UNM scientists find Earth and Moon not identical oxygen twins

March 10, 2020

Scientists at The University of New Mexico have found that the Earth and Moon have distinct oxygen compositions and are not identical in oxygen as previously thought according to a new study released today in Nature Geoscience.

The paper, titled Distinct oxygen isotope compositions of the Earth and Moon, may challenge the current understanding of the formation of the Moon.

Previous research led to scientists to develop the Giant Impact Hypothesis suggesting the Moon was formed from debris following a giant collision between early-Earth and a proto-planet named Theia. The Earth and Moon are geochemically similar. Samples returned from the Moon from the Apollo missions showed a near-identical composition in oxygen isotopes.

Although the Giant Impact Hypothesis can nicely explain many of the geochemical similarities between Earth and Moon, the extreme similarity in oxygen isotopes has been difficult to rationalize with this scenario: either the two bodies were compositionally identical in oxygen isotopes to start with, which is unlikely, or their oxygen isotopes were fully mixed in the aftermath of the impact, which has been difficult to model in simulations.

"Our findings suggest that the deep lunar mantle may have experienced the least mixing and is most representative of the impactor Theia," said Erick Cano. "The data imply the distinct oxygen isotope compositions of Theia and Earth were not completely homogenized by the Moon-forming impact and provides quantitative evidence that Theia could have formed farther from the Sun than did Earth."

To arrive at their findings, Cano, a research scientist, and along with colleagues Zach Sharp and Charles Shearer from UNM's Department of Earth and Planetary Sciences, conducted high-precision measurements of the oxygen isotopic composition on a range of lunar samples at UNM's Center for Stable Isotopes (CSI). The samples included basalts, highland anorthosites, norites and volcanic glass, a product of uncrystallized rapidly cooled magma.

They found that the oxygen isotopic composition varied depending on the type of rock tested. This may be due to the degree of mixing between the molten Moon and vapor atmosphere following the impact. Oxygen isotopes from samples taken from the deep lunar mantle were the most different to oxygen isotopes from Earth

"This data suggests that the deep lunar mantle may have experienced the least mixing and is most representative of the impactor Theia," said Sharp. "Based on the results from our isotopic analysis, Theia would have an origin farther out from the Sun relative to Earth and shows that Theia's distinct oxygen isotope composition was not completely lost through homogenization during the giant impact."

The research is important because it eliminates the need for giant-impact models that include a complete oxygen isotope homogenization between the Earth and the Moon, and provides a foundation for future modeling of the impact and lunar formation.
-end-


University of New Mexico

Related Moon Articles from Brightsurf:

New mineral discovered in moon meteorite
The high-pressure mineral Donwilhelmsite, recently discovered in the lunar meteorite Oued Awlitis 001 from Apollo missions, is important for understanding the inner structure of the earth.

First measurements of radiation levels on the moon
In the current issue (25 September) of the prestigious journal Science Advances, Chinese and German scientists report for the first time on time-resolved measurements of the radiation on the moon.

Researchers develop dustbuster for the moon
A team led by the University of Colorado Boulder is pioneering a new solution to the problem of spring cleaning on the moon: Why not zap away the grime using a beam of electrons?

First global map of rockfalls on the Moon
A research team from ETH Zurich and the Max Planck Institute for Solar System Research in Göttingen counted over 136,000 rockfalls on the moon caused by asteroid impacts.

Going nuclear on the moon and Mars
It might sound like science fiction, but scientists are preparing to build colonies on the moon and, eventually, Mars.

Astronaut urine to build moon bases
The modules that the major space agencies plan to erect on the Moon could incorporate an element contributed by the human colonizers themselves: the urea in their pee.

How moon jellyfish get about
With their translucent bells, moon jellyfish (Aurelia aurita) move around the oceans in a very efficient way.

Does crime increase when the moon is full?
Noting that anecdotal beliefs can affect public policies and practices, a 'pracademics' team from NYU's Marron Institute of Urban Management worked with public safety personnel to examine the commonly held axiom that crime rises with the full moon -- and found that the evidence is just not there.

Soil on moon and Mars likely to support crops
Researchers at Wageningen University & Research in the Netherlands have produced crops in Mars and moon soil simulant developed by NASA.

Are we prepared for a new era of field geology on the moon and beyond?
Space agencies must invest more resources on field geology training of astronauts to take full advantage of scientific opportunities on the moon and other planetary bodies, Kip Hodges and Harrison Schmitt urge, in an Editorial.

Read More: Moon News and Moon Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.