Planetary scientists calculated the possible chemical compositions of the planets in the TRAPPIST-1 system and came to the conclusion that all of them, with the exception of one exomer, are very similar to our planet in terms of the structure of their interior and atmosphere, according to an article sent to publication in the Astrophysical Journal Letters.
“The main goal of the existence of planetary science is to search for planets similar to the Earth in their chemical composition and possessing all the conditions for the origin of life. We can say that astronomers have been looking for other worlds for millennia where life can exist and originate,”says Billy Quarles of the University of Oklahoma in Norman (USA).
In May last year, astronomers from MIT announced the discovery of an extremely unusual star system in the nearest vicinity of the Earth - TRAPPIST-1, located only 40 light years away from us towards the constellation Aquarius. All three planets orbiting this red dwarf are located within the so-called "zone of life", where water can exist in liquid form, and supposedly have a mass comparable to that of Earth.
Later, scientists studied the spectrum of the rays of the star TRAPPIST-1, trying to study the composition of the atmosphere of its planets, and unexpectedly discovered that they are actually not three, but seven, and six of them are within the zone of life. All of these planets are almost "Earth" in size and have a Martian or Earth climate, with the exception of the first planet, TRAPPIST-1b, which looks more like Venus than Mars or Earth.
According to Quarles, the location of a planet within the "zone of life" does not guarantee that life can exist on it. Even rather small exoworlds, whose size or mass is only 2-3 times larger than similar parameters for the Earth, may turn out to be “ocean planets” unsuitable for the existence of complex life forms. In addition, they may lack an atmosphere or it may be too thick, which will turn them into analogues of Venus, not Earth.
For this reason, Quarles and his colleagues decided to test whether the "seven sisters" in the TRAPPIST-1 star system could be anything other than Earth analogs. To do this, scientists analyzed all known data on the passages of these planets along the disk of a red dwarf and tried to calculate their exact masses, density and thickness of the atmospheres. In turn, based on these data, planetary scientists determined how much water can be present on the surface of these planets.
As these calculations showed, only one planet, TRAPPIST-1f, located in the center of the life zone and considered one of the main candidates for the role of the Earth's twin, is in fact an “ocean planet” - 20-25% of its mass is water. This water, due to its short distance to the star, will be heated to very high temperatures and will cover the planet with a thick cloud of vapor, which will make life impossible on it.
All the other six planets, according to them, are more similar to the Earth - the proportion of water in their mass should not exceed a few percent, and their bowels should be composed of rocks similar in composition and density to terrestrial minerals.
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The most suitable for life, therefore, will not be TRAPPIST-1f, but its smaller neighbor TRAPPIST-1e, located a little closer to the star. In addition, life can exist on the planet TRAPPIST-1g, which makes one revolution around the star in 13 incomplete days. On their study, scientists plan to focus their efforts in the future, which, they hope, will help us get more accurate data on their composition and suitability for life.
