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Are There Rainbows on Mars? 
That's a great question.

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We Asked a NASA Scientist.

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There are water clouds in the thin atmosphere 
of Mars, so why not rainbows? You may have even

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seen an image from the Perseverance rover 
with an arc across the sky. That was not a

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rainbow; it was a lens flare. We saw that lens 
flare even in brightly lit laboratory images.

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Rainbows, as it turns out, need more than just 
water, the substance. In a rainbow, sunlight

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enters a spherical droplet, reflects off the 
back and comes back toward you. Unlike ice,

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liquid water droplets are made into spheres by the 
water's surface tension — it pulls itself together.

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Snow does not make rainbows because it has a\h
complex shape. Martian clouds are far below

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freezing. You do not get liquid droplets that can\h
make rainbows; there's just not enough water.

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The droplets are 20 times smaller across than a human\h
hair, 10 times smaller than Earth's cloud droplets,

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and far smaller than rain. They would have to be\h
more than 10 times bigger to make a rainbow

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with a thousand times more water. While there\h
aren't rainbows on Mars, there are many Earth-like

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weather phenomena. There are still clouds on Mars\h
when the season is right, both water ice like

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we have on Earth and clouds of dry ice carbon\h
dioxide. And there are dust devils, dust storms

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and winds that blow the clouds and dust around. So,\h
weather is still a big part of what the rovers are

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looking at on Mars. But I'm sorry to disappoint you.\h
Mars has some Earth-like weather, but no rainbows.