Just How Much Cosmic Dust falls to Earth Each Year?

 

On almost any dark, clear night away from city light pollution, even the casual sky observer may see one or several “shooting stars.” Tiny bits of rock, typically less than an inch across, create these brief streaks of light. The rocky bits move so quickly through the air that they create a huge amount of friction, heating the air to incandescence which creates the streak of light.

Eventually, the cosmic rock is broken into tiny dust particles which float serenely down to the surface of our planet. This cosmic dust comes primarily from two sources. A research team studying this phenomenon, led by Julien Rojas, a doctoral student at the University of Paris–Saclay, found that more than 60% of the dust originates from the family of comets that Jupiter’s huge gravitational pull herds into orbits of less than 20 years and which can pass close to Earth’s orbit. Another 20% of the dust likely came from the main asteroid belt.

                          Meteor entering Earth atmosphere as seen from the ISS. Credit NASA

Astronomers want to know just how much of this cosmic dust Earth accumulates each year. But the problem is that with dust constantly blowing around all over our planet, it becomes virtually impossible to separate space dust from Earthly dust.

There is one place where terrestrial dust does not contaminate extraterrestrial dust, Antarctica. The study team collected ice cores from that continent in an attempt to quantify the amount of cosmic dust landing on our planet each year. And, because the snow and ice cover there can be melted, it is easy to separate the tiny dust particles from the otherwise dustless environment. Jean Duprat, a cosmo-chemist and co-author of the study, said “The South Pole is by far the best location because you are surrounded by oceans, you are completely isolated from mainlands.”

 Extrapolating the three-year study of Antarctic cosmic dust measurements to the entire planet, the team found that between 4,000 and 6,700 metric tons of space dust falls to Earth each year. Rojas explained that the study’s range is simply a matter of statistics due to the inherent difficulty of extrapolating the worldwide accumulation from a series of limited, local measurements. “Depending on the volume of snow,” Rojas said, “you would expect a certain uncertainty by just counting the particles.”

Between 4,000 and 6,700 tons a year! And you think you have a problem keeping weight off.

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

 This is reprinted by permission from the Oklahoman and www.newsok.com.