(ORDO NEWS) — The new analysis showed that in the last million years alone, the Earth has experienced at least four impacts of celestial bodies with a diameter of more than a kilometer.
If these conclusions can be confirmed, it will turn out that we greatly underestimated the level of the asteroid threat to our planet and civilization.
The fall of a large asteroid can be extremely dangerous for life on Earth, and even more so for our civilization. In the past, they have repeatedly caused global and local catastrophes.
However, it is not easy to estimate the frequency of such impacts: the geological activity of the planet and erosion quickly erase all traces.
Therefore, scientists usually focus on evidence that is not on the surface of the Earth, but on the Moon.
It is close and should receive about the same number of impacts, and their craters persist for many millions of years.
Another source of risk information is provided by the number and size of near-Earth celestial bodies potentially capable of colliding with our planet.
Similar calculations show that asteroids and comets larger than a kilometer fall to Earth on average every 600-700 thousand years.
However, new work by scientists at NASA‘s Goddard Space Flight Center yields far more frightening numbers. According to them, in the last million years alone, the Earth has experienced at least four impacts.
A report on this was made at the recent 54th Scientific Conference on the Moon and Planets (LPSC).
Using satellite imagery and lidar scan data taken from various angles, James Garvin and his colleagues have compiled 3D maps of four large craters with a resolution of up to four meters.
They were then analyzed using an algorithm designed to search for circular structures on the surface of Mars.
The system found traces of a rounded shaft, located much further than previously found and unnoticed in past work.
All four studied craters turned out to be much larger than previous estimates.
For example, the diameter of the Pantasma crater (Nicaragua, about 800 thousand years old), according to new data, is not 14.8 kilometers, but more than 35; the crater Zhamanshin (Kazakhstan, 870 thousand years old) “grew” from 13 to 30.4 kilometers.
These indicators indicate that the craters were left by much more massive celestial bodies than previously thought.
It is possible that the craters considered by Garvin and his co-authors appeared as a result of the fall of objects larger than a kilometer in diameter.
At the same time, the age of the oldest of them is a maximum of 1.05 million years. It turns out that during this period the Earth experienced at least four such impacts.
And if we take into account the fact that most of the planet’s surface is covered with oceans, then their number could reach 10-11.
The new estimates are radically different from the generally accepted ones. Therefore, many experts said that more serious and weighty arguments are required for proof.
It is possible that the weak ring structures detected by the algorithm are debris and soil thrown off by the impact and not related to the craters themselves.
They were probably formed as a result of the erosion of ancient craters. New research will help to clarify all this, primarily field studies, with a study of the composition of local rocks.
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