This Rare Meteorite Will Help Explain When Mars Went Dry

When it comes to understanding the planets in our solar system, scientists have to get creative, as they can't simply take a day trip to Mars. But sometimes, nature hands them a geological gift in the form of a meteorite, which gives researchers a tangible piece of evidence to study.

That's what scientists at the National High Magnetic Field Laboratory at Florida State University are doing with an ancient Martian meteorite known as Black Beauty. The result is new insight into the history of Mars' dramatic climate changes. A report on the new findings was published in Nature Geoscience.

Black Beauty, otherwise known as NWA (Northwest Africa) 7034, was discovered in the Sahara Desert. Munir Humayun, a professor from Florida State University, was on a team of scientist who subsequently looked at the zircon in meteorite to determine that the rock is about 4.4 billion years old, meaning it's about the same age as Mars and was likely formed at a time when Mars might have been able to sustain life.

In short, this rock holds secrets of "one of the most important epochs in the history of Mars," as Humayan told the BBC last year. Scientists have since looked at that zircon to unravel the story of ancient Mars' climate history.

Zircons forms on Earth when lava cools, and are highly durable. Because they contain uranium, they can be used to tell geologic time. Zircons also contain oxygen, and since oxygen exists on Mars the same way it does on Earth — it's in the atmosphere as carbon dioxide, molecular oxygen and ozone, and also exists as water ice—oxygen isotopes trapped in zircons can lend insight into Martian history.

When water vapor in Mars' atmosphere condenses into the Martian soil, it interacts and exchanges oxygen isotopes with zircons in the soil. And because of its thinner atmosphere, ultraviolet light from the Sun shifts the proportions of oxygen isotopes on the planet. That means that the sunlight affects the water locked in the Martian soil and at the same time leaves a time stamp in the zircons. It's effectively a dated record of climate changes on Mars.

"First we learned that, about 4.5 billion years ago, water was more abundant on Mars, and now we've learned that something dramatically changed that," said Humayun in a statement. "Now we can conclude that the conditions that we see today on Mars, this dry Martian desert, must have persisted for at least the past 1.7 billion years. We know now that Mars has been dry for a very long time."

Having a clearer idea of how and when Mars' climate changed will ultimately help scientists answer the big question of whether ancient Mars was ever habitable.