An international team of scientists has deemed Jupiter to be the most senior member of the solar system.
Scientists from the Lawrence Livermore National Laboratory and the Institut fur Planetologie at the University of Munster have discovered that meteorites are comprised from two genetically distinct nebular reservoirs that co-existed but remained separated between one million and three-to-four million years after the solar system formed.
The scientists made this observation after examining tungsten and molybdenum isotopes on iron meteorites.
“The most plausible mechanism for this efficient separation is the formation of Jupiter, opening a gap in the disc [a plane of gas and dust from stars] and preventing the exchange of material between the two reservoirs,” Thomas Kruijer, of LLNL and lead author of the paper, said in a statement. “Jupiter is the oldest planets in the solar system and its solid core formed well before the solar nebula gas dissipated, consistent with the core accretion model for giant planet formation.
“We do not have any samples from Jupiter, in contrast to other bodies like the Earth, Mars, the moon and asteroids,” he added. “In our study, we use isotope signatures of meteorites [which are derived from asteroids] to infer Jupiter’s age.”
After analyzing the isotopes, the scientists found that through rapid formation, Jupiter acted as an effective barrier against inward transport of material across the disc, potentially explaining why the solar system lacks an extrasolar planet with a mass higher than Earth’s.
Jupiter’s core grew to be about 20 Earth masses within one million years. Jupiter then saw a more prolonged period of growth to about 50 Earth masses until at least three-to-four million years after the solar system formed.
Previous theories have proposed that gas-giant planets involved the growth of large solid cores of about 10 to 20 Earth masses, followed by the accumulation of gas onto the cores. This meant that Jupiter and Saturn must have been formed before dissipation of the solar nebula—the gaseous circumstellar disc surrounding the young sun—which occurred between one million and 10 million years after the formation of the solar system.
While the researchers confirmed the earlier theories, they were able to more precisely target Jupiter’s age using the isotopic signatures of meteorites.
“Our measurements show that the growth of Jupiter can be dated using the distinct genetic heritage and formation times of meteorites,” Kruijer said.
Jupiter is the most massive planet in the solar system and is known for effecting the dynamics of the solar accretion disc due to its size. By calculating the age of Jupiter scientists can begin to understand how the solar system evolved toward its current architecture.
