A scientist explained an exoplanet's potential habitability can be determined by studying its atmosphere. The scientist noted that the presence of life on an exoplanet can be determined using Earth and space-based observatories such as NASA's James Webb Space Telescope.
To determine the habitability of exoplanets, scientists usually check if they are orbiting their host stars from a region known as the Goldilocks Zone. Orbiting within this region indicates that the planet is neither too far nor too close to its host star, which means it might have the right condition to host life.
Biosignatures As Clues To Life
Aside from an exoplanet's proximity from its host star, an alien world's potential habitability can also be determined through its biosignature. Biosignatures are chemical traces in the atmosphere that serve as telltale signs regarding an exoplanet's environmental conditions.
For example, Earth's atmosphere is composed of 21 percent oxygen. This biosignature is attributed to the oxygen produced by the planet's plant life through photosynthesis. According to Victoria Meadows, an exoplanet researcher from the University of Washington, detecting biosignatures will play a crucial role in the missions of new observatories.
Identifying The Correct Biosignatures
As noted by Meadows, one of the biosignatures that space and ground-based telescopes will look for is carbon dioxide. Although CO2 is not technically a biosignature on its own, Meadows' finding carbon dioxide existing with another chemical in the atmosphere could indicate that an exoplanet contains life.
"Both Venus and Mars have atmospheres with high levels of CO2, but no life," Meadows said during an interview. "Instead [the James Webb Space Telescope] can look for another potential biosignature, methane gas in the presence of CO2. Methane should normally have a short lifetime with CO2. So if we detect both together, something is probably actively producing methane. On Earth, most of the methane in our atmosphere is produced by life."
Exploring The TRAPPIST-1 System
According to Meadows, laboratories operating the new observatories have already identified the exoplanets that they will analyze. Many of these are about 40 light-years from Earth and orbit small stars. Some of the exoplanets that will be included in the observations are those orbiting a cool red dwarf star known as TRAPPIST-1.
"We've identified TRAPPIST-1 as the best system to study because this star is so small that we can get fairly large and informative signals off of the atmospheres of these worlds," Meadows stated. "These are all cousins to Earth, but with a very different parent star, so it will be very interesting to see what their atmospheres are like."