by Unfortunately, recent reports from the James Webb Space Telescope (JWST) that detected signs of life on a distant planet outside the solar system are a little premature. That’s the conclusion of research conducted by scientists from the University of California Riverside (UCR).
Although it will probably disappoint all of us who are eager to confirm extraterrestrial life, however, it does not mean that JWST will not find traces of life in the atmosphere of an extrasolar planet, or “exoplanet,” in the future.
Excitement recently began over the possible detection of life signs on an exoplanet in 2023 when the JWST discovered possible “biosignal” elements in the atmosphere of the exoplanet K2-18 b, a Super-Earth located about 120 light years from Earth.
While many exoplanets are extreme, violent or at least “alien” in nature – whether they are blasted by intense radiation from their stars, lack a solid surface or are frozen remnants at the edge of their systems – K2-18 b was a real culprit. . a target in the search for life because it is quite similar to our planet.
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A sea world similar to Earth
K2-18 b is two to three times the width of Earth and 8.6 times the mass of our planet. It is also located in its star’s habitable zone, the region that is neither too hot nor too cold to support liquid water. The exoplanet is therefore theorized to be an ocean world, or “hycean” world, full of liquid water – a vital ingredient for life as we know it. Unlike Earth, however, this exoplanet’s atmosphere appears to be mostly hydrogen rather than nitrogen.
“This planet receives almost the same amount of solar radiation as Earth. And if the atmosphere is removed as a factor, the temperature of Earth is close to K2-18 b, which is also an ideal situation for life to occur,” staff member and UCR project scientist Shang-Min Tsai said in a statement.
The main takeaway from the 2023 investigation of K2-18 b, by Cambridge University scientists using the James Webb Space Telescope, was the discovery of carbon dioxide and methane. These molecules were detected without any traces of ammonia, which indicated that this should indeed be a hydrogen world with a large ocean under a hydrogen-rich atmosphere. But there was also the hint of something else – something very exciting.
“What was icing on the cake, in terms of the search for life, was that last year these researchers reported the temporary detection of dimethyl sulfide, or DMS, in the atmosphere of that planet, produced by ocean phytoplankton on Earth,” Tsai said. That means if DMS is accumulating to detectable levels, there must be something on K2-18 b, possibly a life form, which it produces at 20 times the rate found on Earth.
There is icing on the Super-Earth cake, but can we eat it?
Because the detection of DMS was inconclusive, however, even the team leader of the investigation, University of Cambridge scientist Nikku Madhusudhan, urged caution regarding the discovery of DMS. He said future JWST observations would be needed to confirm its presence in K2-18’s atmosphere – but not everyone got the memo.
However, the inconclusive nature of the DMS detection prompted the UCR team to follow up on the detection.
“The DMS signal from the JWST was not very strong and only showed up in some ways when analyzing the data,” Tsai said. “We wanted to know if we could be sure what was like a clue about DMS.”
What this second team found was that while computer models accounted for a hydrogen-based atmosphere and the physics and chemistry of DMS, the original data was unlikely to suggest detecting DMS. “The signal overlaps strongly with methane, and we think it is beyond the ability of this instrument to pick DMS out of methane,” Tsai said.
That means that the JWST will have to look at the world with instruments other than the NIRSS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph) used to carry out the initial investigation that discovered the DMS hints. Fortunately, Madhusudhan’s team is continuing to observe K2–18 b with JWST’s other main instrument, the MIRI (Mid-Infrared Instrument), and the researchers are gathering more information about the environmental conditions on the exoplanet. .
“The best biosignatures on an exoplanet may differ significantly from the most abundant ones on Earth today,” said team leader and UCR astronomer Eddie Schwieterman. “On a planet with a hydrogen-rich atmosphere, we may be more likely to find DMS made by life instead of oxygen made by plants and bacteria like on Earth.”
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Does this small disappointment deter scientists who are searching the cosmos for signs of life? Not a chance – and it does not emphasize the importance of the initial investigation as a step forward in our understanding of the world of ion medicine, some of the most promising goals in that search.
“Why are we exploring the cosmos for signs of life?” Tsai asked rhetorically. “Imagine you’re camping in Joshua Tree at night, and you hear something. Your instinct is to shine a light to see what’s out there. That’s what we’re doing too, in a way.”
The new study discussing these results was published on May 2 in The Astrophysical Journal Letters.
