Water is an important element without which life cannot exist on Earth. But it has remained largely unclear how it came about on the planet. Now, evidence from a new study published in the journal Nature Astronomy suggests that it had been around well before Earth was formed.
Researchers probe carbon and water chemistry in a bid to get a better understanding of how life came to be on Earth. They examine isotopes of major water components, hydrogen, and oxygen, to discover how the liquid compound came into existence.
Isotopes are forms of an element with varied numbers of neutrons. For instance, the isotope deuterium (heavy hydrogen) has a proton and a neutron while protium (light hydrogen) has one proton and lacks neutrons. These can help tell the water to which a rock has been exposed.
The new research, led by geochemist Jerome Aleon, hone in on these two hydrogen isotopes. Their ratios in one of the oldest known meteorites showed that water had been in the solar system before Earth.
The study is the result of collaboration between researchers from the French National Museum of Natural History, the CNRS, and the French Alternative Energies and Atomic Energy Commission. Paris-Saclay University and the University of Pau and the Pays de L’Adour were also represented in the team.
Meteorites as time capsules
According to scientists, a star forms when a gas and dust cloud collapses under its own gravity – what is called the protostellar collapse. The material present in the cloud surrounding the star compresses and feeds into it to increase the size. Planets, asteroids and all other things in the star’s system form from what remains after the star reaches its full size.
Scientists regard primitive meteorites as the oldest rocks in the solar system. They land on Earth now and then but mostly go unseen.
These rocks have been described as the “time capsules” of the solar system. Some of them carry materials that date back to millions or billions of years ago.
Studying the water content of meteorites has proven quite difficult. This is because the asteroidal accretion process turns primal materials into forms that make tracing the origin impossible, most notably because of heat.
However, rock samples that make it all the way to the surface of the Earth once in a while show minimal signs of excessive baking. These give scientists a good opportunity to carry out studies, such as the current one.
Existence of water before Earth
Aleon and his colleagues used a novel technique designed exclusively for this research to analyze the Efremovka meteorite. This meteorite, which was found in Kazakhstan about 60 years ago, dates back to more than 4.5 billion years ago – before Earth was supposedly formed.
Using focused ion beam imaging, the scientists isolated and examined materials present in the sample. They compared their results with eight earthly reference materials having varied water content. They probed the ratio of hydrogen isotopes in the meteorite to discover precise water exposure.
The analyses revealed that there existed two large gas reservoirs during the first 200,000 years in the history of our solar system. One of these contained solar gas that resulted in the solar system’s matter. The second reservoir was rich in water vapor, with isotopes matching those of water on Earth today.
Water detected in the meteorite resulted from a massive influx of water into the inner solar system during the collapse of the protostellar envelope, scientists said. The finding, thus, suggests that water was already present in the solar system before Earth formed.