A team of researchers from the University of Buckingham and Armagh Observatory claim that the hundreds of massive comets that have been observed in our solar system in the last 20 years pose a greater threat to life on Earth than asteroids. The comets, called centaurs, possess unstable orbits and cross the paths of outer planets including Jupiter, Saturn and Uranus. The danger lies in the fact that these planetary gravitational fields have the potential to deflect these comets toward Earth.
With their massive size, typically between 50 to 100 kilometers across or larger, a single centaur contains more mass than every Earth-crossing asteroid found to this day. According to the researchers, centaurs could wipe out the population of the Earth in a single swoop, although the rate at which they are deflected onto a path that crosses the Earth's orbit is approximately once every 40,000 to 100,000 years.
"In the last three decades, we have invested a lot of effort in tracking and analyzing the risk of a collision between the Earth and an asteroid," Bill Napier, who participated in the research, said in a press release. "Our work suggests we need to look beyond our immediate neighborhood too and look out beyond the orbit of Jupiter to find centaurs. If we are right, then these distant comets could be a serious hazard, and it's time to understand them better."
Analysis of environmental disasters in ancient civilizations, in combination with what we now know about interplanetary matter in near-Earth space, indicates a centaur collision approximately 30,000 years ago, which would have thrown debris across the inner planetary system.
Supporting the researchers findings is the ages of sub-millimeter craters that were identified in lunar rocks gathered from the Apollo program, almost all of which were younger than 30,000 years, which points to an increase in the amount of dust in the inner Solar system since that time period.
The findings were published in the Dec. issue of Astronomy and Geophysics.
