<p id="d2678525e174">Jupiter is the most massive planet of the Solar System and its
presence had an immense
effect on the dynamics of the solar accretion disk. Knowing the age of Jupiter, therefore,
is key for understanding how the Solar System evolved toward its present-day architecture.
However, although models predict that Jupiter formed relatively early, until now,
its formation has never been dated. Here we show through isotope analyses of meteorites
that Jupiter’s solid core formed within only ∼1 My after the start of Solar System
history, making it the oldest planet. Through its rapid formation, Jupiter acted as
an effective barrier against inward transport of material across the disk, potentially
explaining why our Solar System lacks any super-Earths.
</p><p class="first" id="d2678525e177">The age of Jupiter, the largest planet in our
Solar System, is still unknown. Gas-giant
planet formation likely involved the growth of large solid cores, followed by the
accumulation of gas onto these cores. Thus, the gas-giant cores must have formed before
dissipation of the solar nebula, which likely occurred within less than 10 My after
Solar System formation. Although such rapid accretion of the gas-giant cores has successfully
been modeled, until now it has not been possible to date their formation. Here, using
molybdenum and tungsten isotope measurements on iron meteorites, we demonstrate that
meteorites derive from two genetically distinct nebular reservoirs that coexisted
and remained spatially separated between ∼1 My and ∼3–4 My after Solar System formation.
The most plausible mechanism for this efficient separation is the formation of Jupiter,
opening a gap in the disk and preventing the exchange of material between the two
reservoirs. As such, our results indicate that Jupiter’s core grew to ∼20 Earth masses
within <1 My, followed by a more protracted growth to ∼50 Earth masses until at
least
∼3–4 My after Solar System formation. Thus, Jupiter is the oldest planet of 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.
</p>