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NASA's SpaceX astronauts to bring back a very special flag from the ISS

"Nine years later," Elon Musk tweeted. The US flag flew on the first and last shuttle missions, and could only be claimed by a crew launched from Florida.

This flag will finally come home after flying on the first and last shuttle missions.

It's a game of capture the flag that's taken nine years and billions of dollars. NASA astronauts Bob Behnken and Doug Hurley will lay claim to a unique patriotic symbol that's been waiting for them on the International Space Station.

Behnken and Hurley arrived at the ISS on Sunday after Saturday's successful launch of the SpaceX Demo-2 mission. Perhaps the most important souvenir they'll bring back to Earth is a small American flag that traveled on both the first space shuttle mission (STS-1 in 1981) and the last (STS-135 in 2011). 

SpaceX seemed to telegraph its intentions to claim the flag way back in 2011 with a tweet: "SpaceX commencing flag capturing sequence..." SpaceX founder Elon Musk resurfaced the tweet on Sunday with a simple statement: "Nine years later."

SpaceX was locked in a race with Boeing, the other company involved in NASA's Commercial Crew Program, to reach the ISS first. Boeing is working through some technical issues with its Starliner crew capsule, so SpaceX was able to claim the prize.

NASA astronauts Bob Behnken, Doug Hurley and Chris Cassidy during a June 1 press conference. Hurley shows off the shuttle flag.

Video screenshot by Amanda Kooser/CNET

The flag has a special connection to Hurley, who was one of the final shuttle crew members who left the artifact on the ISS in 2011. 

In a press conference from orbit on Monday, Hurley said the flag represents the hard work of thousands of NASA and SpaceX people who helped to bring human launches back to US soil.

Hurley showed off the flag. It now bears a note from NASA astronaut Chris Cassidy, who was already on the ISS: "Do not forget to take with Crew Dragon." 

"We are lucky enough to be able to take it home with us," Hurley said.

The flag's journey isn't meant to end when it returns to our planet with Crew Dragon. 

"The flag will remain displayed on board the station until the next crew launched from the US retrieves it for return to Earth so that it can be carried by the first crew launched from the US on a journey of exploration beyond Earth orbit," said NASA in a 2011 statement about STS-135.  

That means the well-traveled flag could end up visiting the moon or even Mars one day. If NASA's ambitious 2024 moon plans work out, it may not have to wait long.