The solar system is full of dust. Some comes from planets, some from asteroids and comets. As the Earth orbits, much dust inevitably falls on the Earth. This dust can produce meteor showers, and a small fraction falls to the ground as micrometeorites.
Micrometeorites are extraterrestrial dust with a diameter between 30 and 200 microns. How can we find this smallest dust? Let alone distinguish them from earthly material and summarize their content.
An international research group has been working on this topic for 20 years. Their recently released study estimates that 5.2 million kilograms of micrometeorites fall to Earth each year, and about 10,000 kilograms of larger meteorites.
Researchers from the French National Center for Scientific Research (CNRS), the University of Paris-Saclay (Université Paris-Saclay) and the National Museum of Natural History (National Museum of Natural History) collaborated to explore these dust trails from as far away as Antarctica.
Their analysis was carried out on Dome C, the heart of this southernmost continent on Earth. This area is more than 3,000 meters above sea level. The study says this area has very little fresh snow and very little dust from the ground, so it is an ideal location for analyzing extraterrestrial dust. The research team made a total of six trips to complete this analysis of how many micrometeorites fall to the ground each year.
The analysis showed that 80% of the micrometeorites come from comets, mainly from Jupiter-Family comets, and the remaining 20% from asteroids. Jupiter-family comets are comets with an orbital period of less than 20 years. Astronomers have given them this name because their orbits are mainly influenced by Jupiter.
The study also found that the content of micrometeorites larger than 100 microns is about what scientists expected, but micrometeorites smaller than that are much smaller than theoretical estimates. Scientists call the distance between the Earth and the Sun an astronomical unit (AU), and have made an estimate of how much extraterrestrial dust should be received at this distance. That said, the data measured in this study found that the amount of dust smaller than a hundred microns was much less than this prediction.
Why is there such a big difference? The researchers offer three explanations: there may be a problem with the current method of collecting such small particles in Ice Dome C, resulting in inaccurate data collection; it may be that such small particles are blocked outside the Earth’s atmosphere by some factor that scientists did not estimate; or it may be that the diameter of alien dust at this location, one astronomical unit from the Sun, is smaller than scientists expected. The researchers hope to find the cause by collecting alien dust in other ways in the future.
The study was published April 15 in Earth and Planetary Science Letters.
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