Water and life on exoplanets: New study simplifies the search process

The new research findings could make the search for liquid water and life on exoplanets a little easier in the future.

Cambridge – More than 5,500 exoplanets – planets outside our solar system – are known to date. But life has not been discovered on any of them yet, and liquid water is rare in the universe. However, this does not mean that it is not sought after. A research team has now discovered a new way to identify liquid water on an exoplanet.

To do this, a team made up of researchers from different universities did not look outside the solar system at all. In fact, it was found in the immediate vicinity of Earth, explains Amory Triwood (University of Birmingham), co-leader of the study. The researcher once said: “We had an idea when we looked at what was happening to the terrestrial planets in our own system.” notice.

Searching for liquid water on exoplanets: Venus, Earth and Mars provide the evidence

Venus, Earth and Mars have several things in common: among other things, they are made of rock and orbit the Sun in a relatively temperate zone. However, there are also clear differences: only Earth currently has liquid water – and at the same time, Earth has much less carbon dioxide in its atmosphere than the other two planets. “We assume that these planets formed in a similar way,” Triaud says. “If we now see a planet with much less carbon, it must have disappeared somewhere.”

But how could carbon dioxide disappear from Earth's atmosphere? “The only process that can remove a lot of carbon from the atmosphere is a powerful water cycle containing oceans of liquid water,” the expert asserts. Over hundreds of millions of years, Earth's oceans absorbed nearly as much carbon dioxide as is now in Venus' atmosphere. This is why Earth's atmosphere contains much less carbon dioxide than its planetary neighbors.

There was a lot of carbon dioxide bound to seawater and rocks on Earth

“On Earth, much of the carbon dioxide in the atmosphere has been bound up with seawater and solid rock over geological time, helping to regulate Earth's climate and habitability over billions of years,” explains study co-author Frieder Klein. The research team comes to the study that In the specialized magazine Nature astronomy published He concluded that he had found a reliable signal of liquid oceans and perhaps even life on the surface.

“After an extensive review of the literature from many fields, from biology to chemistry to carbon sequestration in the context of climate change, we believe that if we do see carbon depletion, it is more likely to be a clear sign of the presence of liquid water and/or water,” says Julian de Wit. (MIT), study co-leader:

Focus on planetary systems with multiple terrestrial planets

According to the team, when searching for liquid water on exoplanets, one should first focus on planetary systems in which many terrestrial planets are close to each other. So the first step should be to find out if there is any atmosphere around the planets. Once you identify several planets with atmospheres, you can measure the carbon dioxide content of the atmosphere. “CO2 is a very strong absorber of infrared radiation and can be easily detected in exoplanetary atmospheres,” de Wit explains.

If the planet has much less carbon dioxide in the atmosphere than other planets, it would likely be habitable — with large amounts of liquid water on the surface. But this does not mean that the planet is inhabited. To find out, the study says, researchers must look for another element in the atmosphere: ozone.

“When we see ozone, there is a high probability that it is related to the consumption of carbon dioxide by an organism,” Treaud points out. “And if that's life, it's amazing life. It won't just be a few bacteria. It will be a planet-wide biomass capable of processing and interacting with an enormous amount of carbon.”

The James Webb Space Telescope can measure carbon dioxide and possibly ozone

The research team hypothesizes that the James Webb Space Telescope (JWST) of space organizations NASA, ESA and CSA will be able to measure carbon dioxide and possibly ozone in nearby planetary systems – which is good news for research, as de Wit explains: “Although With many early hopes, most of our colleagues concluded that large telescopes like the James Webb Space Telescope would not be able to detect life on exoplanets.

The scientist believes this is changing with the new research results: “Our work gives new hope. By harnessing the carbon dioxide signature, we can not only infer the existence of liquid water on a distant planet, but we can also find a way to identify life itself.”

The Trappist-1 planetary system is particularly interesting for this method. It consists of seven terrestrial planets and is only about 40 light years away from Earth. The Trappist-1 planets were already within range of the JWST space telescope and will continue to be studied in the future.

“Trappist-1 is one of the few systems where we can perform atmospheric studies using the James Webb Space Telescope,” says de Wit. “We now have a roadmap for finding habitable planets. If we all work together, paradigm-shifting discoveries can be made in the next few years.” (unpaid bill)