A team of scientists has determined that twice as many asteroids have hit the Earth for 290 million years as during the previous 700 million years. But, rest assured, your security is not threatened.
These celestial objects rarely fall on Earth, about once every few million years.
NASA is not planning any event in the near future. The biggest threat to humanity is a 1.3 km wide asteroid, which has only 0.1% chance to hit us in 861 years.
“It’s a game of probabilities,” says lead author of the study in the journal Science , Sara Mazrouei. Events are still rare and distant, she adds. I’m not too worried. ”
Together with her American and British colleagues, the Planetary Science Professor at the University of Toronto has compiled and dated a list of impact craters on Earth and the Moon.
Only impacts wider than 20 km were retained. To create such a big hole, you need an asteroid at least 800 meters wide.
The team identified 29 craters that date back less than 290 million years, and only nine dated between 290 and 700 million years ago.
But we can see relatively few large craters on Earth because the planet is made up of more than 70% of oceans, warns Rebecca Ghent, a Toronto colleague who participated in the study.
Extrapolating, they brought the total to about 260 space accidents on Earth over the last 290 million years, a rate 2.6 times higher than in the past.
Scientists have studied the Moon to validate their observations, since the Earth’s natural satellite is close enough to end up in the same asteroid bombardment.
Unlike the Earth, there is no environmental upheaval that can make a crater disappear. Lunar craters have a longer life span.
The results of this research do not reach consensus in scientific circles.
Jay Melosh, of Purdue University in the United States, believes the crater count is too small to reach a reasonable conclusion. Avi Loeb, of Harvard, was rather convinced by the demonstration of the study.
The American professor recalls that humanity may not have existed if an asteroid had not struck Earth at least 65 million years ago. “This more frequent impact rate is a threat to the next mass extinction event, which we should monitor and try to avoid with the help of technology,” he suggests.
This shows how human life is arbitrary and fragile, concludes the scientist.
- Asteroid: A celestial object whose orbit around the Sun is weakly elliptical.
- Meteor: the trace of visible light in the sky during the fall in the Earth’s atmosphere of a solid body.
- Meteorite: an asteroid fragment that reaches the Earth’s surface.
- Meteoroid: a very small object outside the Earth’s atmosphere from an asteroid or a cometary nucleus.
- Comet: a star of dirty ice which, when approaching the Sun, releases gas and dust to form a tail.
- Impact crater: the trace left by a large meteorite when it hits the Earth.