https://en.m.wikipedia.org/wiki/Ceres_(dwarf_planet)
Which makes sense, with little to no atmosphere.
If that's correct I'm a little surprised this got voted up to top comment.
The Dawn probe in 2017[2] got a better measurement, of 110K-155K.
1 - https://en.wikipedia.org/wiki/Geology_of_Ceres 2 - https://sites.nationalacademies.org/cs/groups/ssbsite/docume...
I hope it doesn't feel like I'm picking on you but I can't help myself saying something because this is a pet peeve of mine. Rounding appropriately is taught in physics class at school but I think most people don't learn that or think it doesn't apply outside of class.
Not rounding values after conversion has an advantage that it does not change the meaning of the claim, while rounding requires evaulating assumptions of the original claim to ensure it is done properly.
Also note that rouding of intervals is different than rounding of each of its bound value separately. If the original claim is 'the value is between 110 - 155 K', then proper rounding should be -164 - -119 degC to ensure that the original inverval is inside the new interval so the meaning of the original claim (with its implicit probabilistic assumptions) still holds, just is less accurate.
Of course one should assume something about the acccuracy from the number of displayed digits. It's a pretty fundamental concept in physics or even engineering. You can argue that it is just a convention but then again so are numbers in the first place. When writing down a number you will have to make a choice on how many digits to write down (even if its just zeroes), so we might as well use that to convey some meaning. Yes it does not always suffice and so we can use a more elaborate notation when needed, but by default it is a useful convention.
> Not rounding values after conversion has an advantage that it does not change the meaning of the claim, while rounding requires evaulating assumptions of the original claim to ensure it is done properly.
In other words, don't try to understand the claim and just compute. It can make sense in some context but I don't generally think it is the right approach.
One common convention is that the value is written in a way that matches the accuracy. For example, you would never write 73.458 +/- 0.1 because the last digits are meaningless given the accuracy. Similarly, if you measure distances with a tape and round you inputs to the nearest cm, you wouldn't give areas in square mm. In turn, if you give the area in mm^2, then this implies that you think your error bounds are precise enough for this to make sense.
So it is not about readers not "assuming things" but a pretty explicit, though wrong, claim of precision on part of the previous post.
Writing 2 extra decimal places is assuming the original values also have 2 decimal places with zeros in them.
It's reasonable to assume the digits the author gave are correct and there are no other unwritten zeros after them. Even if the scientists really did measure 110.00 - 155.00 K, the author of the source document decided to remove that information and we don't know what it "really" was so we shouldn't guess.
As long as you have at least one digit of precision, scientific notation is unambiguous as to the number of significant figures.
Ceres doesn't have any companion to help in that regards, but hints of cryovolcanism have been detected (emission of water vapor on several spots), so at least _some_ internal temperature is driving volcanic processes.
Still, this isn't really my area and you should definitely consider what a planetary scientist has to say, should one chime in to this conversation.
> Surface Temperature: -105°C
but also:
> the average surface temperature is about ... minus 38 degrees Celsius
https://en.wikipedia.org/wiki/Hydrothermal_vent
https://en.wikipedia.org/wiki/Hydrothermal_vent_microbial_co...
That's yet to be determined as far as I know: extremophiles have all evolved from less tolerant life forms as far as I'm aware.
It's uncontroversial that life is much denser in more hospitable environments. If the extreme environments are in regular contact with the hospitable environments, and if evolution is sufficiently random, you would expect over time that most organisms anywhere have an ancestor in the hospitable environment.
Even if life can arise in the extreme environment.
See the excellent book The Vital Question by Nick Lane.
What are your odds?
Once in orbit it's possible to reach things in the asteroid belt entirely through very high efficiency ion/hall effect thruster propulsion, which can have specific impulse as high as 8000.
Any probe capable of drilling or melting into the crust of ceres or Europa or similar will have to be quite large...
Before SpaceX commercial launch payloads cost $5,000 to $10,000 per pound.
Falcon 9 payloads cost around $1,500 per pound.
Falcon Heavy payloads cost around $1,100 per pound.
Starship payloads will cost between $100 and $500 per pound. It will be able to lift at least 100 tons to orbit. And using in orbit refueling, it will be able to accelerate that 100 ton payload 6.9 km/sec, making landing it on Ceres trivial.
That's still not cheap enough to do lander/surface manipulation science in the asteroid belt without significant philanthropic or government funding.
At $500/pound, if a Ceres unmanned probe lander with drill/melting apparatus weighs 15000 kg when placed in low earth orbit (before whatever staging/fuel it expends to get to ceres and land), that's still a $16.5 million launch cost before you add the cost of the R&D to build the spacecraft, operate its command and control network, etc.
I will be very pleased and enthusiastic but also shocked if something like that is accomplished for a project budget under $30-40m in the next 20 years.
Not saying it's impossible but we're well within the realm of "big budget" science. Like the operating budgets of one of the smaller (not McMurdo or Amundsen-Scott) permanent research bases in Antarctica, or something like the this:
https://en.wikipedia.org/wiki/Chiky%C5%AB
Big enough that even top tier universities form consortia to collaborate in science projects such as the ALMA array.
Starship enters LEO with empty fuel tanks, meaning it can lift much more payload per pound of fuel. Being refueled in orbit is cheap, because fully reusable flights are cheap. And for Mars, Starship only needs enough fuel to get there, it can make fuel on Mars. That means it doesn’t have to carry even more fuel to fly the return fuel to Mars.
How it will likely work is passengers will take a Starship to orbit. It will be refueled in LEO, then accelerate to Mars injection velocity to match orbit with a passing Cycler. It will dock with the Cycler, passengers will switch to the Cycler for the duration of the journey. The Cycler will be much roomier, have better shielding, and likely rotate to provide Mars level artificial gravity. Passengers will have far better work, entertainment and workout options.
Once the Cycler approaches Mars, passengers will reboard their Starship, and it will Aerobrake to land, while the Cycler continues on in its orbit, which returns to Earth. The Cycler never slows to orbit either Earth or Mars, it just coasts between them but occasionally will need fuel for course optimizations.
The only problem is that Cyclers will take 9 months to go to or return from Mars. They will be like large cruise ships. Starship can make the trip to Mars in as little as 3 months, and some will still do that. They will be the equivalent of the long distance direct flight, trading a less comfortable and less healthy trip for a big time savings.
The trajectory adjustments may be small enough that Hall thrusters, or even just reorienting solar panels or inactive radiators get enough light pressure to make it work. If we are OK with spending a little more propellant, the cycler can be put on a shorter quasi-cyclic orbit that requires course corrections on every pass (IIRC, the shortest trajectory Aldrin considered in his paper would enter Earth's atmosphere, or crust, I don't remember). The cycler maintenance cycles also don't need to coincide with in-transit crews and, in some passes, crews can bring more cargo (or the cycler can dock with autonomous cargo freighters).
If the cycler is large enough, it may have its own food production, so you don't need to carry that too, but then we can also imagine it as a full habitat that's permanently populated and passes by Earth and Mars every now and then and also plants us firmly into science fiction territory. IIRC, the shortest real cyclic path also takes a trip to the Asteroid belt before passing Mars on its way back to Earth. That, I imagine, would be a popular destination for future space colonists looking for resources in the belt to supply passing cyclers.
But Cyclers won’t save much fuel. Starships (or their descendants) still have to accelerate and decelerate the same, and still need almost as much shielding (a solar flare during descent once you’ve left the cycler is still deadly). Most of the starship mass isn’t radiation shielding, it’s reentry shielding, tankage, engines, etc.
But once we get to the Cycler stage I think fuel costs will be low on our lists of concerns anyways.
Manufacturing fuel in space would be the way to go.
Or eg have giant solar panels in orbit that power a laser to shine at your spaceships. Either to propel them directly, or to transmit power for their ion thrusters etc.
Starship will be fully reused. It will launch a 5x larger payload than the partially reusable Falcon 9 at a lower launch cost. So somewhere in the $5M to $20M range.
Starship can be fully refueled in LEO with eight tanker flights, Even at $20m per flight, that costs no more than the Atlas V that just launched perseverance to Mars, only with 40 times more mass.
And, perhaps let's talk about a conditional bet that removes the difficulty of space exploration:
The bet pays me X dollars, if human vessels can go to the asteroid belt and not find life. It pays you Y dollars, if we find life. And no payment in either direction, if we can't go to the asteroid belt and don't find life. Say, all limited to the next 100 years.
What's the ratio of X to Y that would make you accept such a bet?
1. Backtrapolating exponential evolution finds an origin older than Earth. https://arxiv.org/abs/1304.3381
I'd be happy to pay up in case of pre-historic panspermia.
Do you mean NERVA?:
Imagine a universe of only helium. No valence electrons would be readily available, so chances are you are not going to see helium molecules. Lithium, sure, as a metal. Continue examining various smaller (and more plentiful elements). Fluorine? Well, only one slot available, so you can make molecules with two atoms, but no chains. If you have two slots open, you can make a chain, but little else. Although try making a chain of oxygen -- even the three-link ozone is not particularly stable. Carbon can have four different bonds going at once, which is pretty crazy, and so you want something with three or four slots available.
But then you say, well, silicon could have four. And it could ... but for the fact that it is so huge by comparison to carbon (that whole other "electron shell") that it rarely has analogues to organic (carbon-based) compounds. Also, it doesn't like to do much until you get it fairly hot. So you climb back up a row and it looks like carbon, nitrogen, boron ... those are going to do your heavy lifting when you need multiple bonds, with hydrogen, oxygen, and the halogens or alkali metals somewhere on the outside. Hence carbon chauvinism. Carbon is something like the fourth most common element in the universe after all.
Then you start talking about solvents -- all of this stuff has to slosh around in something after all, your chemistry experiments take place in liquids -- and the field is a bit wider but dang, water has some crazy properties that make it quite a catch when it comes to solvents.
You've got temperature ranges: down in the single digits of Kelvin you're not going to have much chemistry happening, and up in the thousands of Kelvins even iron boils and then again, no more structure.
Once you start looking for these various "sweet spots" it all comes down to finding a place where you can have liquids (your solvent), solids (for structure), and gases (even if they are dissolved in liquids). Combine that with the more common elements (especially those that are friendly to complex chemistry) and you have something not entirely un-Earthlike.
There's tons of Wikipedia articles on it, but ... the restrictions of chemistry are the bulk of the culprit, I'm afraid.
Also, a big drawback of searching only chemistry-based life is that it limits a lot the range of viable temperatures. Would be too slow and simplistic at low temperatures, and a complete uncontrollable chaos at high temperatures.
In particular, finding a brine on an ice dwarf like Ceres is not very exciting, as the temperature is too low, and no interesting chemistry can happen.
Whereas other substrates could be totally fine at different temperature ranges.
One point I have with Baxter is that his premises are just bananas, but the people acting in them are pretty recognizable. To be fair, if the characters were also nutter-butter, no one would read it, as it wouldn't be a story anymore, just a strangely formatted research paper.
Not many authors can go the distance from the beginning of the universe, to the end, and then back around again.
They Hyperion Cantos is also good reading. It starts with a re-write of the Canterbury Tales in the far future, and has the pilgrims making their way, not to Canterbury, but to face off with a six-limbed red-eyed spike-covered murder beast that exists outside of time. It ends with hyper-evolved humans and the second-coming facing off against god-like AIs.
Trust, me, it actually works really well.
Yes, I know that makes me sound like the boring, hide bound characters in such novels that are incapable of understanding this new amazing form of life, but frankly in the real world those guys would be absolutely right. The protagonists who contact the amazing new life forms just make far too many fundamental errors and intellectual shortcuts to really be credible.
Specifically for your point on entropy and stability of vortices, I don't disagree totally though I'd like to call your attention on what is known with magnetic skyrmions. They are stable because to change spin the particles would need to overcome huge energy barriers. Then, the only difference with fluid vortices is that in a fluid there is friction that can bring the fluid elements to gradually shed their angular momentum at the contact of other elements with a different momentum. But in superfluid states that you could encounter at very low temperatures (like on some distant planet etc), it is plausible that there would exist analogous energy barriers preventing the fluid elements to directly shed their momentum! And even though, you can of course imagine fluidic circuits and rotational computations, which would have some stability thanks to the superfluid state.
Of course all of that is baseless speculation, but the point of SF is precisely to appreciate the vastness of the world of plausible phenomena...
If we seeded a planet with sufficiently advanced robots, that can mine and build and learn and make copies of themselves on their own, and a few centuries later they have a civilization, does it matter what they're made of?
For all intents and purposes, it would be life.
Perhaps at some point we should/will have to stop saying "life" at some point and use terms like "agent" instead, to include disembodied intelligences shaping the universe through their decisions and stuff like that. :)
It does stuff on its own. That's agency.
Why would it not?
I could talk about how the various conditions at the surface of a neutron star probably cannot support the kind of interactions that would lead to a nuclear pseudo-chemistry (the elements aren't as important so much as the kind of bonds, and therefore structure supported, are, with the other physical properties being less important), but I would like to take a different tack and think about life arising. How would all of those little cycles, circadian down to Krebs, get started?
My intuition? guess? is that just as we are big bags of internalized seawater, life would have hijacked, replicated, and then encapsulated already existing cycles, multiple cycles. Just once cycle wouldn't cut it, probably not even two. I think for us it was all about warm little tidepools, water comes in, then the day-night cycle keeps changing the concentrations. Another tide comes, more water and something, perhaps waste, is washed out. Enough times, enough luck, maybe something sticks, holds something back in case the next splash isn't as big. The next big trick is a membrane, something to isolate the cycles. Separates the outside from the inside. Now there's something to separate.
Overall, though? You're still going to need matter that supports both structure (at least for a membrane, a boundary between in and out) and fluidity (for those cycles). I've thought a lot about what the bare minimum would be, but the Earth chemistry is just a shorthand for "what bonds, and therefore structure, can be maintained?" and "how will it flow?" I am pretty confident in saying it would have to obey Fermi statistics, instead of Bose, because bosons love to play follow the leader, but fermions need to stand out (and apart) enough that they can at least stand. The convection cell entities were interesting to think about but would require an almost unparalleled level of stability and uniformity across large expanses of matter, sort of a large-scale "lab conditions" environment, free of fluctuation and interference, somewhere relatively calm. I have considered something not too far away from that, life existing in an environment where the average energy levels were constant, but the entropy wasn't: life optimized to hunt not for calories but for pockets of order to bolster its own.
Non-chemical life is fun to speculate about but ... I keep coming back to structure and fluidity. It's difficult to find phases of matter that support both that aren't in the chemical domain.
I agree, I would be surprised if we discover first alien life in a non-chemical form. Somehow though I would love to be surprised!
There are so many possible environments and substrates, and we cannot think of all of them. The multiplicity of the places where things could happen, and the scale and age of the universe, also increase the possibilities that there are places with the right conditions or stability. The conditions on Earth were kind of lab-grade perfect too! Any nearby supernova, ill-directed solar flare, etc. could have nipped life in the bud. Only the huge number of Earth-like environment in the universe, and the large interval of time allotted, can justify that we have had the chance to arise in these conditions.
PS: also, to be fair, a lot of life forms in Baxter are actually engineered. But our First Contact (or First Observation) could be as well with a "natural" form as with an artifact! And that would not matter that much.
If you assume water based life, there is almost certainly going to be oxides involved, such as how CO2 is involved with earth life.
And I think water based life chemistry is an extremely good bet, because alternative liquids based off of light, common elements are either only liquid at very low temps, (ammonia, methane) extremely reactive ( Hydrogen fluoride, hydrogen sulfide), or both.
Another consideration with silicon is that the earth contains vastly more silicon than it does carbon (in many ways life on earth is fairly carbon starved), yet life based on carbon arose, not silicon.
I was amused once by reading an MSDS for silicon dioxide.
As I presume is required, they do list some hazards of exposure, but if you read the sheets for other substances the contrast is pretty striking. Look at the health effects listed on https://fscimage.fishersci.com/msds/09890.htm :
> Eye: Dust may cause mechanical irritation.
> Skin: Dust may cause mechanical irritation.
> Ingestion: May cause irritation of the digestive tract.
> Inhalation: Dust is irritating to the respiratory tract.
> Chronic: May cause cancer in humans. Prolonged exposure to respirable crystalline quartz may cause delayed lung injury/fibrosis (silicosis).
> NFPA Rating: (estimated) Health: 1; Flammability: 0; Instability: 0
So yeah, as long as you're not inhaling sand, you're fine.
> [Chlorine trifluoride is] also a stronger oxidizing agent than oxygen itself, which also puts it into rare territory. That means that it can potentially go on to “burn” things that you would normally consider already burnt to hell and gone, and a practical consequence of that is that it’ll start roaring reactions with things like bricks and asbestos tile. It’s been used in the semiconductor industry to clean oxides off of surfaces, at which activity it no doubt excels.
—Derek Lowe, “Sand Won’t Save You This Time”
> Hazardous combustion products: None that are more toxic than the product itself.
( https://www.boconline.ie/en/images/chlorine_trifluoride_tcm6... )
It's a fun read.
> Contains no other components or impurities which will influence the classification of the product.
In the unlikely event you survive adding something, you won’t make it any better. You certainly can’t make it worse.
> Unsuitable extinguishing media: Water, Foam, Halons
> Specific methods: Move away from the container and cool with water from a protected position.
Um.
> May react violently with combustible materials.
Specifically, everything.
> Seek medical advice before using product.
“Don’t.”
> Ensure vehicle driver is aware of the potential hazards of the load
Driving is a strong indication that he is not aware.
> and knows what to do in the event of an accident or an emergency.
“Run.”
—also Lowe
> Danger! May be fatal if inhaled, absorbed through the skin or swallowed. Both liquid and vapor can cause severe burns to all parts of the body. Specialized medical treatment is required for any exposure... can cause metabolic imbalances with irregular heartbeat, nausea, dizziness, vomiting and seizures. Long-term exposure may cause bone and joint changes. Will attack glass and any silicon-containing material. Corrosive to metal.
> Potential Health Effects
> Eye: Contact with liquid or vapor causes severe burns and possible irreversible eye damage.
> Skin: May be fatal if absorbed through the skin. Causes severe burns with delayed tissue destruction. Substance is rapidly absorbed through the skin. Penetration may continue for several days. Causes severe tissue necrosis and bone destruction.
> Ingestion: Causes severe digestive tract burns with abdominal pain, vomiting, and possible death.
> First Aid Measures
> Eyes: Do NOT allow victim to rub eyes or keep eyes closed. SPEEDY ACTION IS CRITICAL! GET MEDICAL ATTENTION IMMEDIATELY!
> Skin: Discard contaminated clothing in a manner which limits further exposure. Destroy contaminated shoes. Spills should be flushed until medical attention arrives. SPEEDY ACTION IS CRITICAL! GET MEDICAL ATTENTION IMMEDIATELY.
> Ingestion: Get medical aid immediately. SPEED IS ESSENTIAL. A DOCTOR MUST BE NOTIFIED AT ONCE.
> Inhalation: SPEED IS ESSENTIAL, OBTAIN MEDICAL AID IMMEDIATELY. POISON material. If inhaled, get medical aid immediately.
(ALL CAPS are original to the MSDS.)
> Wear chemical splash goggles and face shield.
> Wear butyl rubber gloves, apron, and/or clothing.
> Wear appropriate protective clothing to prevent skin exposure.
> Wear a NIOSH/MSHA or European Standard EN 149 approved full-facepiece airline respirator in the positive pressure mode with emergency escape provisions.
> Never work alone with this chemical.
> Substance is noncombustible
I would also argue that CO2 and dry powder isn't an suitable extinguishing media for this, as CF3 doesn't give much of a shit when it's got it's own hyperactive oxidizer on board.
But it's pretty much inert chemically (for human levels of chemical reactions)
But they are very low temps on our scale, which is centered around water.. There are many places, even in our own solar system, where these are liquid all the time, and water is solid all the time.
http://www.bigear.org/CSMO/HTML/CS09/cs09p05.htm
I was surprised to realise (that besides being N author) that he was a professor of biochemistry.
1. fluorosilicone in fluorosilicone 2. fluorocarbon in sulfur 3.*nucleic acid/protein (O) in water 4. nucleic acid/protein (N) in ammonia 5. lipid in methane 6. lipid in hydrogen Of this half dozen, the third only is life-as-we-know-it. Lest you miss it, I've marked it with an asterisk."
What about non-chemical life. What I mean by that is something like a giant CPU with traces literally the size of freight trains? I recently finished the first Dark Tower book and it’s got me thinking about scale.
You know that, in the past when you lost your wallet, you dropped it somewhere or you left it behind somewhere. However, because you are a free individual and because the universe is full of possibilities (including the event that the quantum froth poofed your wallet away and created an identical one in your hedge), you can do practically anything now in search of your wallet. Do you:
* Retrace your steps to see if your wallet is anywhere along the path
* Call your mother and see if she has your wallet
* Begin a global wallet-hunt in case the wallet was transported to Cuba
Like most people you have an intuitive understanding of what to do: Given limited resources you should allocate them in order of decreasing likelihood of success.
Most things do not lead to life. Our prior on "There is silicon-potassium self-replication on Charon" is pretty low because our prior on "X self-replication" is pretty low for most things.
Try it out. Suggest an alternative and honestly set your priors on it, then condition those priors on the evidence that you have seen on Earth, and the limited evidence from the Moon and Mars. Now look at those posteriors for your alternative and compare it with the kind of life we know. Almost certainly microscopic, but if it isn't, you should publish.
(The trouble is that those places don't have sunlight and probably fewer energy sources overall.)
It could be the answer to why we don't meet aliens: they couldn't care less about dry places like the Earth. You could travel the stars hopping comet to comet, but after spending 10,000 years like that you might be comfortable enough in your lifestyle that you wouldn't want to stop at a star. (All contingent on solving the energy problem, either you get lucky and find a lot of uranium or you invent D-D fusion.)
Plus, as you say, most liquid water is in the deep dark under ice sheets far from the nearest star which makes photosynthesis difficult.
But that might have been the final item in a long list of requirements. Maybe life form quickly (on a planetary-scale of quickness) once they are met, but who knows how long that list is.
TBH, I think people fixate on "life" because of some star-trekkian fantasy about aliens, and specifically, other space-faring aliens. There are lots of interesting life-forms on earth that are ignored. We have a lot yet to learn about chemistry, let alone the biochemistry of bacteria, algae, mould. Dolphins and octopi have yet to build boats, let alone spaceships (arguably the monkeys are ahead on this game).
TBH, I'm more interested in what kind of interesting materials and phenomena might exist on other planets. As for life, I think its more interesting to think about what kind of alien environments we can seed with life (and what would form) rather than the moon-shot of actually finding life we are exited about.
Also keep in mind: life or not, it might be more likely we find something else interesting or dangerous. e.g. some kind of adaptable self-replicating enzyme, but made of something more durable than protein (and reproducing in the environmental). Consider the rubber-eating contaminant in https://en.wikipedia.org/wiki/The_Andromeda_Strain
(I think multicelularity of eucaryotes is easier in comparison with the other two steps, it has evolved like 20 times. But in the timeline, it took a long time...)
"If all your friends descended to the bottom of a gravity well, you would too? After all, we're not savages."
But do we really know enough to assume that's only way?
And to be fair, we are not exclusively looking for Earth-like biological markers. Lots of people looking out for signs of Dyson spheres or other biology-agnostic possible signs of life.
Here's an interesting article exploring the lowest possible temperature for life on earth (which is largely focused on vitrification blocking cellular metabolism but has both theoretical and empirical insights): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3686811/pdf/pon...
Google says, https://van.physics.illinois.edu/qa/listing.php?id=1593
(Thinking of those interactive diagrams for temperature on the kinetic energy of molecules zooming around in closed space)
It's a speculative hard sci-fi that posits ultra-fast evolution for life on the surface crust of a neutron star!
Although I was previously recommended Rocheworld by a former NASA researcher, with the note that Robert L. Forward made every effort to describe a scientifically plausible double planet.
Incidentally, it looks like Dragon’s Egg is his only work available on Audible. I’ll add it to my list.
TIL!
Oh, looks like this movie "Evolution" ( https://en.wikipedia.org/wiki/Evolution_(2001_film) ) was also on those lines then!
(badum tish)
Also, the book does describe a character's apprehension at climbing to the dizzying heights of a few millimeters off the surface.
Sorry, can you explain what you mean by this? Are you using "water" figuratively for all liquid, as opposed to H2O?
https://en.m.wikipedia.org/wiki/Extraterrestrial_liquid_wate...