The final days of NASA’s Spirit rover on Mars marked the end of a historic mission that lasted 344 Martian days, or sols. When Spirit first entered Mars’ atmosphere, the world watched as it crashed into the red planet’s vast desert at over 19,500 km/h. Despite facing major challenges early on with both software and hardware, Spirit far exceeded its original 90-sol life expectancy. The rover went on to send thousands of images of Mars, as well as evidence supporting the existence of water on the planet.
In the last episode, we saw Spirit climbing Husband Hill, eager to uncover the secrets beneath Mars’ surface and achieve its ambitious mission goals. I’m Alex McColgan, and today we continue Spirit’s journey as it reaches the top of Husband Hill, pushing beyond NASA’s expectations. We’ll revisit Spirit’s significant discoveries and follow its path all the way to the end. This is a tale of scientific discovery and adversity, one that still inspires us today, two decades later.
Spirit’s first anniversary on Mars was marked by a study of a rock named “Champagne” on Husband Hill’s slopes. While Spirit celebrated alone with its science payload, it made groundbreaking measurements using tools like the Rock Abrasion Tool (RAT), the microscopic imager (MI), the alpha particle X-ray spectrometer (APXS), and the Mössbauer spectrometer (MB).
Though Spirit’s team discovered a small electrical short, it didn’t affect the rover’s daily operations. The team carefully navigated Spirit up increasingly challenging slopes, mindful of dust accumulating on its solar panels, reducing energy. Along the way, Spirit studied rocks like Peace and Alligator, before imaging Mars’ largest moon, Phobos, which is destined to collide with Mars in 10 million years.
Spirit’s journey took an unexpected turn when it discovered Paso Robles, a soil area rich in salt and phosphorus. NASA speculated that water had played a role in shaping the area, a significant clue in understanding Mars’ hydrological history. Spirit continued its trek, even overcoming a malfunctioning front wheel by reversing to reduce strain.
After reaching Larry’s Lookout, Spirit captured an impressive panorama on sol 413, revealing the distant summit of Husband Hill. A Mars dust devil swept over the rover on sol 421, clearing dust from its solar panels and improving efficiency, which helped it climb toward the hill’s summit. Spirit’s energy boost allowed it to send data more frequently, keeping its mission going strong.
By sol 581, Spirit reached the first summit of Husband Hill, but it didn’t stop there. The rover took a detailed 360º panorama, imaging Mars’ moons and helping calibrate measurements with Hubble. Despite growing older, Spirit adapted, with software updates that enabled it to operate autonomously. Even as Spirit encountered a challenging choice between analyzing rocks named “Comanche” and “Miami,” it ultimately chose Comanche, which revealed surprising levels of magnesium iron carbonates—an important discovery for understanding Mars’ potential to harbor life.
Spirit pressed on and eventually reached Home Plate on sol 744, an area with weathered rocks that suggested past water flow. However, by March 2006, a wheel failure forced Spirit to drag itself across Mars’ surface, slowing progress. With winter approaching, NASA chose Low Ridge Haven as Spirit’s temporary resting place to maximize energy capture through solar panels.
In the following months, Spirit made more discoveries, including two suspected iron meteorites, Zhong Shan and Allan Hills, before a surprising find: silica deposits in the Martian soil. These deposits were linked to environments conducive to microbial life on Earth. Despite the malfunctioning wheel, Spirit continued its research, making crucial discoveries that would otherwise have gone unnoticed.
Spirit’s ability to function improved after a cleaning event in 2007, boosting its power generation. Later that year, it captured a remarkable panorama of the Martian landscape, which gained attention for its eerie resemblance to a humanoid figure—nicknamed “Little Bigfoot.” But Martian storms began to worsen, and the rover’s energy levels decreased.
By April 2009, Spirit was experiencing memory gaps, and by sol 1892, it got stuck in soft soil, marking the beginning of its final days. Despite efforts to free it, Spirit remained immobile, and NASA reclassified its mission as a stationary research platform. Over the next months, the rover continued to study the Martian atmosphere and take images, including its last panorama. But as winter approached again, Spirit’s energy dwindled to critical levels.
In its final moments, Spirit continued to perform research, but by sol 2208, it suffered a low-power fault. The rover quietly came to a rest at Troy, marking the end of a mission that lasted 2088 sols and covered 7.7 kilometers. Spirit transmitted over 128,000 images and achieved its goals of advancing our understanding of Mars’ history of water and the potential for life.
Spirit’s legacy lives on in asteroid 27452 Spirit, and its memory is carried by NASA’s Perseverance rover today. Spirit’s story is one of resilience—just as the rover and its twin, Opportunity, overcame challenges, so too did Sofi, the seven-year-old who named them. Spirit’s final moments were lonely, but its mission was a triumph. As the rover’s internal heaters shut down, its journey came full circle with Sofi’s words: “It was dark and cold and lonely. At night, I looked up at the sparkly sky and felt better. I dreamed I could fly there.”
