In a new study, an international team of scientists shows that the lack of carbon in an exoplanet’s atmosphere compared to other objects in the system can be taken as a clear sign of the presence of liquid water on its surface. Indicated. Importantly, this method of finding habitable worlds can still be used today.
To date, more than 520 exoplanets and approximately 10,000 candidates are known. The launch of the James Webb Space Telescope and the construction of his ELT observatory brought about qualitative changes in the field of study of these otherworldly objects, from simple exploration to the study of the properties of exoplanets. By observing how exoplanets fly in front of their stars (so-called transits), astronomers can now draw conclusions about temperature differences, pressure, and, if necessary, the composition of the atmosphere. . With sufficient precision, it is possible to identify isotopes of elements, measure wind speeds, and study the delicate atmosphere.
So far, these methods have mainly been applied to gas giant planets flying close to their stars. But with the help of theoretical calculations and modeling, scientists are exploring ways to use them to study Earth-like exoplanets. The study’s results will allow James Webb to study carbon dioxide and water in the atmospheres of nearby terrestrial planets with warm surface conditions in just 10 passes. For example, the TRAPPIST-1 system of planets. But it would take the James Webb more than 1,000 passes to detect oxygen, O2, the biological signal that indicates the presence of life. In fact, he has to spend all his working time on this object.
Another difficult problem to solve is the presence of large amounts of liquid water on the surfaces of exoplanets. Scientists use surface reflections and the reflection of sunlight to look for it in our solar system. In particular, the presence of liquid on the surface of Saturn’s largest moon, Titan, was confirmed. Of course, the capabilities of our telescopes are not sufficient for such observations in other systems. But it was the search for life on nearby celestial bodies that got the new study’s authors thinking about carbon dioxide. Venus, Earth, and Mars are similar in many ways in their configuration and position relative to the Sun. However, Earth is the only planet with liquid water, and only Earth has significantly less carbon dioxide in its atmosphere: 0.04% compared to more than 95% on Venus and Mars. Moreover, low carbon dioxide levels are not a modern feature of our planet. The CO2 content in the atmosphere 4 billion years ago (the age of the Earth is approximately 4.5 billion years) was approximately 10%, and 2.5 billion years ago it was 2.5%.
“We think these planets formed in a similar way, and if we find that one of the planets today is significantly depleted in carbon, that means it has gone somewhere else. “A strong water cycle capable of removing the atmosphere would need to involve an entire ocean of liquid water,” said Professor Amaury Tryaud of the University of Birmingham, UK, one of the study’s authors. explained. So an international team of scientists from the Massachusetts Institute of Technology (USA), the University of Birmingham (UK), and other institutions in France and the USA investigated the possibility of using CO2 deficiency as a sign of the habitability of exoplanets. did. The research results were published in the journal Nature Astronomy and were promising.
The main “emission” of carbon dioxide from the atmosphere is liquid water in which carbon dioxide is dissolved. The carbonates formed at the bottom then become “trapped” in the planet’s crust and mantle. Therefore, not enough carbon returns to the atmosphere for the atmospheres of Venus or Mars.
When it comes to life, the two main biological pathways that “absorb” carbon from Earth’s atmosphere are photosynthesis and shell production. Biology contributes about 20% to the Earth’s carbon cycle, so other evidence, such as the presence of ozone, is needed to confirm its impact. Based on this analysis, the authors developed a strategy for exploring habitable worlds. According to their calculations, a suitable system would need observational data from 10 passes to record an exoplanet’s atmosphere. 40 passes to assess the lack of carbon dioxide in her one of the planets. We then make 100 transits to estimate the amounts of ozone, methane, and carbon monoxide. Using this data, it will be possible to determine the cause of carbon deficiency: the presence of life, liquid water, or both.
Today, the James Webb Space Telescope can begin searching for carbon dioxide starvation in late red dwarf terrestrial planets, the study’s authors say. “Only TRAPPIST-1 and a few other systems are suitable for studying the atmospheres of terrestrial planets with James Webb, and now we have plans to look for habitable worlds there. “If we work together, we will make breakthrough discoveries within the next few years,” said study author Julian de Witt, an assistant professor at the Massachusetts Institute of Technology.