Large asteroid impacts on Earth would leave traces on the Moon

Over the past billion years, the Moon and Earth may have been hit simultaneously by clusters of small celestial bodies accompanying at least one major impact, such as the one that caused the Chicxulub astroblem. This is suggested by a recent study of lunar soil samples brought back to Earth by the Chinese Chang’e 5 mission.

Plate tectonics and erosion have erased many pages of our blue planet’s history. Some of these pages relate to the history of Solar systemSolar systemfor example in connection with the bombardment of small celestial bodies, possibly cometscomets or some asteroidsasteroids. However, a few giant astroblems are known on Earth, for example Manicouagan in Quebec, which is one of the oldest known impact craters and also the largest “visible” impact crater on Earth. With a diameter of about a hundred kilometers it is geologistsgeologists giving it an age of about 213 to 215 million years. Let’s remember right away that it happened about ten million years beforeExtinctionExtinction Triassic-Jurassic and therefore cannot be responsible for it.

Larger, but not very significant and also not visible from space, we know well about the astroblem at Chicxulub in Yucatán, astroblemastroblem as we know played a major role in the grand scheme of things Cretaceous-Tertiary biological crisisCretaceous-Tertiary biological crisis about 66 million years ago, a crisis characterized spectacularly by the disappearance of non-avian dinosaursnon-avian dinosaurs.

Our satellite, the MoonMoondo not have the same memory problems, are devoid of tectonic platestectonic platesa water circuit and a atmosphereatmosphere with some winwin. We could therefore hope to find ancient traces of the history of both the Earth-Moon pair and the history of the Solar System and even of GalaxyGalaxy in various forms i regolithregolith moon.

Overall, the theory of the formation of the solar system tells us that the impacts of small celestial bodies on Earth not only diminish in frequencyfrequency but also in the size of the influencing bodies. Thus, if the Earth was undoubtedly hit by one small planetsmall planet the size of Mars more than 4.4 billion years ago, the famous TheaThea At the origin of the Moon, such an event has not been able to occur for a few billion years, although we must be careful to protect ourselves from impacts that could release energiesenergies much higher than that of the Hiroshima bomb (the Earth is regularly hit every year by impacts that release a comparable energy).

A chaotic asteroid bombardment?

However, the discovery of chaos in celestial mechanics and the emergence of the phenomenon of planetary migration in the history of the solar system are described by simulations such as Nice modelNice model suggests that there are times when the bombardment may become a bit more intense. We can also think of the occurrence of collisions between large asteroids in the Main Belt between Mars and JupiterJupiterwhich leads to the emission of several small bodies that come by fragmentation from these large asteroids, and which will then charge towards the inner Solar System, acting a bit like a sudden rain for planets like the Earth and the Moon.

In fact, a team of researchers led by Alexander Nemchin, of Center for Space Science and Technology (SSTC) from Curtin University in the state of Western Australia, has just provided interesting elements in support of this scenario in a paper published in open access in The progress of science.

The researchers studied some of the lunar rock samples brought back from the Moon thanks to the Chinese Chang’e 5 mission in 2020. They came from the northwestern part of the Ocean StormsStormsin a predominantly flat area, located about 90 kilometers northeast of the Mons Rümker region.

These samples contained a type of volcanic glass beads, that is, droplets of rock melted by the energy released by an impact from a small celestial body of significant size, and also projected far away by the impact energy before cooling. On Earth, these would be microscopic examples of what are called tektites, from the German term Tektitecoined by the Austrian geologist Franz Eduard Suess from the Greek τηκτός / tēktós which means “melted”.

The methods of cosmochemistry make it possible to date these pearls and more ” waveswaves of production over the past two billion years, waves indicating peaks in meteorite bombardment of the Moon on the background of exponential decay.

Remarkably, some of these peaks appear to correlate with the age of large astroblems on Earth, such as Chicxulub.

Indeed, this is what Alexander Nemchin explains in a press release from Curtin University: We have combined a wide range of microscopic analytical techniques, modelsmodeling digital and geological surveys to determine how and when these microscopic glass beads from the Moon formed. We have discovered that some of the moon’s glass beads age ranges exactly coincide with the ages of some of Earth’s largest impact cratering events, including the Chicxulub impact crater responsible for the extinction of the dinosaurs. The study also revealed that large impact events on Earth such as Chicxulub CraterChicxulub Crater 66 million years ago could have been accompanied by a series of minor impacts. If correct, this suggests that age-frequency distributions of impacts on the Moon can provide valuable information about impacts on Earth or the inner Solar System. »

For as yet unknown reasons, there will therefore be periods when orbitorbit regular intervals of small bodies in the solar system are destabilized, causing them to head into orbits where they may collide with the Earth or the Moon. Similar increases are no doubt possible in the future, but when?

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