• A scientist from NASA explained why comets are more dangerous than asteroids
  • Spotting a comet that's on a collision course with Earth is challenging
  • A comet impact would be worse than the asteroid strike that killed off the dinosaurs

A scientist from NASA explained the factors that make comets serious threats to Earth. According to the scientist, an impact event caused by a comet would be much more catastrophic than the asteroid strike that led to the extinction of the dinosaurs millions of years ago.

Steve Chesley is one of NASA’s top asteroid and comet experts. He is currently working at the agency’s Jet Propulsion Laboratory to keep track of comets. Recently, he appeared as a guest for the latest episode of NASA’s “On a Mission” podcast to discuss the dangerous nature of these space rocks.

According to Chesley, compared to asteroids, comets follow a much more elongated orbit since they usually inhabit the outer edges of the Solar System. Most of these icy space rocks come from the Oort cloud, a region near the border of the Solar System that’s filled with massive pieces of frozen debris.

Due to their natural orbit, comets are known to move much faster than asteroids. This means that if they hit Earth, comets will do so at a much faster velocity than their rocky counterparts.

In addition to their speed, comets are known to be very massive. Many of them are known to be as big as mountains while others have diameters that are as long as towns and even cities.

“Because their orbits are eccentric, elongated, they are moving much faster than asteroids are when they come into the area around the Earth, and so comets pack a bigger punch,” Chesley said during the podcast.

“Adding to that is the ones that are coming from the far, far reaches of our solar system, these appear not to be small. And so not only are they going faster, but they're probably larger,” he continued.

Since comets are known to come from the outer regions of the Solar System, Chelsey noted that detecting one that’s on a collision course with Earth can be a bit tricky. Usually, current tracking systems can detect an incoming comet once it has passed Saturn or Jupiter. By this time, Earth only has about a year or two to do something about the approaching comet.

Due to their size and speed, Chesley noted that an impact event caused by a comet would be more devastating than the one that destroyed Earth and its environmental conditions 65 million years ago.

“That's a kind of hazard that’s truly catastrophic for the globe, for the planet,” he stated. “You think dinosaur killer. That was 65 million years ago. This is even worse.”

Comet 67P
This view shows Comet 67P/Churyumov-Gerasimenko as seen by the OSIRIS wide-angle camera on ESA's Rosetta spacecraft on September 29, 2016, when Rosetta was at an altitude of 14 miles (23 kilometers). ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA