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Is There Life On Europa?
Welcome back to the Abstract!
This week in science got off to a bombastic start with the successful launch of NASA’s Europa Clipper on Monday, marking the beginning of the first dedicated mission to study Jupiter’s tantalizing ocean moon.
The mission will swing into orbit around Jupiter in April 2030 with its sights on Europa, an ice world about the size of our own Moon that bears a vast subsurface ocean. This hidden marine environment has distinguished Europa as one of the most promising targets in the search for extraterrestrial life.
Europa Clipper will perform a series of flybys that will eventually bring it to within 16 miles of the moon’s frozen terrain. While it’s possible that life might exist on the sunlit surface, it would have to endure harsh radiation from Jupiter. There are, perhaps, better odds for life in the liquid water ocean that exists beneath miles of ice, beyond the range of Jupiter’s particle bullets, where the Sun doesn't shine.
Photosynthesis would not work in Europa’s dark inner ocean, but the moon may well be geologically active at its seafloor due to the immense tidal forces that Jupiter exerts. Here on Earth, this type of activity opens hydrothermal vents that leak out heated water and chemical energy. Vents are biological hotspots for extremophile organisms that don't need solar power to survive, availing themselves instead of the chemical fuel at these sites through a process called chemosynthesis.
As an added bonus, vent systems are a leading candidate for the cradle of life on Earth, meaning that the first organisms on our planet could have emerged in these environments. You and I and everyone we know may well be the descendants of vent bugs from the dawn of earthly creation! The possibility that vents could have been a biological spark on Earth raises the prospect that similar ecosystems have sprouted up on Europa.
Europa Clipper is a recon mission; it won’t actually be able to peer into the moon’s depths to confirm if alien beasties lurk below. Its main goal is to check out the moon up close so it can get better specs on the extent and dynamics of the ocean—which could contain more than twice as much seawater as Earth—which can then help to constrain the habitability of this world.
But as it happens, two studies came out this week that are serendipitously relevant to assessing the odds of life on Europa. I’ll break those down below, and then address the age-old question: Lunarphile or lunarphobe? Finally, we’ll close out with some news from the rodent incest beat. Life finds a way this week, whether it’s in space, in the ocean, or in a space ocean.
These Animals Need to Vent
As I mentioned above, hydrothermal vents on Earth’s seafloor are ecological metropolises, home to diverse communities of microbes and animals that have been documented in research dives. However, the biosphere underneath these vents, buried deep in the seafloor, has barely been explored.
To close this knowledge gap, scientists decided to dig up a chunk of seafloor at a vent system in the East Pacific Ridge at a depth of 1.5 miles underwater. The subterranean seabed was full of life, including animals, which had never been observed in these environments before.
“While the subseafloor microbial and viral biosphere at deep-sea vents has been described, we show that animal life also exists in this shallow rocky subseafloor province,” said Monika Bright at the University of Vienna and colleagues. “Here we report, to our knowledge for the first time, the discovery of animals excavated from fluid-filled, shallow cavities in the subseafloor of deep-sea hydrothermal vents.”
This study is amazing for a few reasons. First, the team gets bonus points for naming their site Fava Flow Suburbs, which sounds like a sick Mario Kart track, and for conducting the observations from a research vessel named after Falkor from The Never-Ending Story, which is excellent luckdragon representation.
But more importantly, the discovery of animal life in these crustal spaces—including tubeworms, regular worms, and snails—reveals that the vent ecosystems are far bigger and more complex than previously known. Hydrothermal vents are clearly resilient and dynamic pockets of habitability, which is good news for people holding out for alien life on Europa. It’s also a reason to protect these environments on Earth from human-driven threats, such as deep-sea mining.
“The study of the subseafloor biosphere for animal life has just begun,” Bright and her colleagues said. “The uniqueness of active hydrothermal vents is well recognized, and protection against potential future anthropogenic impact such as deep-sea mining has been suggested or is in place. The discovery of animal habitats in the crustal subseafloor, the extent of which is currently unknown, increases the urgency of such protections.”
In other news…
Mars Is a Death Trap….Except for Maybe This Lil Part
Let’s keep the alien ball rolling here, but pass it on over to Mars. Most searches for life on the red planet, including NASA’s Perseverance mission, are focused on finding fossils from its hospitable heyday some 3.5 billion years ago, when liquid water rivers flowed and lakes pooled on its surface.
Since that time, Mars’ atmosphere and magnetic field have collapsed, exposing its landscape to damaging ultraviolet radiation, which has dehydrated the planet. Life on Mars would need to retreat into subterranean water reservoirs to survive, so the thinking goes, putting it out of reach of our missions.
Now, however, scientists have proposed that life could potentially exist at the Martian surface in pockets of meltwater shielded by ice cover that is clear enough to allow sunlight through for photosynthesis.
“Our analysis shows that despite higher surface ultraviolet radiation levels on Mars than on Earth, it is possible for terrestrial photosynthetic organisms to find locations within exposed ice on Mars with favorable solar radiative conditions,” said Aditya Khuller of NASA’s Jet Propulsion Laboratory and colleagues.
“These potential present-day habitats are centimeters to meters below the surface and could be the most easily accessible locations to find extant life on Mars via future robotic and human missions,” the team concluded.
The white area on this Martian gully is the type of dusty ice environment that could be habitable according to the study. Image: NASA/JPL-Caltech/University of ArizonaIn other words, legit Martian microbes could be hanging out in these lightly dusted ice patches, close enough to the surface that we could probably drive a rover right up to them to say hi.
It’s also possible, of course, that Mars is lifeless, and always has been. But this study, along with the above story about hydrothermal vents, hints that organisms have opportunities to emerge and persist in all kinds of habitable zones on a planet, even if that world is otherwise not all that welcoming to life. That’s worth keeping in mind as Europa Clipper embarks on its journey to a world that may contain habitable zones both in its irradiated surface ice, and in seafloor vents far below.
Lunarphobe or a Lunarphile? Tropical Forest Edition
Humans are highly attuned to the phases of the Moon, a preoccupation that has inspired lunar calendars, rich folklore, and alleged werewolf outbreaks. Now, scientists have observed how the lunar cycle influences animals that live on forest floors sheltered by dense tropical canopies.
A team observed 86 mammal species in protected forests on three continents and discovered that even in these environments, where hardly any moonlight penetrates through the trees, wildlife is still affected by the phases of the Moon. Some were “lunar phobic,” and avoided moonlight, while others exhibited “lunar philia” and were attracted to it.
“Half of all species in our study responded to lunar phases, either changing how nocturnal they were, altering their overall level of activity, or both,” said Richard Bischof of the Norwegian University of Life Sciences and colleagues. “Avoidance of full moon was more common, exhibited by 30% of all species compared with 20% of species that exhibited attraction. Nocturnal species, especially rodents, were over-represented among species that avoided full moon.”
Image: Bischof et alThe study is interesting not only for its identification of freaky lunarphiles—looking at you, four-toed elephant shrew—but also because it highlights yet another disruption that stems from deforestation.
“Our findings indicate that lunar phases influence animal behavior even beneath the forest canopy,” the team said. “Such impacts may be exacerbated in degraded and fragmented forests.”
An Update on the Weird Mammal that Thinks It’s a Bug
Last but not least, an update on incest avoidance in the Damaraland mole-rat. Any study on mole-rats catches my attention because these creatures are simply delightful. They are the only mammals to exhibit eusociality, the highest form of social organization in nature, which is normally the domain of ants and bees.
Mole-rats, like those insects, anoint a queen who is solely responsible for reproduction, while workers support the colony’s needs. But though it is very trippy for a mammal to just up and live a bug’s life, it also raises challenges for ensuring genetic diversity.
To that end, scientists set out to learn how mole-rats avoid inbreeding by rearing females and males together, and apart. They found that the rodents tend to mate and reproduce with partners that are unfamiliar to them, regardless of how genetically close they were to those partners.
“Here, we aim to determine the mechanism of kin recognition for incest avoidance in the Damaraland mole-rat Fukomys damarensis,” said Amy E. Leedale of the University of Salford and colleagues. “We found that unfamiliar pairs were more likely to engage in sexual behaviors and bred more successfully than familiar pairs, regardless of their genetic similarity. Females paired with unfamiliar males were also more likely to exhibit reproductive activation, characterized by increased levels of oestradiol and progesterone.”
“This study shows that in Damaraland mole-rats, inbreeding avoidance can be achieved through a discrimination mechanism that relies on association during rearing,” the team concluded. In this way, mole-rats have evolved to enhance genetic diversity by exhibiting a preference for strange bedfellows. And that is your weekly brief from the rodent incest news desk.
Thanks for reading! See you next week.
