THREE POTENTIAL EXPLANATIONS

Scientists have come up with numerous theories for why Ceres has lots of ammonia on its surface

Ceres formed in the asteroid belt

Maybe Ceres really is an oddball, forming in the asteroid belt and accumulating ammonia in a way that differentiated it from other neighbouring asteroids. But if so, why did the Sun not vaporise the ammonia?

Ammonia came from afar

It’s possible that materials from the outer Solar System found their way to Ceres over millions of years, bringing the ammonia to it. Somehow this activity would have centred on Ceres and bypassed the other objects in the asteroid belt.

Ceres moved in from elsewhere

The prevailing theory is that the dwarf planet formed in an orbit beyond Saturn, where ammonia could survive. It may have been one of thousands pulled in by Jupiter’s massive gravity, causing it to end up in orbit in the asteroid belt.