The Water on Earth Might Have Been Delivered From Space by Comets Billions of Years Ago
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The Water on Earth Might Have Been Delivered From Space by Comets:
Comets may have been potential sources of water for early Earth, researchers said this week.
When Earth formed around 4.6 billion years ago, some water likely existed in that gas and dust - though much of it would have been vaporized by the sun's intense heat. How Earth got so much liquid water remains a source of debate, but research has shown some came through volcanic vapor that became rain.
There is also new evidence that a substantial portion of Earth's oceans came from ice and minerals on asteroids - and maybe comets - that crashed into Earth. Measurements of Jupiter-family comets, controlled by the planet's gravitational effects, have shown a strong link between their water and Earth's based on a key molecular signature.
NASA says its scientists found that water on Jupiter-family Comet 67P/Churyumov-Gerasimenko, the first comet to be orbited and landed upon by robotic spacecraft from Earth, had a similar molecular signature to the water in Earth's oceans and that cometary dust infects the interpretation of spacecraft measurements.
These results, the agency said, contradict some recent research. In 2014, the European Space Agency's Rosetta mission to the comet analyzed water measurements, finding the highest concentration of deuterium on it compared to of any other comet - and about three times more deuterium than there is in Earth's oceans.
Deuterium is a rare type of the element hydrogen, and the molecular signature is its ratio to regular hydrogen in the water of any object. The ratio helps researchers figure out where the object was formed, and water with deuterium is more likely to form in cold environments. There are 33 grams of deuterium in every cubic meter of seawater.
"It was a big surprise and it made us rethink everything," Kathleen Mandt, planetary scientist at NASA's Goddard Space Flight Center, said in a statement.
That research might now be incorrect based on the new findings after the robot spacecraft landed on the comet and scientists analyzed the findings. Mandt led the new research that was published last month in the journal Science Advances.
Measurements of deuterium in the last couple of decades in the water vapor of other Jupiter-family comets had shown similar levels to Earth's water.
"It was really starting to look like these comets played a major role in delivering water to Earth," said Mandt.
Journal Reference: Kathleen E. Mandt et al., A nearly terrestrial D/H for comet 67P/Churyumov-Gerasimenko. Sci. Adv. 10, eadp2191(2024). DOI:10.1126/sciadv.adp2191
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