Scientists still don't know where it came from

May 28, 2010 10:46 GMT  ·  By
Finding the origins for the Moon's peculiar nitrogen isotopes could lead to a better understanding of the early solar system
   Finding the origins for the Moon's peculiar nitrogen isotopes could lead to a better understanding of the early solar system

Astronomers and astrophysicists have for a long time known that the Moon is home to a particular type of nitrogen. The isotopes that can be found in the lunar soils and dust have little in common with the chemical that makes up a vast portion of Earth's atmosphere, or to the element that can be found in other locations throughout the solar system. Following a new set of investigations, it would appear that a possible explanation for the bizarre nitrogen's origin is cosmic material that deposits slowly, over billions of years, Space reports.

The Moon does not feature only this peculiar type of nitrogen. Various isotopes of the chemical exist on Earth's natural satellite, but the real puzzle is how the element got there, not its variety. “Somehow, we see a substantial amount of nitrogen on the moon, over and above the well-known solar wind, and we don't have a single clue as to where it comes from. It's just baffling,” explains University of California in San Diego (UCSD) cosmochemist John Kerridge. He was a part of the team that conducted the recent investigation into the lunar mystery.

“The nitrogen in the atmosphere we're breathing is not the same that was initially present in the solar system,” adds Kurt Marti, who is also a cosmochemist at the UCSD, and a co-investigator on the research. The two scientists published their results in the May 28 issue of the highly-regarded journal Science. They say that the NASA-operated Genesis satellite discovered that some of the nitrogen on the Moon came from the Sun. However, the star only features lighter nitrogen isotopes, and none of the heavy variety that can be found on our satellite. On the Moon, the ration of heavy to light isotopes is 10-to-1, the experts add.

Studying the possible origins of these chemicals could have important implications for understanding the origins of the solar system, and indeed those of all inner planets, including our own. Some experts have proposed that the non-solar chemicals may have been brought in by comets coming from the Kuiper Belt and beyond. “It's not a complete fit, though – comets also are strongly enriched in deuterium [a form of hydrogen], which we don't see as much of on the Moon. The lunar surface is like a history museum. If we can identify when this nitrogen was implanted in the lunar surface, then we can trace back what its history was,” Marti concludes.