Certain planets can be rich in soot rather than with water -based. Atmosphere studies will be essential to understand their true nature.
Astronomers generally consider water worlds as among the most common types of planets of our galaxy, largely because of their low densities and the abundance of water ice beyond the “snow line” of a star. However, a new study by JIe Li and his colleagues from the University of Michigan offers an alternative explanation: some of these planets may not be dominated by water, but rather by a very different material called SUIE.
In astronomy, a soot planet is not literally a planet in black powder. Here, the “soot” refers to refractory organic carbon, a compound containing carbon, hydrogen, oxygen and nitrogen that scientists often shorten as chon. This type of carbon -rich material is widespread in the solar system, with estimates suggesting that it represents up to 40% of the total mass of comets.
Compets with soot lines in the formation of the planet
Because comets are often considered as snapshots of the first history of the solar system, in particular during its protoplanetary phase, their composition suggests that the soot was abundant during the formation of planets. Researchers propose that, just as there is a “snow line” marking the distance of a star where water ice can remain stable, there can also be a “soot line”. This border, located closer to the star than the snow line, would define the region where the soot could persist and contribute significantly to the composition of development planets.
https://www.youtube.com/watch?v=9TGSJ8VZJGO
Fraser discusses the water worlds and the way life could form on them.
In fact, according to the article, there are three distinct zones of protoplanetary records, each giving birth to a unique type of planet. The interior zone would only do rocky works, such as earth and "Red planet" Due to its surface rich in iron. It was a major objective of robotic exploration and is considered a potential site for future human missions.
“Data-Gt-Translate-attributes =”[{” attribute=”” tabindex=”0″ role=”link”>Mars, and it would be too hot for the soot to stay together, making “soot” in this area very unlikely. Past the “soot line” but before the “snow line”, planets could form that were mainly composed of soot, but with very little water, as it would still be too hot for water ice to exist in this area.
These planets would look a lot like Titan, with methane atmospheres or something equivalent, and could be made up of as much as 25% soot by mass. Farther out past the “snow line”, most planets would be a combination “soot-water world”, where soot would still play a large role in the composition of the planet, but water would as well. In fact, the paper models two different types of soot-water worlds, a “dry” version that was only 25% water, and a “wet” one that contains 50% water, both of which would still contain 15-20% soot in their compositions.
The problem of distinguishing planet types
Those models show a particularly interesting feature – based on the mass-radius relationships, it is impossible to tell apart soot worlds and more traditional water worlds. In other words, many of the “mini-Neptunes” in the exoplanet catalog that were originally thought to be water worlds could actually be composed of carbon-rich materials rather than water. It would take looking at their actual atmospheres to determine which category they belonged to.
https://www.youtube.com/watch?v=cyKDQNCUM68
Fraser discusses the discovery of methane, considered one of the main components of Sot Worlds, on exoplanet wasp-80b.
THE James Webb space telescope has already started to do so for certain exoplanets. He detected methane and carbon dioxide in the atmosphere of K2-12B and TO-280D, two “sub-neptunes” which, although they are currently located in the soot line for their respective stars, could have formed outside and migrating inward during their lives.
In particular, VOI-280D has a significantly high carbon / oxygen ratio, indicating that it could be a soot planet as described in the article. These types of planets have interesting implications for habitability. They could have diamond nuclei, which would slow cycling of volatiles in the planet’s coat and would be much more difficult to provide a magnetic field to protect all primitive life from cosmic rays. However, they would also be rinsed with methane and other volatile biological products, which would be prerequisites for prebiotic chemistry.
In the end, understanding the fate of many of these planets will require – you have guessed it – more data. Atmospheric controls, as well as more detailed models in different ways to differentiate the worlds of water and the soot world, must be explored and delimited. While astronomers are getting to work to do, perhaps an enterprising director can launch a film on a character sailing on the methane of an exoplanet in an isolated boat. Kevin Costner still acts actively after all.
Reference: “Soot planets instead of Water Worlds” by Jie Li, Edwin A. Bergin, Marc M. Hirschmann, Geoffrey A. Blake, Fred J. Ciesla and Eliza M.-R. Kempton, August 22, 2025, Arxiv.
DOI: 10.48550 / Arxiv.2508.16781
Adapted from an article originally published on Universe today.
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