This kind of study might provide a better understanding of the climate changes that Earth is currently experiencing and how its atmosphere might change in the future.
The Barcelona Supercomputing Center - Centro Nacional de Supercomputación (BSC-CNS) researcher Paolo De Luca has participated in the study contributing with his extreme climate events expertise.
An international research team, led by the researcher Assaf Hochman of the Fredy & Nadine Herrmann Institute of Earth Sciences at the Hebrew University of Jerusalem in collaboration with Paolo De Luca at the Barcelona Supercomputing Center - Centro Nacional de Supercomputación (BSC-CNS) and Thaddeus D. Komacek at the University of Maryland, has successfully developed a state-of-the-art framework to study the climate variability of the atmospheres of exoplanets—i.e. planets that orbit stars different than the Sun. The joint study was published in the prestigious Astrophysical Journal.
The astronomical research of exoplanet climates is approaching the point at which climate variability will need to be taken into account to characterise their atmospheres. The processes that drive climate variability on exoplanets are a priori unknown, but for rocky exoplanets they are likely to include weather and extreme climate events similar to Earth, such as heat waves, hurricanes and cold spells. Classifying climate conditions and measuring climate sensitivity are central elements when assessing the viability of exoplanets as potential candidates for inhabitance.
“With this study we applied for the very first time techniques which have been only used for studying Earth. Understanding the mean climate sensitivity to carbon dioxide and extreme climate events on exoplanets, along with their physical drivers, is very important for assessing potential inhabitance”, explains Paolo De Luca, a climate scientist at the Earth Sciences Department at BSC. And he adds: “For example, we, as humans, would not be able to survive on planets with an average temperature of 50º C or with extreme temperatures of 100º C. Therefore this is why we are comparing exoplanets' characteristics with the ones of Earth's: to find similarities between the planets that can provide insights into possible places where life could emerge or is already present.”
TRAPPIST-1e habitability
In this direction, the here presented study documents a new pathway for understanding the effect that varying planetary parameters have on the climate variability of potentially inhabitable exoplanets and on Earth. The research focuses on investigating the sensitivity of the exoplanet TRAPPIST-1e’s climate to increases in greenhouse gases and to compare it with similar conditions on Earth.
TRAPPIST-1e is a temperate rocky, close-to-Earth-sized exoplanet orbiting within the habitable zone of the ultracool dwarf star TRAPPIST-1. By means of a computerised simulation of the exoplanet’s climate, the research team could assess the impact of changes in greenhouse gas concentration. They focused on the effect of an increase in carbon dioxide on extreme weather conditions, and on the rate of changes in the weather of the planet. “These two variables are crucial for the existence of life on other planets, and they are now being studied in depth for the first time in history,” explains Hochman, the first author of this study.
The scientists found that TRAPPIST-1e has a significantly more sensitive atmosphere than Earth, composed of carbon dioxide, nitrogen, and water. They estimate that an increase in greenhouse gases there could lead to more extreme climate changes than would be experienced here on Earth because, in the case of TRAPPIST-1e, one side of the planet constantly faces its own sun (in the same way that the Moon always has one side facing Earth).
The novelty of the presented methodology lies in the fact that it is not necessary to physically visit the exoplanets to characterise the changings in their atmospheres; now it is possible to do it via transmission spectroscopy, a technique which studies how the atmosphere of the planet affects starlight that is filtered through the planetary limb. As Hochman concluded, “the research framework we developed, along with future observational data from the James Webb Space Telescope (JWST), will enable scientists to efficiently assess the atmospheres of many other planets without having to send a space crew to visit them physically. This will help us make informed decisions in the future about which planets are good candidates for human settlement and, perhaps, even to find life on those planets.”
Future work studying a range of tidally locked rocky exoplanets is required to further elucidate the mechanisms that regulate extreme climate behaviour in exoplanet atmospheres relative to Earth.
More about TRAPPIST-1e
Located approximately 40 light-years away from Earth, in the constellation of Aquarius, TRAPPIST-1e orbits its parent M-type star, TRAPPIST-1. The planet’s mass is 0.692 Earths and it takes 6.1 days to complete one orbit around its star. Its discovery was announced in 2017.
It is scheduled that the JWST will document TRAPPIST-1e in the coming year and the eventual atmospheric characterization resulting from this observation may potentially enable the detection of an atmosphere along with key atmospheric species and biosignature pairs, such as carbon dioxide and methane.
- Caption: Artist’s concept of TRAPPIST-1 planetary system based on available data about the planets' diameters, masses and distances from the host star, as of February 2018. TRAPPIST-1e is the rockiest planet of them all, but still is believed to have the potential to host some liquid water. Credit: NASA/JPL-Caltech/R. Hurt & T. Pyle (IPAC).