Zircon grains shed new light on Mars’ watery past

Artist's conception of a watery Mars.

NASA/Goddard Space Flight Center

It’s become clear in recent years that Mars had lots of water in its distant past. But that raises the question—when did Mars stop being so Earth-like? And what happened to cause the change?

One way to address such questions is by analyzing rocks from different times in the planet's history. While no samples from the red planet have ever been brought back, meteorites have landed on Earth that scientists identified as originating on Mars.

One such meteorite is called Northwest Africa (NWA) 7533. This dark, glossy meteorite originally formed some 4.43 billion years ago, not long after Mars itself finished accreting. And, crucially, it contains zircon grains, which provide clues to the planet’s past.