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)

Residents carry a slaughtered pig with a bamboo pole as they walk home on a street, which was shut to traffic due to ice, in Leishan county, Guizhou province January 31, 2015. Blizzards and icy rain that lasted for several days at the end of January have disrupted traffic, collapsed houses and decimated crops in central Chinese provinces, Xinhua News Agency reported. (Photo by Reuters/Stringer)

A man, wearing a protective mask following an outbreak of the coronavirus disease (COVID-19), walks in Tokyo, Japan on March 17, 2020. (Photo by Edgard Garrido/Reuters)

Border guard officers, wearing masks against COVID-19 infection adjust their outfits before a distinguished service awards ceremony for employees of the interior ministry in Bucharest, Romania, Thursday, July 16, 2020. Romania has registered on Thursday the highest number of COVID-19 infection cases since the pandemic reached the country in February, 777 in a 24 hours interval, as many fail to observe the mandatory protection measures, like the use of a face mask indoors or maintaining social distancing. (Photo by Andreea Alexandru/AP Photo)

A dog from the K9 Division of the Sri Lanka Army’s Commando Regiment performs during an event to mark International Children’s Day at a school in Welisara, Colombo, Sri Lanka, 01 October 2016. Sri Lanka marks the Children's Day on 01 October with more emphasis on prevention of child abuse. (Photo by M.A. Pushpa Kumara/EPA)

A couple dance tango for tourists at Caminito, a touristic hotspot of La Boca neighborhood in Buenos Aires, Argentina, October 15, 2016. (Photo by Enrique Marcarian/Reuters)

A lone protester sings outside the offices of Republican president-elect Donald Trump at Trump Tower in New York, New York, U.S. November 14, 2016. (Photo by Carlo Allegri/Reuters)

A girl stands against strong wind caused by Typhoon Mangkhut at a pier on the waterfront of Victoria Habour Hong Kong, Sunday, September 16, 2018. Hong Kong and southern China hunkered down as strong winds and heavy rain from Typhoon Mangkhut lash the densely populated coast. The biggest storm of the year left at least 28 dead from landslides and drownings as it sliced through the northern Philippines. (Photo by Vincent Yu/AP Photo)