Water covers 70 percent of the Earth’s surface and is crucial to life, but how it got here has been a longstanding scientific debate.
The puzzle was a step closer to being solved on Thursday after a French team reported in the journal Science they had identified which space rocks were responsible, and suggested our planet has been wet ever since it formed.
Cosmochemist Laurette Piani, who led the research, said the findings contradicted the prevalent theory that water was brought to an initially dry Earth by far-reaching comets or asteroids.
According to early models for how the solar system came to be, the large disks of gas and dust that swirled around the sun and eventually formed the inner planets were too hot to sustain ice.
This would explain the barren conditions on Mercury, Venus and Mars — but not the Blue Planet, with its vast oceans, humid atmosphere and well-hydrated geology.
Scientists therefore theorized that the water came along after, and the prime suspects were meteorites known as carbonaceous chondrites that are rich in hydrous minerals.
The problem was that their chemical composition does not closely match Earth’s rocks.
The carbonaceous chondrites also formed in the outer solar system, making it less likely they could have pelted the early Earth.
Another group of meteorites, called enstatite chondrites, are a much closer chemical match, containing similar isotopes of oxygen, titanium and calcium.
This indicates they were Earth’s and the other inner planets’ building blocks.
However, because these rocks formed close to the sun, they had been assumed to be too dry to account for Earth’s rich reservoirs of water.
To test whether this was true, Piani and her colleagues at Centre de Recherches Petrographiques et Geochimiques used a technique called mass spectrometry to measure the hydrogen content in 13 enstatite chondrites.
The rocks are now quite rare, making up only about 2 percent of known meteorites in collections, and it is hard to find them in pristine, uncontaminated condition.
The team found that the rocks contained enough hydrogen in them to provide Earth with at least three times the water mass of its oceans — and possibly much more.
They also measured two isotopes of hydrogen, because the relative proportion of these is different from one celestial object to another.
“We found the hydrogen isotopic composition of enstatite chondrites to be similar to the one of the water stored in the terrestrial mantle,” Piani said, comparing it to a DNA match.
The isotopic composition of the oceans was found to be consistent with a mixture containing 95 percent of water from the enstatite chondrites — more proof these were responsible for the bulk of Earth’s water.
The authors further found that the nitrogen isotopes from the enstatite chondrites are similar to Earth’s — and proposed these rocks could also be the source of the most abundant component of our atmosphere.
Piani added that research does not exclude later addition of water by other sources like comets, but indicates that enstatite chondrites contributed significantly to Earth’s water budget at the time it formed.
The pitch is a classic: A young celebrity with no climbing experience spends a year in hard training and scales Mount Everest, succeeding against some — if not all — odds. French YouTuber Ines Benazzouz, known as Inoxtag, brought the story to life with a two-hour-plus documentary about his year preparing for the ultimate challenge. The film, titled Kaizen, proved a smash hit on its release last weekend. Young fans queued around the block to get into a preview screening in Paris, with Inoxtag’s management on Monday saying the film had smashed the box office record for a special cinema
CRITICISM: ‘One has to choose the lesser of two evils,’ Pope Francis said, as he criticized Trump’s anti-immigrant policies and Harris’ pro-choice position Pope Francis on Friday accused both former US president Donald Trump and US Vice President Kamala Harris of being “against life” as he returned to Rome from a 12-day tour of the Asia-Pacific region. The 87-year-old pontiff’s comments on the US presidential hopefuls came as he defied health concerns to connect with believers from the jungle of Papua New Guinea to the skyscrapers of Singapore. It was Francis’ longest trip in duration and distance since becoming head of the world’s nearly 1.4 billion Roman Catholics more than 11 years ago. Despite the marathon visit, he held a long and spirited
CARTEL ARRESTS: The president said that a US government operation to arrest two cartel members made it jointly responsible for the unrest in the state’s capital Mexican President Andres Manuel Lopez Obrador on Thursday blamed the US in part for a surge in cartel violence in the northern state of Sinaloa that has left at least 30 people dead in the past week. Two warring factions of the Sinaloa cartel have clashed in the state capital of Culiacan in what appears to be a fight for power after two of its leaders were arrested in the US in late July. Teams of gunmen have shot at each other and the security forces. Meanwhile, dead bodies continued to be found across the city. On one busy street corner, cars drove
‘DISAPPEARED COMPLETELY’: The melting of thousands of glaciers is a major threat to people in the landlocked region that already suffers from a water shortage Near a wooden hut high up in the Kyrgyz mountains, scientist Gulbara Omorova walked to a pile of gray rocks, reminiscing how the same spot was a glacier just a few years ago. At an altitude of 4,000m, the 35-year-old researcher is surrounded by the giant peaks of the towering Tian Shan range that also stretches into China, Kazakhstan and Uzbekistan. The area is home to thousands of glaciers that are melting at an alarming rate in Central Asia, already hard-hit by climate change. A glaciologist, Omarova is recording that process — worried about the future. She hiked six hours to get to