in on.
Source: arXiv blog
Image: An asteroid drifts past Earth (Getty)