A rock collected by an Apollo 17 astronaut in 1972 reveals the age of the moon

WASHINGTON, Oct 23 (Reuters) – During the Apollo 17 mission in 1972 – the last time a human walked on the moon – American astronauts Harrison Schmidt and Eugene Cernan collected about 110.4 kg of soil and rock samples that were returned to Earth. For further study.

Half a century later, crystals of the mineral zircon found inside a piece of coarse-grained igneous rock collected by Schmidt are giving scientists a deeper understanding of the composition of the Moon and the precise age of Earth’s celestial partner.

Scientists said on Monday that the moon is about 40 million years older than previously thought, having formed more than 4.46 billion years ago, that is, within 110 million years after the birth of the solar system, based on crystallographic analyses.

The main hypothesis for the formation of the Moon is that during the chaotic early history of the solar system, a Mars-sized body called Theia collided with the primordial Earth. This magma – molten rock – exploded into space, forming a disk of debris that orbited the Earth and collected in the Moon. But the exact timing of the moon’s formation was difficult to determine.

Mineral crystals were able to form after the magma cooled and solidified. The researchers used a method called atom probe tomography to confirm the age of the oldest known solids that formed after the giant impact, which are zircon crystals found inside part of a type of rock called norite that Schmidt collected.

“I like the fact that this study was performed on a sample that was collected and brought to Earth 51 years ago. At that time, atomic probe tomography had not yet been developed, and scientists could not have imagined the types of analyzes we do today,” said cosmochemist Philipp Heck. Senior director of research at the Field Museum in Chicago, professor at the University of Chicago and senior author of the study published in the journal: Geochemical Perspectives Letters.

“Interestingly, all the oldest minerals found on Earth, Mars and the Moon are zircon crystals,” added UCLA planetary scientist and study co-author Bidong Zhang. “Zircon, not diamond, lasts forever.”

Zircon-containing rocks were collected in the Taurus-Littrow Valley at the southeastern edge of the moon Mare Serenitatis (Sea of ​​Serenity) and stored at NASA’s Johnson Space Center in Houston.

“Zircon is very hard and strong and survives rock collapse during weathering,” Heck said.

a Stady Led by Zhang and published in 2021, he used a technique called ion probe analysis to measure the number of uranium and lead atoms in the crystals, and calculated the age of zircons based on the decay of radioactive uranium to lead over time. This age must be confirmed by another method due to potential complications involving lead atoms if defects are present in the zircon crystal structure.

The new study used atom probe tomography to determine there were no complications related to the lead atoms, confirming the age of the crystals.

“I see this as a great example of what the nanoscale, or even the atomic scale, can tell us about big picture questions,” said study author Jenica Greer, a cosmochemist at the University of Glasgow in Scotland.

The Moon, which orbits Earth at an average distance of about 239,000 miles (385,000 km), has a diameter of about 2,160 miles (3,475 km), a little more than a quarter of the diameter of our planet.

Heck said: “The giant collision that formed the Moon was a catastrophic event for the Earth and changed the speed of the Earth’s rotation. After that, the Moon had an effect on the stability of the Earth’s rotation axis and slowed down the speed of the Earth’s rotation.” “The formation date of the Moon is important because only after that did Earth become a habitable planet.”

“The moon helps stabilize the Earth’s axis for a stable climate,” Zhang added. “The Moon’s gravity helps shape the ocean ecosystem. The Moon is an inspiration for human cultures and exploration. NASA and other space agencies see the Moon as a launching pad for future deep space explorations.”

Our standards: Thomson Reuters Trust Principles.