Prof. Amri Wendel: The habitable zone of planets is wider than we thought

In an interview with the Hayadan website, the astrobiologist from the Hebrew University, who recently published two articles, explains that liquid water may also exist outside the classic habitable zone – the Goldilocks zone – on the dark side of tidally locked planets or under ice cover.

Two new papers, which address the question of the conditions for life beyond Earth in different ways, place the need to rethink the boundaries of the "habitable zone" around stars at the center of the debate. In an interview with "Hayadan," Prof. Amri Wandel, a senior scientist at the Racah Institute for Physics at the Hebrew University of Jerusalem, explains that the new models show that liquid water may exist even in conditions that were previously considered too extreme - for example, on the dark side of tidally locked planets or under thick layers of ice - and therefore the number of worlds suitable for life may be greater than previously estimated.

Wandel, an astrobiology expert and chairman of the Israeli Society for Astrobiology and the study of the Origin of Life (ILASOL), is engaged in the study of the physical conditions that enable the emergence of life on planets outside the solar system. According to him, the latest research in the field undermines one of the central assumptions of planetary <a href="#" class="google-anno" data-google-vignette="false" data-google-interstitial="false" style="color-scheme: initial !important; forced-color-adjust: initial !important; math-depth: initial !important; position: initial !important; position-anchor: initial !important; text-size-adjust: initial !important; appearance: initial !important; color: revert-layer !important; direction: inherit !important; font-family: inherit !important; font-feature-settings: initial !important; font-kerning: initial !important; font-language-override: initial !important; font-optical-sizing: initial !important; font-palette: initial !important; font-size: inherit !important; font-size-adjust: initial !important; font-stretch: initial !important; font-style: inherit !important; font-synthesis: initial !important; font-variant: initial !important; font-variation-settings: initial !important; font-weight: inherit !important; 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The life zone, sometimes also called the"Goldilocks Zone."The Goldilocks zone is defined as the range of the circumstellar region from a star where liquid water can exist on a planet. The name is taken from the story "Goldilocks and the Three Bears" because conditions in this zone are neither too hot nor too cold—but "just right." In our solar system, Earth is almost in the center of this zone, while Mars and Venus are near its edges.

For many years, the concept served as the basis for the search for extraterrestrial life, but according to Wandel, planetary reality is much more complex.

He said, "The habitable zone is a very useful concept, but it is simplistic. Once you introduce the real physics of atmospheres, oceans, and heat trannsport mechanisms into the models, it becomes clear that planets can maintain liquid water even outside the classical range."

One of the main examples of this is planets that are in a state oftidal lock– A condition in which one side of a planet always faces its star while the other side is in constant darkness. This condition is especially common aroundRed dwarf stars, which are by far the most common stars in the galaxy.

Early models thought that such a situation would create too extreme temperature differences: one side very hot and the other completely frozen. But new research suggests other possibilities.

"If the planet has a sufficiently dense atmosphere or a deep ocean," explains Wandel, "the heat can spread across the entire globe. In such cases, temperate zones can form, for example, in the twilight zone between day and night, or on the night side moderated by heat transport from the dayside, where the temperature allows liquid water to exist."

Another possibility is the existence of water beneath thick layers of ice. In such cases, the source of energy is not necessarily radiation from the star but rather internal heat of the planet or heating resulting from tidal forces.

"We know from our solar system itself that oceans can exist beneath the ice," says Wandel. "Moons like Europa and Enceladus show that life doesn't necessarily appear on the surface."

This approach has significant implications for the search for life in the universe. For years, researchers have focused on Earth-like planets around stars similar to our Sun that are similar in distance to their sun. But if the right conditions can also exist in other scenarios, the number of potential worlds for life could be much larger.

According to Wandel, the rapid development of advanced telescopes makes it possible to examine these questions more directly than ever before.

"The James Webb Space Telescope is allowing us to begin measuring the composition of the atmospheres of distant planets," he says. Already, we know we are detecting spectral signatures of water, and in the future, we may find molecules that could indicate biological activity."

However, he emphasizes that the road to discovering life is still long and complex.

"We're just getting started," he says. "Every few years we discover how diverse planetary systems are. Nature is probably much more creative than the simple models we built at the beginning."

According to him, the universe may be full of worlds where liquid water exists in completely different ways than we are used to thinking.

"It is very possible that nature has found ways to sustain liquid water – and perhaps life – under conditions we never imagined," he concludes.

For articles in the Astrophysical Journal:

• Planets can support life even outside the conservative zones
• Extrasolar planets beyond the conservative habitable zone – Part Two: Their frequency
  
  

More of the topic in Hayadan:

• Golden zones abound: hundreds of millions of planets in the Milky Way could possibly support life
• Jeff Bezos predicts: Millions of people will live in outer space
• NASA's discovery of seven terrestrial planets in one system will spur a widespread hunt for similar systems
• The discovery that the crater on Mars where Curiosity landed was a lake increases the possibility of extraterrestrial life
• Considerable amounts of water were discovered in the Bennu asteroid, did the asteroids bring the water to Earth?