科学家发现上古之水，或含原始生命

STEVE INSKEEP, HOST: You know how people sometimes create a time capsule? They seal some things in a box and plan to open it generations later. Well, think of this as nature's time capsule, and the amount of time here is incredible. Scientists have discovered water that's been sealed away from the rest of the world for more than one billion years. It might contain the descendants of ancient microbes, and this discovery could tell us more about how life evolved on Earth, and maybe help us find life on other planets. NPR's Adam Cole reports.

ADAM COLE, BYLINE: The small town of Timmins, Ontario produced the golden voice of Shania Twain. The nearby mines produce thousands of pounds of golden gold. Deep in the Canadian bedrock, miners drill holes and collect samples. Sometimes they hit paydirt. Sometimes, they hit water. It seeps out from tiny crevices in the rock itself.

Recently, a team of scientists who had been investigating water from other mines approached the miners and asked them, very politely...

GREG HOLLAND: Can we please have some of these fluids that come out of these newly drilled boreholes?

COLE: That's Greg Holland, a geochemist at Lancaster University in England. He and his colleagues wanted to know just how long that fluid had been trapped in the rock. They looked at the decay of radioactive atoms found in the water and calculated that it had been bottled up for a long time.

HOLLAND: One-point-five billion years.

COLE: At least.

HOLLAND: That is the lower limit for the ages.

COLE: It could be a billion years older. That means the water was trapped in that rock before humans evolved, before pterodactyls, before multi-cellular life. As Holland announced this week in the journal Nature, this is the oldest cache of water ever found. But how did it end up underneath that gold mine in northeastern Canada? Where did it come from?

HOLLAND: The fluids that we see now are actually preservations of ancient oceans.

COLE: About 2.7 billion years before Shania Twain took the stage at a bar in Timmons, the neighborhood looked a bit different. On the prehistoric sea floor, magma was welling up between cracks. As it cooled and hardened, it trapped sea water inside the new rock, and that rock drifted around the globe for eons, helping form continents and mountain ranges. And all the while, it kept its cargo of water sealed up tight inside.

HOLLAND: It's managed to stay isolated for almost half the lifetime of the Earth.

COLE: It's a time capsule. And it doesn't just hold water.

HOLLAND: There's a lot of hydrogen in these samples.

COLE: And that's significant, because hydrogen is food for some microorganisms. Hydrogen-eating microbes have been found deep in the ocean and in South African mines. The hydrogen is produced by chemical reactions in the rock, so there's a steady supply of food.

HOLLAND: That could provide the energy for life to survive in isolation for two billion years.

COLE: If life is found in these samples - and Holland's colleagues are looking for it now - it would have evolved distinct from the surface world, and might give a unique insight into the earliest forms of life on Earth. Its discovery would also give hope to people searching for life in places that are even more remote.

CAROL STOKER: My specific job is focused on searching for life on Mars.

COLE: Carol Stoker is a research scientist with NASA.

STOKER: If you go back to the very early history of Earth and Mars, sort of the first billion years after the planets' surfaces cooled, Earth and Mars looked very similar.

COLE: They both had vast surface oceans and thick atmospheres. They were good places for life to begin. On Earth, it did.

STOKER: The logic is if that if that happened on Earth, why shouldn't it have happened on Mars?

COLE: As Mars got colder and drier, surface life would have died off. But Martian microbes might still survive deep in the planet's crust, preserved in isolated pockets of water, just like the ones found in Canadian bedrock. Adam Cole, NPR News.