The results of the study were published in the journal Nature Astronomy.

Scientists speculate that if an Earth-like planet has significantly less carbon dioxide in its atmosphere compared to other planets in the same system, this could be a sign of the presence of liquid water on that planet’s surface. For example, in the solar system, the Earth’s atmosphere contains less carbon dioxide compared to the atmospheres of Venus and Mars due to the water cycle, which removes large amounts of carbon from the gas envelope.

Over hundreds of millions of years, Earth’s oceans absorbed enormous amounts of carbon dioxide, almost equal to what remains in the atmosphere of Venus today. This effect on a planetary scale led to the fact that the Earth became suitable for the existence of living organisms.

In addition, the authors noted that another sign of the possible habitability of the planet is the presence of ozone. On Earth, plants absorb carbon dioxide and release oxygen, which undergoes a photochemical reaction in the stratosphere and turns into ozone. Ozone is easier to detect when observing exoplanets than oxygen itself.

The team estimates that NASA’s James Webb Space Telescope will be able to measure carbon dioxide and possibly ozone in nearby multiplanet systems such as TRAPPIST-1, a system of seven planets 40 light-years from Earth.