Recent reports that NASA’s James Webb Space Telescope has detected signs of life on a distant planet have understandably caused excitement. The new study casts doubt on that conclusion, but also explains how the telescope could test the gas produced by life.

A study published at UC Riverside Astrophysics Journal LettersIt may disappoint alien enthusiasts, but it doesn’t rule out a discovery in the near future. In 2023, there were surprising reports of a biosignature gas called K2-18b in the planet’s atmosphere, which appears to have a variety of conditions that make life possible.

Many exoplanets, planets orbiting other stars, are difficult to compare with Earth. Their temperatures, atmospheres and climates make it difficult to imagine terrestrial life on them.

But K2-18b is a little different. “This planet receives almost the same amount of solar radiation as Earth. And if the atmosphere is excluded as a factor, K2-18b’s temperatures are close to those of Earth, making it an ideal situation for the search for life,” said the UCR project scientist. and article writer Shang-Min Tsai.

K2-18b’s atmosphere consists mostly of hydrogen, unlike our nitrogen atmosphere. But there are suggestions that K2-18b has water oceans, just like Earth. This makes K2-18b a potentially “Hycean” world; This means the combination of hydrogen atmosphere and water oceans.

Last year, the Cambridge team detected methane and carbon dioxide in the atmosphere of K2-18b using JWST; These were other elements that could be signs of life.

“The icing on the cake in terms of finding life is that last year these researchers reported the preliminary detection of dimethyl sulfide, or DMS, in the atmosphere of this planet, produced by ocean phytoplankton on Earth,” Tsai said. DMS is the main source of sulfur in the air on our planet and may play a role in cloud formation.

Because the telescope data was inconclusive, UCR researchers wanted to understand whether sufficient DMS could accumulate at the levels detected in K2-18b, which is about 120 light-years from Earth. As with any planet this distant, it is impossible to obtain physical samples of atmospheric chemicals.

“The DMS signal from the Webb telescope was not very strong and was only somehow detected during data analysis,” Tsai said. “We wanted to know if we could be sure about what appeared to be a clue to DMS.”

Based on computer models that took into account the physics and chemistry of DMS, as well as the hydrogen-based atmosphere, the researchers found that the data was unlikely to indicate the presence of DMS. “The signal overlaps strongly with methane, and we believe that separating DMS from methane is beyond the capability of this device,” Tsai said.

However, researchers believe DMS can accumulate to detected levels. For this to happen, plankton or another life form would need to produce 20 times more DMS than is present on Earth.

Detecting life on exoplanets is a difficult task given their distance from Earth. To find DMS, the Webb telescope will need to use a better instrument at detecting infrared waves in the atmosphere than the one used last year. Fortunately, the telescope will use such an instrument later this year to definitively detect whether a DMS is present in K2-18b.

“The best biological signatures on an exoplanet can be significantly different from what we most find on Earth today. On a planet with a hydrogen-rich atmosphere, we are more likely to find DMS produced by life rather than oxygen produced by plants and bacteria,” said the study’s senior author. author UCR astrobiologist Eddie Schwieterman, “On Earth.

Given the difficulty of finding signs of life on distant planets, some wonder about the researchers’ motivations.

“Why do we keep exploring space to find signs of life? Imagine you’re camping in Joshua Tree at night and you hear things. Your instinct is to turn on the light to see what’s out there. In a way, that’s what we’re doing,” Tsai said.