A man photographs the main engines of the space shuttle orbiter Discovery on display at the Udvar-Hazy Smithsonian National Air and Space Annex Museum in Chantilly, Virginia August 28, 2015. Shuttle Discovery had 27 years of service and flew 39 times before being retired in 2011. (Photo by Gary Cameron/Reuters)

An employee of the National Park Service takes a selfie with President Barack Obama, left, in the background meeting with the crowd after a tour of Everglades National Park on Earth Day, Wednesday, April 22, 2015, in Florida. Obama used the visit to warn of the damage that climate change is already inflicting on the nation's environmental treasures. (Photo by Lynne Sladky/AP Photo)

The New World porcupine, family Erethizontidae, 1280 Gram born at 11 April 2015 Inventory in Zoo. Counting trade Fairs Weighing the Zoo is at 7 May 2015 too the 108 Birthday Zoo Hagenbeck Hamburg, Germany. (Photo by Imago/ZUMA Wire)

The Jet Propulsion Lab team's RoboSimian robot turns on a valve at a simulated disaster-response course during day one of the Defense Advanced Research Projects Agency (DARPA) Robotics Challenge finals in Pomona, California, June 5, 2015. (Photo by David McNew/Reuters)

Government officials in protective suits carry a mock coffin as they walk around a busy intersection during a coronavirus awareness campaign to remind people of the risk of contracting COVID-19 and to always obey health protocols to curb the spread of the outbreak in Jakarta, Indonesia, Friday, August 28, 2020. (Photo by Dita Alangkara/AP Photo)

People wearing face masks to help curb the spread of the coronavirus enjoy a social dance at a public park in Beijing, Tuesday, January 12, 2021. Lockdowns have been expanded and a major political conference postponed in a province next to Beijing that is the scene of China's most serious recent COVID-19 outbreak. (Photo by Andy Wong/AP Photo)

Farmers take a break for lunch while celebrating National Paddy Day, also called Asar Pandra, that marks the commencement of rice crop planting in paddy fields as monsoon season arrives, in Kathmandu, Nepal, June 29, 2020. (Photo by Navesh Chitrakar/Reuters)

A restaurant worker wearing a mask cleans the windows as the restaurant reopens amid the COVID-19 pandemic in Sao Paulo, Brazil, Monday, July 6, 2020. Bars, restaurants and beauty salons were allowed to re-open Monday after over three months of quarantine, and are required to observe preventative measures and reduced operating hours only during the day. (Photo by Andre Penner/AP Photo)