Hemispheric color differences on Saturn's moon Rhea are apparent in this false-color view from NASA's Cassini spacecraft in this March 2, 2010 file photo. (Photo by Reuters/NASA/JPL/SSI)

A coach wipes away tears and comforts a girl who was feeling tired during gymnastics lessons at the Shanghai Yangpu Youth Amateur Athletic School in Shanghai, China, May 4, 2016. (Photo by Aly Song/Reuters)

A girl takes a nap during a Christmas eve mass at a Catholic church on the outskirts of Taiyuan, North China's Shanxi province, December 24, 2016. (Photo by Jason Lee/Reuters)

The sun rises beside St Mary's Lighthouse in Whitley Bay, Tyne and Wear, as the unseasonably cool weather continues on Thursday, April 28, 2016. (Photo by Owen Humphreys/PA Wire)

This photo taken on October 8, 2017 shows dancers posing in formation to celebrate the upcoming Party Congress, in Rongan in China' s southern Guangxi region. China will convene its 19 th Party Congress on October 18, state media said, a key meeting held every five years where President Xi Jinping is expected to receive a second term as the ruling Communist Party' s top leader. (Photo by AFP Photo/Stringer)

A visitor poses for a picture during Sao Paulo Fashion Week in Sao Paulo, Brazil, March 16, 2017. (Photo by Nacho Doce/Reuters)

Gymnasts from the Pyongyang Circus Theater perform during Mother's Day Monday, November 16, 2020, in Pyongyang, North Korea. (Photo by Jon Chol Jin/AP Photo)

Vlada Nikolchenko of Ukraine performs with the ribbon during the 36th European Rhythmic Gymnastics Championships in Kyiv, Ukraine, Sunday, November 29, 2020. Athletes from 23 countries participate in the championship in Kyiv. (Photo by Efrem Lukatsky/AP Photo)