A 4.1-billion-year-old piece of Mars, found in the Sahara, says the young planet was wet

It was blasted off Mars by an impact, drifted through space for an age, and came down in the Sahara. The meteorite Teghaza 001 is 4.1 billion years old, chemically distinct from every other known Martian rock, and — say researchers including Lee Saper of NASA's Ames Research Center — it preserves a snapshot of early Mars when a thick atmosphere and liquid water made the planet potentially habitable. The conditions faded within Mars's first billion years. The rock cannot say whether anything lived there. But it proves the ingredients and the setting were real, written in stone older than almost anything on Earth.