How does life happen when there's barely any light?

https://www.quantamagazine.org/how-does-life-happen-when-theres-barely-any-light-20250129/

by abe94 • 1 year ago

56 41 1 year ago

floxy• 1 year ago

That's pretty interesting stuff. From the article it doesn't sound like anyone is doing a lab test to determine the lower bound for light intensity. Any reason not to? I mean, take a batch of this algae and shine 2x the theoretical minimum light intensity for photosynthesis on it. And another batch of algae with 1.5x, and 1.0x, and 0.8x, and 0.5x, etc.. And see which batches of algae die off? Devil is in the details, I guess?

mmooss• 1 year ago

I'd look at the paper and see who they cite for those numbers and theory.

bozhark• 1 year ago

What’s the control?

SaberTail• 1 year ago

The control is daylight, where countless species of life survive on a daily basis. You are comparing the hypothesis that life can survive with very little light to the hypothesis that it needs normal amounts of light to survive.

rightbyte• 1 year ago

Maybe it is really hard to produce such weak illumination with accuracy?

eternauta3k• 1 year ago

No, you can practically go down to single photons.

abe94• 1 year ago

Expanding on this, from what i understand there aren't too many labs (understandably) that are able to grow extremophiles in lab conditions.

It would be great to run a bunch of experiments at various different conditions and see minimum and maximum on a variety of variables like salinity, acidity, heat, etc

SrijjanSubedi• 1 year ago

This is very intereresing!

celpgoescheeew• 1 year ago

First off its always nice to see researchers using infrastructure based in Kiel. Makes me a bit proud! But why can't the articles author give numbers instead of word salad descriptions like one droplet in three litres... For light. The amount, intensity or what?

flobosg• 1 year ago

The linked study presents details in a more technical format.

paulmooreparks• 1 year ago

In the paragraph right above the one you reference:

Beneath that ice, the light sensors recorded an astronomically small number of photons: an upper range of 0.04 micromoles per square meter per second, a number very close to the theoretical minimum amount of light that photosynthesis can run on. The actual amount of light was probably lower.

magicalhippo• 1 year ago

It's not a direct conversion it seems, but assuming daylight then 0.04 umol/s/m^2 should be around 2 lux.

I was curious how this compared to being on Pluto, but apparently Pluto gets a lot more sunlight than I imagined[1]:

So at high noon on Pluto you’d get at least 60 lux of sunlight.

Civil twilight is roughly enough light to read by, and that’s 3.4 lux. Moonlight is less than 0.3 lux.

60 lux would be comparable to indoor lighting in a hall or stairway.

[1] https://www.johndcook.com/blog/2018/03/09/could-you-read-on-...

TheSpiceIsLife4• 1 year ago

Yeah, PpFF (Photons per Football Field) are much easier to understand, especially if you have to divided them equally between a family of Base4.

For the Metric Heads, we here in Australia use the SI unit Photons per Olympic Swimming Pool, which unit of measure is the Centiquantalap, naturally.

Edit to add: Under the modern US customary measurement system, 1 drop is 1/72th of a US customary fluid dram, and 793 and 1000 conveniently have no common factors, so it should be self evident that 3 litres is 793/1000th of a US fluid gallon. Converting that to lux or lumens is left as an exercise for the reader.

cogman106• 1 year ago

An interesting fact I learned from an evolutionary biologist is that when there's a gap in suitability life has a tendency to rapidly evolve and adapt to that gap.

That's why after mass extinction events, we see explosions in evolution in creatures that had essentially stagnated. Mammals being the best example of this. They went from being small little creatures with little distinction for generations to everything from a mouse to a mammoth. It wasn't until the rapid extinction of the dinosaurs with all the environmental gaps that created that we saw an explosion of different creature types. There were niches to fill.

This is likely part of the reason we see life in such extreme conditions. There was a hole to fill and the creatures best suited to survive in that niche did.

tbrownaw• 1 year ago

The problem comes when the niche something fills happens to line up with "this one small pond where someone wants to put an infrastructure project".

TheSpiceIsLife4• 1 year ago

If what ecologists tend to want to say is accurate, long term this will lead to a gap in suitability, where humans find themselves in a progressively less suitable environment.

In a similar way to how the solution to inflation is higher prices, it may turn out to be a self righting process.

TheSpiceIsLife4• 1 year ago

Also, the interface between mediums, and energy gradients.

Also that this part of the galaxy, and the Universe as a whole, seems to be favourably quiescent.

Slightly tangential, have you come across the terms island dwarfism and island gigantism (also insular -), and did you know the New Zealand Kiwi is the T-Rex’s closest living genetic relative. Here’s hoping it never makes it off the island!

cogman106• 1 year ago

Yes! Islands are fascinating because the creatures that get trapped on them take or represent weird routes of evolution.

It's no wonder that Darwin started thinking "what's happening here" after visiting a bunch of islands.

My favorite island creature is the cold blooded dwarf goat Myotragus balearicus. Likely a victim of human expansion.

beAbU• 1 year ago

"Life, uh, finds a way"

sandworm1012• 1 year ago

Not every gap. The temperature range is rather small, say about 200c. Anything much above boiling water, or below hard freezing, and the life we know stops. Some critters can survive, but they do not thrive outside that range.

cogman106• 1 year ago

I agree.

Just pointing out strange fact of accelerated evolution after mass extinction. There are limits to what earth chemistry will allow for in life, and likely earth's climate and temperatures have been particularly hospitable to life forming and propagating.

markovs_gun2• 1 year ago

Fundamentally we're limited by two things- the boiling point of water, and the fact that biological macromolecules are very complex and fall apart or crumple up at high temperatures. Deep sea creatures can bypass the first one due to the intense pressure in the deep ocean, but you're still going to have to deal with the fact that atoms bounce around and move more at higher temperatures, and that isn't good for the precision molecular machinery that life relies on.

On the low end, we're pretty much limited by the same things, but in reverse- the freezing point of water, and the fact that chemistry slows down at low temperatures.

So that puts us with a fundamental limit of 0-100 C for any system that relies liquid water at atmospheric pressure, and only a little bit beyond that for extremophiles. There is another fundamental limit beyond 100 for high temp when any organic molecule will start to burn or pyrolyze, but the boiling point is already a huge evolutionary hurdle on its own for most places on Earth.

29athrowaway• 1 year ago

The last universal common ancestor (LUCA), the organism that all branches of life descend from, lived in deep sea alkaline hydrothermal vents.

https://en.wikipedia.org/wiki/Last_universal_common_ancestor

ttoinou• 1 year ago

We can reverse the question and rather wonder why outside creatures waste so much of light getting on us

mrguyorama• 1 year ago

My understanding is that photosynthesis is optimized for CARBON, not light usage. Photons are abundant, CO2 availability is high, but plants run into the same problem that carbon sequestration does: Gas is not dense, and that low density reduces the gradients you can take advantage of to make things happen.

Some types of photosynthesis ALSO optimize for water usage.

Protostome• 1 year ago

Life existed before photosynthesis. Taking electrons from H2S and oxidizing H2 coming out of hydrothermal vents. Photosynthesis allowed primitive cells to venture out of those vents and into the world.

Therefore, it's hardly a surprise that "life finds a way" :)

adrian_b• 1 year ago

Life existed before photosynthesis.

However there are only 2 known ways of obtaining energy for living without photosynthesis, which are called acetogenesis and methanogenesis.

In both cases the inputs are free H2 and carbon dioxide (or alternatively carbon monoxide and water), while the output contains acetic acid for acetogenesis and methane for methanogenesis. Methanogenesis is confined to a certain group of archaea, while the simpler acetogenesis is widespread among bacteria and archaea and there is good evidence that the last common ancestor of all cellular living beings was able to do acetogenesis, using the free hydrogen provided by volcanic gases or hydrothermal vents.

H2S can be used as a source of energy in 2 ways, both of which require photosynthesis. H2S can be used instead of water and oxidized by bacteria that are capable of anoxygenic photosynthesis, or it can be oxidized by using free oxygen that has been produced elsewhere by algae or plants, using solar energy (instead of free oxygen, other oxidizers may be used, for instance nitrate or sulfate, but those must have been produced elsewhere by using free oxygen, so ultimately also by using solar energy; sulfate can also be produced directly using solar energy, in anoxygenic photosynthesis). So H2S cannot be used to obtain energy in the absence of living beings that capture the solar light. (Because the reaction of H2S with CO2 does not produce energy, but it consumes energy.)

Similarly, the living beings that oxidize H2 coming out of hydrothermal vents, using either oxygen or other oxidizers derived from oxygen or from anoxygenic photosynthesis, like nitrate or sulfate, are also completely dependent on the photosynthesis carried on by algae or plants elsewhere.

Only the acetogenic and methanogenic bacteria and archaea are completely independent of solar energy and they depend only on the internal heat of the Earth as a source of energy (which is the ultimate cause of the production of H2 in volcanic gases and in hydrothermal vents, by the reaction of water with magmatic rocks that are chemically stable only at the temperatures from higher depths).

Like other anaerobic bacteria, acetogens, methanogens, and also sulfate-reducing bacteria, are widespread in human guts, where all 3 groups consume the H2 produced by other bacteria in fermentations.

roenxi• 1 year ago

Worth a moment to recall (particularly as we watch the 2024 YR4 impact odds creep up; not that it is that big) that there are relatively regular events where life has to cope with long sunless periods. A big asteroid impact can blot the sky for years.

It is quite amazing to think what evolution has to handle with. The aftereffects after a bad asteroid impact are staggering. No sun for years & the entire earth can get cooked for a few hours from the kinetic energy of the ejecta that gets kicked up. Then everything freezes. So survivors typically do well eating carrion, hibernating and burrowing.

greenavocado• 1 year ago

Historically, volcano ejecta have caused far more devastation than asteroid impacts

AnotherGoodName• 1 year ago

If you do any caving you see this regularly. Deep deep in the cave wherever there’s moisture there’s moss. The tiny tiny amount of light that reflects/refracts into the cave is enough to grow. You can’t really see in that level of light but as you shine the torch around moss everywhere. Hundreds of meters in and around multiple corners and that level of light is enough!

rurban• 1 year ago

Life is not just plants, also bacteria and animals. They don't do photosynthesis.

markovs_gun2• 1 year ago

Well yeah but when you look at almost all of the life we come in contact with on a daily basis, it's all ultimately using solar energy at the end of the food chain. You don't photosynthesize, but the plants you eat to survive do, and the animals you eat eat plants that rely on the sun too.

tim333• 1 year ago

Most of life’s engines run on sunlight.

There's a huge amount of life that runs on zero sunlight and instead runs on chemical energy deep in the earth. It makes up maybe 10% to 20% the biomass on earth and a good chunk of its biodiversity and is quite likely where life originated, hundreds of millions of years before photosynthesis evolved. It also quite possibly exists in a similar way on Mars.

An interesting example is D. audaxviator, which runs on uranium and is named after a passage in Jules Verne’s “Journey to the Center of the Earth.”

A lot of it has been discovered fairly recently - there's an unusually interesting nyt article on it all, including how they may transform rocks and continents https://www.nytimes.com/2024/06/24/magazine/earth-geomicrobi... or https://archive.ph/VgzKD

How does life happen when there's barely any light?

Related Stories