Thursday, June 2, 2016

Scientists Identify Source of the Moon's Water

Potential origins of the Moon's water, delivered while it was still partially molten. CREDIT: LPI / DAVID A. KRING

According to a new study published in Nature Communications, most of the water inside the Moon was delivered by asteroids (not comets) during the early evolution of the Moon, approximately 4.5–4.3 billion years ago. In the Apollo era, the Moon was often described as being devoid of water. As analytical techniques improved, scientists realized that water resided in the lunar interior, but in quantities that had simply been impossible to detect when lunar samples were originally returned to Earth. The discovery of water in lunar samples prompted a new question: What was the source of the Moon’s water?

In the current study, an international science team compared the chemical and isotopic composition of lunar volatiles (including water) with those of volatile materials in comets and meteoritic samples of asteroids. They then calculated the proportion of water that could have been delivered by those two populations of objects. Their results indicate that most (>80%) of the water in the lunar interior was derived from asteroids that are similar to carbonaceous chondritic meteorites. That water was delivered when the Moon was still surrounded by a magma ocean and before a massive crust (now seen as the bright white highlands of the Moon) prevented impacting objects from delivering significant amounts of material to the lunar interior. A similar delivery of water to Earth would have been occurring within this same interval of time.

These results were derived by an interdisciplinary team with extensive experience studying both the Moon and meteoritic samples of impacting asteroids. The lead author of the paper is Jessica Barnes (The Open University, Milton Keynes). Co-authors are David Kring [Lunar and Planetary Institute (LPI), Houston], Romain Tartèse (Muséum National d'Histoire Naturelle, Paris), Ian Franchi (The Open University), Mahesh Anand (The Open University), and Sara Russell (The Natural History Museum, London).

“We believe that asteroids delivered the majority of water to the moon and comets delivered very little - they weren’t major players in the first few hundred million years of inner solar system history,” said Barnes.

“[The hydrogen isotopes are] like a fingerprint or a barcode for where water may have come from in the solar system - these different types of objects have different hydrogen isotope compositions,” she added.

Barnes, is a former graduate student intern in the Center for Lunar Science and Exploration (CLSE) Lunar Exploration Summer Intern Program, is currently a CLSE postdoctoral international partner, and is an incoming postdoctoral researcher at the NASA Johnson Space Center and the LPI, which is managed by the Universities Space Research Association (USRA) for NASA.

Kring’s portion of the work was supported at the LPI by cooperative agreements to USRA from NASA’s Planetary Science Division and NASA’s Solar System Exploration Research Virtual Institute.


1 comment:

  1. I'm always fascinated with space and all the planet surrounding it, that's why I always schedule a star gazing day with my children once a week to relax and unwind. These gives me ideas on how to buy papers for college which I can use in my master degree class.