LONDON (TIP): An international team of planetary scientists have now calculated the exact age of the Moon. The team of researchers from France, Germany and the US has simulated the growth of the terrestrial planets (Mercury, Earth and Mars) from a disk of thousands of planetary building blocks orbiting the Sun. By analysing the growth history of the earth-like planets from 259 such simulations, the scientists have discovered the relationship between the time the earth was impacted by a mars-sized object to create the moon and the amount of material added to the earth after that impact.
The conclusion they have reached is that the moon formed nearly 100 million years after the start of the solar system. This is the first geologic clock in early solar system history that does not rely on measurements and interpretations of the radioactive decay of atomic nuclei to determine age. The conclusion, they say, is based on measurements from the interior of the earth combined with computer simulations of the proto-planetary disk from which the earth and other terrestrial planets formed. The research was funded by the European Research Council, as well as NASA’s Astrobiology Virtual Planetary Laboratory.
Augmenting the computer simulation with details on the mass of material added to the earth by accretion after the formation of the moon revealed a relationship that works much like a clock to date the moon-forming event. “We were excited to find a clock for the formation time of the moon that didn’t rely on radiometric dating methods. This correlation just jumped out of the simulations and held in each set of old simulations we looked at,” says lead author Seth Jacobson of the Observatory de la Cote d’Azur in Nice, France.
From geochemical measurements, the newly established clock dates the moon to just over 95 million years after the beginning of the solar system. This estimate for the moon-formation agrees with some interpretations of radioactive dating measurements. Because the new dating method is an independent and direct measurement of the age of the moon, it helps to guide which radioactive dating measurements are the most useful for this longstanding problem.
“This result is exciting because in the same simulations that can successfully form Mars in only 2 to 5 million years, we can also form the Moon at 100 million years. These vastly different timescales have been very hard to capture in simulations,” says author Dr Kevin Walsh from the Southwest Research Institute Space Science and Engineering Division.