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)

Devotees ride on the roof of a train as they return to the city after attending the final prayers on the first phase of Bishwa Ijtema in Dhaka January 11, 2015. Hundreds of thousands of pilgrims congregated in the Bangladeshi capital Dhaka as the first phase of this year's Bishwa Ijtema, one of the biggest Islamic gatherings in the world after the Haj in Saudi Arabia, came to an end. (Photo by Reuters/Stringer)

A boy plays in a swollen creek under a bridge in Manila on October 16, 2016. Typhoon Sarika lashed the main Philippine island of Luzon on October 16, flattening homes and toppling trees and power pylons as more than 12,000 people fled to safer ground, officials said. Shanties built beside a river, under a creek are the usual victims of floodings. (Photo by Noel Celis/AFP Photo)

A man dressed as a traditional character in the “Baile de Negras” dance poses for a picture on the feast day of the Virgin of the Candelaria (Candlemas) in the town of Diriomo, some 45 km from Managua, Nicaragua on February 2, 2017 Candlemas falls forty days after Christmas and is celebrated by Catholics as the presentation of Christ at the Temple. (Photo by Inti Ocon/AFP Photo)

Tibetan monks dressed as demons attend the Beating Ghost festival at the Yonghe Temple, also known as the Lama Temple, in Beijing on March 19, 2015. The Beating Ghost festival, or Da Gui festival in Chinese, is an important ritual of Tibetan Buddhism and is believed to expel evil spirits and shake off troubles. (Photo by Wang Zhao/AFP Photo)

Zoo keepers feed crocodiles in their enclosure at the Madras Crocodile Bank, closed due to the outbreak of coronavirus disease (COVID-19), in Mahabalipuram, India, August 3, 2020. (Photo by P. Ravikumar/Reuters)

An Indian Paramilitary soldier stands guard during snowfall in Srinagar, the summer capital of Indian Kashmir, 05 January 2021. Kashmir continues to witness medium to the heavy snowfall across all the areas for the third consecutive day, while traffic on the 300-kilometer long Srinagar-Jammu highway continues to be halted for the third day, the air traffic has also remained disturbed for the last two days with the majority of flights getting cancelled. The weather department has issued a weather advisory to hilly areas that is prone to avalanches. The department has also predicted moderate to heavy snowfall for next two days. (Photo by Farooq Khan/EPA/EFE)

The reflection of a man dressed as Hindu deity of death Yamaraj (R) to raise awareness about the coronavirus is seen on the wing mirror of a vintage car during a government-imposed nationwide lockdown as a preventive measure against the COVID-19 coronavirus, in Kolkata on April 24, 2020. (Photo by Dibyangshu Sarkar/AFP Photo)