Scientists proposed a new theory about the origin of oceans on Earth.科学家就地球上海洋的来源提出了一项新理论。They suggested that comets played a key role in delivering the life-enabling water to our planet billions of years ago.The study published in the latest journal Astronomy and Astrophysics Letters showed that water in many comets may share a common origin with Earths oceans.The worlds largest airborne observatory1 SOFIA operated by the U.S. space agency NASA found that Comet Wirtanen, as it made its closest approach to Earth in December of 2018, contains ocean-like water.SOFIA, the Stratospheric Observatory for Infrared2 Astronomy, is a Boeing 747 jetliner modified to carry a 2.7-meter diameter telescope, according to NASA.Observing at high altitudes above much of the Earths atmospheric3 water allowed the telescope to accurately4 measure the ratio of regular to heavy water in Comet Wirtanen. The regular water is H2O, while the heavy water is called HDO, which has an extra neutrally-charged particle called a neutron5 inside one of the hydrogen atoms.The data showed that Comet Wirtanens water ratio is the same as the Earths oceans, according to the study.Comparing the new data with previous studies of comets, the scientists found the ratio of regular to heavy water was not linked to the origin of the comets, for example, whether they were from the Kuiper Belt or the outer fringe of the solar system.Instead, the ratio was related to how much water was released from ice grains in the comets coma6 compared to directly from the snowy surface, implying that all comets could have a heavy-to-regular water ratio similar to Earths oceans.If comets have the same ratio of these water types as Earths oceans, it indicates that the water in both may share a common origin, according to the researchers.
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1 observatory n.天文台，气象台，瞭望台，观测台 参考例句： Guys house was close to the observatory.盖伊的房屋离天文台非常近。 Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的员工们天天对大钟检查两次。
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