A competitor walks on tightrope during a performance in Taizhou, Zhejiang Province, China, May 7, 2016. (Photo by Reuters/China Daily)

Soldiers of China's People's Liberation Army (PLA) jump as part of their winter training in temperature of negative 26 degrees Celsius at China's border with Russia in Heihe, Heilongjiang province, December 14, 2015. (Photo by Reuters/Stringer)

Jiff with Playboy Playmates arrives at the Playboy Super Bowl XLIX Party on Friday, January 30, 2015 in Scottsdale, Ariz. (Photo by Omar Vega/Invision/AP Photo)

An Afghan girl harvests Cotton buds at a field on the outskirts of Balkh province, Afghanistan, November 15, 2014. (Photo by Sayed Mustafa/EPA)

A woman dressed up as a zombie participates in a zombie walk in Stockholm, Sweden on August 19, 2017. (Photo by Jonathan Nackstrand/AFP Photo)

A man wearing an aquarium with goldfishes on his head walks among the pedestrians at the “Village de Saint-Malo”, the start point of the Route du Rhum solo sailing race, in Saint-Malo on November 1, 2022. The Route du Rhum solo sailing race starts on November 6, 2022, from Saint-Malo to Pointe-a-Pitre in Guadeloupe. (Photo by Loic Venance/AFP Photo)

A man strikes a pose in front of a giant torta, or sandwich, during a press conference to promote the 13th annual Torta Festival, in Mexico City, Wednesday, July 20, 2016. The five day festival presents a variety of the Mexican street food made from the most exotic ingredients that include ostrich or stingray, to the classic ham, grilled steak or slow cooked pork. The festival's purpose is to maintain the tradition of eating tortas, and promote the vendors of the Mexican sandwich. (Photo by Marco Ugarte/AP Photo)

The NASA Extreme Environment Mission Operations (NEEMO) 21 mission began on July 21 as an international crew of aquanauts splashed down to the undersea Aquarius Reef Base, located 62 feet below the surface of the Atlantic Ocean in the Florida Keys National Marine Sanctuary. The NEEMO 21 crew will perform research both inside and outside the habitat during a 16-day simulated space mission. During simulated spacewalks carried out underwater, they will evaluate tools and mission operation techniques that could be used in future space missions, including journeys to Mars. (Photo by Karl Shreeves/NASA)