Moon crater Was it a lot about 800 million years ago?

Moon crater Was it a lot about 800 million years ago? Asteroid debris poured down July 22, 7:05

Approximately 800 million years ago, a group such as Osaka University announced a research result that a large amount of asteroid debris fell on the moon and many craters appeared at the same time.
It is attracting attention as a new perspective on how the moon has become as it is.

This was announced in the British science magazine Nature Communications by a group of Professor Kentaro Terada of the Graduate School of Science, Osaka University.


The group analyzed the condition of the ground surface around a particularly large crater with a diameter of 20 km or more and calculated the age of the crater from the photo of the moon taken by the Japanese lunar exploration satellite "KAGUYA".

As a result, it was found that 17 out of 59 craters seemed to have been formed at the same time about 800 million years ago.

It is believed that many craters formed at the same time because asteroid debris poured all at once like a shower.

The established theory that the crater of the moon was formed by asteroids and their fragments colliding with each other with a certain frequency, and the results of this research are noteworthy as a new perspective on the process of the moon's appearance. It has been.

Furthermore, by inferring the asteroid that is the source of the debris from the positional relationship, it was also found that it could be seen to be in the same group as the asteroid "Ryugu" explored by the asteroid explorer "Hayabusa 2".

Professor Terada pointed out that a large amount of debris from the asteroid also fell on the earth, and at this time, phosphorus, which is greatly related to the diversification of life, may have been brought to the earth, "In addition to the history of the moon, We can make new proposals for changes in the global environment 800 million years ago."

Asteroid fragments that have fallen down Are they the same as "Ryugu"?

Professor Terada's group also conducted an analysis to search for the asteroid that is the source of the debris that poured into the moon about 800 million years ago. It means that I also understood that.

When asteroids fall apart in outer space, their orbits are gradually disturbed by the influence of the gravity of other celestial bodies, and they are scattered.

By back-calculating from the size and positional relationship of the scattered lumps of debris, we can derive when the original asteroid broke.

Based on various research data in the past, the research group narrowed down to three asteroids that were broken down about 800 million years ago.

He further narrowed down the conditions based on the size of the craters remaining on the moon, and concluded that the asteroid that is the source of a series of asteroid fragments is an asteroid called "Eulalia".

One of the broken pieces of "Eulalia" is considered to be "Ryugu" explored by "Hayabusa 2", so the sand of "Ryugu" that seems to have entered the capsule that will reach the earth in December, etc. It is expected that the relationship with the moon can be further elucidated by analyzing the.

One of the research groups, Associate Professor Tomokatsu Morota of the Graduate School of Science, The University of Tokyo, said, "I am deeply impressed by the fact that both Kaguya and Hayabusa2 were Japanese spacecraft, and I was able to connect the two." I am talking.

To clarify the process of life evolution of the earth

Based on the results of this research, Professor Terada's group is proposing a new way of thinking about the evolutionary process of life on Earth.

The key to this is "phosphorus," which is believed to have brought to Earth a large amount of debris from the asteroid that has poured down.

Phosphorus is a substance that is said to have played an important role in diversifying life on Earth.

According to the group, other studies to date have shown that the amount of phosphorus on the earth surged 800 million years ago.

The reason for the rapid increase in phosphorus is unclear, but about 540 million years ago, Earth entered the Cambrian era, where life was diversified.

The group said the asteroid fragments that landed on the Earth, revealed in this study, were believed to contain ten times as much phosphorus as the Earth's oceans today.

Professor Terada said, "So far, the reason why phosphorus has increased has been pointed out to be the effect of volcanic activity and crustal movement, but it may be explained that it has fallen from outside the earth. I want to expect it."