See the 9/11 'Interplanetary Memorial' NASA Sent to Mars Using Ground Zero Debris

Two shields made from remnants of the Twin Towers protect cables on two NASA rovers on Mars and serve as an interplanetary memorial to the events of 9/11.

According to the International Business Times, the rovers were outfitted with these aluminum shields -- each with an American flag -- to protect cables on the rovers, and were sent to the Red Planet in 2003, landing in 2004:

The tributes were made possible by Stephen Gorevan, the founder and chairman of Honeybee Robotics, which was based less than a mile away from the World Trade Center at the time of the Sept. 11 attacks.

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Through Gorevan's contacts, the team was able to acquire pieces of aluminum from the World Trade Center site on Dec. 1, 2011. The fragments came with a note from former Mayor Rudy Giuliani's office reading, "Here is debris from Tower 1 and Tower 2."

The rovers, which scientists say should be able to last on the dry planet for millions of years, aren't the only NASA tribute to 9/11, there were astronauts up there at the time who caught a rare view of the day's events.

Space.com has more:

The United States had one citizen off-planet on Sept. 11, 2001 — NASA astronaut Frank Culbertson, who was commanding the International Space Station at the time.

Culbertson had a bird's-eye view as the terror attacks on New York City's World Trade Center went down.

"I didn't know exactly what was happening, but I knew it was really bad, because there was a big cloud of debris covering Manhattan," Culbertson recalled in a NASA video marking the 9/11 anniversary. "It was like seeing a wound in the side of your country, of your family, your friends."

After 9/11, NASA scientists and its satellites helped find aerial contaminants near Ground Zero. Endeavor, which was launched later in 2011 as the first shuttle after 9/11, carried nearly 6,000 tiny American flags into space.