Saturn's largest moon most likely uninhabitable
phys.org
phys.org
Titan’s underground ocean is 12x larger than the Earth’s oceans? I had no idea. Wow.
If this result holds, it’s a shame because the gas giant moons always seemed like the only chance of discovering some interesting extraterrestrial life within my lifetime (or the next few dozen generations — the stars are incomprehensibly distant and nearly impossible to visit).
I have never seen any of those things in real life, yet journalists making stupid comparisons. I guess the field must be full of people that were deathly afraid of maths and numbers.
In regular football the spherical ball spends more time in the air than rolling, too. And in popular variants like Australian rules football or Rugby the ball is egg shaped, and that doesn't seem to cause any problems with enjoyment of these sports.
On a far more serious note, the day we can send just one AI system (and wait) must be just a few decades away.
So paperclips. As many as it can make.
We can request more useful constructions after it has demonstrated skill at that...
Whatever your AI could do, you could do remotely from earth (with some light lag). However, AI can't magically conjure resources like carbon.
You would also need some good robotics and production capacity, preferably able to self-replicate.
AI is great, but it's not solving the greatest current bottleneck here.
Same here. I just looked up Titan's size [1] and it's in between the Moon and the Earth in size. I know water is just a thin layer on the crust of our planet, but 12x?
If you look up "all of Earth's water in a ball," [2] it's about a quarter the size of the moon. Titan isn't that much larger. It must just be a floating blob of water or someone's estimations/illustrations are way off.
1. https://upload.wikimedia.org/wikipedia/commons/f/f5/Titan_Ea...
2. https://www.usgs.gov/media/images/all-earths-water-a-single-...
The mass of Earth's hydrosphere is about 1.4 × 10^21 kg, while the mass of water in Earth's atmosphere is merely about 0.00002 × 10^21 kg[3].
[1] https://upload.wikimedia.org/wikipedia/commons/f/f6/Ocean_wo...
As for what's common, we don't have many examples of rocky planets (or moons) with atmospheres in our system to use as examples, and we can't see rocky exoplanets very well at this time, so who knows.
As far as I can tell, Earth's atmosphere seems to extend further into space than Venus'.
Depends on where you want to draw the line for "atmosphere".
About 100km out is where the word "pressure" starts becoming near-meaningless on Earth, while on Venus you'd still have about three times as much to work with.
Technically, Earth's atmosphere extends infinitely far into space. It's not like there's some force-field holding it in; it just gets less and less dense with altitude. So the line depends on your definition, which must be some threshold.
Anyway, Venus has about 90% of the gravity of Earth, so with 92x as much pressure at the surface (of a slightly smaller solid body), I think it stands to reason that at any given altitude, Venus's atmosphere has much higher density than Earth's. If Venus had far higher gravity, then this might not be the case at some altitude, but since its gravity is lower, then Earth's meager atmosphere should show slightly greater stratification I would think.
Are you sure about that math? According to your [2] the diameter of the water ball is 1384 km while the diameter of the moon is about 3,475 km. The volume of the water is less than a tenth of the volume of the moon: ((1384/2) ^ 3) / ((3475/2) ^ 3) => ~6.3%
Titan has a lot of ice, or maybe water, we don’t really know. Depending how much heat is produced in its core it could have a liquid water/ammonia layer 200 kilometers deep. On the other hand it might be mostly ice.
By contrast the Mariana Trench is only 10 kilometers deep.
200Km is uncharted territory for earth, with a maximum depth of almost 11 Km. But life is able to stand until 800 bars at least. More than this is metabolically defiant in organisms made of cells. Vertebrates can survive 760 bars at least.
The majority of the volume on is oceans could be empty and barred to life, but there is still a lot of space for conventional life (and Titanlings could be very different and defy our standards)
Titan is 71.6 × 10^9 km^3 by volume. Earths oceans are 1.335 × 10^9 km^3 by volume.
I've also soon a diagram comparing earths oceans to titan, and the water looks to have a diameter around the same radius as titan, which would mean a volume of 1/8th.
That would require earths oceans to have a volume of about 8.95 × 10^9 km^3, so I guess the illustrations are wrong (or from the perspective of the ocean ball being closer..).
Edit: correction, the diagram was a comparison of water per plant - the ocean ball was titans ocean, not earths..
So 12x earths ocean is 16.02 × 10^9 km^3
that's 1/4.46th the volume of Titan. I guess Titans Ocean ball is bigger than the radius..
The actual article's conclusion is basically "for there to be life on Titan, there needs to be more carbon in the ocean than would be transferred solely by surface impactors". It absolutely does not rule out the existence of those carbon source.
> It is unlikely that the calculated fluxes are sufficient to maintain a detectable biosphere, unless the thickness of organics on Titan’s surface is greater than currently estimated, abundant biomolecules are available from Titan’s rocky core, or surface biomolecules can be delivered to the ocean by a process other than impact. Our calculations suggest that despite Titan being the most organic-rich ocean world in the Solar System, this does not automatically imply an organic-rich and habitable ocean.
With GPT, at least the writing quality would be better.
https://en.wikipedia.org/wiki/Titan_(moon)#/media/File:Titan...
https://www.planetary.org/space-images/interiors-of-icy-bodi...
There were plenty of opportunities for compounds in the rocky center of the moon to get mixed into its ocean.
This reasoning is too limited IMAO. Titan oceans may not have whales, but for sure could still afford a lot of animals.
1) It seems that Titan has been there since the early phases of solar system creation, so I'll assume that is older than 3 billions of years (to pick a conservative value). One elephant a year for 3 billions of years is still a lot.
2) Titan could have been bombed with much more matter on the early phases of solar system history.
3) Live on earth is perfectly able to cope with a poor nutrient aquatic environment. Most of the earth falls exactly on this category after all.
4) Some life forms need just a little bit of carbon to be functional. Earth has very big animals that are 99% water.
5) Cold water promotes slow metabolism. Life just adapts growing really slow, being carried by currents, and adopting a poiquiloterm life style.
Entire ecosystems on Earth developed at high pressures, close to catastrophic scorching temperatures, without the need of any sunlight or photosynthesis, just using chemical energy from hydrothermal vents.
This does not prove that Titan has life, but life has proven several times that can flourish in such circumstances. I'm not an astrobiologist and can miss essential details about the moon, but in my opinion being isolated under a several km layer of ice, with cold and absolute obscurity, does not prevent life on Titan at all, because it didn't prevented it on Earth. Bioluminiscence still ranks among the more common methods of communication on Earth.
[1] (Having salt on the water could help a lot with that liquid state. I assume that we could find easily several layers of saltwater and also methane)
But after some good replies above, it seems that the real question here is not "if the water is liquid" as much as "if the liquid is water". That changes the game totally.
Unless you're counting the warmth itself as the energy source warming it, I don't think this has to be true. Earth's core is hot mostly from residual heat from the Earths formation. It's cooling. It just takes a long time.
Thermodynamics won't let you extract useable energy from the ambient temperature. Lifeforms could extract energy from a strong temperature gradient, but not from something like 1°C per kilometer.
The energy source for deep ocean life on Earth is life from near the ocean's surface that dies and falls down. The study in the article was investigating if something similar could happen on Titan due to surface impacts.
> Unless biologically available compounds can be sourced from Titan's interior, or be delivered from the surface by other mechanisms, our calculations suggest that even the most organic-rich ocean world in the Solar System may not be able to support a large biosphere.
Which is much less sensationalist, to put it politely.
The middle of the Sahara is uninhabitable. Unless you introduce sufficient water and plants that is.
Not that that makes it likely to be hospitable. I'm only surprised by the headline because I wouldn't have thought anyone had expected anything different, so a headline like "as uninhabitable as you might figure" would have made more sense, but nevertheless this doesn't rule it out to about the same extent as it wasn't deemed unlikely already in my perception (as a follower of space news)
Libya gets most of its water from that aquifer.
https://en.wikipedia.org/wiki/Nubian_Sandstone_Aquifer_Syste...
This is really an upper bound on accessible energy (the "carbon" explanation in the press office release is hand-wavey). The idea is that solar photochemistry in Titan's atmosphere creates chemical energy gradients, in the form of energetic compounds like that glycine; and these energy gradients could migrate through the ice and support a biosphere in the subsurface ocean. The abstract* says that, actually, very little of that energy gradient can get through the ice shell.
This situation is different from that of some of the other icy moons: they potentially have much larger geochemical energy sources, from chemical reactions between the water ocean and primordial rock. The problem with Titan is it (probably) has a weird ice shelf on the bottom of its underground ocean, which isolates it from rock. So rock-ocean weathering probably doesn't happen there.
* (The paper's not on arXiv or SciHub if you were wondering)
It might not be sustainable. I don't know.
1) Why are organic materials (probably any carbohydrates) only supposed to come from the surface? Would it not be plausible to assume that Titan's ocean ground contains significant amounts of carbon?
2) Why do they assume that there are only dilution processes in an ocean (surface or subsurface). There could be currents and suboceanic terrain features concentrating carbon-rich water (at least I do not know any reason against this).
There could be a habitable zone deep in Titan's oceans. I don't even know if "habitable" is the right word, because the concern seems greater to do with the genesis of life, not the sustainability of existing life that might have existed on Titan for millions of years already, from a time where perhaps conditions were very different from what they are today.
The journal article asked the question "is the carbon transferred from Titan's surface to its ocean sufficient, on its own, to sustain a biosphere?" to which their answer is "probably not". It explicitly does not claim there are no other sources of carbon in the ocean, nor that Titan is "probably uninhabitable".
Titan has a methane atmosphere, due to prior outgassing from its surface. Methane is destroyed by sunlight; i.e. over time, the atmosphere is reacting with itself and sunlight to form more complex carbon molecules, which fall out of the atmosphere onto the surface. The study does not look at the carbon content of the ocean itself, it simply evaluates whether these complex carbon molecules, that we know are forming in Titan's atmosphere through well-understood processes, can also mix with the liquid ocean.
As the ice sheet covering the ocean is at minimum 40km thick, and over 100km thick in places, it is difficult for surface molecules to penetrate.
Whether or not other carbon sources, such as from within the planet, contribute carbon to Titan's oceans are beyond the scope of this study, and will remain beyond the scope of our knowledge until we manage to place equipment on Titan capable of drilling through tens of kilometers of ice.
The actual paper concludes that carbon transfer from the surface to the ocean is not sufficient to support a biosphere if that is the sole source of carbon. It specifically calls out "unless biologically available compounds can be sourced from Titan’s interior" as something that would allow a biosphere.
EDIT: link to article full text: https://www.researchgate.net/publication/377929149_Organic_I...
I am all for shooting some equipment up to Titan. Although I am not sure we have the technology and the will to commit resources to analyze Titan's oceans in detail, yet.
I think this was an important study to be done, because if the conclusion came out the other way, that would have been very exciting. We would then be able to say "using only the aspects of Titan we know for certain to be true, we can model a plausible sustainable biosphere".
A positive result would have been very promising, but this negative result should not be seen as discouraging.
Pressure = density * g * h
...with density of water as 997 kg/m^3, g = 0.138 * 9.8 m/s^2, and h = 40000 m, you get a pressure of ~540 atmospheres. But I don't know if the ice sheet would have a structural component that doesn't add as much as a naive calculation would suggest.
Presumably for the same reason that mine operators assume that all minerals are evenly distributed throughout the earth's crust.
I definitely get this is a limited research here, and I'm not faulting it for that. Its good to know it seems like this kind of cycle wouldn't be consistent in adding organic molecules to the subsurface oceans. But let's not necessarily see this as "there's no way organic molecules could have been pushed down in relevant amounts."
Titan is old 4 billion years. That alone is enough to not be able to conclude that its oceans are poor in organics.
So many things could have happened during the evolution of Titan during those 4 billion years that we just don't know about.
Plus what about mixing from under the oceans.
I vote for sending meaningful probes as soon as we have tech for it. I dream of an era where humanity will spend 1 trillion per year on exploratory space tech and not on war machinery.
What if your peaceful probe starts an interplanetary war with the inhabitants of those oceans?
But more seriously, an interesting project would be to simulate the conditions of our solar system's "candidate" for life ecosystems in laboratory conditions as precisely as we can based on known information, and then subject some of the toughest microorganisms we have living on earth to them, to see if at least they could survive or even thrive.
For example: recreate conditions of pressure, cold, radiation and chemical composition like those we think are the case in Titan's subterranean ocean, and then see how well a colony of water bears (tardigrades) endures.
Seems a lot more practical then speculating. I'm curious if this has been done in a systematic way by any organization on Earth.
The paper contrastingly is rather descriptive and much less assertive, and doesn’t jump to the same conclusions the article is pushing. You would expect this from a tabloid headline rather than Phys.org.
If we make conclusions that we cannot find life on Titan, then we never will because we won't be looking. Life could be thriving on Titan, but we won't know unless we look for ourselves.
Also, for all we know, Titan's oceans are loaded with organic compounds that are don't originate from the surface. We don't know what the actual internal structure of Titan looks like because we lack the data.
We know Titan has two things that seem so promising for life as we know it! Organic compounds on the outside, liquid water on the inside.
And then it asks:
Might those two promising things meet? Other work hasn't found the tectonics that would do it; could cratering do it?
And that very particular answer is pretty definitively no.
Water, carbon, etc.
I heard eons ago that Spock's green blood was inspired by the blue-green blood of horseshoe crabs which has a copper-based system instead of iron, among other oddities:
A horseshoe crab's blood has a blue to blue-green color when exposed to the air. The blood is blue because it contains a copper-based respiratory pigment called hemocyanin.
https://dnr.maryland.gov/ccs/Pages/horseshoecrab-medical.asp...
Though this piece contradicts that origin story:
https://www.mentalfloss.com/article/578911/why-star-treks-mr...
I'm failing to come up with the right search terms to find what I recall about zooplankton and the oceanic food web. It differs from other food webs and this shows up starkly in certain kinds of charts/models.
Zooplankton are tiny creatures found in relatively small amounts on the surface but breed like crazy and feed huge animals, including some types of whales. So where other food webs are kind of pyramidal and you have a huge amount of plants at the base of the web and a smaller amount of animals that eat those plants and a smaller mass of animals that eat those animals, the ocean's food web doesn't follow a similar pattern. It's not pyramidal. There is much more mass found in other layers of the food web than of zooplankton at any given time.
(Included because of the claim that "One elephant per year of this substance can't sustain life..." How do we know that?)
Furthermore, on Earth we have life sustained by undersea volcanoes which defies our usual patterns of life. I'm out of my depth on exactly how these lifeforms differ from the norm on Earth, so I won't try to give a nutshell version of how they differ, but here are some links:
https://oceantoday.noaa.gov/underwatervolcanoes/
https://www.mpg.de/19982028/0309-mbio-life-in-the-smoke-of-u...
https://en.wikipedia.org/wiki/Sulfurimonas
That's what I know as a former homeschooling mom and Earthbound human who reads. Surely we can do a little better than "It doesn't readily match the patterns of the dominant lifeforms of this planet, so we cannot imagine that some other planet with dramatically different chemical makeup and other details has lifeforms that are fundamentally different from that, and never mind that Earth has some oddities living on it."
Cue the plot from the Star Trek episode where humans were being attacked by the guardian of the eggs that they were destroying willy-nilly without realizing they were eggs:
Its weird that there's any narrative at all around this.
https://www.discovermagazine.com/planet-earth/did-life-evolv...
It's only Titan's surface that is at -292F, anyway, The theory is that life, if it exists, would be present in the subsurface ocean, which would be significantly warmer.
The speculation that is based on things we already know to be possible, speculates that life could be possible in the subsurface ocean.
Alright, I suppose I do actually. Its right up there with Fermi paradox papers wrt the number of wide and wild assumptions required to justify a dramatic headline and clickbait-ha-ha measurement like "one elephant."
It's a reasonable hypothesis, but despite the drama, this sort of thing has no predictive power in our actual universe. Only one where those assumptions all hold.
Could be ours. Probably not though.