September 24, 2013
New Evidence Indicates Moon Is 100 Million Years Younger Than Thought
[ Watch the Video: Moon May Be Much Younger Than Previously Believed ]
Lawrence LeBlond for redOrbit.com - Your Universe Online
Earth’s closest neighbor, the moon, has been studied intently by astronomers for centuries. In that time, we thought we had discovered nearly everything there is to know about the origins of our natural satellite.
However, new research by geochemist Richard Carlson of the Carnegie Institution of Washington has shaken things up a bit. According to Carlson's studies, our orbiting partner is somewhat younger than previously thought – about 100 million years younger to be exact.
Previously, astronomers had pegged the moon to be around 4.56 billion years old, with prevailing theories suggesting a planet similar in size to Mars may have slammed into earth 4.56 billion years ago. The dust and debris from this impact was thrown back out into space and eventually amalgamated to create the moon.
While experts generally concur that the impact theory is the most likely scenario, Carlson is not so much investigating how this event happened, but rather when the moon formed as a result of this impact.
Carlson’s radioactive dating analysis of lunar rocks collected and returned during the Apollo missions suggest the moon formed between 4.4 and 4.45 billion years ago. If this new understanding holds any water, then all we think we have known about the history of the satellite can be thrown out the cosmic window.
Carlson had also analyzed levels of zircon in Earth rock taken from Western Australia, according to io9. Zircon, which is an extremely durable mineral, can give clues to the geologic events that occurred early in the planet’s history. These rocks do indicate a “major differentiation event” occurred at around the same time as the hypothetical impact event that created the moon.
Carlson said previous studies in this area had a large margin of error, but he believes improved technology has allowed him to make a more accurate measurement of when the moon formed, greatly narrowing any margin of error.
"Back in the 1970s, you couldn't distinguish between 4.45 and 4.55 billion years," he told Deborah Netburn of the Los Angeles Times. "Today, we can, and everything we are seeing suggests the 4.4 billion number."
Scientists know that the Solar System is 4.568 billion years old, and they can determine the age of smaller interplanetary bodies, such as asteroids, with a fair degree of accuracy – analyzing periods of extensive melting that typically occur when they collide with even smaller bodies known as “planetesimals.”
Another leading theory suggests the moon had a global ocean of molten rock shortly after its formation. The lunar rocks that may have formed that ocean have been aged to about 4.360 billion years, according to researchers.
Carlson noted that one of the most interesting aspects of his research is imagining what the Earth may have been like before an impact; before it had a moon.
He suggests that “the Earth had two phases of its life -- one before the giant impact, and another one greatly modified by the impact."
With the recent discoveries, and with improved dating methods, scientists may now be able to create more accurate estimates of the moon’s and, perhaps, the Earth’s age. Estimating the age of planets is much more difficult than estimating age of smaller bodies, but the new techniques could help paint a clearer picture.
Carlson’s research could lead to new questions about the origins and early history of our planet, including the possibility that the Earth’s early atmosphere was destroyed by the impact that led to the creations of our orbiting partner.
Carlson presented his "Age of the Lunar Crust: Implications for the Time of Moon Formation" research on Monday at the “Origins of the Moon” conference of the Royal Society.
The “Origins of the Moon” conference continues today, with an “Origins of the Moon – Challenges and Prospects” meeting scheduled for Wednesday and Thursday as well.