Water on our planet can be distinguished from extraterrestrial water by how often its molecules contain the “blocked” variety (deuterium) rather than ordinary hydrogen atoms. Scientists have concluded that in the famous comet Churyumov-Gerasimenko their proportions are approximately the same as in the World Ocean.

The most interesting thing we managed to learn about Churyumov’s Comet Gerasimenko was learned thanks to happy coincidences. It all started in 1969, when Soviet astronomer Klim Churyumov unexpectedly examined it in images of a completely different comet. And when the Rosetta mission in the 2000s was preparing to study comets, at first this celestial body was not chosen as a target, but they missed the right moment for launch: they had to look for another “target”, and the Churyumov-Gerasimenko comet turned out to be a suitable option in all respects appeared.

Undoubtedly, scientists have never regretted that their spacecraft went to this comet.

Other examples of such a strange appearance are also found in space; the brightest is the asteroid Arrokot in the Kuiper Belt (beyond Neptune). Such celestial bodies are called double-contact minor planets: they are probably the result of the meeting and merging of two initially separate bodies. There is a version that an asteroid and its satellite are sometimes connected to each other in this way.

Later, scientific instruments on the Rosetta probe recorded the ejection from the comet’s surface of various complex organic compounds, as well as molecular oxygen, which is extremely rare in space.

All this comes out of the interior of the comet, together with streams of evaporating water, which, as it approaches the Sun, rise above it and diverge in different directions, like rays. At the closest point of its orbit to the armature, the Churyumov-Gerasimenko comet is between Earth and Mars, and at the farthest point it is behind Jupiter.

Thanks to the Rosetta probe, it was possible to create an idea about comet water. Later the picture turned out to be unexpected and could disappoint some scientists: it turned out that the water vapor on this celestial body is strikingly different from terrestrial water. The difference is how often heavy hydrogen – deuterium atoms are present in water molecules. It is called heavy because an ordinary hydrogen atom has only one proton and one electron, and the deuterium “charge” has one neutron.

Comet Churyumov-Gerasimenko turned out to have an almost solid heavy water vapor above it, which is unusual for the Earth’s environment: our water contains relatively little deuterium. From this many people have concluded that the Earth’s oceans cannot have a cosmic origin.

But recently a team of planetary scientists from the United States, Switzerland and France examined the results of these measurements. In an article I wrote for a magazine Science Developments scientists expressed the opinion that the data itself is correct, but does not show the true state of water in the comet Churyumov-Gerasimenko: its substance contains a large number of dust particles, and they retain heavy water molecules well.