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.
Le Tuan Binh keeps his Moroccan soldier father’s tombstone at his village home north of Hanoi, a treasured reminder of a man whose community in Vietnam has been largely forgotten. Mzid Ben Ali, or “Mohammed” as Binh calls him, was one of tens of thousands of North Africans who served in the French army as it battled to maintain its colonial rule of Indochina. He fought for France against the Viet Minh independence movement in the 1950s, before leaving the military — as either a defector or a captive — and making a life for himself in Vietnam. “It’s very emotional for me,”
The Chinese Communist Party’s (CCP) Central Committee is to gather in July for a key meeting known as a plenum, the third since the body of elite decisionmakers was elected in 2022, focusing on reforms amid “challenges” at home and complexities broad. Plenums are important events on China’s political calendar that require the attendance of all of the Central Committee, comprising 205 members and 171 alternate members with Chinese President Xi Jinping (習近平) at the helm. The Central Committee typically holds seven plenums between party congresses, which are held once every five years. The current central committee members were elected at the
Indian Prime Minister Narendra Modi reaffirmed his pledge to replace India’s religion-based marriage and inheritance laws with a uniform civil code if he returns to office for a third term, a move that some minority groups have opposed. In an interview with the Times of India listing his agenda, Modi said his government would push for making the code a reality. “It is clear that separate laws for communities are detrimental to the health of society,” he said in the interview published yesterday. “We cannot be a nation where one community is progressing with the support of the Constitution while the other
CODIFYING DISCRIMINATION: Transgender people would be sentenced to three years in prison, while same-sex relations could land a person in jail for more than a decade Iraq’s parliament on Saturday passed a bill criminalizing same-sex relations, which would receive a sentence of up to 15 years in prison, in a move rights groups condemned as an “attack on human rights.” Transgender people would be sentenced to three years’ jail under the amendments to a 1988 anti-prostitution law, which were adopted during a session attended by 170 of 329 lawmakers. A previous draft had proposed capital punishment for same-sex relations, in what campaigners had called a “dangerous” escalation. The new amendments enable courts to sentence people engaging in same-sex relations to 10 to 15 years in prison, according to the