This site is not maintained. Click here for the new website of Richard Dawkins.

What Created Earth's Oceans? Comet Offers New Clue

For the first time, astronomers have found water on a comet that's a chemical match for water on Earth, a new study says. The discovery backs up theories that water-rich comets helped fill ancient Earth's oceans.

Planet-formation models indicate that early Earth was much too hot to sustain liquid water on its surface, making the origin of Earth's oceans a mystery.

So scientists speculated that our planet's surface water came from comets that slammed into Earth once the planet had cooled.

This theory was dealt a serious blow in the 1980s, however, due to measurements of the ratio of normal to "semiheavy" molecules—the D/H ratio—in comet water.

In a semiheavy water molecule, one hydrogen atom (H) is replaced with a heftier version called deuterium (D). All water in nature has a D/H ratio, and since deuterium is a very stable atom, this ratio can go unchanged for eons.

Since the 1980s researchers have found that several comets in our solar system have D/H ratios that are very different from that of Earth's water.

Those results indicated that, at best, only about 10 percent of Earth's water could have come from comets, with the rest probably coming from water-rich asteroids, explained study leader Paul Hartogh, an astronomer at the Max Planck Institute for Solar System Research in Germany.

Read more

TAGGED: EARTH SCIENCES


RELATED CONTENT

Draining of world's aquifers feeds...

Damian Carrington - The Observer 3 Comments

"In the long run, I would still be more concerned about the impact of climate change, but this work shows that even if we stabilise the climate, we might still get sea level rise due to how we use water."

'Ring of fire' eclipse to begin

- - BBC News - Science & Environment 6 Comments

An "annular eclipse" will be visible from a 240 to 300km-wide swathe of Earth stretching from Asia across the Pacific to the western US on Monday.

Arctic melt releasing ancient methane

Richard Black - BBC News - Science &... 6 Comments

Scientists have identified thousands of sites in the Arctic where methane that has been stored for many millennia is bubbling into the atmosphere.

How much water is there on, in, and...

- - USGS Water Science for Schools 27 Comments

'Save the planet', science leaders urge...

Pallab Ghosh - BBC News - Science &... 35 Comments

No Love for Comet Wipeout

Sid Perkins - Science - AAAS.org 8 Comments

Did a comet wipe out woolly mammoths and an ancient Indian culture almost 13,000 years ago? Geologists have fiercely debated the topic since 2007. Now a new study says an extraterrestrial impact wasn't to blame, though the scientists who originally proposed the impact idea still aren't convinced.

MORE

MORE BY KER THAN

Gorilla Youngsters Seen Dismantling...

Ker Than - National Geographic News Comments

After a poacher's snare had killed one of their own, two young mountain gorillas worked together Tuesday to find and destroy traps in their Rwandan forest home

Human Ancestors Ate Bark—Food in Teeth...

Ker Than - National Geographic News Comments

Bits of food stuck in the two-million-year-old teeth of a human ancestor suggest some of our forebears ate tree bark, a new study says.

Elephants Took 24 Million Generations...

Ker Than - National Geographic News 15 Comments


Large mammals such as the black rhino (pictured) take longer to evolve than do small mammals.

Why Does Evolution Allow Some People to...

Ker Than - National Geographic News 33 Comments

Densest Matter Created in Big-Bang...

Ker Than - National Geographic News 40 Comments

"Besides black holes, there's nothing denser" we've seen, physicist says.

MORE

Comments

Comment RSS Feed

Please sign in or register to comment