Mars is a cold, dry desert world with only a thin atmosphere. But four billion years ago, the planet was much warmer and wetter — an environment that would have been a comfortable abode for life.
Ancient Martian rocks may preserve a record of this milder climate, but no spacecraft has ever brought any of them back to Earth for analysis. Even so, scientists are studying Martian rocks in the laboratory: meteorites. Impacts by large asteroids kicked bits of the Martian crust into space, and a few of them have fallen to Earth. In fact, one recently discovered meteorite contains the oldest Martian minerals yet seen.
The meteorite landed in the Sahara Desert, and betrayed its Martian origin through the composition of gas found in tiny bubbles inside it.
The meteorite also contains tough minerals called zircons, which trap uranium. The uranium decays at a known rate, so scientists were able to deduce the age of the minerals: about 4.4 billion years. That means they formed a mere 150 million years after Mars itself did.
The Martian minerals are as old as the oldest known zircons on Earth and the Moon, suggesting the crusts of all three worlds formed at about the same time — not long after the birth of the solar system.
And Mars is putting in a good showing right now. The planet rises in late evening and shines like a bright orange star. It’ll get even brighter over the coming weeks as Earth moves closer to it.
More about the Red Planet tomorrow.
Script by Ken Croswell, Copyright 2013
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