Researchers suggest that, apart from being the largest planet in our Solar System, Jupiter is also the oldest. They say it appeared during the four-million-year period after the formation of the Sun, providing a new way of understanding the evolution of the Solar System.
The lack of samples from Jupiter made its age approximation difficult
Until now, researchers knew that Jupiter was quite old, but they weren’t able to date the exact moment of its formation. Thomas Kruijer, scientist at Lawrence Livermore National Laboratory (LLNL), said that this had happened mostly because there was no Jupiter sample available for study. Therefore, they had to resort to other methods to determine the age of the planet.
For the study, published in the journal Proceedings of the National Academy of Sciences, researchers analyzed meteorites and tried to decode their isotope signatures to gather information on the age of Jupiter. They looked at isotopes of molybdenum and tungsten from iron meteorites and found something interesting.
Analyzing meteorite isotopes
They saw how the meteorites were made up of two nebular reservoirs with clearly distinct composition. These reservoirs merged only three or four million years after the formation of the sun. The fact that the two reservoirs remained separated until then suggests that a new planet was forming and this kept them apart.
“[Jupiter’s] solid core formed well before the solar nebula gas dissipated, consistent with the core accretion model for giant planet formation.”
The isotope analysis revealed that Jupiter’s core formed only one million years after the Sun formed. Up until three-four million years, the core kept growing until it reached 20 Earth masses. Then, the rest of the planet extended for a longer period of time, and ended up with the mass of 50 Earths.
Previous theories suggested that, after the core grew, gas started accumulating until it reached the present-day form of the planet. What scientists discovered now is the fact that the core started forming before the solar nebula created when the Sun formed had dissipated.
Image Source: NASA Jet Propulsion Laboratory