When NASA launched Opportunity and its twin Spirit in 2003, the mission team was aiming for a three-month journey on Mars. Both rovers fundamentally changed what we know about ancient Martian water, confirming that Mars once had long-standing liquid water on its surface. In Endeavour Crater, Opportunity discovered clay minerals, which form in milder water, further expanding the possible history of water on Mars. The last message from NASA’s Opportunity rover: an incomplete glimpse of the sky. The final attempt to contact Opportunity had failed, marking the close of a 15-year chapter in Mars exploration.