HOUSTON: Scientists say they discovered what might be the oldest rock of the Earth in a lunar sample returned from the Moon through the Apollo 14 astronauts.
An international team associated with the Center for Luna Science and Research (CLSE) in the United States found evidence that the rock was launched by the Earth with a great efficient asteroid or comet.
This impact separated material through the Earth's initial atmosphere, into the space where it hit the surface of the Moon – which was three times closer to Earth than it is now – about four billion years ago, researchers said.
The rock was later mixed with other lunar surface materials into one specimen, according to the study published in the Earth and Planetary Science magazine.
The team developed techniques to locate impathetic fragments in the lunar regolite, which urged CLSE Chief Investigator David Kringo to challenge them to locate a piece of Earth on the Moon.
The researchers found a two-gram fragment of rock formed by quartz, feldsparo, and zircon, all commonly found on Earth and very unusual on the Moon.
Chemical analysis of the rocky fragment shows it crystallized in a terrestrial similar oxidized system, at ground temperatures, rather than in the reducing and higher temperature conditions of the Moon.
"It's an extraordinary search that helps paint a better picture of the early Earth and the bombardment that modified our planet during the dawn," said Kring, a researcher at the Space Research Association of Luna and Planetary Institutes (LPI).
It is possible that the sample is not of ground origin, but instead crystallized on the Moon, however, which will require conditions never previously defined by lunar specimens, researchers have said.
It would require the example to be formed in horrible depths, in the lunar mantle, where very different rock compositions are predicted, they said.
The simplest interpretation is that the sample has come from the Earth, according to researchers.
The rock was crystallized about 20 kilometers below Earth's surface 4.0 to 4.1 billion years.
It was then excavated with one or more effective events and launched in a lunar space.
The team's previous work showed that triggering asteroids then produced craters a thousand kilometers of diameter on Earth, quite comprehensive to bring material from those depths to the surface, said researchers.
After the sample reached the lunar surface, it was affected by several other effective events, one of which partially melted it up to 3.9 billion years, and probably buried it under the surface.
The sample is therefore a relic of an intense bombing period, which formed the solar system during the first billion years.
After this period, the Moon was affected by smaller and less frequent effective events.