Stone accumulated by Apollo 17 spaceman in 1972 discloses age of moon


The celestial body is approximately 40 million years older than formerly assumed – originating over 4.46 billion years ago, within 110 million years of the birth of the solar system

During the 1972 Apollo 17 mission – the most recent occasion individuals trod on the celestial body – United States astronauts Harrison Schmitt and Eugene Cernan amassed approximately 243 pounds (110.4 kg) of soil and rock samples that were conveyed back to Earth for additional examination.

Scientifics are obtaining a deeper comprehension of the celestial body’s formation and the precise age of Earth’s celestial partner, utilizing crystals of the mineral zircon inside a coarse-grained igneous rock fragment amassed by Schmitt a half-century later.

Based on analyses of the crystals, scientifics stated the celestial body is approximately 40 million years older than formerly assumed – originating over 4.46 billion years ago, within 110 million years of the birth of the solar system.

The leading hypothesis for lunar formation posits that during the chaotic initial period of the solar system’s history, a Mars-sized object named Theia impacted primordial Earth. This collision expelled molten rock, or magma, into space, forming a disk of debris that orbited Earth and eventually consolidated into the moon. However, pinpointing the exact timing of the celestial body’s formation has proven challenging.

Mineral crystals managed to form after the magma cooled and solidified. Researchers deployed a technique called atom probe tomography to verify the age of the oldest-known solids that formed following the colossal impact: the zircon crystals contained within the norite rock fragment gathered by Schmitt.

“I appreciate the fact that this study was conducted using a sample that was gathered and brought to Earth 51 years ago. During that time, atom probe tomography had not yet been developed, and scientists could not have envisioned the types of analyses we perform today,” said senior author of the study, cosmochemist Philipp Heck, who is also the senior director of research at the Field Museum in Chicago and a professor at the University of Chicago. The study was published in the journal Geochemical Perspectives Letters.

Study co-author Bidong Zhang, a planetary scientist from UCLA, added, “Curiously, all the oldest minerals discovered on Earth, Mars, and the celestial body are zircon crystals. Zircon, not diamond, persists eternally.”

The rock containing the zircon crystals was collected in the Taurus-Littrow valley, located at the southeastern edge of the lunar Mare Serenitatis (Sea of Serenity), and stored at NASA’s Johnson Space Center in Houston.

“Zircons are highly resistant and durable, and they endure the disintegration of rocks during weathering,” remarked Heck.

A study led by Zhang and published in 2021 used a technique known as ion microprobe analysis to determine the quantity of uranium and lead atoms within the crystals, thus calculating the age of the zircon based on the radioactive decay of uranium into lead over time. Due to the potential existence of defects in the crystal structure of the zircon, another method was required to verify this age.

The new study used atom probe tomography to ascertain the absence of any complications associated with the lead atoms, therefore confirming the age of the crystals.

“I perceive this as an excellent illustration of the insights the nanoscale, or even atomic scale, can provide to us regarding fundamental questions,” remarked the lead author of the study, Jennika Greer, a cosmochemist at the University of Glasgow in Scotland.

The celestial body, which orbits Earth at an average distance of approximately 239,000 miles (385,000 km) possesses a diameter of around 2,160 miles (3,475 km) – slightly more than a quarter of Earth’s diameter.

“The colossal impact that led to the formation of the celestial body was a cataclysmic event for Earth, altering Earth’s rotational speed. Afterward, the celestial body played a role in stabilizing Earth’s rotational axis and decelerating Earth’s rotational speed,” Heck explained. “The celestial body’s formation date is significant because only after that did Earth evolve into a habitable planet.”

“The celestial body aids in stabilizing Earth’s axis, resulting in a stable climate,” Zhang added. “The moon’s gravitational forces contribute to shaping the ecosystem of the oceans. The celestial body serves as an inspiration for human cultures and explorations. Additionally, NASA and other space agencies consider the celestial body a steppingstone for future deep-space expeditions.”

(Reported by Will Dunham; Edited by Lisa Shumaker for Reuters)

Additionally, read: Nasa’s solar probe attains the status of the fastest man-made object

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