Tuesday, November 30

What are “eggshell” planets? | Digital Trends Spanish


A group of scientists has discovered a new type of planet, which is known as an “eggshell”. These orbit distant stars (so they are exoplanets) and, as their name suggests, these rocky bodies have an ultra-thin and brittle outer shell.

This means that the new planets could not support plate tectonics, and for that reason doubts have arisen about the possibility that these planets are habitable.

That is why an international team of geologists based in the United States, Switzerland, France and the St Andrews University Scotland has developed a new computational model, which will help identify whether the newly discovered planets could support plate tectonics in a similar way to Earth, adding a new geological dimension to the exoplanet classification.

“The new model provides a template with which you can predict the nature of plate tectonics in exworlds. You could say that we are looking for a new parameter of the Goldilocks planet, but instead of the right temperature for the water, we want to explore the right conditions for plate tectonics, ”said Dr. Sami Mikhail from the Faculty of Sciences. of the Earth and the Environment from the University of St Andrews.

Scientists believe that Earth-like subduction zone tectonic plates are an important component for planets to be habitable, but not only because they are the most Earth-like geological processes recognized by science.

The chain reaction of plate tectonics is enhanced by volcanism and chemical weathering, both of which have lasted for billions of years. These two factors, combined with the presence of some water, are what regulate the Earth’s climate and keep the planet habitable.

“Earth is unique in the Solar System. However, there are only three other rocky planets: Mercury, Venus and Mars, and they are also different from each other. Astronomers have discovered more than 4,000 planets orbiting other stars, known as exoplanets. Do any of these look like Earth? What do you mean “similar to Earth”? And how representative are the planets in our Solar System for the broader cosmos? ”Said Dr. Sami Mikhail.

The team behind this research ran a large set of computational models with the aim of observing how combinations of planetary and stellar properties influence the thickness of the outer shell of a planetary body.

What these models predicted was that worlds that are small, old, or far from their star are likely to have thick, rigid layers. However, in some circumstances, the planets could have a brittle outer shell only a few kilometers thick, which are called “eggshells.”

According to the researchers, these fragile layered planets may be similar to the lowlands of Venus, and the term could potentially apply to at least three of those already known extrasolar planets.

The outer layer of a rocky planetary body is generally rigid and brittle, and the thickness of this layer is important in governing numerous aspects of the geological character of that body, including the ability to withstand plate tectonics and even retain habitable conditions on the surface.

On the other hand, factors inherent to the planet, such as size, interior temperature, composition, and even climate, affect the thickness of this outer layer, although factors specific to the host star, such as luminosity and brightness, do too. remoteness.

For the research on the outer shell, several factors were considered, such as the size of the exoplanet, the distance from the host star, the surface temperature and the internal temperature. And with this it was discovered that the surface temperature was more important than all other factors, including the internal temperature of the planet.

According to the team, “eggshell” planets have brittle crusts just one kilometer deep, while Earth and Mars have scabs down to depths of 40 and 100 kilometers, respectively.

St Andrews University

The researchers believe that the developed model should be used to predict which exoplanets are given telescope time for planned and future research. These aim to determine the chemistry of the atmospheres around an exoplanet to find evidence of active geochemical processes and marks left by a supposed biology beyond our Solar System.

Paul Byrne, associate professor in the department of earth and planetary sciences at the Washington University in St. Louis and who is the first author of the research published in the Journal of Geophysical Research: PlanetsHe said: “Our overall goal goes beyond understanding the ups and downs of exoplanets.”

Ultimately, we want to help identify the properties that make a world livable. And not only temporarily, but habitable for a long time, because we believe that for there to be life it probably takes a period to start up and become sustainable, “said Byrne, who adds that the fundamental question behind this research is:” Are we alone? ”.

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