Alan Shepard planting the American flag on the Moon, 1971. Image: Edgar Mitchell/NASA
A Moon rock picked up by the Apollo 14 astronauts in 1971 may contain the oldest known sample of Earth ever discovered, according to a study published this week in Earth and Planetary Science Letters.At an estimated 4.1 billion years old, the sample is senior to the earliest known samples on Earth, which are dated to about four billion years.
The tiny, two-gram sample represents “potentially the first evidence of a terrestrial meteorite,” meaning a rock originating from Earth, report the authors of the study, which was led by Jeremy Bellucci, a research scientist at the Swedish Museum of Natural History, and Alexander Nemchin, a planetary scientist at Curtin University in Australia.
The team concluded that the sample was likely dislodged from our planet by an asteroid impact some 3.9 billion years ago. At that point, the solar system was only about 600 million years old, and the Moon was three times closer to Earth than it is now.After it had been catapulted from Earth to the Moon, the rock spent billions of years in the lunar subsurface, but was eventually excavated by another impact 26 million years ago.This event produced Cone Crater, a 1,000-foot-wide depression that was within walking distance of Apollo 14’s landing site. Astronauts Alan Shepard and Edgar Mitchell collected samples from the ejecta of the crater and brought them back to Earth. One of those lunar rocks, nicknamed “Big Bertha,” contained this tiny speck of baby Earth.
Bellucci, Nemchin, and their colleagues at NASA’s Center for Lunar Science and Exploration (CLSE) identified this small specimen as terrestrial by the presence of quartz, feldspar, and zircon.These minerals are common on Earth but rare on the Moon, and the crystallization patterns suggest they were formed in an environment that matches Earth’s temperatures and oxidation levels. There is an outside chance that the sample originated on the Moon, the team said, but it’s far more likely that it hails from Earth.
According to David Kring, CLSE principal investigator and a senior author on the recently published journal article, the next step is to look for similar mineral signatures in lunar samples to find more relics of our young planet.“It is an extraordinary find that helps paint a better picture of early Earth and the bombardment that modified our planet during the dawn of life,” Kring said in a statement.How mind-boggling that crystals formed on primordial Earth ended up making a cataclysmic voyage to the Moon, only to be eventually brought home by some random ape species that made the same trip four billion years later.Get six of our favorite Motherboard stories every day by signing up for our newsletter.