Webb telescope probably didn’t find life on an exoplanet — yet

The UC Riverside study, published within the Astrophysical Journal Letters, could also be a disappointment to extraterrestrial enthusiasts but doesn’t rule out the near-future possibility of discovery.

In 2023 there have been tantalizing reports of a biosignature gas within the atmosphere of planet K2-18b, which appeared to have several conditions that may make life possible.

Many exoplanets, meaning planets orbiting other stars, are usually not easily comparable to Earth. Their temperatures, atmospheres, and climates make it hard to assume Earth-type life on them.

Nonetheless, K2-18b is a bit different. “This planet gets almost the identical amount of solar radiation as Earth. And if atmosphere is removed as an element, K2-18b has a temperature near Earth’s, which can also be an excellent situation during which to seek out life,” said UCR project scientist and paper creator Shang-Min Tsai.

K2-18b’s atmosphere is principally hydrogen, unlike our nitrogen-based atmosphere. But there was speculation that K2-18b has water oceans, like Earth. That makes K2-18b a potentially “Hycean” world, which implies a mix of a hydrogen atmosphere and water oceans.

Last yr, a Cambridge team revealed methane and carbon dioxide within the atmosphere of K2-18b using JWST — other elements that would point to signs of life.

“What was icing on the cake, by way of the search for all times, is that last yr these researchers reported a tentative detection of dimethyl sulfide, or DMS, within the atmosphere of that planet, which is produced by ocean phytoplankton on Earth,” Tsai said. DMS is the essential source of airborne sulfur on our planet and should play a job in cloud formation.

Since the telescope data were inconclusive, the UCR researchers wanted to grasp whether enough DMS could accumulate to detectable levels on K2-18b, which is about 120 light years away from Earth. As with every planet that distant, obtaining physical samples of atmospheric chemicals is unimaginable.

“The DMS signal from the Webb telescope was not very strong and only showed up in certain ways when analyzing the information,” Tsai said. “We desired to know if we might be sure of what appeared like a touch about DMS.”

Based on computer models that account for the physics and chemistry of DMS, in addition to the hydrogen-based atmosphere, the researchers found that it’s unlikely the information show the presence of DMS. “The signal strongly overlaps with methane, and we expect that picking out DMS from methane is beyond this instrument’s capability,” Tsai said.

Nonetheless, the researchers imagine it is feasible for DMS to build up to detectable levels. For that to occur, plankton or another life form would have to supply 20 times more DMS than is present on Earth.

Detecting life on exoplanets is a frightening task, given their distance from Earth. To search out DMS, the Webb telescope would wish to make use of an instrument higher capable of detect infrared wavelengths within the atmosphere than the one used last yr. Fortunately, the telescope will use such an instrument later this yr, revealing definitively whether DMS exists on K2-18b.

“The very best biosignatures on an exoplanet may differ significantly from those we discover most abundant on Earth today. On a planet with a hydrogen-rich atmosphere, we could also be more prone to find DMS made by life as a substitute of oxygen made by plants and bacteria as on Earth,” said UCR astrobiologist Eddie Schwieterman, a senior creator of the study.

Given the complexities of searching far-flung planets for signs of life, some wonder in regards to the researchers continued motivations.

“Why will we keep exploring the cosmos for signs of life? Imagine you are camping in Joshua Tree at night, and also you hear something. Your instinct is to shine a light-weight to see what’s on the market. That is what we’re doing too, in a way,” Tsai said.