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)

A couple of monkeys look from inside their cage at a rescue and rehabilitation center in Santiago, Chile, Saturday, November 22, 2014. Elba Munoz who runs the center, says that one of the goals of the Center for the Rescue and Rehabilitation of Primates is to stop the trafficking of the animals. (Photo by Luis Hidalgo/AP Photo)

In this undated photo made available by journal Nature on January 15, 2014, a northern bald ibis (Geronticus eremita) flies in Tuscany, Italy. A new study released Wednesday, January 15, 2014 says the birds choreograph the flapping of their wings, getting a boost from an updraft of air in the wake of the flapping wings by flying behind the first bird and off to the side. When a flock of birds take advantage of these aerodynamics, they form a V. (Photo by Markus Unsöld/AP Photo)

Monks dressed as Tibetan Buddhism characters attend a religious ceremony, known as “Da Gui” or beating ghost, to celebrate the upcoming Tibetan New Year which starts on March 1 at Yonghegong Lama Temple, in Beijing February 28, 2014. This Tibetan ceremony is held annually at the end of the first lunar month with mask dancing to expel ghosts, according to a press release. (Photo by Jason Lee/Reuters)

Elephants spray tourists with water in celebration of the Songkran water festival in Thailand's Ayutthaya province, about 80 km (50 miles) north of Bangkok, April 9, 2014. (Photo by Rungroj Yongrit/EFE)

Two Scottish shorthair cats dressed with red hats are pictured during a cat exhibition in Bishkek, on October 16, 2016. Cat lovers from Kyrgyzstan, Kazakhstan and Uzbekistan took part in the exhibition. (Photo by Vyacheslav Oseledko/AFP Photo)

In this February 26, 1962 file photo, Mercury astronaut John Glenn, and his wife, Annie, ride in the back of an open car with Vice-President Johnson during a parade in Glenn's honor in Washington. The Capitol is seen in the background. Glenn, the first American to orbit Earth who later spent 24 years representing Ohio in the Senate, died Thursday, Dec. 8, 2016, at the age of 95. (Photo by AP Photo)

A woman walks with her child past a Soyuz rocket, installed as a monument at the Russian leased Baikonur cosmodrome, the world's first and largest operational space launch facility, in Baikonur, Kazakhstan, Saturday, November 12, 2016. The new Soyuz mission to the International Space Station (ISS) is scheduled for Friday, Nov. 18. (Photo by Dmitri Lovetsky/AP Photo)