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Are There Rainbows on Mars? We Asked a NASA Scientist: Episode 20

Are there rainbows on Mars? Sadly no. But there are a whole lot of other conditions on Mars that we have right here on Earth! NASA scientist Mark Lemmon explains why the Red Planet is a rainbowless world. 

That’s a great question. There are water clouds in the thin atmosphere of Mars, so why not rainbows? You may have even seen an image from the Perseverance rover with an arc across the sky. That was not a rainbow; it was a lens flare. We saw that lens flare even in brightly lit laboratory images.

Rainbows, as it turns out, need more than just water, the substance. In a rainbow, sunlight enters a spherical droplet, reflects off the back and comes back toward you. Unlike ice, liquid water droplets are made into spheres by the water’s surface tension — it pulls itself together. Snow does not make rainbows because it has a complex shape. Martian clouds are far below freezing. You do not get liquid droplets that can make rainbows; there’s just not enough water.

The droplets are 20 times smaller across than a human hair, 10 times smaller than Earth’s cloud droplets, and far smaller than rain. They would have to be more than 10 times bigger to make a rainbow with a thousand times more water. 

While there aren’t rainbows on Mars, there are many Earth-like weather phenomena. There are still clouds on Mars when the season is right, both water ice like we have on Earth and clouds of dry ice carbon dioxide. And there are dust devils, dust storms and winds that blow the clouds and dust around. So, weather is still a big part of what the rovers are looking at on Mars. But I’m sorry to disappoint you. Mars has some Earth-like weather, but no rainbows. Get more Martian science:


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Last Updated
Nov 17, 2023
Tricia Talbert