Science.-Iron in the mantle, An indicator of habitability in rocky planets

10/22/2020 University of Sydney for Scientific and Technological Research in Exoplanet Policy

Madrid, 4 (Europe Press)

New research is using the geology of early planetary formation to help determine which ones might be able to support life.

“The discovery of any planet is very exciting, but almost everyone wants to know if there are smaller Earth-like planets with iron cores,” says Dr. Brendan Dick, assistant professor of geology at the University’s College of Science, from British Columbia. Lead author of the study.

“Usually we would expect to find these planets in what is called a” temperate “or habitable zone, where they are at an adequate distance from their stars to support liquid water on their surfaces.

Dyck says that while locating planets in the habitable zone is a great way to classify thousands of candidate planets, it isn’t enough to say whether the planet is actually habitable.

“Just because a rocky planet has liquid water doesn’t mean that,” he explains. “Take a look at our solar system. Mars also lies within the habitable zone, and while it previously contained liquid water, it dried up long ago.”

There, according to Dyck, the geology and formation of these rocky planets could play a major role in narrowing the research. His research was recently published in The Astrophysical Journal Letters.

“Our findings show that if we know how much iron is in a planet’s mantle, we can predict the thickness of its crust and, accordingly, whether there could be liquid water and an atmosphere,” he says. “It is a more accurate way to identify potential new Earth-like worlds than relying solely on their location in the habitable area.”

Dyck explains that within any planetary system, the smallest rocky planets have one thing in common: They all have the same proportion of iron as their orbiting star. He says what sets it apart is how much of this iron is in the mantle versus the core.

“When a planet formed, those with a larger core would form thinner scales, while those with smaller cores would form thicker, iron-rich scales like Mars.”

The thickness of the planetary crust will determine whether a planet can hold tectonic plates and the amount of water and atmosphere, which are two of the main components of life as we know it.

“While the orbit of a planet may be within its habitable zone, its early formation history may eventually render it habitable,” says Dick. “The good news is that with a basis in geology, we can see if a planet will support surface waters before planning future space missions.”

Later this year, in a joint project with NASA, the Canadian Space Agency and the European Space Agency, the James Webb Space Telescope (JWST) will be launched. Dyck describes this as a golden opportunity to put his findings to good use.

“One of the goals of JWST is to investigate the chemical properties of exoplanet systems,” he says. “It would be able to measure the amount of iron present on these space worlds and give us a good idea of ​​what their surfaces might look like, and it might even give an idea of ​​whether they were home to life.”

“We are about to take great steps to better understand the countless planets around us and discover how unique the Earth is or not. It may still be some time before we know if any of these strange new worlds contain new life or civilizations.” But it is an exciting time to be part of this exploration. “

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