The US Army parachute team Golden Knights perform during the opening ceremony of the 50th anniversary of the Apollo 11 moon landing at Space Center Houston in Texas, the United States, July 20, 2019. (Photos:Qiu Ma/Xinhua)

People visit the mission control room during the 50th anniversary of the Apollo 11 moon landing at Space Center Houston in Texas, the United States, July 20, 2019.

Visitors look at the gravity simulator during the 50th anniversary of the Apollo 11 moon landing at Space Center Houston in Texas, the United States, July 20, 2019.

Visitors select souvenirs during the 50th anniversary of the Apollo 11 moon landing at Space Center Houston in Texas, the United States, July 20, 2019.