In 1997, NASA’s Mars Pathfinder mission made history by sending Sojourner, the first wheeled rover to operate on Mars. The tiny six-wheeled robot captured global attention by sending back photos, analyzing Martian rocks, and proving the value of autonomous planetary exploration. While Sojourner explored an ancient floodplain called Ares Vallis collecting evidence of past water and navigating rocks like “Barnacle Bill” its identical twin, Marie Curie, stayed behind at NASA’s Jet Propulsion Laboratory.
Marie Curie played a crucial but overlooked role. Engineers used it in large indoor sandboxes to simulate Martian terrain and practice remote operations, accounting for the communication delay between Earth and Mars. This allowed NASA to test safe paths, troubleshoot problems, and plan Sojourner’s daily movements. The rover’s success supported NASA’s “faster, better, cheaper” strategy, proving that smaller, lower-cost missions could still deliver major scientific results.
Although Sojourner became famous, Marie Curie continued to serve as a test vehicle and was later transferred to the Smithsonian’s National Air and Space Museum, where the public can see it today. Together, the twin rovers laid the groundwork for later missions such as Spirit, Opportunity, and Curiosity, shaping the future of planetary exploration.