New York City Mayor Michael Bloomberg gets on a custom made World Trade Center inspired motorcycle in front of the 9/11 Memorial Preview Site on October 5, 2011 in New York City. The motorcycle was designed by Paul Teutul Jr. of the television show “American Chopper” and was built to commemorate the rebuilding of the World Trade Center Site. Another motorcycle, nearly identical to the one unveiled, will also be built by Paul Jr. and raffled to raise money for the 9/11 Memorial. (Photo by Spencer Platt/Getty Images)

Astronaut Edwin E. Aldrin Jr. walks near the Lunar Module during the Apollo 11 extravehicular activity July 20, 1969 on the Moon. (Photo by NASA/Newsmakers)

Samba dancers arrive to perform ahead of the athletics competitions of the 2016 Summer Olympics at the Olympic stadium in Rio de Janeiro, Brazil, Sunday, August 14, 2016. (Photo by Jae C. Hong/AP Photo)

Sally Gomez drives to rescue of friend Michele Moore in flooded parking lot at Hyannis, Mass., September 9, 1969, after torrential rains of Hurricane Gerda flooded low areas of Cape Cod. Ann Davis of Osterville stands up in roof opening to lend a hand. Sally and Michele are from Centerville on the Cape. (Photo by Frank C. Curtin/AP Photo)

Leon Samson, 24-year-old showman, grimaces as an automobile is driven across his chest at Perth, Australia on October 9, 1960. Samson said the towel on his chest is to prevent the wheel from tearing his flesh. (Photo by AP Photo)

Puerto Rico's Grace Claxton warms up before competing in the Women's 400m Hurdles Round 1 during the athletics event at the Rio 2016 Olympic Games at the Olympic Stadium in Rio de Janeiro on August 15, 2016. (Photo by Jewel Samad/AFP Photo)

“NASA's Mars rover Opportunity just celebrated its ninth anniversary on Mars – a mission that was originally meant to last just 90 days...” – The Atlantic. Photo: NASA's rover Opportunity visits Victoria Crater, viewed from orbit by the High Resolution Imaging Science Experiment on NASA's Mars Reconnaissance Orbiter in october of 2006. Opportunity is a small dot on the crater's lip, at top right. Opportunity first reached the crater's rim on September 27, 2006. (Photo by NASA/JPL-Caltech/University of Arizona via The Atlantic)

Metropolitan Transit Authority (MTA) Police Officer Keith Flood trains with his K-9 partner Doc, a German Shepherd, inside the “warehouse room” at the new MTA Police Department Canine Training Center in Stormville, New York, U.S., June 6, 2016. (Photo by Mike Segar/Reuters)