When it comes to detecting the presence of liquid water, and thus the conditions necessary for life, on planets outside the solar system, the James Webb Space Telescope (JWST) may want to look for what is missing rather than what is there. Here’s what it means.
A research team, including scientists from the Massachusetts Institute of Technology (MIT) and the University of Birmingham, suggests that rocky worlds outside the solar system, such as Earth, have less carbon dioxide in their atmospheres than other planets in the same system. This could be a sign that they contain liquid water. As we know from the occurrence of life on our own planet and the conditions required to support life there, the presence of liquid water is an important indicator of potential habitability.
While searching for key chemical compounds that indicate habitability on extrasolar planets, or exoplanets, remains just within the reach of current technologies, depleted carbon dioxide is a signature that JWST is now poised to detect.
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“The Holy Grail in exoplanet science is the search for habitable worlds and the existence of life, but all the features talked about so far are beyond the reach of the newest observatories,” said expedition team member Julien de Wit. assistant professor of planetary sciences at MIT, said in a statement. “We now have a way to find out if there is liquid water on another planet. And that’s something we could achieve within the next few years.”
Roadmap to discovering life on exoplanets
Currently, scientists are very good at using tools to determine how far a planet is from its host star and therefore whether it is in that star’s “habitable zone.” Liquid water.
However, in our own solar system, Earth, Mars and even Venus are in the habitable zone around the sun. But only one of these planets is capable of supporting life as we currently know it. This means that for exoplanets, habitability and preservation of liquid water isn’t just location, location, location. So right now, scientists don’t have a solid way to confirm whether a planet is habitable.
Considering the differences between the trio, as well as Earth, Mars and Venus, the team realized that Earth, the only habitable place, has an atmosphere devoid of carbon dioxide compared to its neighbors in the habitable zone.
“We assume these planets were created in a similar way, and if we now see a planet with much less carbon, it must have gone somewhere,” Triaud said. “The only process that could remove this much carbon from the atmosphere is a powerful water cycle that includes oceans of liquid water.”
For billions of years, our planet’s oceans have been responsible for depleting large amounts of atmospheric carbon dioxide; This means it currently has less carbon dioxide than Venus or Mars.
“On Earth, much of the carbon dioxide in the atmosphere has been sequestered in seawater and solid rocks over geological time periods, helping to regulate climate and habitability over billions of years,” said Frieder Klein, study co-author and scientist at Woods Hole. The Oceanographic Institute (WHOI) said in the statement.
This led the team to think that a similar decrease in carbon dioxide in an exoplanet’s atmosphere might also indicate the presence of a liquid ocean.
Performing a search with these parameters is best suited for “peas in a pod” planetary systems that, like the solar system, host numerous rocky or terrestrial worlds of similar sizes, orbiting their stars at similar distances.
The first step in the team’s proposed research is to hunt for carbon dioxide and use it as an indicator that exoplanet targets have an atmosphere. Once it has been determined that multiple planets in a single system have atmospheres, the next step will be to determine how much carbon dioxide is present in the atmospheres.
This should reveal whether one or more planets have significantly less carbon dioxide than the others; This indicates that it probably had oceans of liquid water and thus could have been habitable.
Of course, there’s a little more to this method than just comparing carbon dioxide abundance. “Livable” does not mean “built-in.” To check whether life really exists on an exoplanet where carbon dioxide deficiency is prominent, the team proposes to look for another molecule: ozone.
Composed of three oxygen atoms, ozone is a molecule formed when life forms such as plants and microorganisms remove carbon dioxide from the Earth’s atmosphere and then emit oxygen molecules when struck by sunlight. Ozone is a good indicator of these processes on alien worlds because it is easier to detect in the atmospheres of distant exoplanets than oxygen itself.
The team says that if a planet’s atmosphere shows signs of carbon dioxide abundance and ozone abundance, it may be both habitable and habitable.
“If we see ozone, there’s a good chance it’s linked to carbon dioxide being consumed by life,” Triaud added. “And if this is life, it’s amazing life. It wouldn’t just be a few bacteria. It would be a planet-wide biomass that can process and interact with large amounts of carbon.”
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Researchers believe JWST can already measure the abundance of carbon dioxide and ozone in near-Earth multi-planetary systems.
This includes the TRAPPIST-1 system, located 40 light-years away and known to host seven Earth-like planets, many of which are in the habitable zone of their cool stars.
De Wit concluded: “TRAPPIST-1 is one of the few systems where we can perform terrestrial atmospheric studies with JWST.” “We now have a roadmap to find habitable planets. If we all work together, paradigm-shifting discoveries could be made in the next few years.”
The team’s research was published December 28 in the journal Nature Astronomy.