The TRAPPIST-1 system made headlines last year when scientists announced that it had been found and called it a "holy grail" discovery. It consists of a total of seven planets subsequently named in alphabetical order, with the third and fourth planets in particular (TRAPPIST-1d and TRAPPIST-1e) being the most likely to harbor life.
According to Simon Grimm, an astronomer for the Center for Space and Habitability at the University of Bern in Switzerland, the two planets could potentially have life on them based on their composition. Describing both of the planets, Grimm said that they are "the most likely to have liquid water on them." And what's more, TRAPPIST-1e is said to be quite similar to Earth because it "receives the same amount of energy from its star" as the Earth does from the Sun.
In fact, both planets D and E are in the best possible location in their system, which then contributes to the likelihood that they could have a similar composition to the planet Earth. Compared to Earth's 0.02 percent ocean density, some of the planets on the TRAPPIST-1 system contain as much water as five percent of their masses.
According to Dr. Amaury Triaud, a professor from the University of Birmingham who helped the team that worked on the study, planet E does indeed present the highest chance of containing life as we know it -- or something close to that. "Of the seven planets, and of all the exoplanets that have been identified so far, TRAPPIST-1e is the most resembling Earth," he explained, "when we consider the amount of energy a planet receives from its star, and its density, which reflect its internal composition."
As for the other planets in the system, they are deemed to be either too hot or too cold, based on their proximity to their star. As Grimm stated, planets B and C are most likely to contain "gaseous" water, while planets F, G, and H are likely the coldest planets of the bunch and might have water "in the form of ice."
With all this talk of the possible water situation in each of the seven planets, it's currently not possible to determine for sure whether or not water is present in them. At the same time, scientists have been unable to confirm whether or not oxygen is present anywhere in the TRAPPIST-1 system.
With that said, Triaud makes it clear that while oxygen may be a prerequisite of life here on Earth, the same doesn't necessarily need to be true for other planets, especially those outside of the solar system. "Oxygen is not required for life to exist," he explained, "however, if present, oxygen gas is useful to reveal that biological processes such as photosynthesis are active."
"When astronomers refer to life, we often mean any sort of organism, including micro-organisms and plants, which are living beings that have most profoundly changed the chemistry of our atmosphere."
Knowing exactly what conditions they are looking for, scientists are now planning to study the TRAPPIST-1 planets even further, especially to figure out their exact compositions. Part of this effort involves a plan by the National Aeronautics and Space Administration (NASA) to launch what it calls the James Webb telescope sometime next year. They will undoubtedly share the details of their findings as soon as they discover something new.
Follow the latest updates regarding the search for life outside of the solar system in Space.news.