Scientists may soon be able to determine the exact age of huge impact basins on the Moon, thanks to a detailed new geological map of the Great Eastern basin. This is the youngest large impact basin on the Moon and offers important perspectives for understanding the history of cosmic impacts that have shaped both the Earth's natural satellite and our planet.
Located on the border between the visible and the hidden side of the Moon, the Mare Orientale basin stands out for its unique and complex structure. With a diameter of approximately 930 kilometers, this basin features impressive concentric rings, formed by a colossal impact that occurred approximately 3,8 billion years ago. In its center, the basaltic melt resulting from the collision offers clues about the geological processes that followed the impact.
Although the exact age of the basin remains uncertain, estimates place the event in the period of intense formation of lunar craters, shortly after the formation of the solar system. By comparison, the oldest impact basin on the Moon, South Pole-Aitken, is over 4,3 billion years old.
The main problem in determining the exact age of the Orientale basin is its complex stratification. Its surface has been covered over billions of years with more recent lava flows, debris from later impacts and fresh craters. This agglomeration of materials makes it difficult to isolate samples that accurately reflect the moment of the initial impact.
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However, a team led by Kirby Runyon of the Planetary Science Institute in Tucson, Arizona, has created a detailed geological map that identifies areas where the original impact melt may still be accessible. This map helps differentiate initial melt from more recent rocks, providing a promising method for studying other lunar basins.
Studying lunar basins such as the Mare Orientale not only has implications for understanding the Moon, but also for the Earth. Cosmic impacts on the Moon provide clues about similar events that could have affected our planet in the distant past. Such collisions could have vaporized entire oceans and even delayed or wiped out emerging life on Earth.
"Large impacts on Earth could have caused cycles of destruction and regeneration," explains Runyon. "Our oceans could have been vaporized several times, and life would have developed only after conditions stabilized."
The map produced by Runyon's team could guide future lunar sample collection missions. If the materials taken from the Orientale basin confirm the impact melting dating methods, this could revolutionize the understanding of the age of other lunar basins, including the oldest and most degraded ones.
"The Orientale Basin is a perfect combination of old and young," Runyon said. "It's young enough to have freshly exposed melt, but old enough to challenge us to decipher its complex history."
Future studies could reveal more about the connection between cosmic impacts and the development of life on Earth, offering new insights into our beginnings. The moon thus remains a unique geological laboratory, where the past can be discovered and understood.
