Where do Earth’s oceans come from? The debate on whether water may have been originally delivered to our planet by comets striking its surface has reopened after a new groundbreaking study.
Published this month in Science Advances, a paper by NASA-led researchers examines a comet called 67P/Churyumov-Gerasimenko, which the European Space Agency’s Rosetta mission visited in 2014. It was the first mission ever to rendezvous with a comet and the first to deploy a lander to a comet.
Water Source
The paper reveals that 67P’s water may share similarities with Earth’s oceans, making comets a plausible water source for our planet. This new finding challenges earlier results and strengthens the case that Jupiter-family comets — short-period comets that orbit the sun in less than 20 years — could have been crucial in delivering water to early Earth. The new statistical research contradicts an earlier finding in 2014, which ruled out the link.
Missing Link
Understanding the origin of Earth’s water is central to unraveling how life began and why it did not exist on other planets in the solar system. About 71% of Earth’s surface area is oceans, which contain 97% of Earth’s water. Human bodies are 55-60% water. Its origin is a missing link in scientists’ understanding of our planet’s hydrological history.
‘Dark Comets’
In July, a study suggested that “dark comets” — a new category of cometary bodies with low albedo due to dark surfaces — may have played a key role in bringing water to Earth. These comets, originating from the outer regions of the solar system and a new class of objects somewhere between an asteroid and a comet, could have contributed to Earth’s oceans through impacts during the planet’s formative years, claimed the authors.
Comets or Asteroids?
A paper in June 2023 claimed that water-bearing asteroids from the outer regions of the asteroid belt delivered significant amounts of water to Earth. The researchers revealed that the water in carbonaceous chondrite meteorites is similiar to the water in Earth’s oceans. The authors also identified hydrated minerals on asteroids like Itokawa and Ryugu, samples of which were retrieved by the Hayabusa and Hayabusa 2 missions, respectively.
Interstellar Origin
The theory that comets and asteroids primarily delivered Earth’s water after the planet’s formation remains controversial. According to research published in March 2023, Earth’s water may predate the formation of the sun. Scientists found at least 1,200 times the amount of water in all of Earth’s oceans around a protostar — a very young star in the early stages of its evolution — 1,305 light-years distant in the constellation Orion. This first-ever discovery of ancient interstellar ice around a young star suggests that a significant portion of Earth’s water originated from interstellar space— and implies that water is more prevalent in planetary systems than previously thought, potentially increasing the likelihood of life elsewhere in the universe.
Wishing you clear skies and wide eyes.
