The Moon, our natural satellite, has not always illuminated Earth’s sky. Scientists have long believed that it formed after a catastrophic collision between the young Earth and the protoplanet Theia about 4.5 billion years ago. However, new research presented at the Lunar and Planetary Science Conference has shifted that date even further back in time.
Hypothesis of a giant collision
The theory is that Theia, the size of Mars, crashed into Earth, ejecting millions of tons of molten rock into space. These debris later combined to form the Moon, explaining its similarity to Earth’s composition and lack of its own core. But when exactly did this event take place? Estimates ranged from 4.35 to 4.52 billion years, with discrepancies attributed to more recent geologic processes like the formation of the Aitken Basin.
Key in the moon rocks
To solve the mystery, a team of scientists examined ferroan anorthosites (FAN), the oldest known lunar rocks. They used the radioactive decay of rubidium-87 into strontium-87, which “solidified” in these rocks after they crystallized. Thermionization mass spectrometry was used for the analysis: samples were heated to 1000°C, studying the ionized particles.
Five of the eight samples, including one 4.36 billion years old, showed stable isotope ratios, indicating that they formed immediately after the collision. The other three probably underwent chemical changes later. By modeling different collision scenarios, the scientists obtained a new date of 4.502 ± 0.021 billion years ago. That’s only 65 million years later than the birth of the Solar System!
Artemis will find the exact answer
The exact time of the moon’s formation will help us understand how the planets formed and when conditions for life appeared on Earth. Despite the errors, this work opens the way to refined models where all parameters of the space catastrophe are taken into account. Who knows – perhaps the next samples from the Artemis mission will reveal new details of this impressive story.
Do you know that the Moon moves away from the Earth by 3.8 cm every year? This means that billions of years from now, our descendants will see much less of it.
Earlier we reported on how scientists determined the age of the largest crater on the Moon.
According to universetoday.com
