Water containing the "building blocks" of life arrived on Earth later than scientists previously thought.

Understanding when water first appeared on Earth is crucial for reconstructing the history of life's origins. It has long been believed that a collision with the hypothetical planet Theia played a key role in delivering water to Earth. At that time, the remaining debris likely formed the Moon. However, there is also another, quite convincing theory regarding the origin of our natural satellite.

The authors of a new study, published in the journal Geochimica et Cosmochimica Acta under the leadership of Katherine Bermingham from Rutgers University (USA), analyzed the isotopic composition of molybdenum (Mo)—a chemical element capable of preserving information about the processes that occurred in the young Solar System—in samples of terrestrial rocks and meteorites.

The sample included rocks from Greenland that are approximately 3.8 billion years old, modern basalts obtained from the ocean floor, as well as samples from the meteorite Campo del Cielo, which was discovered in 1576. This meteorite fell in what is now Argentina about four to five thousand years ago.

To analyze the changes in the isotopic composition of molybdenum in meteorites and terrestrial rocks, which date back to the later stages of the planet's formation, the scientists employed thermal ionization mass spectrometry. The results indicated that most of the materials added to Earth during the final stages of its growth and core formation originated from the inner part of the Solar System.

It's important to note that meteorites, from which samples are taken for such analysis, are conventionally divided into two groups: the first (NC-meteorites) formed in the inner part of the Solar System, where conditions were relatively "dry," while the second (CC-meteorites) formed in the outer part, where there was more water and volatile substances.

Thus, by comparing the signatures of molybdenum in terrestrial samples with those from meteorites, the researchers concluded that the water containing the building "bricks" of life arrived on our planet during the late stage of its formation. This means after the "birth" of the Moon (during the so-called late accretion, when the addition of material constituted the last 10-20 percent of its mass). The authors of the new scientific work noted that the delivery of water occurred in several stages.

However, opinions among scientists regarding the origin of Earth's water vary. For instance, according to a study by the research group led by Artem Oganov, the source of the oceans could be a specific mineral from the Earth's interior. Other research teams have calculated that the primary Earth’s oceans did not evaporate. It is likely that the conclusions of the new study will soon be challenged.