Early in its history, Earth’s oceans contained considerably more water than they do today. A new study shows that hydrogen from split water molecules has escaped into space. Although water covers 70 percent of the Earth’s surface, it is actually a rare substance, making up only 0.05 percent of the Earth’s total mass.
Nevertheless, water played a crucial role in the emergence of life on Earth. Without water, the Earth would likely be a dead planet. However, the amount of water on the planet has not always been the same. A research team from the Natural History Museum of Denmark found this out by measuring how the ratio of hydrogen isotopes in the oceans changed over time.
“The water that covered the Earth at the dawn of time contained more of the light hydrogen isotope than the heavier hydrogen isotope known as deuterium today,” says Emily Pope, an associate professor who played a central role in the study.
“By studying how the ratio of these isotopes changed, we were able to determine that over four billion years, Earth’s oceans lost about 25 percent of their original mass.”
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