A new NASA analysis of comet composition records from a pioneering mission has found that comets have a molecular signature similar to that of Earth’s oceans. These findings add evidence to the theory that Earth’s water came from space in the past, transported aboard frozen rocks from the edges of the solar system.
The Rosetta mission of the European Space Agency (ESA) ended in 2016. Through an orbiter module and a lander module, scientists managed to descend on the surface of a comet for the first time in history. Thanks to experiments carried out on comet 67P/Churyumov-Gerasimenko, science obtained the most detailed records to date of a frozen space body.
During the mission’s arrival, researchers analyzed the ratio of regular hydrogen and deuterium (a heavy, stable isotope of hydrogen) that appeared in the vapor cloud around 67P/Churyumov-Gerasimenko. Measuring the ratio of deuterium to hydrogen in water is crucial because it helps determine in which part and stage of the Solar System the molecule was formed. Earth’s water has its own signature, and that of other planets will likely be different. If a comet has the same proportion as Earth’s oceans, there is likely an origin relationship.
Deuterium is formed in cold environments. Astrochemists explain that there is a higher concentration of heavy hydrogen isotopes in objects that formed far from the Sun. The most accepted theory maintains that comets formed in the outer regions of the Solar System, while asteroids formed in the outer regions of the Solar System. close to the Sun.
The Rosetta mission found that the comet’s ratio of deuterium to hydrogen was much higher than usual. Scientists were disappointed because that seemed to blur the connection between Earth’s water signature and that of the comet. However, according to the reanalysis by researcher Kathleen E. Mandadt’s team, it is likely that there were biases in the original measurement due to the dust raised by the mission. The pioneer probe’s instruments would have captured more particles than were actually there, which could make the number of isotopes closer to the signature of the planet’s water.
“The isotope ratio measured at a distance from the core where the gas is well mixed is close to Earth’s, similar to that of other comets in the Jupiter family. This low D/H ratio has implications for understanding the formation of comets and the role of comets in providing water to the Earth,” mentions the research published in ScienceAdvance.
Where did the water come from?
The origin of water on Earth is one of the great enigmas of science. According to physics, it is unlikely that the molecules have been on the planet since its formation 4.6 billion years ago. “Much of the water would have vaporized because the Earth formed near the intense heat of the Sun,” says NASA.
One of the best proposals for the origin of water is that it was formed from steam expelled by volcanoes during the first years of Earth’s life. The vapor condensed and caused rain that formed the oceans. “However, scientists have found evidence that a substantial part of our oceans comes from ice and minerals from asteroids, and possibly comets, that crashed into Earth. A wave of collisions of comets and asteroids with the inner planets of the Solar System 4 billion years ago would have made it possible,” says the space agency.
There is still not enough evidence to say that Earth’s water came from space, but information is increasing as new missions are carried out to comets and asteroids.
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