Lunar impacts since Nov. 2005. Numbers 14-16 and 19-20 are Geminids. Number 18 is a probable Geminid.
Credit: NASA Meteoroid Environment Group.
Scientists have discovered the first evidence of graphite on the moon the same carbon-rich stuff used in pencils today after taking a new look at a lunar rock collected by astronauts nearly 40 years ago.
This graphite appears to have originated in a lunar meteorite strike around 3.8 billion years ago, researchers said. It could shed light on cosmic impacts that rocked the moon and our planet just when life was starting on Earth.
Scientists found roughly 70 tiny graphite needles, which scientists called "whiskers," on a lunar rock from Mare Serenitatis, "the Sea of Serenity," brought back in 1972 by Apollo 17, the last of the manned lunar landings. They were originally looking for another mineral, phosphate-rich apatite, as part of research into water on the moon.
"We came across the graphite by total accident," said researcher Andrew Steele, an astrobiologist at the Carnegie Institution of Washington in Washington, D.C.
The rock in question is an "impact breccia," part of a jumble of smaller fragments that formed when the moon was struck by an asteroid or other object. The researchers suggest this graphite could have come directly from the impactor itself or formed from the condensation of carbon-rich gas released during the impact. [Greatest Moon Crashes]
Although past studies of lunar rock have identified carbon-loaded minerals before, this is the first time pure-carbon minerals such as graphite was discovered. Previous studies suggested the carbon came from deposits left by solar wind.
The moon graphite formed in a period scientists dub the Late Heavy Bombardment. During this time, the moon, the Earth and most of the other bodies in the inner solar system apparently underwent massive cosmic impacts. Since craters from this cataclysmic time have eroded on Earth, this graphite on the moon could shed vital clues to this mysterious era.
In addition, the fact this form of carbon survived on the moon suggests the lunar surface could still possess remnants of carbon-rich organic molecules from ancient cosmic impacts the same kind of compounds delivered to the early Earth about when life was emerging on our planet.
"We believe that the carbon we detected either came from the object that made the impact basin, or it condensed from the carbon-rich gas that was released during impact," said study co-author Francis McCubbin. "The most exciting prospect from the discovery is that we now know that the moon holds a record of that period and the materials that contributed to the rise of life on Earth."
Although organic molecules such as amino acids have been seen on lunar samples before, "most of these measurements were put down to contamination at the time," Steele said.
"Perhaps a reappraisal of the Apollo samples would yield significant data on the organic inventory that was delivered to earth by meteorites at the time life was potentially starting on Earth," he added.
The research is detailed in the July 2 edition of the journal Science.