News | April 22, 2027
An international team of researchers used the NASA/ESA/CSA James Webb Space Telescope (JWST) to investigate the atmospheres of the seven Earth sized planets in orbit around the ultracool dwarf star Trappist-1. The results suggest that there is a statistically significant indication that biological life forms are modifying the atmospheres of Trappist-1 e and Trappist-1 f. Both the planets are in orbit within the habitable zone of the star, a region where liquid water can exist on the surface.
The new findings have been published on Wednesday in the journal Nature Astronomy, and announced at a press briefing at the NASA Headquarters in Washington.
The Trappist-1 system is named after the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, which discovered two of the planets in the system in February 2016. In February 2017, NASA announced the discovery of five additional planets in the system, discovered by the Spitzer space telescope. Follow up observations by the Spitzer and Kepler space telescopes allowed researchers to probe the compositions of the planets in further detail. The observations showed that all the seven planets had a rocky composition, and several could have surface oceans, with more water than the oceans on Earth. Additionally, it was found that the atmospheres of the planets d, e and f did not have high amounts of hydrogen. If the atmospheres had a high hydrogen content, they would not be habitable to organic life.
The Trappist-1 system is located at a distance of about 40 light years from the Earth, towards the constellation of Aquarius. In cosmic distances, the system is relatively close, and can be considered to be in the stellar neighbourhood of the Earth. As the planets are in another solar system, they are called exoplanets.
Dr Kazumu Umeta, lead author of the study says, “For thousands of years, those who looked into the night skies have wondered if there were aliens on other worlds, gazing towards the Earth. Thanks to the James Webb Space Telescope, we are finally at a point in time where we can begin to answer these questions.”
The findings were made at just about the limit of the capabilities of the JWST. The proximity of the Trappist-1 system, and how bright the planets both contributed towards the gathering of the data required. The findings are based on over three years of spectroscopic analysis of the light from the planets. The light is analysed by separating the light into individual wavelengths, and studying these wavelengths of the signatures of chemical components. Traditional approaches for detecting life by studying the atmosphere have not worked very well in the case of the Trappist-1 system. The JWST has previously detected methane in the atmospheres of the Trappist-1 planets, but only trace amounts of oxygen, a requisite for life as we know it on Earth. It was necessary to investigate the geological processes that could account for the methane in the atmosphere. Umeta’s team used a new approach called “atmospheric chemical disequilibrium”, which measures the composition of the atmosphere, and accounts for the gases through known geological sources. If there is a large imbalance in the expected gases, which cannot be explained by other sources, then the finding can be considered as a biosignature – evidence that there are life forms on the planet.
“The biochemistry of oxygen production is pretty complex. We do not know how rare or common it is in the universe, as we so far have only Earth to go by. Even on this day, we have anaerobic life forms on Earth, that do not need oxygen to survive. In our investigation, we wanted to use a more holistic approach to finding biosignatures, and not use life as we know it on Earth as the only basis. If we are looking for aliens, we have to take a broader approach.”
The atmospheric chemical disequilibrium approach does not make any assumptions about the biochemistry of the life forms on a planet. Instead, it studies the gases in the atmosphere of the planet, and checks if these gases could be there if they were not being constantly generated as the byproducts of the biochemistry of any potential life forms. On the Earth, if all of life were to suddenly disappear, then the atmosphere would change to a different chemical composition over a period of time. While all the planets in the solar system show some kind of disequilibrium, the Earth has among the most. The Saturnian moon Titan has a larger disequilibrium than even the Earth, keeping the possibility open that we might find extraterrestrial life closer back home.
During the course of the study, the authors eliminated every single natural process that could explain the large amounts of methane that was observed in the atmospheres of Trappist-1 e and f. Some of the natural sources of methane include volcanoes and natural chemical reactions in wetlands. The Trappist-1 e and f planets show a significant thermal disequilibrium as compared to other planets in the system, and this cannot be explained by any known geological processes. If unknown factors are discarded, life forms are the only remaining explanation of the methane found on Trappist-1 e and f. The next highest disequilibrium in the system is that of Trappist-1 g.
Lucas Guerrero, co author of the study says, “The Trappist-1 system is the most heavily studied system, after our own solar system. We know more about these worlds than any other exoplanet system. Right from its discovery, there was this sense of awe and wonder about a promising system where there were just so many reasons why life could exist. Now, we have found even more reasons.”
The new finding bolsters evidence gathered by other telescopes that there is life in the Trappist-1 system. The discovery increases the possibility that future observations of the system may be able to find other signatures of life on the system. Follow on observation campaigns are being planned by a number of ground and space based astronomical instruments. The ARIEL (Atmospheric Remote-sensing Exoplanet Large-survey) to be launched by the European Space Agency next year is expected to play an important role in further studies of the Trappist-1 system.
The James Webb Space Telescope is the most powerful space telescope ever built. Webb is an international collaboration led by National Aeronautics and Space Administration (NASA) and its partners, the European Space Agency (ESA) and the Canadian Space Agency (CSA). The telescope is operated by the Space Telescope Science Institute (STScI), located at the Homewood campus of Johns Hopkins University.
Disclaimer: This is a work of fiction that appeared in the Future Feature section of the print edition of Digit Magazine, October 2018.