News made quite a stir last year, when the James Webb Space Telescope discovered signs of potential alien life on a distant planet. It was a thrilling revelation, but according to a recent study, the conclusion may have been a bit premature. The researchers, however, remain hopeful that the real discovery will not be far off.
Detecting Life on Distant Planets
The crux of the matter lies in the presence of certain gases in the atmosphere of the exoplanet K2-18b, which could potentially be produced by living organisms. These gases are known as biosignatures. The exoplanet already exhibited several intriguing characteristics that could support the existence of extraterrestrial life, which were further supplemented by the discovery of DMS, a gas that is emitted by certain life forms, in its atmosphere. This revelation sent waves of excitement throughout the astronomical community.
A Livable Exoplanet
Most of the exoplanets that Webb scrutinizes are nearly uninhabitable, with their temperature, atmosphere, and climate rendering life almost impossible. There is, however, an odd one out – K2-18b. “This planet receives almost as much sunlight as Earth and disregarding its atmosphere, K2-18b’s temperature is close to that of Earth. This makes it an ideal situation for finding extraterrestrial life,” states scientist Shang-Min Tsai from the University of California.
The atmosphere of K2-18b is predominantly hydrogen-based, unlike our nitrogen-based atmosphere. Moreover, it appears that the exoplanet also possesses oceans of water, making K2-18b a potential ‘Hycean’ world, i.e., a planet with both a hydrogen atmosphere and water oceans.
Discovery of DMS
Last year, a team from Cambridge, utilizing data from Webb, revealed that methane and carbon dioxide were present in the atmosphere of K2-18b. These elements too could be indicative of life. “The cherry on top is that these scientists detected DMS in the planet’s atmosphere last year. This biosignature is produced on Earth by ocean phytoplankton,” Tsai explains. DMS is the primary source of sulfur in the air on our planet and plays a crucial role in cloud formation.
Interpreting Telescope Data
However, the telescope data was open to multiple interpretations. As such, researchers from UC Riverside decided to further analyse the DMS levels on K2-18b, which is a staggering 120 lightyears from Earth, using measurements from the James Webb. “The DMS signal from the Webb telescope was not very strong and it only popped up in certain ways when analyzing the data”, Tsai says. “We wanted to know for sure if what appeared to be a sign of DMS, was indeed an indication of the biosignature”.
No Confirmation of DMS
By utilizing computer models that took into account the hydrogen-based atmosphere of the exoplanet and the chemistry of DMS, the team concluded that there’s no evidence of the biosignature on K2-18b. “The signal highly overlaps with methane. We believe that Webb does not currently have the capacity to detect DMS”, Tsai notes. Only if the DMS in the atmosphere was about twenty times more than the DMS on Earth, then Webb could possibly detect the signal with near certainty.
A Question of Patience
Detecting life on exoplanets is a challenging task, given the huge distance from Earth. To detect DMS, the Webb telescope would need an instrument that is better capable of detecting infrared wavelengths in the atmosphere than the one used last year. The good news is that such an instrument will be activated via Webb later this year, hopefully providing a definitive answer to the presence of DMS in the atmosphere of K2-18b.
“The best biosignatures on an exoplanet usually differ greatly from those commonly found on Earth today. On a planet with a hydrogen-rich atmosphere, it’s more likely to discover DMS produced by living organisms than to find oxygen from Earth-like plants and bacteria,” says astrobiologist Eddie Schwieterman.
