So…an atmosphere of super-heated steam? Sounds nice.


I’ve been seeing a lot of excitement about this new discovery on an extrasolar planet: it’s got water.

“We know that water vapor exists in the atmospheres of one extrasolar planet and there is good reason to believe that other extrasolar planets contain water vapor,” said Travis Barman, an astronomer at the Lowell Observatory in Arizona who made the discovery.

That’s cool. Not at all surprising, but cool. I shouldn’t think it unexpected that H2O is found throughout the universe. I’ve also been seeing naive gushing about prospects for colonizing other worlds. They never seem to take the other parameters of this planet into account.

HD209458b is separated from its star by only about 4 million miles (7 million kilometers)-about 100 times closer than Jupiter is to our Sun-and is so hot scientists think about it is losing about 10,000 tons of material every second as vented gas.

It’s also 220 times the mass of Earth and has a surface (I’m curious about what kind of surface this gas giant has) temperature of about 1000°C. Since it’s 159 light years away, I won’t be taking a vacation there in my lifetime.

Well, when you put it that way, maybe I’d like to visit, just a little bit.


Correction: the latest buzz is about K2-18b, a rocky planet that is only 7-10 times Earth’s mass, and a mere 110 light years away. Compared to HD209458b, it’s a paradise practically right next door!

How to interpret the data they’ve got seems to be complicated.

Ingo Waldman, on the University College London team, explained that three different scenarios fit the data equally well: The atmosphere could be pure hydrogen with lots of water, or the atmosphere could contain hydrogen and nitrogen with just a little bit of water. Or a third option allows for a hydrogen atmosphere, a “tiny speck” of water, and high-altitude clouds or hazes that obscure the view.

Benneke and his colleagues throw in another option: liquid water in addition to water vapor. Their calculations suggest that it could rain in the mid-atmosphere of this world.

I don’t think that, after our quick jaunt for a vacation on K2-18b, we’re going to be breathing that atmosphere. H2 on Earth is present in less than one part per million, so that they’re even discussing how much hydrogen fills the skies of K2-18b is a little off-putting.

Comments

  1. anchor says

    As ethicsgradient notes, water vapor has been detected in hot exo-Jupiter type exoplanets before – as long ago as 2007. They’re nothing new. That one is just riding on the coattails generated by the far more interesting discovery just reported last week: a super-earth called K2-18b located in the habitable zone with water vapor detected in its atmosphere:

    https://www.nature.com/articles/s41550-019-0878-9

    Since that’s behind a hefty paywall, here are a few more accessible links:

    https://en.wikipedia.org/wiki/K2-18b
    https://www.skyandtelescope.com/astronomy-news/astronomers-discover-water-vapor-super-earth/

    [Though ethicsgradient beat me to it, i figured to post this anyway since I went to the trouble to assemble it)

  2. methuseus says

    It is actually notable how much water is in the atmosphere. As the others mentioned, you got details wrong, but overall you’re right. It’s got a surface inhospitable to even robots we would send, from what I remember. If it has a surface you can get to, the pressures would be astronomical. It’s also tidally locked to the star, so that means no day cycles, which could make it harder for life to develop even without all the other issues.

    I really don’t get why so many news stories talk about water on a planet in the habitable zone with such excitement, then, at the end of the article, mention that it’s a gaseous planet, not rocky.

  3. birgerjohansson says

    A couple of weeks ago, a statistical study -taking into account the detection bias of the planet-hunting technologies- estimated that the probability for an “Earth-like” planet -defined as up to 125% the radius of the Earth, with an orbital period between 220 and 500 days in the habitable zone is about 27%.
    The big caveat is that this refers to stars of the F, G and K spectral classes.
    M dwarfs have a lot of stellar flares, especially in their youth, and this will erode atmospheres of any nearby planets. Also, the planets in the habitable zone will probably be tidally locked unless their orbits are quite excentric. Therefore red dwarf stars (class M) seem to be ruled out as having planets hospitable for life.
    Nearby, the (orange) K dwarfs Tau Ceti and Epsilon Eridani are of interest. Both are about 12 light years away, and at least one of them has a planetary system.
    .
    Of course, by the time we have technologies to travel between such distances, we will probably have “strong” AI, and such entities can travel for a few hundred years without ageing the way biological entities do.
    And they will not require what we regard as “hospitable”. They may even prefer worlds we regard as too dry or too cold, as this reduces corrosion. The cold, dark side of a tidally locked planet could be regarded as optimal for settlement!

  4. birgerjohansson says

    Re. @ 5, worlds orbiting brown dwarf “stars” could also be useful to AI travellers. So the emptiness between what we regard as habitable systems might be filled up with cousins of HAL9000, or replicants. The first humans on properly habitable worlds will probably be decanted by AI robots after 9 months in test tubes. The film “Mother” comes to mind.
    -Since stable biospheres are likely few and not as long-lived as on Earth (Fermi paradox, remember?) those AIs will have their work cut out for them repairing and re-terraforming a lot of formerly habitable worlds.

  5. PaulBC says

    methuseus@4

    I really don’t get why so many news stories talk about water on a planet in the habitable zone with such excitement, then, at the end of the article, mention that it’s a gaseous planet, not rocky.

    Because if they started with the disappointing part, fewer people would read it? (Just a wild ass guess here.)

  6. Artor says

    An atmosphere with significant amounts of free hydrogen floating around is going to smell like vomit. Mmmm… So just like Palm Beach during spring break, right?

  7. Peter B says

    An atmosphere with significant amounts of free hydrogen floating around is incompatible with significant amounts of free oxygen. I am talking about H2 and O2. Perhaps Artor@8 may have been thinking about H2S.

  8. monad says

    @5 birgerjohanssen: Which of Epsilon Eridani and Tau Ceti do you count as having a confirmed planetary system? I had thought both did, but maybe that’s me over-accepting what are only possible results.

  9. blf says

    The mildly deranged penguin is annoyed. Uh-oh… She claims water, atmosphere, surface, and not being boiled or frozen or eaten by the natives are all mere frivolities. The really interesting question are the local cheeses. This focus on frivolities is like admiring the works of Shakespeare without ever mentioning they were all about cheeses. Rather like mistaking trees and forests, or rather, mistaking walruses and volcanoes. She stomps off in a huff…

  10. Pierce R. Butler says

    Atsa nice. Pls wake me when mass spectrometry confirms presence of free oxygen in an exo-planet’s atmosphere…

  11. says

    I wonder what would be required to make Venus habitable. A major asteroid strike, maybe? Something to blow off 90+% of the existing atmosphere, then something to ratchet down the surface volcanic activity. We’d still have to breakdown the H2SO4 that remains in the atmosphere to release actual water. But then, what happens to the leftover SO2? Is Venus tidally locked? I forget. Mars? Minimal atmosphere. Too cold for any plant life. Best bets are Triton and Miranda. Maybe. Hella cheaper and easier to try to save Earth.

  12. blf says

    Evolve an ability to survive a greater temperature range, high radiation, sulfuric acid, and a lack of cheese.

  13. jack16 says

    @ 13 Jonathan Norburg
    If you live in balloons its habitable now. (“google” for articles)
    jack16

  14. unclefrogy says

    what is cool about all of this is we are really beginning to get much better at detecting planets and learning things about them. the details are new and interesting, it will likely be a long time until we can do much with the new information but it wasn’t that long ago that we could only guess about other solar systems. All of them are really a long time away from us.
    I am amazed
    uncle frogy

  15. a_ray_in_dilbert_space says

    I am afraid that my role in life has become bursting the bubbles of technophiles.
    1) We will never (as human beings–as satellites, maybe) travel to the stars.
    2) We will likely never succeed in transforming Mars.
    3) Earth is and will remain the only quasi-permanently habitable piece of rock we will ever know–at least until we render it uninhabitable.
    4) You can’t travel faster than the speed of light.
    5) There is no such thing as a warp drive and there never will be.
    6) Time travel is impossible.
    7) Earth has not been visited by aliens. It is too remote and insignificant to draw attention even in the unlikely event that said aliens have a very different biology from ours and have developed the ability to travel through interstellar space.

    If you would like me to poke holes in your own personal technofantasy, just let me know.

  16. says

    #17 a_ray_in_dilbert_space: Are you suggesting that aliens don’t land in remote rural areas, adorn themselves with fake antennae and walk around in front of people no one will ever believe making beepbeep* sounds and kidnapping them for butt probes? Teh horrorz.

  17. PaulBC says

    a_ray_in_dilbert_space@17

    I mostly agree, but as for “2) We will likely never succeed in transforming Mars.”, first the “likely” part kind of makes it hard to refute, but I have some thoughts.

    I don’t see why, given hundreds of years of technological advance, we would not have the capability to terraform Mars, if that’s what you mean by transform. And hundreds of years from now (or even thousands) is not the same as “never.”

    There are reasons we might not actually do it (supposing that civilization has not collapsed and we have the ability). (a) We might want to leave Mars pristine for science or based on cultural values (b) We might not see the potential living space as having great economic value (c) The cost/benefit of going back and forth to another gravity well might argue against any reason to visit besides science and tourism.

    But choosing not to is not the same as not “succeeding”. I may never “succeed” at building a model of the Eiffel tower out of toothpicks. I may never see any reason to do that, in fact. But that’s not the same as not succeeding, is it? There’s nothing stopping me right now from putting other things in my life on hold and getting really into toothpick models.

    So it’s by no means a given that Mars will ever be populated by humans, and it may even be unlikely, but are you saying it’s infeasible? I think that large-scale engineering could potentially be enabled by self-replicating robots capable of exploiting off-world resources. Yes, we have to figure out how to make them first, and it’s not likely in my lifetime. There are no clear physical barriers to it though.

    I’m a little more divided on (1) interstellar travel. There are things that make it exceedingly difficult to accomplish, in terms of getting even a small number of living things across interstellar distances (and alive over that timespan and protected from radiation the whole way), let alone a large number of humans. It’s also unclear that there are any incentives for doing so.

    The main way I would see to do it is to presuppose that we could synthesize* a living eukaryote cell completely along with a DNA sequence (DNA sounds like the easy part) and that we have sufficiently advanced self-replicating hardware to exploit energy and matter in the neighborhood of the star it eventually reaches. We send that along with a pure information payload, or even beam the information along separately as a high-energy laser signal. Then, if for some bizarre reason, we consider it important to have biological humans in another star system, this machinery, after perhaps hundreds of years of preparation, could possibly incubate and raise these humans who would be the first humans in another star system.

    Above poses new technology, but does not contradict any physical limitation. I am not saying it is likely to happen, only that it is not literally impossible.

    Note that if we could contact a sufficiently advanced and trustworthy extraterrestrial intelligence, we could save the step of sending hardware and just beam the information, though I don’t really recommend it.

    *Or if the biological “starter culture” is sufficiently small, perhaps it could be shielded for travel even while exposing most of the probe to interstellar radiation.

  18. Pierce R. Butler says

    birgerjohansson @ # 5: … the planets in the habitable zone will probably be tidally locked unless their orbits are quite excentric.

    Howcome? None of the four inner planets in this solar system have that problem (nor do any of the others).

  19. nomdeplume says

    @19 “We might want to leave Mars pristine for science or based on cultural values“. We can’t even guarantee leaving a few areas on Earth “pristine for science or based on cultural values”. Think of the Amazon, the Arctic, Trump’s hacking into National Parks, same thing in Australia. Everywhere you look the small number of areas set aside for conservation are under attack from human greed and stupidity. As soon as Mars can be exploited by the Robber Barons of the future it will be hacked about.

  20. says

    If they want to get excited they need to look for processed CO2 and NH3. Water? Boring. Rock/Metallic planets may pump the stuff out of magma as the largest part of the gasses if the Earth is anything to go by.

    Hydrothermal vent FeS chemistry has the potential to produce a couple of C1s (methanol, formic acid), a C2 (acetic acid), and a C3 (pyruvic acid).
    https://pubs.rsc.org/en/content/articlelanding/2015/cc/c5cc02078f#!divAbstract

    The same chemistry can fix N2 with UV.
    https://www.pnas.org/content/113/20/5530

    After that my money is on the “business end” of cofactors being an early product of Geo/hydrochemistry.

  21. aziraphale says

    a_ray_in_dilbert_space@17:

    “7) Earth has not been visited by aliens. It is too remote and insignificant”

    Remote from where? We already have conceptual designs for starships to reach 5% of lightspeed. We haven’t surveyed all the nearby stars for planets yet, and there has been plenty of time for a spacefaring species or its robots to have reached us from anywhere in this corner of the galaxy. As to “insignificant”, the rarer intelligent life is the more interesting each example of it will be.

  22. PaulBC says

    nomdeplume@21

    Well, it was intended as a hypothetical reason we might not terraform Mars even if we had the technology. At that level of technology, it’s possible Mars would have relatively little value (say compared to the asteroid belt) and this would be enough reason to avoid massive exploitation. I can’t predict what will actually happen. It’s not even obvious to me why Mars would have any commercial value at all.

  23. tacitus says

    a_ray_in_dilbert_space@17:

    Never…

    Never is a very long time. Interstellar travel and terraforming Mars are not something we are going to be doing within the next few hundred years, but assuming human civilization doesn’t implode, then both are likely to be technologically feasible eventually, perhaps a thousand or two years from now. Whether either is worth the effort or cost involved is another issue entirely, but then if we’re still around 2,000 years from now, who’s to say what our motivations will be.

    Earth has not been visited by aliens. It is too remote and insignificant to draw attention even in the unlikely event that said aliens have a very different biology from ours and have developed the ability to travel through interstellar space.

    If intelligent life is rare enough, Earth is neither too remote or insignificant. Interstellar space exploration over the next few hundred years is going to be done through the end of a telescope, and while practical interstellar travel is out of the question for the foreseeable future, sending fleets of telescopes out beyond Jupiter where viewing is most idea, is not, and they will eventually be used to image millions of extra-solar planets, some of which may betray signs of oxygen-rich atmospheres, with might even contain signs of technological activity, such as trace elements of industrial pollution.

    So, any curious intelligent civilization even slightly more advanced than ours will be scanning the skies for the same thing, and they can detect Earth, you can bet they’ll train every instrument they can to see what’s going on.

    Of course, whether they would have the will or resources to visit us is doubtful, for obvious reasons, but it won’t be because we are insignificant. If intelligence is rare in the Universe, that makes us very significant indeed.

  24. Ed Seedhouse says

    @20: “Howcome? None of the four inner planets in this solar system have that problem (nor do any of the others)”

    Mercury is actually very close to being tidally locked and but for an orbital resonance with Venus likely would be.
    The “habitable zones” of red dwarfs are extremely close to the star. The zone where water could be liquid is way closer to their stars than Mercury is to ours, Red dwarfs are very cool compared to our sun and much less massive.
    Astronomers say this, and you should believe them.

  25. Dunc says

    Pierce R. Butler, @ #12:

    Pls wake me when mass spectrometry confirms presence of free oxygen in an exo-planet’s atmosphere…

    Pedant alert: I would suggest that even developing the ability to do mass spectrometry on an exo-planet’s atmosphere would be worth waking up for. You probably meant spectroscopy.

  26. John Morales says

    [ Dunc, :) ]

    Well, I did wait, because I see new posts just before I retire for the day.

    So, when reading this post, well before any comments, I saw …

    “That’s cool. Not at all surprising, but cool.”
    &
    “It’s also 220 times the mass of Earth and has a surface (I’m curious about what kind of surface this gas giant has) temperature of about 1000°C.”

    … and I thought, “Not cool at all, then”.

    (Yeah, weak, I know. Colour me literal)

  27. a_ray_in_dilbert_space says

    Mars will not be terraformed mainly because it lacks a planetary magnetic field. The solar wind will rip away any atmosphere we generate. Humans may live on Mars one day, but they’ll live under domes or more likely under ground, and they won’t be self-sustaining.
    At 5% of the speed of light, it would take 80 years to reach the nearest star (excepting Sol). Also note that even getting to 5% is purely hypothetical. Even if we can travel at 20% of the speed of light, that’s still 20 years. Galactic cosmic rays would totally shred your DNA within 5 years. You could try to shield against this threat, but 6 inches of Al would only cut the flux down by <<10x, and good luck accelerating a spacecraft with that amount of shielding.

    We are in the far exurbs of the galaxy. We are a small planet orbiting an unremarkable star. Most of the life in the galaxy is probably closer to the center–you know, where all the stars are. Even if aliens had sufficiently advanced technology, there would be no reason to prioritize Sol and its environs over any other spot on the galaxy’s edge, and much advantage in looking closer to home.

    Given the trajectory humans are on, I feel pretty safe with “never”.

  28. KG says

    We will never (as human beings–as satellites, maybe) travel to the stars. – a_ray_in_dilbert_space@17

    I’m not sure what “satellites” is doing there – surely the definition of a satellite is simply something orbiting something else, – but IIRC, it’s not long ago you were denying the possibility of any form of interstellar travel. What changed your mind?

  29. PaulBC says

    a_ray_in_dilbert_space@29

    At 5% of the speed of light, it would take 80 years to reach the nearest star (excepting Sol). Also note that even getting to 5% is purely hypothetical. Even if we can travel at 20% of the speed of light, that’s still 20 years. Galactic cosmic rays would totally shred your DNA within 5 years. You could try to shield against this threat, but 6 inches of Al would only cut the flux down by [much less than] 10x, and good luck accelerating a spacecraft with that amount of shielding.

    I’ve heard this argument before, which is I why I replied as I did in @19. First off, what’s so bad about 80 years? In fact, why not piddle along at 0.5% of the speed of light (at least 100x less energy) and take 800 years to get there? Obviously, you don’t send live humans. You grow them when you get there. You don’t grow them on the machinery you sent, which is necessarily small. The payload is a von Neumann replicator that builds massive infrastructure using abundant material and stellar energy at its destination.

    How long till it’s done this step? Does it matter? Maybe it spends 100 years doing a survey and another 1000 years converting the most likely source of usable material. If it lands on the wrong asteroid the first time, it tries again, or maybe it starts with multiple tries assuming it is able to find enough material to build a few new copies of the replicator.

    Then it either synthesizes the germ cells and DNA from pure information, or it has some of the initial organic material (non-DNA part of cells) available as part of a well-shield payload of under 1 kg. It is relatively simple to protect information from damage with error-correcting codes, so don’t rely on the shielded DNA as the source of truth. You synthesize the usable DNA at the destination.

    And, again, the information does not even have to be sent within the probe, for short enough distances between stars, it could be sent as a series of high-energy laser pulses. The transmission rate can be very slow because of the amount of time involved.*

    You don’t grow humans like potatoes, so this presupposes some form of education, including language acquisition and acculturation. There are human rights considerations. I am not claiming my idea is ethical. But when it’s done you have… Tada! Biological human beings in another star system, and with appropriate background education, they know as much about what they’re doing there as I knew what the fuck I was doing on earth when I got old enough to wonder (and am not really sure now). They can feel they are as much a part of “humanity’s progress” as anyone born on earth, and even send messages back and forth with other human outposts admittedly with substantial time delays.

    Is all of this well beyond any technology I am likely to see in my lifetime? Yes. Beyond the next few hundred or a thousand years? I am not sure, but I don’t see what it couldn’t happen in hundreds of years.

    Is any of it contrary to physical laws? No. The clunky vaporware I just outlined presents an engineering problem, and the amount of energy needed for the interstellar travel itself is quite modest compared to many of these proposals.

    Will biological humans ever want to do anything like this? Eh, maybe not. That isn’t my point. It is just that “never” and “impossible” are the most difficult claims to back up, so please don’t make them unless you have an actual proof of impossibility (e.g. based on a real physical law such as energy conservation).

    *An interesting question here is how dumb can you make the payload. It does have to be able to manipulate matter at the target, but the vast complexity of its blueprints need not be stored in the probe itself (though I think it could be anyway, with sufficient shielding). You could have a certain amount of self-repair of inevitable damage during the trip. However, information loss is the one thing you need not be concerned with, because the information is the part that actually can move along at the speed of light.

  30. PaulBC says

    Finally, I think that any technology capable of placing biological humans in another star system is probably far in advance of the obsolescence of biological humans as the primary intelligence driving technological progress on earth. Note: (a) I am not predicting a “singularity” any time soon or in the next thousand years and (b) there is no reason biological humans will not want to continue to exist as such. But assume (contrary to reasonable expectations) continued progress and no collapse of civilization, I don’t see why we could not have biological humans in distant star systems if for some reason our descendants (biological or not) consider this a worthwhile goal.

  31. PaulBC says

    I don’t want to understate the amount of bulk equipment (and tonnage) required to bootstrap any kind of autonomous manufacturing in another star system. However, there are a couple of points to be made here.

    (a) Some forms of autonomous manufacturing may already be within the grasp of current technology. Search keywords like lunar regolith solar power. I can’t find the specific article I was thinking of and most of these go off into a lot of wild claims. But a fairly simple device could slowly and steadily transform a rock surface into an inefficient, but massive solar electric plant eventually providing abundant electrical power. The device would begin under its own power (maybe a nuclear battery or high-efficiency solar panel) and then plod along creating solar cells in situ, eventually drawing power from this grid if it has to. So I think it is not infeasible to imagine sending a payload to another star system that merely creates a giant, purposeless solar energy grid.

    (b) Other things are really hard. Eventually your autonomous equipment will need more local computers. It is hard enough to fabricate silicon wafers on earth in a clean-room environment starting with refined materials. First off, there is no reason the autonomous robots need the best possible autonomous controllers. On earth, we optimize for speed and scale, because we can. But there are all kinds of ways to compute, and these controllers need not look like anything like today’s electronics, nor do they need to be as fast.

    (c) If your probe has spent 800 years traveling 4 lightyears, the communication roundtrip to base of 8 years isn’t all that big a deal. I assume that the distant equipment, while autonomous to a large degree, has access to orders of magnitude more computing power at the base. It should make use of this for longterm logistics. It should stream back observations at whatever bandwidth is permitted at that distance (this may presuppose a large energy source, see (a)… or could do like a semaphore system by reflecting or blocking local star light with large mirrors–it doesn’t have to be fast). The base computer would use this stream to propose long term decisions for the remote unit and possibly reprogram it as necessary, taking into account the 8 year lag.

    Still, you are still talking about a shitload of hardware. Note that you could scale back to 0.0005c for an 8000 year trip and an energy budget for 100x as much mass.

    I can see this scheme criticized as impractical (or even too conservative). It is not “impossible” however.

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