21 years of 9/11: Plume of smoke rising above Twin Towers seen from space, NASA shares pic

To commemorate the 21st anniversary of the 9/11 terrorist attacks, in which hijacked planes crashed into the World Trade Center's twin towers, NASA tweeted a photo of New York City shot from space by one of its astronauts on Sunday. After two planes crashed into Manhattan's towers, astronaut Frank Culbertson snapped this view of the city's smoke plumes.

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On September 11, 2001, @NASA astronaut Frank Culbertson took this photo from the ISS of smoke rising from the Twin Towers in New York City. On this 21st anniversary of that terrible day, we honor the victims and heroes of the 9/11 terrorist attacks.

More: https://t.co/MpwLNcPoHq pic.twitter.com/gPg5vX06SM

— NASA History Office (@NASAhistory) September 11, 2022

"On this 21st anniversary of that terrible day, we honour the victims and heroes of the 9/11 terrorist attacks," the US space agency said in the social media post. "The attacks of Sept. 11, 2001, were a national tragedy that resulted in a staggering loss of life and a significant change in American culture. Each year, we pause and never forget," it said separately in a release.

NASA included a statement from American astronaut Frank Culbertson, who was the station's lone American resident at the time of the assaults, in their news release. He saw what seemed like a "odd bloom" in the photographed smoke and commented on it.

"It's horrible to see smoke pouring from wounds in your own country from such a fantastic vantage point. The dichotomy of being on a spacecraft dedicated to improving life on the earth and watching life being destroyed by such willful, terrible acts is jolting to the psyche, no matter who you are," he added. 

Two aircraft hit the World Trade Center in New York City, the Pentagon in Washington, DC, and a field in Pennsylvania on September 11, 2001. Nearly three thousand people were killed and countless more were wounded in the terrorist strikes.

On Sunday, US President Joe Biden laid a wreath at the Pentagon in a sombre observance of the 21st anniversary of the September 11 attacks.