A team of U.K. scientists have given a new estimate for the amount of meteorites falling to Earth each year in a paper published in Geology yesterday. The research team was formed from a partnership between the University of Manchester, Cambridge University, Imperial College London, and British Antarctic Survey, and was led by Dr. Geoff Evatt, a mathematician at the University of Manchester.
The researchers calculated that more than 16,000 kg of meteorite material greater than 50 g in mass falls to the planet each year. This estimate does not take into account smaller fragments or the dust that is continuously settling over the Earth. As such, it gives a good indication of the amount of rock debris that is falling from space, something that was not previously known.
"The vast majority of objects to hit the Earth are really small. We're talking about objects for which, when they strike the ground, the fragments sum together to over 50 g. So, typically, 50 g to 10 kg in total. Objects bigger than this are very, very infrequent," Dr. Evatt explained to the BBC.
Currently, Antarctica is where the most meteorites have been recovered, simply because they stand out more against the white backdrop, making it the perfect location for such studies. Dr. Evatt and the team chose an area known as the Outer Recovery Ice Fields, near the Shackleton mountain range in East Antarctica, where they worked out the total number of fallen objects. They found just under 120 meteorites in the sample area during two searches conducted between 2019 and 2020.
From this initial data, the team was able to calculate the global estimate by creating a model, accounting for variations between the planet's latitudes, and expanding the Antarctic results to a global scale. This model revealed new information that is able be used for the future risk assessment of larger impacts.
For example, the data showed that the number of impacts at the Earth's poles is just 60 percent of what could be expected at the equator. This puts the equator at a 12 percent higher risk than was previously estimated, and the poles at a 27 percent lower risk. With this in mind, it appears that long-term contingency plans for meteoroid strikes are most important at higher latitudes and, knowing this, appropriate measures can now be put in place.
The team's findings have been applauded by their fellow experts in the field.
"I think this is an amazing study, and this estimate sounds like it is in the right sort of ballpark. We think a total of about 40,000 tonnes (so 40,000,000 kg) of extra-terrestrial material falls to Earth each year, but the vast majority of this is in the form of tiny dust grains," Professor Sara Russell, head of the planetary materials group at the Natural History Museum, told BBC.
She went on to explain why estimates such as the one made by Dr. Evatt and his team have been so difficult in the past. She stated that, since most meteorite falls are not observed, and many fall in the ocean where they cannot be retrieved, it is very challenging to produce accurate numbers. As such, these findings are set to open new possibilities in meteorite fall research.