Scientists have proposed a new technique that would help researchers map oceans on exoplanets, a key step in finding extraterrestrial life. – Writes live sciences.
In a new study published December 28 in the journal Nature Astronomy, researchers hypothesize that if an exoplanet's atmosphere contains less carbon dioxide than its neighbors, it might have significant amounts of water on its surface — or even life.
Currently, finding liquid water on planets outside the solar system is a major task. Liquid water has not been confirmed to exist on any of the approximately 5,000 exoplanets discovered so far. The best scientists can do is detect traces of water in exoplanet atmospheres and determine whether it is possible in principle for the planet to contain liquid water. We know that initially Earth's atmosphere was mainly carbon dioxide, but that carbon dissolved into the ocean and made the planet capable of sustaining life over the past four billion years or so.
When carbon dissolves in the ocean, tectonic activity traps it in the Earth's crust, creating an effective carbon reservoir. Part of the reason is that the level of carbon dioxide in Earth's atmosphere is much lower compared to that of our neighbours: Earth's atmosphere contains about 0.04% carbon dioxide, while the atmospheres of Venus and Mars are over 95%.
If scientists observe a similar low-carbon atmosphere on an exoplanet, it could mean the existence of giant oceans similar to our own.Finding carbon dioxide is easier than finding liquid water. Carbon dioxide absorbs infrared radiation very well, which means it produces a strong signal that scientists can detect.
It is also possible to perform this technique using existing telescopes, such as the James Webb Space Telescope. Observations on the ground are also possible because carbon dioxide is measured at distinct wavelengths – while Earth's atmosphere experiments at other wavelengths because it partially absorbs the signals.
Another scenario that could contribute to the decline in carbon dioxide content in the atmosphere is life itself. The main ways carbon is sequestered on Earth is through photosynthesis and shell formation, and about 20% of total carbon sequestration on Earth is through biological processes.
Despite initial high hopes, most colleagues have concluded that Large telescopes like the James Webb Space Telescope cannot detect life on exoplanets. This work offers new hope. Using the CO2 signal, not only can we infer the presence of liquid water on a distant planet, it also provides a way to identify life.
Although the method appears successful in principle, there may be hurdles because it is not known how many Earth-like planets have atmospheres. Finding the perfect system to test will be a little harder than previously thought, but as researchers discover more and more exoplanets, they will discover more atmospheres. Can this technology help us find out if they can sustain life?
(Source: Live Science: https://www.livescience.com/)
