Does Uber-Ancient Earth Water Mean Life Started Earlier?

Just 14 million years after the start of the solar system, Earth and the rest of the inner planets were inundated with water, setting back the clock for when life could have evolved, a new study shows.

Analysis of meteorites from the mini-planet Vesta, located in the main asteroid belt between Jupiter and Mars, show hydrogen isotope ratios that match what has been found in ancient, unaltered meteorites known as carbonaceous chrondrites.

Scientists already had a match between the chemical fingerprints of Earth’s hydrogen and the carbonaceous chrondites, but what they didn’t know is when the water would have been available to accrete into Earth.

The new analysis pushes water’s first appearance in Vesta and presumably on other rocky, planet-like bodies including Earth to just 14 million years after the start of the solar system.

“All the the planets could have gotten their water very early, which means the planets could have been habitable immediately after they formed. They weren’t just sitting there and looking at their watch, waiting for water to come,” Adam Sarafian, a geophysics doctorate student at the Woods Hole Oceanographic Institution in Massachusetts, told Discovery News.

Water is necessary for life as we know it.

Geologic activity on Earth has destroyed the earliest records of the planet’s formation, with its oldest rocks dating back to about 200 million years after the formation of the solar system some 4.6 billion years ago.

Analysis of rocks from the moon, retrieved during the 1969-1972 Apollo missions, show water was available in the inner solar system about 150 million years after the solar system’s formation.

The Vesta meteorites, known as eukrites, date back to 14 million years after the start of the solar system. Sarafian and collegues measured a mineral called apatite in the samples to determine their water content.

“This is the oldest water that anyone has measured that has accreted to something that resembles a planet,” Sarafian said.

The scientists plan additional studies on an ever rarer group of meteorites called angrites that date back to just 2 million years after the formation of the solar system.

The findings aren’t at odds with the idea that comets delivered water to Earth, said astronomer Donald Brownlee, with the University of Washington, the lead researcher in NASA’s Stardust comet sample return mission.

“The early solar system contained tens of Earth masses of materials that could be considered carbonaceous chondrites or comets -- they were the most common planetesimals in the solar nebula. Almost all of them are gone, but surely there were great numbers of comets that formed close enough to the sun to have (hydrogen isotope) ratios similar to carbonaceous chondrites and Earth,” Brownlee wrote in an email to Discovery News.

“Many people consider (comets and carbonaceous chrondites) to be quite different beasts, but I am more impressed with how similar they are to each other. Surely there was a continuum of rocks that were identical to carbonaceous chondrites and rocks (planetesimals) that contained very low temperature ices and would be considered comets,” he said.

Read more at Discovery News