From the Arizona desert, a fist-sized stone has quietly rewritten a chapter of planetary history. Known as Stardust Mine, this Martian meteorite — the first recovered on U.S. soil with a fully documented chain of custody — carries within its crystals evidence of volcanic processes on Mars that science had not previously imagined. Its chemically evolved magma and unexpectedly shallow crystallization depths remind us that the story of our solar system is still being told, one ancient rock at a time.