Missing
asteroids in our solar system may be the handiwork of rampaging giant planets
as they migrated to their current positions, according to a new computer
simulation.
Scientists
have known that planets such
as Jupiter, Saturn, Uranus and Neptune migrated during the first several
million years of early existence. The new simulation showed that the giant planets
would have disturbed many asteroids as they fled the scene, leaving behind
"footprints" that match the real-life patterns in the main asteroid
belt.
"It
really showed evidence that the footprints of planet migration are visible
today in asteroid distribution," said David Minton, a planetary sciences
researcher at the University of Arizona in Tucson.
Patterns
of planet migration
Previous
evidence has suggested that the giant planets once formed a more compact
huddle. But their gravitational interactions with the then-larger Kuiper Belt,
an icy region beyond Neptune filled with comet-like
bodies, ended up fueling a migration.
"Each
time the planets tossed these Kuiper Belt objects around, they would move a
little," Minton told SPACE.com.
Jupiter
ended up moving slightly closer to the sun, while the other giant planets moved
farther apart from both the sun and each other. Minton and Renu Malhotra,
another planetary scientist at the University of Arizona, wanted to examine possible
aftereffects of that unstable period.
Gaps
as evidence
They
first looked at the current configuration of the main
asteroid belt between Mars and Jupiter, which has remained largely stable
for 4 billion years. Astronomers had discovered a series of gaps in the main
belt known as Kirkwood gaps back in the 1860s. These unstable regions are
relatively empty of asteroids because of Jupiter's and Saturn's current
gravitational influence.
The
researchers started their simulation with a uniform distribution of main belt
asteroids larger than 30 miles (50 km) in diameter, but ended up with far more
than what actually remains in real life. The simulated asteroid belt matched
the real asteroid belt quite well on the sunward-facing sides of the Kirkwood
gaps, but the real asteroid belt is largely devoid of asteroids on the
Jupiter-facing sides.
That
puzzle came together only when Minton and Malhotra ran other simulations which
included the giant planet migration. The simulated asteroid patterns then
matched up "surprisingly well" with the current main belt
configuration, Minton said.
Collateral
damage
Giant
planets may have scarred our solar system in other ways. The inner system
planets suffered a period
of heavy bombardment around 3.9 billion years ago, which some scientists
argue may have represented a spike in asteroid impacts rather than just the
normal planetary formation chaos.
The
new simulation may hint at the bombardment as being a collateral effect of the
violent planet exodus, when main belt asteroids went zipping off like stray
bullets.
"We
can't say from this study when that migration happened, but it's a good
plausible mechanism," Minton noted. "Once the asteroids get kicked
out of the asteroid belt, they have to go somewhere. Earth, the moon and Mars
are all great targets for these asteroids."
However,
full closure on this case will have to wait for more evidence to turn up.
advertisement
