Tag: exobiology

Hycean Worlds

Hycean worlds are hot mini-Neptunes with hydrogen-rich atmospheres and vast oceans on their surfaces. The heat and the pressure wouldn’t be very inviting to us humans, but it’s possible that some forms of life might find it idyllic. these worlds can be up to 2.6x the width of Earth, up to 10 Earth masses, and temperatures in their atmospheres could reach 200 °C. However, conditions in their oceans might be more comfortable. They’re likely to be common too, nestled in between the smaller, rockier Super-Earths and the gaseous, larger mini-Neptunes. Hycean planets could be one of the most promising places to look for signs of life. Not only because they’re common, but biomarkers of life, such as methyl chloride and dimethyl sulphide, could be readily spotted in their atmospheres

Radiolyctic Life

Radioactive decay can sustain life deep below the surface. Radiation from unstable atoms in rocks can split water molecules into hydrogen and chemically reactive peroxides and radicals; some cells can use the hydrogen as fuel directly, while the remaining products turn minerals and other surrounding compounds into additional energy sources. Radiolysis is instrumental not just in the hydrogen and sulfur cycles on Earth, but in the cycle most closely associated with life: that of carbon. Analyses of water samples from the same Canadian mine showed very high concentrations of acetate and formate, organic compounds that can support bacterial life. Moreover, measurements of isotopic signatures indicated that the compounds were being generated abiotically. The researchers hypothesized that radiolytic products were reacting with dissolved carbonate minerals from the rock to produce the large quantities of carbon-based molecules they were observing.


See also these Chernobyl fungi

a robot sent into the still-highly-radioactive Chernobyl reactor had returned with samples of black, melanin-rich fungi that were growing on the ruined reactor’s walls. “Just as the pigment chlorophyll converts sunlight into chemical energy that allows green plants to live and grow, our research suggests that melanin can use a different portion of the electromagnetic spectrum – ionizing radiation – to benefit the fungi containing it” Since ionizing radiation is prevalent in outer space, astronauts might be able to rely on fungi as an inexhaustible food source on long missions or for colonizing other planets

Life’s Energy Limits

For individual cells, this power minimum hovers around a zeptowatt, or 10−21 watts. That is the power required to lift 0.001% of a grain of salt 1 nanometer once a day. (For reference, a human body uses ~100 watts, the power of a reading light.) The new model suggests that cells living in sub-seafloor sediments are drawing only slightly more power than that.

2022-11-02: Inert spores may be close to that energy limit, and use a passive sensing technique.

The spores might be able to sense small cumulative changes in their environment, until enough signals build up to trigger a sort of wake-up alarm. The mechanism that would induce these changes would be the movement of ions out of the cell—specifically, potassium ions.

These movements can be triggered by positive environmental signals, like the presence of nutrients. When the ions travel out of the cell thanks to passive transport, they generate a difference in potassium concentration inside versus outside the cell. This concentration difference allows the spore to store potential energy. Over time, as the spore continues to sense more positive signals, more ions would move out of the cell. This would also create a corresponding drop in potassium levels, as the ions exit. Eventually, the potassium content in the spore would lower to a certain threshold, signaling that it is safe for the cell to wake up. That would trigger reanimation and germination.

2024-07-23: Most life is dormant

60% of all microbial cells are hibernating at any given time. Even in organisms whose entire bodies do not go dormant, like most mammals, some cellular populations within them rest and wait for the best time to activate. esearchers reported the discovery of a new hibernation factor, which they have named Balon. The protein is shockingly common: A search for its gene sequence uncovered its presence in 20% of all cataloged bacterial genomes. And it works in a way that molecular biologists had never seen before.

Previously, all known ribosome-disrupting hibernation factors worked passively: They waited for a ribosome to finish building a protein and then prevented it from starting a new one. Balon, however, pulls the emergency brake. It stuffs itself into every ribosome in the cell, even interrupting active ribosomes in the middle of their work. Before Balon, hibernation factors had only been seen in empty ribosomes.

Subantarctic life

John Priscu’s search for life that thrives under ice took him to subglacial lakes at the South Pole. Now he has his eye on Mars and Europa.

And there are sessile animals under the ice:

The researchers think it’s likely that the drift of this marine snow has been flipped on its side, so that the food source is moving horizontally instead of vertically. The researchers determined that there are productive regions 630-1500 km away. It may not be much, but it’s possible that enough organic material is riding these currents to feed these creatures. That’s an extraordinary distance, given that in the deepest part of the ocean, the Challenger Deep near Guam, marine snow produced at the surface has to fall 11 km down to reach the seafloor. To reach the animals on this Antarctic rock, food would have to travel as much as 133x that distance—and it would have to do so by floating sideways.

DNA SETI

Should We Search for Messages from Extraterrestrial Intelligences in Terrestrial Genomes? Compared to other methods of interstellar messaging, DNA-encoded messages could have the advantages of being auto- amplifying and blanketing across space and time (i.e., everywhere and persistent)

Drosophila Titanus

This is very cool. In some sense, we have a moral imperative to spread life in the cosmos.

Your experiment involves creating flies that could survive on Titan. I understand that Titan is incredibly cold so the flies have to gradually get used to the very low temperatures but what would be the impact of Titan’s orange sky and the low frequency radio waves that emanate from Titan on their bodies? And how do you prepare them for that? The project involved adapting the flies for a range of environmental conditions that are very different to those found on Earth. The cold is the most obvious along with the different atmospheric composition. There is also increased atmospheric pressure, radiation, chromatic characteristics and so on. To reach what could be conceived as the end of the project I would need to condition the flies for all of the characteristics of Titan. The radio waves experiment has been earmarked for a future stage in the project so I haven’t got too much to say about that right now. However, the chromatic adjustment has been something I’ve been working on over the last couple of years. The natural phototaxis of Drosophila – its instinct to move towards a certain type of light – is geared towards the blue end of the electromagnetic spectrum. To overcome this I kept the flies for a year under a Titan analog orange light before testing for adaptation. The selection experiment was modelled on a Y-Trap apparatus, a simple way of offering an organism 2 choices. The flies crawl up a tube and are faced with a junction offering orange light in one direction and blue light in the other, each tube ending with another non-return trap. Any flies taking the orange option are considered adapted and kept for breeding. Repeated iterations of the project smooth out random events.

Octopus panspermia?

Evidence of the octopus evolution show it would have happened too quickly to have begun here on Earth. “Thus the possibility that cryopreserved Squid and/or Octopus eggs, arrived in icy bolides several 100M years ago should not be discounted as that would be a parsimonious cosmic explanation for the Octopus’ sudden emergence on Earth 270 ma BP.”

2022-01-29:

3 hearts, pumping blue-green blood because their oxygen carrying metal is copper (versus iron in the heme of our blood). They can spend 30 minutes out of the water, to scoot between tidepools.

Alien intelligence: from a distant branch in the tree of life, the octopus is the only invertebrate to have developed a complex, clever brain. Our common evolutionary ancestor is a tubule so ancient, neither brains nor eyes yet existed. They evolved independently, on land and by sea. From the Cambrian explosion of sensing, body plans, and predation, minds evolved in response to other minds. It was an information revolution. It’s where experience begins.

The octopus brain rings around its throat. 500M neurons, similar to dog (vs. human: 86B, fly: 100K).

The octopus has over 50 different functional brain lobes (versus 4 in human)

And furthermore, 60% of its neurons are out in the arms, with a high degree of autonomy. A severed arm can carry on as if nothing has changed for several hours.

It is a distributed mesh of ganglia (knots of nerves) in a ladder-like nervous system. Recurrent neural loops serve as a local short-term memory latch.

“The octopus is suffused with nervousness; the body is not a separate thing that is controlled by the brain or nervous system.” Unconstrained by bone or shell, “the body itself is protean, all possibility. The octopus lives outside the usual body/brain divide.” (PGS)

Structurally, our eyes ended up strikingly similar to the octopus (camera-like with a focusing lens, through a transparent cornea and iris aperture to a retina backing the optic nerves). But octopus eyes have a wide-angle panoramic view, and they move independently like a chameleon.

Their horizontal slit pupil stays horizontal as the body moves, like a steady cam. This is made possible by special balance receptors called statocysts (a sac with internal sensory hairs and loose mineralized balls that roll around with movement and gravity).

They can see polarized light, but not color (making their color-matching camouflage skills all the more intriguing; they also see with their skin).

Their playful interactions with humans exhibit mischief and craft, a sign of mental surplus

Humans internalized language as a tool for complex thought (we can hear what we say and use language to arrange and manipulate ideas). Octopuses are on a different path.

Their entire skin is a layered screen, with about a megapixel directly controlled by the brain.

Skin color, pattern and fleshy texture can change in 0.7 seconds.

3 layers of skin cells control elastic sacks of pigments, internal iridescent reflections, even polarization (which the octopus can see), over a white underbody. They are regulated by acetylcholine, one of the earliest neurotransmitters in evolution.

The octopus can create a voluntary light show on its skin, e.g., a dark cloud passing over the local landscape, or a dramatic display to confuse a predator while fleeing.

30 ritualized displays for mating and other signaling.

Some octopuses have regions of constant kaleidoscopic restlessness, like animated eye shadow.

1600 suckers. 16 kg of lift capacity per sucker. 10k tasting chemoreceptors per sucker. Each is controlled individually.

Octopus muscles have radial + longitudinal fibers (agile like our tongues, not our biceps).

Opposing waves of activation can create temporary elbows at the region of constructive overlap, or pass food sucker-to-sucker like a conveyor belt.

The octopus’ arm muscles can pull 100x its own weight.

It can squeeze through a hole about the size of its eyeball.

Their ink squirts contain oxytocin (perhaps to soothe prey) and dopamine, the “reward hormone” (perhaps to trick predators that they had caught the octopus in the billowy cloud).

2022-02-17:

Soft-bodied cephalopods such as the octopus are exceptionally intelligent invertebrates with a highly complex nervous system that evolved independently from vertebrates. Because of elevated RNA editing in their nervous tissues, we hypothesized that RNA regulation may play a major role in the cognitive success of this group. We thus profiled mRNAs and small RNAs in 18 tissues of the common octopus. We show that the major RNA innovation of soft-bodied cephalopods is a massive expansion of the miRNA gene repertoire. These novel miRNAs were primarily expressed in neuronal tissues, during development, and had conserved and thus likely functional target sites. The only comparable miRNA expansions happened, strikingly, in vertebrates. Thus, we propose that miRNAs are intimately linked to the evolution of complex animal brains.

UV life

red dwarfs may not be as habitable as we thought, as they’re low on uv radiation, which is crucial for RNA formation

ultraviolet radiation may even have played a critical role in the emergence of life here on Earth. As such, determining how much UV radiation is produced by other types of stars could be one of the keys to finding evidence of life any planets that orbit them.

10000x more sensitive Exolife test

The test uses a liquid-based technique known as capillary electrophoresis to separate a mixture of organic molecules into its components. It was designed specifically to analyze for amino acids, the structural building blocks of all life on Earth. The method is 10000x more sensitive than current methods employed by spacecraft like NASA’s Mars Curiosity rover.