What geological sample provides the oldest, most compelling proof of water on Mars?

Answer

Zircon crystals unearthed from Martian meteorites

Zircon crystals are the most compelling current candidate for the oldest proof because they act as durable time capsules, preserving the chemical conditions present when they crystallized deep within the planet.

What geological sample provides the oldest, most compelling proof of water on Mars?

#Videos

Ancient hot water on Mars points to habitable past - YouTube

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