Even when Scott Kelly stopped talking, he spoke volumes.

"Houston as you know, today is Nasa's Day of Remembrance when we recognize, formally recognize, the sacrifices of the crew of the Apollo 1 fire, the Space Shuttle Challenger, and Space Shuttle  Columbia disasters," Scott Kelly — the New Jersey native who has spent more time in space than any other astronaut — said in a video shot from the International Space Station and posted to Twitter Thursday afternoon.

He continued:

"You guys are aware, today is the 30th anniversary of the Space Shuttle Challenger accident, so I'd like to just take a moment of silence and recognize the sacrifice of all those crew members, and how their spirit and their legacy lives on in our achievement in space."

As Kelly and other astronauts bowed their heads, so did the staff of Mission command, seen in the control room.

On Jan. 28, 1986, Space Shuttle orbiter Challenger broke apart just barely a minute into its flight. All seven crew members were killed as the Challenger disintigrated over the Atlantic Ocean.

Among those on board was Payload Specialist Christa McAuliffe, set to be the first teacher in space. The televised launch was broadly viewed, in large part because of McAuliffe's participation. The disaster resulted in a 32-month hiatus of the U.S. shuttle program.

According to the Associated Press, dozens of educators who competed alongside McAuliffe to become the first teacher in space gathered Thursday to remember her and the others lost to the disaaster .

"We felt we all wanted to be part of (the memorial)," said Connecticut semifinalist David Warner, who still teaches science, robotics and rocketry.

McAuliffe's son, Scott, 39, took part in the ceremony as well, the AP reported.

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