Key Points A 4.45 billion-year-old zircon grain from the Martian meteorite NWA7034 provided evidence of ancient water-rich fluids. Nano-scale geochemistry was used to detect elements indicating hydrothermal activity. The presence of water during early crust formation suggests Mars was potentially habitable. This finding enhanced our understanding of Mars’ ancient environment and its potential to support life. Recent research has uncovered compelling evidence of ancient hydrothermal activity on Mars, revealing that the planet may have been habitable billions of years ago....