Revisiting the origin of the Apollo 14 rocks changes our understanding of its history

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[EN VIDÉO] Apollo program: where are the landing sites on the moon?
For each Apollo mission, NASA chose two landing sites. Thus, these are 14 sites that will be checked before sending astronauts there. This choice was a daunting task for NASA, which had to compromise between ease of access, mission safety, and scientific feedback. Our explanations.

One of the goals of the various Apollo missions was to bring back as many lunar soil samples as possible to study the history of our moon. In 1971 Location of the Apollo 14 mission thus was especially chosen for its geological interest. In view: the Fra Mauro geologic formation, a chaotic region located to the west of the crater of the same name, located in the vast Rains Basin (imbrium pool). This vast area, 1300 kilometers in diameter, identified in 1893 by Gilbert, is one of the main structures that mark the surface of the lunar landscape. It is interpreted as the largest impact basin on the near side of the Moon. IN to matter in size, the Pluyes Basin is followed by the Crisis Basin (crisis pool), older, and East Basin, younger. Both are also related to impacts that occurred during the period Late heavy bombardment. Thus, the goal of Apollo 14 was to land as close as possible to the intended center of impact.

Major impact allowing many other craters to be dated.

During the formation of the Raines Basin, a huge amount of debris would have been scattered across the surface of the Moon. This garbage has long been studied, in particular, thanks to observations on telescopebut also thanks to the stones brought various Apollo missions. Scientists soon discovered that different lunar samples taken on different missions showed a similar composition and age of 3.92 billion years. The idea that all these stones were scattered debris from the impact that formed the Rainy Basin, therefore, quickly took hold. This made it possible to date the formation of the basin itself, but not only. Since the exact dating of this impact and ejection also made it possible to establish the age of many other formations and craters all over the surface of the moon.

However, based on spectral analysis and new images of the lunar surface, a team of scientists from the University of Oslo casts doubt on this interpretation.

Analysis of the composition of the lunar soil from space

To do this, the researchers analyzed reflected light over the surface of the moon. The decomposition of this light into several wavelengths lets you know which minerals lunar rocks are formed, and from space. Thus, a spectral analysis of the Apollo 14 landing site shows that it consists of more than just emissions from the rain basin. In fact, the land would have been covered by two levels of rock, the most superficial of which would have been ejecta from another, much younger basin: the Eastern Basin.

Thus, most of the samples taken by Apollo 14 will not be taken from the Pluis Basin, but from the Oriental Basin. And this completely changes the situation! First, these results, published in Journal of Planetary Science, imply a new age for the East Basin impact, which would therefore be 3.92 billion years old, or 200 million years older than previously thought. Therefore, the domino effect, the Pluyes Basin, whose outliers make up the deepest level, will be even older. Therefore, this modification requires clarification of the age of most of the lunar surface. Secondly, the study involves rethinking the chronology of some events, including the beginning of the phase volcanism (leading to the emergence of various “seas”), which would thus coincide with an impact in the Eastern Basin.

Meteor bombardment was less intense than expected

All these results lead to revisiting the thermal history of the moon and suggest that the meteor bombardment that occurred about 3.9 billion years ago was less intense than previously thought. This hypothesis is very important for considering the habitability of the primitive Earth, subjected to the same bombardment at the same time. In other words, the situation would be less catastrophic than we thought.

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