The story began at a company called Honeybee Robotics, based in Lower Manhattan, that was tasked with manufacturing the drilling tools designed to allow NASA's Mars rovers to grind the surface layers off Martian rocks and analyze their composition.

Striving to complete their work before Spirit's and Opportunity's launch window in 2003, work at the company stopped abruptly at 8:46 a.m., on Sept. 11, 2001. That was when the hijacked American Airlines Flight 11 crashed into the North Tower, only a short distance from Honeybee. Seventeen minutes later, United Airlines Flight 175 collided with the South Tower.

The impact of the 9/11 attacks on the Twin Towers, the Pentagon and United Airlines Flight 93 in Pennsylvania reverberated around the world and changed the course of history.

In the weeks following the attacks, Steve Kondos, a JPL engineer working with Honeybee Robotics, suggested the twin rovers could become interplanetary memorials to remember those who died. Sure enough, after working with the New York Mayor's office, the team was able to acquire a piece of aluminum debris from the towers.

The material was then machined to become cable shields for the rock abrasion tools to be attached to the rovers. The American flag was then printed on the sides of the two cable shields (as seen in the photograph above).

"It's gratifying knowing that a piece of the World Trade Center is up there on Mars. That shield on Mars, to me, contrasts the destructive nature of the attackers with the ingenuity and hopeful attitude of Americans," said Stephen Gorevan, Honeybee founder and chairman, and a member of the Mars rover science team.