Home > Earth, Moon > Man in the Moon Looking Younger

Man in the Moon Looking Younger


Earth’s Moon could be younger than previously thought, according to
new research from a team that includes Carnegie’s Richard Carlson and
former-Carnegie fellow Maud Boyet. Their work will be published online
in Nature on August 17.

The prevailing theory of our Moon’s origin is that it was created by a
giant impact between a large planet-like object and the proto-Earth.
The energy of this impact was sufficiently high that the Moon formed
from melted material that was ejected into space. As the Moon cooled,
this magma solidified into different mineral components.

Analysis of lunar rock samples thought to have been derived from the
original magma has given scientists a new estimate of the Moon’s age.

According to this theory for lunar formation, a rock type called
ferroan anorthosite, or FAN, is the oldest of the Moon’s crustal
rocks, but scientists have had difficulty dating FAN samples. The
research team, led by Lars E. Borg of the Lawrence Livermore National
Laboratory, included Carlson of Carnegie’s Department of Terrestrial
Magnetism, Boyet — now at Université Blaise Pascal — and James N.
Connelly of the University of Copenhagen. They used newly refined
techniques to determine the age of a sample of FAN from the lunar rock
collection at the NASA Johnson Space Center.

The team analyzed the isotopes of the elements lead and neodymium to
place the FAN sample’s age at 4.36 billion years. This figure is
significantly younger than earlier estimates of the Moon’s age that
range as old as the age of the solar system at 4.568 billion years.
The new, younger age obtained for the oldest lunar crust is similar to
ages obtained for the oldest terrestrial minerals — zircons from
western Australia — suggesting that the oldest crusts on both Earth
and Moon formed at approximately the same time, and that this time
dates from shortly after the giant impact.

This study is the first in which a single sample of FAN yielded
consistent ages from multiple isotope dating techniques. This result
strongly suggests that these ages pinpoint the time at which the
sample crystallized.

“The extraordinarily young age of this lunar sample either means that
the Moon solidified significantly later than previous estimates, or
that we need to change our entire understanding of the Moon’s
geochemical history,” Carlson said.

# # #

Funding for this work was provided by the Department of Energy, and
portions of the work were supported by the NASA Cosmochemistry
Program.

The Carnegie Institution for Science (http://carnegiescience.edu) is a
private, nonprofit organization headquartered in Washington, D.C.,
with six research departments throughout the U.S. Since its founding
in 1902, the Carnegie Institution has been a pioneering force in basic
scientific research. Carnegie scientists are leaders in plant biology,
developmental biology, astronomy, materials science, global ecology,
and Earth and planetary science.

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