Earth-moon smashup older than previously thought

By studying isotopes trapped inside ancient quartz crystals, researchers at the University of Lorraine in Nancy, France, have been able to more accurately pinpoint the place in geologic time when a massive impact disrupted the rock that formed Earth's moon.
According to their analysis, the formation of Earth and the collision that caused the moon happened earlier than previously thought -- about 60 million years earlier.
Determining the exact age of Earth is extremely difficult, as studying the planet's earliest rock layers using "classical geology" clues -- like a missing layer of rock -- does little to help scientists. But the isotopes of gases, like xenon, trapped inside ancient rock act like a time capsule, helping scientists plot the history of planet Earth.
By comparing isotopes of long ago to today's, scientists can recalibrate their traditional dating techniques and arrive at a more accurate estimate of Earth's age and its major geological events -- like the impact that created the moon.
"The composition of the gases we are looking at changes according to the conditions they are found in -- which of course depend on the major events in Earth's history," explained geochemist Guillaume Avice, who joined Bernard Marty to explain their research at the Goldschmidt Geochemistry Conference in Sacramento, California, on Tuesday.
"We are using standard methods to compute the age of Earth," Avice continued, "but having access to these ancient samples gives us new data and allows us to refine the measurement."
Marty said while 60 million years doesn't seem like much in cosmic time, the discrepancy is important.
"These differences set time boundaries on how the planets evolved," she said, "especially through the major collisions in deep time which shaped the solar system."
Source: UPI