Metal in meteorites sheds light on young Jupiter’s massive migration
If you’re looking for information about Jupiter’s past, you might start by looking in Australia. It’s not that the view into space is necessarily any better, but that was where some key meteorites were found that contained rare grains of condensed metal that were likely formed billions of years ago. Recent simulations put together a scenario where those bits of metal were not only involved in some dramatic collisions, but also Jupiter’s migration through our solar system.
The meteorites in question are known as CB chondrites, named for both their chemical properties and the fact that this group was first found near Bencubbin, Australia. While other meteorites have been found with plenty of iron, CB chondrites stand out thanks to how these tiny flecks of iron were first formed. To get this particular structure crystal structure, the iron must have been vaporized at some point, which is no easy task. The easiest way to get that done outside of a star was probably to have two objects hit each other, at speeds no less than 11 miles per second.
When the original asteroid collided with another object at these speeds, the shockwave probably produced enough energy and compression to heat and crush the iron into a supercritical fluid. The vaporized iron behaves like both a liquid and a gas, until it starts to cool into silicate-covered droplets. This all just leaves the question of how to get some asteroids up to these speeds, which brings us back to Jupiter.
Ambling though the asteroid belt
Simulations show that Jupiter’s gravity would have provided ample momentum to create the CB chondrites. Of course, for Jupiter to be near the asteroid belt where the meteorites came from, it would have had to be a bit closer to the Sun than it is now. This isn’t totally far fetched, as multiple models describing the early days of our solar system put the gas giant planets at points of origin different than their current orbits. In the case of this study, a model called the Grand Tack assumes that Jupiter first formed closer to the Sun than its current orbit, then moved closer still until the formation of Saturn started pulling it back out again. With all this traversing through the current asteroid belt, there would have been ample opportunity to send some asteroids flying, melting and vaporizing along the way.
Source: Stony meteorites reveal the timing of Jupiter’s migration by K.N. Smith, Astronomy Magazine