Join planetary scientist Beth Johnson as we explore a groundbreaking discovery from NASA's Curiosity rover on Mars. Scientists have identified siderite—a rare iron carbonate mineral—within ancient Martian rocks, offering new insights into Mars' once-thicker atmosphere and its now-lost carbon cycle. This discovery reshapes our understanding of the Red Planet's climate history and helps us draw powerful parallels to Earth's carbon processes. Dr. Ben Tutolo, associate professor at the University of Calgary and participating scientist on NASA's Curiosity rover team, explains that as Mars' atmosphere thinned over time, carbon dioxide was sequestered into rock formations, leading to a dramatic climate shift from a warm, wet environment to the cold, arid planet we see today. These findings provide evidence that ancient Mars was habitable and offer insights into the fragility of planetary climates. Dr. Tutolo emphasizes the parallels between Mars' atmospheric changes and current efforts on Earth to mitigate climate change by converting anthropogenic CO₂ into stable carbonates. Understanding the mechanisms of carbon sequestration on Mars could inform strategies to address climate challenges on our own planet. (Recorded live 5 June 2025.)