2024-01-09 18:32:59
MADRID, 9 Ene. (EUROPA PRESS) –
The first planetesimals in the inner solar system must have formed in the presence of water, according to a new study that challenges current astrophysical models of the early solar system.
The research, which combines meteorite data with thermodynamic models, was carried out in the laboratory of Paul Asimow, professor of geology and geochemistry at Caltech, and appears in the journal Nature Astronomy.
When our Sun was a young star, 4.56 billion years ago, what is now our solar system was just a disk of dust and rocky gas. Over tens of millions of years, tiny pebbles of dust coalesced, like an ever-growing snowball, to become kilometer-sized “planetesimals”: the basic components of the Earth and the other inner planets.
Researchers have samples from the early days of the solar system in the form of iron meteorites. These meteorites are the remains of the metallic cores of the first planetesimals in our solar system that avoided accreting into a planet in formation and, instead, They orbited the solar system before finally falling on our planet.
The chemical compositions of meteorites like these can reveal information about the environments in which they formed and answer questions such as whether the building blocks of Earth formed far from our Sun, where colder temperatures allowed water ice to exist, or if instead they were formed. closer to the Sun, where the heat would have evaporated the water and resulted in dry planetesimals. If the latter is correct, then the Earth would have formed dry and obtained water by some other method later in its evolution.
Although meteorites themselves do not contain water, scientists can infer their long-lost presence by examining their impact on other chemical elements.
Water is made up of two hydrogen atoms and one oxygen atom. In the presence of other elements, water often transfers its oxygen atom in a process called oxidation. For example, metallic iron (Fe) reacts with water (H2O) to form iron oxide (FeO). Sufficient excess water can speed up the process, producing Fe2O3 and FeO(OH), the ingredients of rust. Mars, for example, is covered in rusty iron oxide, providing strong evidence that the Red Planet once had water.
Damanveer Grewal, a former Caltech postdoctoral fellow and first author of the new study, specializes in using chemical signatures from iron meteorites to gather information about the early solar system. Although iron oxide has long since disappeared from early planetesimals, the team was able to determine how much iron would have been oxidized by examining the metallic nickel, cobalt and iron contents of these meteorites. These three elements should be present in approximately equal proportions relative to other primitive materials, so if some iron was “missing”, This would imply that the iron had rusted.
“Iron meteorites have been somewhat neglected by the planet-forming community, but they are rich repositories of information about the earliest period in the history of the solar system, once we figure out how to read the signals,” says Asimow. it’s a statement. “The difference between what we measured in meteorites from the inner solar system and what we expected implies approximately 10,000 times greater oxygen activity.”
The researchers found that iron meteorites thought to be derived from the inner solar system had about the same amount of missing metallic iron as meteorites derived from the outer solar system. For this to be the case, the planetesimals of both groups of meteorites must have formed in a part of the solar system where there was water, implying that the basic components of the planets accumulated water from the beginning.
The water signatures in these planetesimals challenge many of the current astrophysical models of the solar system. If planetesimals formed in Earth’s current orbital position, water would have existed only if the inner solar system was much colder than current models predict. Alternatively, they may have formed further away, where it was colder, and migrated inward.
“If water was present in the early building blocks of our planet, it is likely that other important elements such as carbon and nitrogen were also present,” Grewal says. ““The ingredients for life may have been present all along in the seeds of rocky planets.”
“However, the method only detects the water that was used to oxidize the iron,” adds Asimow. “It is not sensitive to excess water that could form the ocean. Therefore, the conclusions of this study are consistent with Earth accretion models that call for the late addition of even more water-rich material.”
#Earths #building #blocks #contained #water