Every year our planet encounters dust from comets and asteroids. These interplanetary dust particles pass through our atmosphere and make beautiful shooting stars. Others reach the ground in the form of micrometeorites. But how many?
Although large asteroids tend to occupy our imagination when it comes to thinking about extraterrestrial impacts, according to a new calculation by researchers at the Center National de la Recherche Scientifique (CNRS) and the University of Paris-Saclay, it is micrometeorites, more than 5,200 tons of interplanetary dust from comets and asteroids, which reaches the Earth’s soil every year (assuming that the ‘rain’ is evenly distributed around the world). They are so small that we don’t even notice them.
For nearly 20 years, scientists have been collecting and analyzing micrometeorites. They have concluded that of the few micrometeorites that survive atmospheric entry they can fall anywhere on Earth but it is almost impossible to distinguish them from dust unless you are in Antarctica (they measure between 30 and 200 micrometers).
For comparison, the annual flow of larger objects, which typically ranges from the size of a pebble to a fist, is less than 10 tons per year.
To collect and analyze these micrometeorites, six expeditions led by CNRS researcher Jean Duprat have taken place in the last two decades near the Franco-Italian Concordia station (Dome C) , which is located 1,100 kilometers off the coast of Adelie Land. , in the heart of Antarctica. The C-dome is an ideal collection location due to the low rate of snow accumulation and the near absence of ground dust.
What is the use of collecting micrometeorites?
Despite its small size, cosmic dust contains valuable information about our solar system. Its materials can also preserve details of the processes that take place in asteroids and comets.
“For example, certain minerals require liquid water to form, so if we find those minerals in a meteor or micrometeorite, it means that the liquid water must have been present at some point on the comet or asteroid from which they originated,” says Penelope Wozniakiewicz , a planetary scientist at the Museum of Natural History on her personal blog.
The findings suggest that 80% of micrometeorites come from comets, mostly comets from the Jupiter family. The remaining 20% of these tiny meteorites emanate from asteroids. Results above 100 microns match theoretical predictions about the amount of extraterrestrial dust we should be seeing. But below 100 microns, we see far fewer micrometeorites than we should, in theory, see.
“ This suggests several possibilities: the existence of very fragile particles that would not be collected with the collection protocol in the snow of Dome C; elimination of the fragmentation of a significant number of small particles before entering the atmosphere; or that the actual amount of small interplanetary particles at 1 AU may be less than expected ”, conclude the authors in their study published in the journal Earth and Planetary Science Letters.
In the future, astrophysicists will be able to use this information to model the formation of the early Earth, which was heavily influenced by the number of available interplanetary dust particles.
Referencia: J. Rojas, J. Duprat, C. Engrand, E. Dartois, L. Delauche, M. Godard, M. Gounelle, J.D. Carrillo-Sánchez, P. Pokorný, J.M.C. Plane, The micrometeorite flux at Dome C (Antarctica), monitoring the accretion of extraterrestrial dust on Earth, Earth and Planetary Science Letters, Volume 560, 2021, 116794, ISSN 0012-821X, DOI: https://doi.org/10.1016/j.epsl.2021.116794.
