Today’s Video of the Day from NASA explains why there are no rainbows on Mars. According to NASA scientist Mark Lemmon, even though there are water clouds in the planet’s atmosphere, rainbows need more than just the substance of water.
“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,” explained Lemmon.
“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.”
Lemmon says that 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.”
Video Credit: NASA