Subhajit Nan, Amity University, Kolkata
Scientists gain important insights into the formation of the solar system by studying meteorite fragments that hit the surface of the earth from space. Presently, in the latest study, they have found water in the liquid form, containing high levels of carbon dioxide, inside a meteorite from an asteroid that is believed to have formed 4.6 billion years ago, at the time of the solar system’s formation. This discovery suggests that the original asteroid of this meteorite was formed beyond the giant planet Jupiter’s orbit before being transported into the inner solar system under the Sun’s gravitational influence. This finding provides key evidence for the dynamics of the Solar System’s formation.
Contrary to what everyone might think, water is not rare in our solar system. Even outside of our home planet, we have already found evidence of ice on the moon, in Saturn’s rings and comets, presence of water in the liquid form on the surface of Mars and under the surface of Enceladus (a natural satellite of the gas giant Saturn), and traces of water vapor in the furnace-like atmosphere of our twin planet Venus. Research has, time and again, proved that water had a pivotal role in the formation of the solar system and its early evolution. In search of more evidence about this role, planetary scientists have searched for the presence of water in the liquid form in spatial objects such as meteorites. Most meteorites originate from those asteroids which are formed in the nascent stage of the solar system.
Water has also been found in form of molecular hydroxide compounds in water-containing minerals of meteorites. These are nothing but solids containing water in ionic or molecular form. They further expect that water in the liquid form would remain in mineral salts as precipitable aqueous fluid inclusions. This means that they are formed from water droplets containing many other dissolved materials. Scientists have observed that these liquid water inclusions within salt crystals are located within the “ordinary chondrites” class of meteorites, which includes nearly all types of meteorites hitting the Earth. However, this mineral salt originated from more primitive parent objects like early asteroids, because meteorites are nothing but smaller fragments of the larger asteroids.
The objective of the scientists was to know whether liquid water inclusions are present in the form of calcium carbonate (known as calcite) within the “carbonaceous chondrites” class of meteorites, which originate from early asteroids formed at the beginning of the formation of the solar system. Hence, they examined the samples of a meteorite named “Sutter’s Mill”. It belongs to the carbonaceous chondrite class of meteorites. Its origins can be traced back to an asteroid that formed approximately 4.6 billion years ago.
The scientists used advanced techniques of microscopy to examine the fragments of the meteorite. They found crystalline calcite containing an aqueous fluid inclusion in nanoscale, that contains a minimum of 15% carbon dioxide. This confirms that calcite crystals in carbonaceous meteorites can contain carbon dioxide as well, apart from water in the liquid form.
The presence of liquid water inclusions within the meteorite named “Sutter’s Mill” has thought-provoking inferences regarding the backgrounds of its parent asteroid and, as an extension, the early history of our solar system. The inclusions are likely to have happened due to the formation of the parent asteroid with traces of carbon dioxide and frozen water inside it. Naturally, this means that an asteroid would have formed in a cold enough part of the solar system for water and carbon dioxide to solidify. These conditions would put the site of formation far outside of the Earth’s orbit, very possibly beyond even the orbit of Jupiter.
Eventually, the asteroid, under the Sun’s gravitational force, got transported to the inner solar system where its smaller fragments (meteorites) later came in the proximity of the Earth and got sucked into it by its gravity. This inference is in accordance with recent studies of the solar system’s evolution that concludes that primitive asteroids containing a huge amount of small and volatile molecules like water and carbon dioxide formed beyond Jupiter’s orbit before being transported to places closer to the sun under its gravity. It is also hypothesized that the gravitational effects of the giant planet Jupiter are also a major reason for the migration of such asteroids in the inner solar system, besides the Sun’s gravity.
We can conclude that the discovery of aqueous inclusions within a primitive carbonaceous meteorite is an important achievement for planetary science. By obtaining chemical screenshots of the contents of an ancient meteorite, this discovery can provide important insights into the molecular processes of the solar system’s early history.
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References:
- Tsuchiyama, A., Miyake, A., Okuzumi, S., Kitayama, A., Kawano, J., Uesugi, K., Takeuchi, A., Nakano, T., & Zolensky, M. (2021). Discovery of primitive CO 2 -bearing fluid in an aqueously altered carbonaceous chondrite. Science Advances, 7(17), eabg9707. https://doi.org/10.1126/sciadv.abg9707
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