Martian rocks photographed by the robotic Spirit rover in 2006 as it rolled across Mars. Photo: Mars Exploration Rover Mission, Cornell, JPL, NASA
Was There Life On Mars?

Martian space rocks tend to be very old. Shergottites, though, are generally thought to be remarkably young. Most scientists believe they were formed by volcanoes about 150 to 250 million years ago. ######

If so, shergottites are a sign that Mars might have had volcanoes not too long ago. And that means it might have been friendly to some form of life, said planetary geochemist Munir Humayun.

But some people believe that shergottites are actually about 4 billion years old. If this turned out to be true, scientists would have to change the way they think about life on Mars. ###### However, "if there hasn't been [volcanic activity in] 4 billion years, ... it would be very difficult to believe there was life left on Mars."

To settle the question, researchers examined a meteorite known as Northwest Africa 5298. They looked at very tiny deposits within it called baddeleyites. These tough, zirconium-rich minerals are "10 times smaller than the diameter of a human hair," said geochemist Axel Schmitt.

A Tiny Rock Might Have The Answer

###### But if a big crash or explosion melts the rock down, that evidence gets erased.

That's why scientists picked the tiny baddeleyites: They are hard little minerals. It's not easy to melt them down. By looking at the radioactive uranium and lead in this tough rock, the scientists found that it formed sometime around 187 million years ago. ######

The scientists could also see that the meteorite had been damaged. This had been caused by whatever sent it shooting off the Martian surface around 22 million years ago. The shock had muddled up the minerals inside, though the chemicals themselves were mostly unchanged.

The result was something like shaking up a sealed box of chocolates." ###### ]]>