Step-by-step explanation:
The outside-in model is best supported by the NASA's DAWN mission sent in 2007, which found the evidence of water on Ceres and Vesta, the largest asteroids in the asteroid belt. Also scientists have discovered opals in meteorites which need water to form, another indication that water came from space rocks. Comets are made up of ice, gas and dust which shows that may be it came from comets.