Not so fast (9/14/23)

Good afternoon, and happy Thursday. Everyone’s talking about the “alien remains” presented to the Mexican government this week. As for me, I’m still thinking about the six UFOs reported to the US intelligence community’s task force last year that, upon review, turned out to be birds and/or plastic bags.

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The Long and Winding Search for Vital Signs

There’s been a lot of alien news this week, but don’t get too excited yet—the hunt for extraterrestrial life is not yet over.

This week, NASA announced that JWST has laid eyes—or, at least, spectrograph readings—on a relatively nearby exoplanet that seems as promising a candidate for life elsewhere in the universe as we’ve found to date. The space telescope identified the signatures for methane, carbon dioxide, and a suspected biomolecule in the atmosphere of the planet, which orbits within the habitable zone and may also be covered in a water ocean.

The research team’s findings were accepted to The Astrophysical Journal Letters.

"Our ultimate goal is the identification of life on a habitable exoplanet, which would transform our understanding of our place in the universe," Nikku Madhusudhan, an astronomer at the University of Cambridge and lead author of the paper, said in a release. "Our findings are a promising step towards a deeper understanding of Hycean worlds in this quest."

• Hycean = hot, covered in water, with a hydrogen atmosphere.

Exoplanet K2-18b: The exoplanet in the study, K2-18b, was first spotted by the Kepler telescope orbiting a red dwarf star 124 light-years away from Earth. The planet is classified as a mini-Neptune due to its size, more than twice as large as our planet and about eight times as massive.

Previously, in 2019, Hubble observations of eight transits—i.e., passes in front of its star—of the same exoplanet identified hydrogen and water vapor in its atmosphere. JWST observed two transits, and identified the chemical signatures of carbon dioxide and methane and a lack of ammonia in the atmosphere, but no water vapor.

• These concentrations of gases hint that K2-18bv has a hydrogen-dominated atmosphere surrounding a water ocean that may or may not be liquid.

The readings from JWST’s spectrometer also show a compound called dimethyl sulfide, which, on Earth, is only produced through biological processes. The presence of this molecule has not been confirmed—follow-up observations are planned—and even if it is, it’s possible that geological processes may be able to produce it on other planets. We just don’t know.

Hitches in the Hunt for Life

One of the primary goals of modern astronomy is to identify life—whatever that might look like—somewhere in the universe besides our own home planet. As with any attempt to do what’s never been done before, this endeavor comes without a rulebook. Scientists have come up with a few key things to look for under the assumption that certain conditions found on Earth could also be conducive to the formation of other types of life in other places.

The right place: Exoplanet researchers often look for something called a “habitable zone,” which is the narrow band around a star where the temperatures are just right for liquid water to potentially exist.

While this is a good place to start, it’s an imperfect method. Even exoplanets with water orbiting within habitable zones may have improper conditions for liquid water due to their mass or makeup. It’s also possible that planets outside their stars’ habitable zones may host liquid water, like when they have very dense, heat-retaining atmospheres.

The right stuff: The chemical makeup of an exoplanet also plays a major role in whether it’s a candidate for life. Researchers often look for carbon-based compounds and hydrogen-rich atmospheres, which resemble Earthly conditions, or biomolecules.

This is very tough to narrow down. In the K2-18b study, different teams of researchers have already come up with conflicting reports of what might be present in the atmosphere. And these conflicts persist in lots of spectrograph readings. Different observations of Venus, for example, have yielded conflicting reports of whether or not there is phosphine, a potential biomarker, in the atmosphere. These findings are very difficult to verify.

Looking ahead: The research team on the study of K2-18b is planning follow-up observations using the spectrograph on JWST’s Mid-Infrared Imager (MIRI) instrument, with which it hopes to verify or debunk the more contentious readings.

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Other News from the Cosmos

• NASA is appointing a director of UAP research. (I promise that’s all the alien news you’re getting from me today.)

• A robot digging below the ice sheets of Antarctica is paving the way for similar projects on the icy ocean moons of Europa and Enceladus.

• Two polar ring galaxies, a type of galaxy with a ring of gas perpendicular to the main spiral disc, have been spotted, hinting that these may be more common than previously thought.

• Haloes of dark matter surrounding ancient galaxies have been “weighed” for the first time.

The View from Space

JWST is, as always, on a roll. This time, it’s captured this image of the bipolar jet Herbig-Haro 211 as it zooms along through space.