Over the past several decades, researchers have come up with two possible — and competing — explanations of how this heavy water took up residence in our solar system.
The first is that it came from interstellar water ice that formed in the huge cloud of gas that gave birth to our sun and the solar system. Stellar nurseries can be found throughout the universe, and they are rich in both heavy water and regular water H20 , the researchers said.
The second possibility is that the violence and energy of star birth ripped apart that interstellar water, and its building blocks got reprocessed within the protoplanetary disk that would eventually coalesce into the planets and other heavenly bodies.
For the past several years, Cleeves has been trying to determine just how much energy was able to penetrate the cold, dense region of the planet-forming disks around stars. Using computer models, she and her colleagues concluded that the disk was certainly cold enough for heavy water to form.
But the gas would have been too dense to allow X-rays to enter, and the solar winds and magnetic fields would have had no trouble deflecting cosmic rays. But it would have been easy for cosmic rays to penetrate the gas cloud before it collapsed into the protoplanetary disk, she said. There, those rays could have helped heavy water get made. He said the paper successfully demonstrates that the young solar wind would have kept cosmic rays out of the disk entirely, making the chemistry inside too slow to produce heavy water.
Ted Bergin , an astronomer at the University of Michigan and co-author of the Science study, said the results suggest there may be an abundance of ancient water in young planetary systems throughout the universe. Most stars and their solar systems are formed in water heavy stellar nurseries similar to the one that birthed our sun. Science rules! Deborah Netburn is a features writer at the Los Angeles Times. She joined the paper in and has covered entertainment, home and garden, national news, technology and most recently, science.
To pin down the exact time of the arrival of Earth's water, the study team turned to analyzing meteorites thought to have formed at different times in the history of the solar system.
First, they looked at carbonaceous chondrite meteorites that have been dated as the oldest ones known. They formed around the same time as the sun, before the first planets. Next they examined meteorites that are thought to have originated from the large asteroid Vesta, which formed in the same region as Earth, some 14 million years after the solar system's birth. The team's measurements show that meteorites from Vesta have the same chemistry as the carbonaceous chondrites and rocks found on Earth.
This means that carbonaceous chondrites are the most likely common source of water. While the authors are not ruling out that some of the water that covers 70 percent of Earth today may have arrived later, their findings suggest that there was enough already here for life to have begun earlier than thought. Circling the sun between the orbits of Mars and Jupiter in the main asteroid belt, Vesta is the second largest asteroid known and has an ancient, battered surface.
For sky-watchers with binoculars, the magnitude 7. It is visible low in the southwestern sky after dusk, about 6 degrees above the bright orange star Antares, but only from a dark location.
For those stuck under light-polluted city skies, I recommend looking at the asteroid with a pair of binoculars or small telescope. Although you can easily see the asteroid with binoculars, a telescope will allow you to watch it move in front of a background of stars. With a help of the star charts above, steadily held binoculars, and some patience, you should be able to find distant Vesta, some million miles million kilometers away. Sky and Telescope's website has some printable sky charts for extra help.
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Water through time: Ices from the parent molecular cloud are incorporated into planet-forming disks around young stars, and eventually into the planets themselves. Already a subscriber? Want more? More From Discover. Recommendations From Our Store. Stay Curious. View our privacy policy.
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