It seems that the many years debate about the origin of water on Earth has been solved with the results of the analysis of the Rosetta probe data. The researchers who studied these data believe that comets can no longer be regarded as the primary source of the water on our planet.
ESA’s Rosetta satellite, which landed on the comet Churyumov-Gerasimenko in November, transmitted probe data about the composition of water vapor from the comet. As a result, it was found that the particles of the comet’s ice have three times as much deuterium – a heavy isotope of hydrogen – as in the Earth’s water, which casts doubt on the theory about comets being the original source of the Earth’s water.
Till recently, most scientists believed that the emergence of water on the Earth’s surface was associated with the word “comet”. According to this point of view, the water brought by these celestial bodies played a key role in the formation of the modern oceans.
Comets can be divided into two groups: near comets that come from the Kuiper belt, which is located beyond the orbit of Neptune, and far comets, the orbit of which is greater of magnitude and reaches the outer limits of the hypothetical area, called the Oort cloud.
In 1986, the core of Halley’s comet, which belongs to the “far comets” category, was studied by space probes. It was found that the composition of water at its core was significantly different from that of the water found on Earth. Thus, astronomers concluded that the comets from the Oort cloud can hardly be considered the primary source of water, which resulted in the formation of the modern Earth’s oceans.
Three years ago, scientists managed to obtain data from the comet Hartley 2 from the Kuiper belt, and the proportion of deuterium atoms in the particles of the comet’s ice turned out to be similar to that of the water on our planet. Researchers suggested that near comets are probably those very celestial bodies that brought water to Earth.
However, the comet Churyumov-Gerasimenko comes from the Kuiper belt, but the composition of its water is very different from the Earth’s one, meaning that, perhaps, it was not comets that brought water to our planet, but some other celestial bodies, probably asteroids.
At the same time, some scientists claim that these data are not enough to debunk the theory about the cometary origin of Earth’s water, which could have arrived to the planet from another type of comets from the Kuiper belt. It seems that further research is needed either to confirm or to refute this theory.