Famed meteorite reveals early water on Mars—and an early outer space bombardment

It was a tough fundraising pitch: Martin Bizzarro, a cosmochemist at the University of Copenhagen, needed some $500,000 to buy—and then grind up—material from one of the oldest and most valuable rocks in the world. Only this rock wasn’t originally from Earth. It came from Mars.

Bizzarro’s bet has now paid off handsomely. With just 15 grams of the 4.4-billion-year-old “Black Beauty” meteorite, discovered in 2011 in the western Sahara, his team has revealed a record of asteroid impacts and volcanic eruptions spanning nearly all of martian history.

One of the most surprising findings: After Mars underwent a pummeling early in its life, all went quiet—even during a time, nearly 4 billion years ago, when our Solar System was thought to have suffered a cataclysmic assault. That’s based on the ages of 51 zircon crystals found within the meteorite that likely formed under the extreme heat of an impact. The ages of the zircons largely cluster around 4.5 billion years ago—indicating a period of planetary assault—but the planet seems relatively calm after that, Bizzarro and colleagues report today in the Proceedings of the National Academy of Sciences.

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