How hard did it rain on Mars?

Heavy rain on Mars reshaped the planet's impact craters and carved out river-like channels in its surface billions of years ago, according to a new study published in Icarus. In the paper, researchers from the Smithsonian Institution and the Johns Hopkins University Applied Physics Laboratory show that changes in the atmosphere on Mars made it rain harder and harder, which had a similar effect on the planet's surface as we see on Earth.