Another Explanation for K2-18b? A Gas-Rich Mini-Neptune with No Habitable Surface

Artist depiction of the mini-Neptune K2-18 b. Credit: NASA, CSA, ESA, J. Olmstead (STScI), N. Madhusudhan (Cambridge University)

Exoplanet K2-18b is garnering a lot of attention. James Webb Space Telescope spectroscopy shows it has carbon and methane in its atmosphere. Those results, along with other observations, suggest the planet could be a long-hypothesized ‘Hycean World.’ But new research counters that.

Instead, the planet could be a gaseous mini-Neptune.

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There are Mysteries at Venus. It’s Time for an Astrobiology Mission

NASA's Magellan spacecraft captured this image of Venusian craters. Image Credit: NASA/JPL

When scientists detected phosphine in Venus’ atmosphere in 2020, it triggered renewed, animated discussions about Venus and its potential habitability. It would be weird if the detection didn’t generate interest since phosphine is a potential biomarker. So people were understandably curious. Unfortunately, further study couldn’t confirm its presence.

But even without phosphine, Venus’ atmosphere is full of chemical intrigue that hints at biological processes. Is it time to send an astrobiology mission to our hellish sister planet?

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Toxic Gas is Leaking out of Enceladus. It’s also a Building Block of Life.

The Cassini spacecraft captured this image of cryovolcanic plumes erupting from Enceladus' ice-capped ocean. Image Credit: NASA/JPL/CalTech

Enceladus’ status as a target in the search for life keeps rising. We’ve known for years that plumes erupting from the ocean under the moon’s icy shell contain important organic compounds related to life. Now, researchers have found another chemical in the plumes which is not only highly toxic but also critical in the appearance of life.

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Webb Finds Icy Complex Organic Molecules Around Protostars: Ethanol, Methane, Formaldehyde, Formic Acid and Much More

Astronomers have used JWST to study the environments around 30 young protostars and found a vast collection of icy organic molecules. A recent survey identified methane, sulfur dioxide, ethanol, formaldehyde, formic acid, and many more. Image Credit: NASA/ESA/STScI

In the quest to understand how and where life might arise in the galaxy, astronomers search for its building blocks. Complex Organic Molecules (COMs) are some of those blocks, and they include things like formaldehyde and acetic acid, among many others. The JWST has found some of these COMs around young protostars. What does this tell astronomers?

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Could Life Exist in Molecular Clouds?

This image from the APEX telescope, of part of the Taurus Molecular Cloud, shows a sinuous filament of cosmic dust more than ten light-years long. Could life exist in molecular clouds like this one? Credit: ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey 2. Acknowledgment: Davide De Martin.

Our search for life beyond Earth is still in its infancy. We’re focused on Mars and, to a lesser extent, ocean moons like Jupiter’s Europa and Saturn’s Enceladus. Should we extend our search to cover more unlikely places like molecular clouds?

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Adolescent Galaxies are Incandescent and Contain Unexpected Elements

Light from 23 distant galaxies, identified with red rectangles in the Hubble Space Telescope image at the top, were combined to capture incredibly faint emission from eight different elements, which are labelled in the JWST spectrum at the bottom. Although scientists regularly find these elements on Earth, astronomers rarely, if ever, observe many of them in distant galaxies, especially nickel. Image Credit: Aaron M. Geller, Northwestern, CIERA + IT-RCDS

If the Universe has adolescent galaxies, they’re the ones that formed about 2 to 3 billion years after the Big Bang. New research based on the James Webb Space Telescope shows that these teenage galaxies are unusually hot. Not only that, but they contain some unexpected chemical elements. The most surprising element found in these galaxies is nickel.

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Wow. JWST Just Found Methane in an Exoplanet Atmosphere

This artist’s rendering shows the warm exoplanet WASP-80 b. When viewed with human eyes, the colour may appear bluish due to the lack of high-altitude clouds and the presence of atmospheric methane identified by NASA’s James Webb Space Telescope. That makes it similar to the planets Uranus and Neptune in our own solar system. Image credit: NASA.

If there’s one chemical that causes excitement in the search for biosignatures on other worlds, it’s methane. It’s not a slam dunk because it has both biotic and abiotic sources. But finding it in an exoplanet’s atmosphere means that planet deserves a closer look.

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A Galaxy Only 350 Million Years Old Had Surprising Amounts of Metal

The JWST has the power to see the most ancient galaxies in the Universe, as shown in this image of its first deep field. Now, astrophysicists have found carbon in one of these ancient galaxies. Image Credit: NASA, ESA, CSA, and STScI

Astrophysicists working with the JWST have found a surprising amount of metal in a galaxy only 350 million years after the Big Bang. How does that fit in with our understanding of the Universe?

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A Robotic Chemist Could Whip up the Perfect Batch of Oxygen on Mars

Astronauts on Mars will need oxygen. There's oxygen in the atmosphere, but only small amounts. But there's lots of subterranean water on Mars, and that means there's lots of oxygen, too. (Credit: NASA)

Humans on Mars will need oxygen, and Mars’ atmosphere is pretty anemic when it comes to the life-sustaining element. NASA’s Perseverance rover successfully extracted oxygen from CO2 in Mars’ atmosphere, but there are other ways to acquire it. There seem to be vast amounts of water buried under the Martian surface, and oxygen in the water is just waiting to be set free from its bonds with hydrogen.

On Earth, that’s no problem. Just run an electrical current through water, and you get oxygen. But Mars won’t give up its oxygen so easily.

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Life Might Be Easiest to Find on Planets that Match an Earlier Earth

Artist's impression of the "pale orange dot" - what early Earth would have looked like. Credit: NASA/Goddard Space Flight Center/Francis Reddy

We’re inching closer and closer to reliably detecting biosignatures on distant planets. Much of the focus is on determining which chemicals indicate life’s presence.

But life can also create free energy in a system, and excess energy can create chemical disequilibrium. That’s what happened on Earth when life got going. Could chemical disequilibrium be a biosignature?

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