By the time Spirit and Opportunity made Time’s “What’s Next” list in 2003, the pair were already millions of miles into their journey to Mars. Earth’s grounded citizens already had been dazzled by the journey of Sojourner, a much smaller rover that ventured to Mars in 1997. But Sojourner was a test run for its larger siblings. Spirit and Opportunity were well equipped to bring back a plethora of scientific information about the planet that once inspired popular visions of little green people.