Astronomers are nearing a statistically significant finding that could confirm the potential signs of life detected on the distant exoplanet K2-18b are no accident.
The team of astronomers, led by the University of Cambridge, used data from the James Webb Space Telescope (which has only been in use since the end of 2021) to detect chemical traces of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS), which they say can only be produced by life such as phytoplankton in the sea.
According to the university, “the results are the strongest evidence yet that life may exist on a planet outside our solar system.”
The findings were published this week in the Astrophysical Journal Letters and point to the possibility of an ocean on this planet’s surface, which scientists have been hoping to discover for years. In the abstract for the paper, the team says, “The possibility of hycean worlds, with planet-wide oceans and H2-rich atmospheres, significantly expands and accelerates the search for habitable environments elsewhere.”
Not everyone agrees, however, that what the team found proves there’s life on the exoplanet.
Science writer and OpenMind Magazine founder Corey S. Powell posted about the findings on Bluesky, writing, “The potential discovery of alien life is so enticing that it drags even reputable outlets into running naive or outright misleading stories.” He added, “Here we go again with planet K2-18b. Um….there’s strong evidence of non-biological sources of the molecule DMS.”
K2-18b is 124 light-years away and much larger than Earth (more than eight times our mass), but smaller than Neptune. The search for signs of even basic life on a planet like this increases the chances that there are more planets like Earth that may be inhabitable, with temperatures and atmospheres that could sustain human-like lifeforms. The team behind the paper hopes that more study with the James Webb Space Telescope will help confirm their initial findings.
More research to do on finding life on K2-18b
The exoplanet K2-18b is not the only place where scientists are exploring the possibility of life, and this research is still an early step in the process, said Christopher Glein, a geochemist, planetary researcher and lead scientist at San Antonio’s Southwest Research Institute. Excitement over the significance of the research, he said, should be tempered.
“We need to be careful here,” Glein said. “It appears that there is something in the data that can’t be explained, and DMS/DMDS can provide an explanation. But this detection is stretching the limits of JWST’s capabilities.”
Glein added, “Further work is needed to test whether these molecules are actually present. We also need complementary research assessing the abiotic background on K2-18b and similar planets. That is, the chemistry that can occur in the absence of life in this potentially exotic environment. We might be seeing evidence of some cool chemistry rather than life.”
The TRAPPIST-1 planets, he said, are being researched as potentially habitable, as is LHS 1140b, which he said “is another astrobiologically significant exoplanet, which might be a massive ocean world.”
As for K2-18b, Glein said many more tests need to be performed before there’s consensus on life existing on it.
“Finding evidence of life is like prosecuting a case in the courtroom,” Glein said. “Multiple independent lines of evidence are needed to convince the jury, in this case the worldwide scientific community.” He added, “If this finding holds up, then that’s Step 1.”