The moon was once covered in a sea of
molten magma, which gradually cooled
and became solid.
Image: iStockphoto

Research led by Curtin University of Technology has discovered the oldest lunar zircon dated at 4.42 billion years.

The newly-discovered zircon sheds important light on the early formation of the Moon’s surface.

The research findings are discussed in a paper, “Timing of crystallization of the lunar magma ocean constrained by the oldest zircon,” scheduled for advanced online publication on 26 January 2008 on the website of the prestigious international scientific journal, Nature Geoscience.

Dr Alexander Nemchin, of Curtin’s Department of Applied Geology and the paper’s lead author, explained the significance of the discovery.

“After the formation of the Moon about 4.52 billion years ago, it experienced a brief period when its outer layer was completely molten,” Dr Nemchin said.

“This molten layer is referred to as the Magma Ocean and it is not very well-known how long this layer existed on the Moon.

“The zircon we discovered would have formed as the Magma Ocean crystallized, and suggests that the Magma Ocean existed for the first 100 million years of the Moon’s history.

“The mineral zircon (ZrSiO4) is well-known for its stability and ability to precisely date geological processes in terrestrial rocks, but the discovery of zircon in the lunar samples we examined means that we can now determine the chronology of major events in the Moon’s evolution,” Dr Nemchin said.
 
“Understanding the time constraints related to the lunar Magma Ocean can also provide important constraints on the development of the Earth-Moon system.”

Dr Nemchin also led a collaborative research effort in 2007 that identified the world’s oldest diamonds found in terrestrial rocks in Jack Hills, Western Australia.

“The success of the Jack Hills discovery led us to approach NASA in the United States for lunar samples that could be examined, and we are very excited to be able to make a similar discovery with these samples,” Dr Nemchin said.

Members of Curtin’s team who co-authored the paper include Dr Nicholas Timms, Professor Robert Pidgeon, and Associate Professor Steve Reddy from the Department of Applied Geology. Dr Thorsten Geisler from the University of Munster’s Institute of Mineralogy and Dr. Charles Meyer from NASA’s Johnson Space Centre are also co-authors on the paper.