Researchers decode why pebbles pulverize after leaving comet

A study by a 45-member international research team, led by Dr Peter Jenniskens, a meteor astronomer at the SETI Institute, has unveiled new insights into the nature and cause of the destruction of comet dust in space, challenging long-held beliefs that high-speed collisions pulverized the comet ejecta.

Published online in the journal Icarus, the study concludes that heat is responsible for the demise of comet dust.

"Comets eject most debris as large sand-grain to pebble-sized particles, called meteoroids, that move in meteoroid streams and cause the visible meteors in our meteor showers. In contrast, the zodiacal cloud is mostly composed of particles the size of tobacco smoke that even radars have difficulty detecting as meteors," says Dr. Jenniskens who leads a NASA-sponsored global network called "CAMS" that monitors the night sky for meteors with low-light video security cameras. 

The researchers determined the ages of meteor showers based on their dispersion and then examined the rate at which they lose their larger meteoroids compared to smaller ones.

The team then examined how close those streams came to the Sun. Had collision been responsible, the pebbles would have been destroyed faster directly proportionally to their proximity to the Sun.

"Because there is more comet dust closer to the Sun, we had expected collisions there would pulverize the pebbles that much faster. Instead, we found that the pebbles survived better than expected," Jenniskens explained.

The researchers concluded that the destruction of pebble-sized particles is proportional to the peak temperatures they encounter along their orbit. The study suggests that thermal stresses, rather than collisions, are responsible for fracturing the large meteoroids near Earth, extending all the way to Mercury's orbit. Deep inside the orbit of Mercury, the particles disintegrate due to substantial material loss.

PRESS RELEASE: https://t.co/LBSkRVt1oL It was long thought that high-speed collisions pulverized comet ejecta, but now a 45-member team of researchers reports, in a paper published online in the journal Icarus this week, that heat is to blame. pic.twitter.com/pPB6zz3wLW

— The SETI Institute (@SETIInstitute) March 21, 2024