Long ago, Mars changed from a warm, wet planet into the cold, dry planet it is today. Scientists study the sedimentary layers of Victoria crater, for evidence of water evaporation. One possible explanation for the climate change is that Mars suffered a massive collision with an asteroid, which removed some of Mars's atmosphere and shut down its dynamo (which powered the planetary magnetic field). The lack of a global magnetic field allowed the solar wind to strip the atmosphere away. The animation in this video exaggerates the possible impact for dramatic effect.
Find out more here.