Earth Twinkles From Space, And Now We Know Why
Twinkle twinkle little... Earth? Yep, our planet does indeed sparkle from space—just like stars. But why? This question has perplexed many scientists for years, including famed astronomer Carl Sagan. That is, until now. In a May 2017 study, a team of NASA researchers explained the source of Earth's shimmer: horizontal ice.
All That Glimmers Is Ice
The globe's glitter was first mentioned by Sagan in his 1993 paper about the discoveries of the Galileo spacecraft. Sagan noticed that the shimmers appeared over the oceans, which makes sense, since the water's surface reflects light. But they were later documented by the Deep Space Climate Observatory (DISCOVR) satellite, a spacecraft tasked with keeping tabs on mass coronal ejections from the sun that began making observations in 2015. The DISCOVR images saw glimmer over land, as well.
It turns out that the common denominator wasn't bodies of water—it was wispy cirrus clouds full of ice crystals. Alexander Marshak, a NASA research scientist and lead author of the May 2017 study, explained how these glints work to the New York Times: when they're oriented just so, tiny ice particles floating high within clouds can reflect sunlight and give off a dazzling reflection. In a way, Sagan was correct when he pointed to water as the Earth's sparkling source—it's just that the water was frozen, and located many miles above the ocean.
Planets That Sparkle
It's worth noting that stars shimmer for a much different reason—it's due to the way our atmosphere refracts the light coming from them, showing us an ever-shifting light source. As far as planets go, however, this new discovery could mean big things in the search for other water-rich planets. If spacecraft like Galileo can see glints from our planet from that far away, we may be able to see the shimmer of ice crystals on alien worlds, as well.
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