Mars: clues to ancient water
Mars has a thin atmosphere dominated by carbon dioxide. Its valleys, lake deposits, and water-altered minerals show that conditions in the past differed from today’s cold, dry surface.
Evidence that a place once had water is not evidence that life definitely lived there. Scientists study geological context and test alternative explanations before making such a claim.
Wonder about this
Do signs of an ancient Martian lake prove there were Martian animals?
A science clue
No. They show past water and a potentially interesting environment, not confirmed life.