This artist’s impression shows how Mars may have looked about four billion years ago.

The young planet Mars would have had enough water to cover its entire surface in a liquid layer about 140 metres deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere, and in some regions reaching depths greater than 1.6 kilometres.

Category: Astronomy, Solar System, Planetary science
Running time:
 1 min
Released in: 2015
Suitable for: KS2, KS3, KS4, KS5, Adults