Why can't it rain on Mars?

Why It Can't Rain on Mars Today

While Mars may look somewhat familiar with its dusty red plains and cloudy skies, one thing you won’t find there is rain. At least, not anymore. Scientists have uncovered strong evidence that liquid water once flowed across the Martian surface—carving canyons, shaping valleys, and leaving behind minerals that only form in water's presence. This suggests that long ago, Mars might have had a much thicker atmosphere and a warmer climate, possibly allowing for rainstorms similar to those on Earth.

But today, the Red Planet is a dry, frozen desert. Its atmosphere is less than 1% as dense as Earth’s, composed mostly of carbon dioxide. With such thin air, any liquid water on the surface quickly evaporates or freezes. For rain to happen, you need both moisture and atmospheric pressure—two things Mars currently lacks. Even if water vapor were present, the low pressure means it wouldn’t condense into clouds capable of producing rain.

There’s another issue: temperature. Mars averages around -60°C, far too cold for liquid water to remain stable. Any moisture in the air tends to freeze into ice crystals, forming frost or polar ice caps rather than clouds that bring precipitation.

Interestingly, Mars does have weather—clouds, fog, even snow. But the snow is typically made of carbon dioxide (dry ice) and sublimates before reaching the ground. So while ancient Mars might have seen gentle rainfalls shaping its landscape, today’s climate makes such a sight impossible. Our neighboring planet stands as a reminder of how delicate the balance of atmosphere, temperature, and water really is—something Earth still has, for now.