Hundreds of massive comets discovered in the last two decades in the outer solar system have led astronomers to believe they may pose greater danger to life than asteroids.
The findings came in a published research conducted by a team of astronomers from Armagh Observatory and the University of Buckingham.
These comets, called Centaurs, traverse on orbits that are unstable and often cross paths with Jupiter, Saturn, Uranus, and Neptune. These comets can be deflected towards Earth because of the planetary gravitational fields.
According to RT, the research team said, “Whilst in near-Earth space they are expected to disintegrate into dust and larger fragments, flooding the inner solar system with cometary debris and making impacts on our planet inevitable.” They further noted that the “assessment of the extraterrestrial impact risk based solely on near-Earth asteroid counts, underestimates its nature and magnitude.”
A single comet, which is typically 50-100 kilometers wide and is normally made up of ice and dust, is expected to have more mass than the population of all Earth crossing asteroids until now. “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,” co-author Bill Napier of said. “Our work suggests we need to look beyond our immediate neighbourhood 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.”
As reported by Yahoo News, it is believed that a comet strike may have brought water and organic molecules to earth, thereby starting life. The extinction of dinosaurs 65 million years ago is also largely attributed to a comet encounter.
While the danger is not “known to be imminent,” the team noted that comet strikes are unpredictable. The researchers wrote that “centaur arrival carries the risk of injecting, into the atmosphere… a mass of dust and smoke comparable to that assumed in nuclear winter studies. Thus, in terms of magnitude, its ranking among natural existential risks appears to be high.”