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)

Children attend a war safety awareness class conducted by civil defence members, in the rebel-controlled area of Maaret al-Numan town in Idlib province, Syria May 14, 2016. (Photo by Khalil Ashawi/Reuters)

A man is silhouetted in front of the Allianz-Arena as he walks his dogs at sunrise in Munich, southern Germany, Friday, April 10, 2015. (Photo by Peter Kneffel/AP Photo/DPA)

Clowns pose for a picture during the International Clown Day in Guadalajara, Mexico, on December 10, 2019. (Photo by Ulises Ruiz/AFP Photo)

Schoolchildren from local schools take part in the children's races prior to the annual Pancake race in Olney, Buckinghamshire, England, Tuesday, February 25, 2020. Every year women clad in aprons and head scarves from Olney and the city of Liberal, in Kansas, USA, run their respective legs of the race with pancakes in their pans. According to legend, the Olney race started in 1445 when a harried housewife arrived at church on Shrove Tuesday still clutching her frying pan with a pancake in it. (Photo by Alastair Grant/AP Photo)

A woman wearing a face mask as a precaution against the COVID-19 while using smartphone in a subway train in Hong Kong, Thursday, February 27, 2020. As the worst-hit areas of Asia continued to struggle with a viral epidemic, with hundreds more cases reported Thursday in South Korea and China, worries about infection and containment spread across the globe. (Photo by Kin Cheung/AP Photo)

Security grab a Just Stop Oil protester during day one of the second Ashes test match at Lord's, London on Wednesday, June 28, 2023. (Photo by Mike Egerton/PA Images via Getty Images)

Refugees and migrants try to find a place on an already full train headed for Serbia, near the city of Gevgelija, The Former Yugoslav Republic of Macedonia, on February 24, 2016. Refugees and migrants from Iraq and Syria continue to pass through Macedonia on their way to the European Union. (Photo by Georgi Licovski/EPA)