Tag: Astrobiology

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Scientists revise view of Titan — and hold out hope for life

Cassini photo of Titan with Saturn in background
An image from NASA’s Cassini spacecraft shows Titan in front of Saturn and its rings. (Credit: NASA / JPL-Caltech / SSI)

A fresh analysis of tidal perturbations on Titan challenges a long-held hypothesis: that the cloud-shrouded Saturnian moon harbors an ocean of liquid water beneath its surface ice. But the scientists behind the analysis don’t rule out the possibility that smaller pockets of subsurface water could nevertheless provide a home for extraterrestrial life.

“The search for extraterrestrial environments is fundamentally a search for habitats where liquid water coexists with sustained sources of energy (chemical, sunlight, etc.) over geological time scales. Our new results do not preclude the existence of such environments within Titan, but rather, further support their plausibility,” University of Washington planetary scientist Baptiste Journaux, a co-author of the study published in Nature, told me in an email.

Journaux acknowledged that the results don’t match up with conventional wisdom. He said they represent a “true paradigm shift” in how scientists think Titan is put together.

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Universe Today

Fresh findings revive debate about life on alien planet

Illustration: K2-18 b planet
An artist's conception shows the planet K2-18 b and its host star. (ESA / Hubble / M. Kornmesser)

Two new studies have sparked fresh debate about a faraway planet with a weird atmosphere. One of the studies claims additional evidence for the presence of life on the planet K2-18 b, based on chemical clues. The other study argues that such clues can be produced on a lifeless world covered with hot magma.

The hubbub illustrates how tricky it can be to determine whether life exists beyond Earth by looking for “biosignatures” with powerful telescopes — in this case, NASA’s James Webb Space Telescope. It also illustrates the potential pitfalls of reporting provocative results.

A study published today in the Astrophysical Journal Letters attracted widespread attention when it reported that the chemical signatures of dimethyl sulfide and dimethyl disulfide had been found in the atmosphere of K2-18 b, which orbits a red dwarf star 124 light-years away from Earth. The findings were a follow-up to an earlier study published by the same researchers, which detected carbon-bearing molecules including methane and carbon dioxide in the atmosphere.

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Scientists identify a potential haven for Martian life

Dusty ice deposits in Martian gullies, as seen in orbital imagery
The white areas on the edges of these gullies in the Martian region of Terra Sirenium, shown in an image from NASA’s Mars Reconnaissance Orbiter, are thought to be areas of dusty ice similar to those identified as potential havens for microbes. (NASA / JPL-Caltech / Univ. of Arizona)

Could microbes endure just beneath the surface of Mars, in layers of dusty ice exposed to just the right amount of sunlight? A newly published study suggests those might be among the most accessible places to search for signs of life on the Red Planet.

The study, published today in Nature Communications Earth & Environment, is based on models developed using impure ice from Greenland. “We did not find any direct evidence for any microbes on Mars,” study lead author Aditya Khuller told me in an email. “We do find that the depths where the radiation (solar and UV) conditions are favorable for photosynthesis within dusty Martian ice intersect with the depths where dusty ice can melt on Mars.”

Khuller is a researcher at NASA’s Jet Propulsion Laboratory who’s due to join the University of Washington’s Applied Physics Laboratory at the end of the month. The paper’s co-authors include one of Khuller’s mentors, UW professor emeritus Steve Warren, whom Khuller says is “the world’s expert in how radiation interacts with snow and ice.”

Modern-day Mars is a cold, dry world, bombarded with life-killing levels of ultraviolet radiation. But scientists say that the planet would have been far more hospitable to life in ancient times. They suggest there’s a chance that hardy organisms could still be hanging on deep down in subsurface havens.

How deep? And how much of a chance? Those are questions that Khuller, Warren and their colleagues sought to answer by modeling the composition of Mars’ ice.

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Universe Today

Europa Clipper starts odyssey to mysterious Jovian moon

Europa Clipper liftoff on SpaceX Falcon Heavy rocket
SpaceX's Falcon Heavy rocket sends NASA's Europa Clipper into space from its Florida launch pad. (NASA Photo / Kim Shiflett)

NASA’s Europa Clipper spacecraft today began its six-year cruise to the Jupiter system, with the goal of determining whether one of the giant planet’s moons has the right stuff in the right setting for life.

The van-sized probe was sent into space from NASA’s Kennedy Space Center atop a SpaceX Falcon Heavy rocket at 12:06 p.m. ET (9:06 a.m. PT). A little more than an hour after launch, the spacecraft separated from its launch vehicle to begin a roundabout journey of 1.8 billion miles (2.9 billion kilometers) from Earth orbit to Europa.

For decades, scientists have been collecting evidence that Europa harbors a hidden ocean of salty water beneath its icy shell. Or are they hidden lakes? Europa Clipper is built to characterize the moon’s surface, and what’s beneath that surface, to an unprecedented degree.

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How to find signs of extraterrestrial life in a grain of ice

Illustration: Europa Clipper flying over Europa
An artist’s conception shows NASA’s Europa Clipper probe flying over Europa. (NASA / JPL-Caltech Illustration)

Scientists have verified that a method to look for cellular life on Europa, an ice-covered moon of Jupiter, just might work. The technique could be put to the test in the 2030s, when NASA’s Europa Clipper probe is due to make multiple flybys over the Jovian moon.

The technique involves analyzing grains of ice that scientists expect one of the instruments on Europa Clipper — known as the Surface Dust Analyzer, or SUDA — to pick up as it flies through plumes of frozen water rising up from Europa’s surface.

“It’s astonishing how the analysis of these tiny ice grains may tell us whether or not there is life on an icy moon. At least we now know that SUDA has these capabilities,” University of Washington planetary scientist Fabian Klenner told me in an email. Klenner is the lead author of a research paper about the process, published today in the open-access journal Science Advances.

SUDA will be capable of analyzing the chemical content of material that hits its detector, using a process called impact ionization mass spectrometry. The key feature of the process described by Klenner and his colleagues is that the analysis would be done on single ice grains, rather than on a blizzard of ice particles. That way, scientists can focus on individual grains that might hold a high concentration of the ingredients of a single cell.

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Scientists visit the kind of lake where life may have arisen

Scientists walking across Last Chance Lake
Researchers walk across Last Chance Lake’s crusty surface in September 2022. (UW Photo / Zack Cohen)

Several years ago, scientists at the University of Washington theorized that key ingredients for life could have built up billions of years ago in special kinds of environments known as soda lakes.

At the time, their hypothesis was based on previously published research, computer modeling and lab experiments. But now the same scientists say they’ve found a shallow lake that just might fit the requirements — and it happens to be just a few hundred miles north of their home base in Seattle.

Their findings, focusing on Last Chance Lake in British Columbia, were published this month in Communications Earth & Environment, an open-access, peer-reviewed scientific journal.

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Cosmic Space

The air of an alien world lifts hopes of detecting life

Blue exoplanet and red parent star in space
An artist's conception shows the exoplanet K2-18 b. (NASA / CSA / ESA / STScI / Cambridge U.)

Readings from NASA’s James Webb Space Telescope confirm the presence of carbon-based molecules including methane and carbon dioxide in the atmosphere of a distant planet known as K2-18 b — which supports previous suggestions that it might be the kind of ocean-covered world capable of harboring marine life.

K2-18 b, which was first detected in 2015 using data from NASA’s now-retired Kepler space telescope, lies in the habitable zone of a star system that’s about 120 light-years away in the constellation Leo. It’s about 8.6 times as massive as Earth, and astronomers regard it as a sub-Neptune — a type of planet that doesn’t exist in our solar system.

Since its initial detection, astrobiologists have been interested in the world’s potential for habitability. They suspected it might be what’s called a Hycean planet — a type of world that’s massive enough to hold onto a hydrogen-rich atmosphere and a globe-spanning sea. The evidence has been piling up: In 2019, researchers reported the chemical signature of water vapor and clouds in K2-18 b’s atmosphere.

The fact that JWST detected an abundance of methane (CH4) and carbon dioxide (CO2), along with a shortage of ammonia (NH3), is consistent with the atmospheric modeling for Hycean planets.

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Fiction Science Club

How we’ll find the first evidence of extraterrestrial life

Illustration: A variety of planets
Astronomers have detected thousands of planets, including dozens that are potentially habitable. (NASA Illustration)

When will we find evidence for life beyond Earth? And where will that evidence be found? University of Arizona astronomer Chris Impey, the author of a book called “Worlds Without End,” is betting that the first evidence will come to light within the next decade or so.

But don’t expect to see little green men or pointy-eared Vulcans. And don’t expect to get radio signals from a far-off planetary system, as depicted in the 1992 movie “Contact.”

Instead, Impey expects that NASA’s James Webb Space Telescope — or one of the giant Earth-based telescopes that’s gearing up for observations — will detect the spectroscopic signature of biological activity in the atmosphere of a planet that’s light-years away from us.

“Spectroscopic data is not as appealing to the general public,” Impey admits in the latest episode of the Fiction Science podcast. “People like pictures, and so spectroscopy never gets its fair due in the general talk about astronomy or science, because it’s slightly more esoteric. But it is the tool of choice here.”

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Scientists say Saturnian moon has all of life’s essentials

Illustration: Cutaway view of Enceladus, highlighting water geysers that rise through ice layer
A cutaway view shows water rising up from Enceladus’ ice-covered ocean. (NASA / JPL-Caltech Illustration)

Phosphorus, an essential ingredient for life as we know it, has been detected for the first time in water samples that can be traced back to Enceladus, an ice-covered moon of Saturn.

The discovery, reported today in the journal Nature, lends further support to suggestions that life could lurk within Enceladus’ ice-covered oceans — and perhaps in similar environments elsewhere in the solar system.

Phosphorus-containing compounds, known as phosphates, provide the molecular backbone for DNA and RNA molecules. Adenosine triphosphate, or ATP, serves as the source of energy for living cells. This research marks the first time that phosphates have been traced to an extraterrestrial ocean. The Nature paper suggests that phosphate levels in Enceladus’ hidden seas could be hundreds or even thousands of times higher than what exists in Earth’s oceans.

“By determining such high phosphate concentrations readily available in Enceladus’ ocean, we have now satisfied what is generally considered one of the strictest requirements in establishing whether celestial bodies are habitable,” study co-author Fabian Klenner, a postdoctoral researcher at the University of Washington, said in a news release.

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A new type of salt crystal could exist on Europa

Galileo's view of Europa's surface
An image from NASA’s Galileo orbiter shows Europa’s surface of salt-streaked ice. (Credit: NASA / JPL / Ted Stryk)

A prime target in the search for extraterrestrial life is Europa, a moon of Jupiter that’s covered with a sheet of salty ice. But what kind of salt is there? Researchers say they’ve created a new kind of salt crystal that could fill the bill, and perhaps raise hopes for finding life under the ice.

This salt crystal is both exotic and common: It’s actually table salt — also known as sodium chloride, with the chemical formula NaCl — but bound up with water molecules to form a hydrate that doesn’t exist naturally on Earth.

Earthly sodium chloride hydrates are composed of one salt molecule linked by hydrogen bonds with two water molecules. In contrast, the hydrates created in the lab consist of two NaCl molecules to 17 water molecules, or one NaCl molecule to 13 water molecules. (The structure for a third type of “hyperhydrated hydrate” couldn’t be determined.)

That’s promising news for scientists who study Europa and other ice-covered worlds — including two other Jovian moons, Callisto and Ganymede; and the Saturnian moons Enceladus and Titan. Spectral observations indicate that Europa’s surface ice contains salts, including sodium chloride, but the observed levels of concentration don’t match up well with Earth’s run-of-the-mill NaCl hydrates.

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