On January 25, 2004, NASA's Opportunity rover landed on Mars!

This was the second of NASA's twin Mars Exploration Rovers to land on the red planet. Its counterpart, the Spirit rover, arrived just three weeks earlier. Opportunity is now the longest-running Mars rover mission. It was only intended to last 90 days, but the rover has been trekking around the Red Planet for more than 50 times its expected lifetime. Over the years, Opportunity has found meteorites on Mars, observed dust storms and looked for clues about the presence of water in Mars' ancient past.