# Do the terrestrial planets form later than gas giants in our solar system?

Sorry I forgot where this statements come from, but I also remember the reason behind it is due to young Jupiter moves inwards and destroys the original super earth in inner solar system, and the current terrestrial planets are formed after that, is that true?

• The argument for late formation of terrestrial planets, which I've heard, is that they must've formed after the Sun blew away the gasses from the protoplanetary disk, or else they would've become gaseous planets. The inner Solar System could've been gas-free while the outer planets still had gas to accrete, but it is maybe more confused in some exoplanetary systems. – LocalFluff Oct 27 '15 at 8:33
• @LocalFluff The gas was too hot to accrete in the inner part of the solar system. – Rob Jeffries Oct 27 '15 at 18:03

## 1 Answer

The current ideas are that both terrestrial planets and giant planets start their formation in a similar manner. Dust settles towards the mid-plane of a predominantly gaseous disk, starts to stick together and eventually small (km-sized) planetesimals are formed. This process may be quicker in the outer parts of the solar systems where the gas is colder and the condensed material (ices) is probably "stickier". The planetesimals then interact with each other gravitationally and can grow by merger. The rate of growth is controlled by their spatial densities and their relative velocities, but is thought to occur quite quickly in both the inner and outer parts of the solar system ($\sim$ 1-3 million years, e.g. Righter & O'Brien 2011).

Thereafter, the inner and outer parts of the solar system differ. The gas is cold enough in the outer parts of the solar system to accrete onto rocky cores and build giant planets on timescales of another few million years. In the inner solar system the gas is too hot to be accreted and instread the next tens of millions of years are characterised by high velocity collisions between planetary embryos and planetesimals. This indeed may be sculpted and influenced by the early migration inwards of Jupiter to about 1.5 au, followed by migration outwards - the so-called "Grand Tack model" (Raymond & Morbidelli 2014).

Overall it probably takes the inner solar system and terrestrial planets of order 100 million years to settle down into its final configuration. The collision that formed the moon may have been several tens of millions of years after the formation of the Sun and certainly long after the giant planets formed.