Researchers want to find water and life on exoplanets

The search for extraterrestrial life may be on the verge of a major breakthrough. A new method aims to find liquid water on exoplanets.

CAMBRIDGE – There are now more than 5,500 known planets outside our solar system – but there is currently no evidence of life on these exoplanets, and liquid water is also rare in the universe. However, this does not prevent scientists from continuing to search for it. A research team has now developed a new method to identify liquid water on exoplanets.

The researchers, who come from different universities, did not focus on distant planetary systems, but rather on our immediate cosmic neighborhood. Amory Triwood from the University of Birmingham, one of the leaders of the study, explains that they found what they were looking for near Earth. “We had an idea when we looked at what was happening to terrestrial planets in our own system,” Triode said in one of the articles. notice.

Searching for liquid water on exoplanets: carbon dioxide as an indicator

Venus has some similarities to Earth and Mars: it is made of rock and orbits the sun in a relatively temperate zone. However, there are also significant differences: only Earth contains liquid water, and at the same time, Earth contains much less carbon dioxide in its atmosphere than the other two planets. “We assume that these planets formed in a similar way,” Triaud says, adding: “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. Earth's oceans absorbed a lot of carbon dioxide over hundreds of millions of years, almost as much as is in the atmosphere of Venus today. Therefore, Earth's atmosphere contains much less carbon dioxide than our neighboring planets.

The carbon dioxide was bound to seawater and solid rock

“On Earth, much of atmospheric carbon dioxide has been sequestered in seawater and solid rock over geological time, helping to regulate Earth's climate and habitability over billions of years,” explains Frieder Klein, co-author of the study. Researchers are studying them In the specialized magazine Nature astronomy published They concluded that they 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. from MIT, who is also the study leader.

Planetary systems containing many Earth-like planets are particularly interesting

When searching for liquid water on exoplanets, the research team recommends first targeting planetary systems in which several Earth-like planets are located close to each other. The first step should be to check whether these planets have an atmosphere or not. Once multiple planets with atmospheres are identified, atmospheric carbon dioxide levels can be measured. “CO2 is a very strong absorber of infrared radiation and can be easily detected in exoplanetary atmospheres,” de Wit explains.

If a planet has much less carbon dioxide in its atmosphere than other planets, it could be habitable, meaning it has large amounts of liquid water on the surface. However, this does not necessarily mean that the planet is inhabited. According to the study, to find out, we must look for another element in the atmosphere: ozone.

Researchers look for carbon dioxide in exoplanet atmospheres

“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.”

Researchers are confident that the James Webb Space Telescope (JWST), operated by space organizations NASA, the European Space Agency and the Canadian Space Agency, will be able to measure carbon dioxide and possibly ozone in nearby planetary systems. This is good news for research, as de Wit explains: “Despite many early hopes, most of our colleagues have concluded that large telescopes like the James Webb Space Telescope will not be able to detect life on exoplanets.”

“New Hope” for the search for life in the universe

The scientist believes that the picture 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 Earth-like planets, and is only about 40 light-years away from Earth. The Trappist-1 planets have already been the focus of the JWST space telescope and will continue to be studied in the future. It appears the telescope could also search for carbon dioxide in the atmosphere there in the future, perhaps detecting signs of liquid water or life. (unpaid bill)

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