Scientists using the Hubble Space Telescope say they found evidence of water on the Earth-sized TRAPPIST-1 planets. On February, scientists announced they had found seven Earth-sized planets orbiting a dwarf star dubbed TRAPPIST-1 located 40 light years away.

Planetary scientists said the planets were likely rocky worlds with atmospheres, which were possibly capable of supporting liquid water, particularly the three planets that orbit in the habitable zone where surface temperatures oscillate between 0 and 100 degrees Celsius. Now, it appears as if the Hubble helped to confirm that theory.

TRAPPIST-1b and TRAPPIST-1c. Image Credit: Mundo TKM
Renditions of the TRAPPIST-1b and TRAPPIST-1c planets. Image Credit: Mundo TKM

The international team of scientists, led by Swiss astronomer Vincent Bourrier of the Observatoire de l’Université de Genève, announced the surprising discovery on Thursday.

Astronomers claim more than one TRAPPIST-1 exoplanet has water on its surface

Last year, a group of scientists using the ESO’s Transiting Planets and Planetesimals Small Telescope, or TRAPPIST, found that a small, dim red dwarf star located about 39 light years away had three planets orbiting it. The exoplanets were all Earth-sized, and scientists estimated that their temperatures were between 0 and 100 degrees C.

The discovery was confirmed using other telescopes, including NASA’s Spitzer Space Telescope and the ESO’s Very Large Telescope. In February this year, the scientists published their findings in Nature, where they explained that there are seven Earth-sized planets, noting that six are likely rocky and all seven could potentially support liquid water.

Those findings are now being supported by an international team of scientists working with the Hubble Space Telescope. The scientists used Hubble to study the amount of ultraviolet light reaching the planets and to measure the amount of hydrogen these bodies are sending into space.

“Ultraviolet radiation is an important factor in the atmospheric evolution of planets,” said Bourrier in a statement. “As in our own atmosphere, where ultraviolet sunlight breaks molecules apart, ultraviolet starlight can break water vapor in the atmospheres of exoplanets into hydrogen and oxygen.”

An artist’s concept of the TRAPPIST-1 star, an ultra cool red dwarf with seven Earth-size planets orbiting it. Image Credit: NASA/JPL-Caltech

Lower-energy ultraviolet radiation breaks up water molecules in a process known as photodissociation, according to the scientists. But ultraviolet rays with more energy and X-rays heat the upper atmosphere of a planet, thus allowing the products of photodissociation (hydrogen and oxygen) to escape into space. Because hydrogen is the lightest element, it’s particularly prone to this process and oozes out of a planet’s atmosphere in more abundance than any other element.  

TRAPPIST-1b and 1c lost massive amounts of water in past eight billion years

The astronomers explained that due to its lightness, hydrogen gas could escape the exoplanet’s atmosphere and be detected with the Hubble telescope. The researchers observed the amount of radiation emitted by TRAPPIST-1 and found the planets could have lost massive amounts of water over the course of their existence.

That theory seemed especially accurate for the innermost planets of the system, b, and c, as they have received the largest amount of ultraviolet energy.

“Our results indicate that atmospheric escape may play an important role in the evolution of these planets,” Julien de Wit, a co-author of the study from the Massachusetts Institute of Technology, said in the statement.

The results showed the innermost planets of the planetary system, TRAPPIST-1b and TRAPPIST-1c could have lost about 20 Earth-oceans-worth of water in the past eight billion years. However, the findings also suggest the outer planets (e, f, and g), which orbit the habitable zone of TRAPPIST-1, could have lost less water and could still retain massive stores of liquid water on their surface.

James Webb Space Telescope could help answer if there’s water on TRAPPIST-1

The researchers claim the outer planets on the TRAPPIST-1 system could still have vast stores of water. They said that the calculated water loss rates, as well as the geophysical water release rates in the innermost planets, support the idea that the outermost and more massive planets have retained their water.

Unfortunately, they noted that with the currently available data and telescopes no conclusion can be drawn on the water content of the TRAPPIST-1 exoplanets.

“While our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope, they also highlight the need for theoretical studies and complementary observations at all wavelengths to determine the nature of the TRAPPIST-1 planets and their potential habitability,” said Bourrier.

NASA’s James Webb Telescope won’t be available for use until October 2018. NASA engineers spent over two decades building the state-of-the-art telescope, which will be launched next year. NASA says the telescope will collect seven times as much information as Hubble, and it will be the largest telescope mirror to fly in space.

Source: Hubble Space Telescope