Can Life Evolve On WOWs?

Around stars, there are “habitable zones”, defined by water on the surface. Several years ago, introduced my own subtility, the “radioactive zone”, where planets have a very active radioactive core, which I viewed as necessary for life. It turns out that new developments (2021) buttress my case (life living off radiation, see below). 

Probes sent around the solar system have revealed water to be much more common than expected. We expected the solar system to be a desert, with just one blue water planet. Well, there is an enormous blue planet in the Solar System, Neptune (blue because CH4 absorbs the red and yellow light). Others may not be blue, but they are full of water. Three worlds seem to have worldwide oceans, below the ice: Callisto, Europa, Enceladus. Move away, old concept of habitability! In general, WORLDWIDE OCEAN WORLDS (WOWs) seem common in the galaxy.

Habitability, that is availability for Earth life colonization is one thing. Clearly many worlds are habitable in the Solar System after extrapolating a bit from present tech.  Another concept is indigenous bioevolvability… a planet where life could evolve. There are going to be a tiny fraction of bioevolvable planets, relative to habitable planets, because catastrophe will be many.

Thus another possibility, unforeseen and new, is life evolving outside of the traditional habitable zone… in WOWs… Worldwide Ocean Worlds… Europa may have twice the water oceanic volume of Earth. Can life evolve on a WOW? We (PA and Ian Miller, see below) do not think so.

Indeed, at first sight there could be more than refueling possibilities for humanity in WOWs. There could be native life. Viroids, maybe?… (Once we have mastered thermonuclear fusion, hydrogen, thus water, will be important because that’s what we will need the most in space, for colonization…) In any case, the concept of WOW augments considerably the habitable zones. In the Solar System, the presence of water may make more than half a dozen worlds colonizable by humanity… once we have compact thermonuclear fusion. This includes Pluto. (Mercury, Luna, Mars, Ceres, Europa, Ganymede, Callisto, Enceladus, Pluto…) 

Water worlds on moons around giant planets may be the way to exo-life (because they have tides, angular momentum stability, comet protection, are geologically alive, etc.). In any case the plethora of water worlds means the galaxy is eminently and imminently colonizable, and colonization is what we do…

In my not so humble opinion, I think it is likely that WOW will have no life, because life requires lightning and cosmic & solar radiation to appear and evolve ever greater complexity in a timely manner, in the genetic material of said life… Both lightning and radiation are found only on the surface of planets… Intriguingly, this idea may be why terrestrial life became more advanced than oceanic life on Earth! Marine mammals are advanced, right… But they evolved on the continents. 

Huge tides would help too, by mixing things up… Plus a mighty nuclear engine inside the planet to bury carbon with plate tectonics in an homeostatic way, and fabricate a huge magnetic shield. (I have proposed that nuclear fission helped in the creation of Luna; my theory would require that Luna and Terra have the same exact isotopic composition… As observed… If that is correct, a huge IF, it would mean that having a big moon, or being a big moon, is a requirement for evolving sophisticated, Earth style life…)

But of course whether WOWs can evolve sophisticated life is an experimental question: missions should be flown to try to detect organic activity… And the Viking experiments on Mars (which apparently found life!) should be repeated (that was refused for “Perseverance”!)  It is rather baffling that a big effort was not made by, say, Europe, to find evidence of life on Europa. Are they all spiritually dead yet, out there? Just waiting for America to design vaccines for them? 

My friend Ian Miller, a chemist, with a broad science background, has opinions on the scientific aspects of life on other worlds:


on April 5, 2021 at 10:47 pm said:

My argument is there is no life under ice on Europa. Reasons include no nitrogen (there is more sodium in the extremely tenuous atmosphere than nitrogen, unless the analyses are wrong), and no significant carbon. Additional reasons include no possibility of reproduction because besides no nitrogen and carbon: phosphates would sink to the bottom, no real mechanism to make lipid equivalents (too wet and cold), and no mechanism to make phosphate esters. The only one so far discovered that is plausibly abiogenic is photophysical, so it needs light, and no phosphate esters, no reproduction. Enceladus at least has nitrogen and carbon, but I think the light is still a killer, as is the limited phosphate.

There is one further issue. Abiogenic chemistry in oceans suffers from the problem of dilution. Even if you can get condensation reactions to work (very difficult in water, without light or enzymes and you can’t start with the latter) the dilution effect means polymers are always far too short to be useful, like two mers.

Patrice Ayme: Wow (pun intended). Very interesting comment Ian! One sees the chemist unfolding wings of understanding. Basically you say Europa’s chemistry is not rich enough. However, there may exist a carapace of 80 kilometers of ice above the Europa ocean… so what we may see may not be much. And Callisto seems also to have liquid water (it generates a magnetic field). 

You seem to be saying that life started on land? One can have concentration in ponds… on land, like in tidal pools. However, continents seem to be an emerging feature on Earth: they are the foam from tectonic plate activity… Thus they may have started after life (????)

On the face of it, except for cephalopods (no culture there), culture bearing animals on Earth evolved mostly on land (that’s my point). Land animals have had migrations for 300 million years apparently, and collective migrations mean culture and society. Instead of dilution, I look at the greater occurrence of genetic evolution through mutations… on land.

Finally there is this:

Now it turns out that bacteria in sediments below the ocean floor use radioactivity as power source: The contribution of water radiolysis to marine sedimentary life

(Justine F. Sauvage, Ashton Flinders, Arthur J. Spivack, Robert Pockalny, Ann G. Dunlea, Chloe H. Anderson, David C. Smith, Richard W. Murray & Steven D’Hondt 

Nature Communications volume 12, Article number: 1297 (2021)) 

Abstract:”Water radiolysis continuously produces H2 and oxidized chemicals in wet sediment and rock. Radiolytic H2 has been identified as the primary electron donor (food) for microorganisms in continental aquifers kilometers below Earth’s surface [This hydrogen is mostly produced by alpha and gamma radiation inside the sediments; this is the point]. Radiolytic products may also be significant for sustaining life in subseafloor sediment and subsurface environments of other planets. However, the extent to which most subsurface ecosystems rely on radiolytic products has been poorly constrained, due to incomplete understanding of radiolytic chemical yields in natural environments. 

… we show that all common marine sediment types catalyse radiolytic H2 production, amplifying yields by up to 27X relative to pure water. In electron equivalents, the global rate of radiolytic H2 production in marine sediment appears to be 1-2% of the global organic flux to the seafloor. However, most organic matter is consumed at or near the seafloor, whereas radiolytic H2 is produced at all sediment depths. Comparison of radiolytic H2 consumption rates to organic oxidation rates suggests that water radiolysis is the principal source of biologically accessible energy for microbial communities in marine sediment older than a few million years. Where water permeates similarly catalytic material on other worlds, life may also be sustained by water radiolysis.

ianmillerblog on April 6, 2021 at 3:06 am said:

Yes, Patrice, what I am saying is that the Jovian system is deficient in nitrogen and carbon, which is why Ganymede and Callisto have no atmosphere worth mentioning, while Titan has. It has to do with the ices that formed the planets. What I am saying is that as the ices warmed up, first the N2 and CO that helped form Neptune vaporized, then the argon and CH4 that helped form Uranus, then the methanol and ammonia that helped form the Saturnian system, leaving the Jovian system essentially with only water and solids.

I think the basics of life came from underground, with geologic processing, and life probably started around fumaroles. the reason being it was easy to get wet-dry cycles. With splashing cycles it is possible to get APM and UPM to form RNA fragments of u to 100 mers in a few hours, so the next trick is how to get AMP and UMP, and that is where sunlight comes in. It is not so much to provide energy, but rather to provide very high vibrational energy from an excited state decaying through internal conversion, which is why we use ribose – it is the only sugar that forms a furanose, and the furanose form is the only form that can relay the vibrational energy. That’s my view, anyway.

The radiolytic provision of hydrogen is interesting because life had to use hydrogen for the early anaerobes. There is obviously a lot more to life than what I outlined above, but I think that would be the way it started because this alone gets reproduction AND catalysis started.

Radioactivity has been ignored all too long in the evolution of life, indeed. Radioactivity was considerable in the past, when life emerged, because Earth was covered with U235… Yes, a concentration of which exploded above Hiroshima… There used to be one hundred times more! Before I come back to that in a future essay, let’s momentarily conclude:

And now a final word for those who believe that wisdom should not worry about other planets: there are two types of wisdom. Mussel wisdom, clinging to the rock one knows well, and human wisdom, clinging to the hope one does not know yet. Humanity and its ancestry has clung to progress as the examination worth having most. We have brains to progress. It was always so, and those believing something else, were wiped out, and always will be.

Patrice Ayme

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