彩民宝典

Kevin Costner, eat your heart out. New research shows that the early Earth, home to some of our planet鈥檚 first lifeforms, may have been a real-life 鈥渨aterworld鈥濃�攚ithout a continent in sight. 听

The study, which , takes advantage of a quirk of hydrothermal chemistry to suggest that the surface of Earth was likely covered by a global ocean 3.2 billion years ago. It may even have looked a bit like the post-apocalyptic, and land-free, future imagined in Costner鈥檚 infamous film Waterworld.听

The group鈥檚 findings could help scientists to better understand how and where single-cell organisms first emerged on Earth, said Boswell Wing, a coauthor of the research.

鈥淭he history of life on Earth tracks available niches,鈥� said Wing, an associate professor in the Department of Geological Sciences at the 彩民宝典. 鈥淚f you鈥檝e got a waterworld, a world covered by ocean, then dry niches are just not going to be available.鈥�

The study also feeds into an ongoing debate over what ancient Earth may have looked like: Was the planet much hotter than it is today?

鈥淭here was seemingly no way forward on that debate,鈥� said lead author Benjamin Johnson, who conducted the research during a postdoctoral position in Wing鈥檚 lab at 彩民宝典. 鈥淲e thought that trying something different might be a good idea.鈥�

A crazy place

For him and Wing, that something different centered around a geologic site called the Panorama district located deep in Northwestern Australia鈥檚 outback.听

鈥淭oday, there are these really scrubby and rolling hills that are cut through by dry river beds,鈥� said Johnson, now an assistant professor at Iowa State University in Ames. 鈥淚t鈥檚 a crazy place.鈥�

It鈥檚 also the resting spot for a 3.2 billion-year-old chunk of ocean crust that鈥檚 been turned on its side.听

In the span of a day at Panorama, you can walk across what used to be the hard, outer shell of the planet鈥攁ll the way from the base of that crust to the spots where water once bubbled up through the seafloor via hydrothermal vents.听

The researchers saw it as one-of-a-kind opportunity to pick up clues about the chemistry of ocean water from billions of years ago.

鈥淭here are no samples of really ancient ocean water lying around, but we do have rocks that interacted with that seawater and remembered that interaction,鈥� Johnson said.

The process, he explained, is like analyzing coffee grounds to gather information about the water that poured through it. To do that, the researchers analyzed data from more than 100 rock samples from across the dry terrain.

They were looking, in particular, for two different flavors鈥攐r 鈥渋sotopes鈥濃�攐f oxygen trapped in stone: a slightly heavier atom called Oxygen-18 and a lighter one called Oxygen-16.

The duo discovered that the ratio of those two isotopes of oxygen may have been a bit off in seawater 3.2 billion years ago鈥攚ith just a smidge more Oxygen-18 atoms than you鈥檇 see today.

鈥淭hough these mass differences seem small, they are super sensitive,鈥� Wing said.

Lost at sea

Sensitive, it turns out, to the presence of continents. Wing explained that today鈥檚 land masses are covered by clay-rich soils that disproportionately take up heavier oxygen isotopes from the water鈥搇ike mineral vacuums for Oxygen-18.听

The team theorized that the most likely explanation for that excess Oxygen-18 in the ancient oceans was that there simply weren鈥檛 any soil-rich continents around to suck the isotopes up. That doesn鈥檛 mean, however, that there weren鈥檛 any spots of dry land around.

鈥淭here鈥檚 nothing in what we鈥檝e done that says you can鈥檛 have teeny, micro-continents sticking out of the oceans,鈥� Wing said. 鈥淲e just don鈥檛 think that there were global-scale formation of continental soils like we have today.鈥�

Which leaves a big question: When did plate tectonics push up the chunks of rock that would eventually become the continents we know and love?

Wing and Johnson aren鈥檛 sure. But they鈥檙e planning to scour other, younger rock formations at sites from Arizona to South Africa to see if they can spot when land masses first roared onto the scene.听

鈥淭rying to fill that gap is really important,鈥� Johnson said.听

For now, Costner may want to start planning the prequel.