Four of the seven TRAPPIST-1 exoplanets may possibly have large amounts of water, scientists say. These findings may increase the possibility of finding life outside of our solar system.
How much water is there on the TRAPPIST-1 planets? [Image by T. Pyle/R. Hurt/NASA/ESO]
The discovery of the seven Earth-size exoplanets just 39 light years away from Earth was one of this year's most exciting discoveries. When news broke that they were also possibly habitable, the excitement grew. However, as more and more information about the planets came in, scientists began to waver a little on the habitability of the planets. For one thing, the planets were tidally locked to their star, which means that only one side of the planets face the star. As a result, one side of the planets are scorching hot, while the other side is freezing cold.
This tidbit of information doesn't bode well for hopes that life can thrive on the planets. However, scientists are now closing in on which planets are more likely to be habitable than the others.
Planets e, f, g, and h may be able to host life. [Image by NASA/JPL-Caltech]
An international team of scientists used the Hubble space telescope to analyze TRAPPIST-1's ultraviolet radiation levels. This way, they can calculate the possibility that water can exist on the planets.
Why ultraviolet radiation? A star's ultraviolet radiation can greatly affect the atmosphere of its planets. Lower ultraviolet radiation levels can break water molecules down to oxygen and hydrogen, while higher levels of radiation can be absorbed by oxygen and hydrogen, allowing the two gases to escape out to space. Scientists now say that four of the system's outer planets may be able to host water.
The researchers used computer models to make sense of data like TRAPPIST-1's UV radiation, the distance of the planets from their host star, and the changes that the star's radiation and habitable zone underwent over thousands of years. It turns out that, at least for the four outermost planets, there isn't enough radiation to break water molecules down or evaporate them.
According to the computer models, the four outermost TRAPPIST-1 exoplanets have possibly lost an amount of water equivalent to three times the amount of water in Earth's oceans over eight billion years. However, significant amounts of water could still be present on the planets.
Could this be what surface of the TRAPPIST-1 planets look like? [Image by NASA/JPL-Caltech]
It's also possible that the four outermost planets regained a lot of water through volcanic events, which may have released water from under the planets' surface. Interestingly, the researchers also found that TRAPPIST-1 emits enough radiation that the planets could have lost 20 times more water in the last eight billion years.
While calculations are all well and good, however, measurements are still necessary. Thus, further observations are crucial to ascertaining whether or not the four outermost planets do indeed have plenty of water.
The TRAPPIST-1 exoplanets are one of the prime candidates in the search for alien life. As a general rule, the presence of water on another planet can mean that life is possible. Even if the TRAPPIST-1 planets don't host life, however, they're still a treasure trove of information on what exoplanets are like and how they differ from the planets in our solar system.
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