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Upwelling Oceans: Modeling Exoplanet Habitability

We usually talk about habitability in binary form — either a planet is habitable or it is not, defining the matter with a ‘habitable zone’ in which liquid water could exist on the surface. Earth is, of course, the gold standard, for we haven’t detected life on any other world.

But it is conceivable that there are planets where conditions are more clement than our own, as Stephanie Olson (University of Chicago) has recently pointed out. The work, presented at the just concluded Goldschmidt Geochemistry Congress in Barcelona, models circulatory patterns in oceans, some of which may support abundant life if they exist elsewhere. The emphasis here is not so much on surface ocean currents but upwelling water from deep below. Says Olson:

“We have used an ocean circulation model to identify which planets will have the most efficient upwelling and thus offer particularly hospitable oceans. We found that higher atmospheric density, slower rotation rates, and the presence of continents all yield higher upwelling rates. A further implication is that Earth might not be optimally habitable–and life elsewhere may enjoy a planet that is even more hospitable than our own.”

All this has implications for how we use the term ‘Earth-like,’ and reminds us to be careful, as Olson told a Los Angeles Times interviewer in 2018:

“The phrase Earth-like does not refer to a planet that necessarily resembles modern-day Earth at all… It’s actually a very broad term that encompasses a broad variety of worlds. It includes hazy worlds like the Archean; it includes icy worlds like the ‘snowball Earth’ intervals; it includes anoxic worlds with exclusively microbial ecosystems; it includes worlds with complex and intelligent life; and it includes worlds that we haven’t even seen yet.”

Image: Geophysicist Stephanie Olson. Credit: University of Chicago.

Stephanie Olson makes the case that life has to be far more common than what we can detect at our current stage of technology. An ecosystem beneath the surface of an icy moon may defeat our methods, as could microorganisms deep within a planet’s mantle. So what we need to do, in this scientist’s view, is build our target lists for future study around a subset of planets, those that meet the habitability demands of forms of life that are global, active and detectable. This also builds the list of those worlds for which a non-detection would be the most telling.

In general, our developing models for habitability have tracked our interest in finding atmospheric biosignatures, for we are closing in on the capability of doing this for small, rocky worlds circling nearby M-dwarf stars. The complexities of ocean dynamics have been left out of the picture other than when used as a mechanism for climate regulation or heat transport.

In her conference abstract at the Goldschmidt conference, Olson argues that the implications of circulatory patterns in oceans should be folded into the habitability question. Cycles of ocean upwelling driven by winds can recycle nutrients from the deep ocean back to shallower waters where they can play a role in stimulating photosynthesis. From the abstract:

Photosynthesis,,,provides energy in the form of chemical disequilibrium that sustains life more broadly on our planet. Ocean circulation is thus a first-order control on the productivity and distribution of life on Earth today and throughout our planet’s history. Moreover, ocean circulation patterns, sea ice coverage, and sea-to-air gas exchange kinetics modulate the extent to which biological activity within the ocean is communicated to the atmosphere. The chemical evolution of Earth’s atmosphere has ultimately been an imperfect reflection of the evolution of Earth’s marine biosphere owing to these oceanographic phenomena.

Models of Habitability

Olson’s tool for exploring ocean dynamics on a range of modeled, habitable exoplanets is a global circulation model (GCM) called ROCKE-3D. The software is designed to examine different periods in the evolution of terrestrial-class planets, with the goal of finding what kind of techniques might flag the presence of life in these environments. You can have a look at ROCKE-3D in action in this NASA page on the simulation of planetary climates. Different parameters can be selected on a form to create maps of a number of climate variables.

Below is an example of one of these maps, as created by the ROCKE-3D software.

Image: The discovery of the planet Proxima Centauri b orbiting the star closest to Earth has generated much research about whether it has a chance to be habitable. With ROCKE-3D we have imagined Proxima Centauri b as an “aquaplanet” covered by water. Because the planet is close to its star, it may show the same face to the star all the time, as the Moon does to the Earth. If so, the dayside remains a few degrees above freezing (yellow colors). Elsewhere, the ocean is perpetually covered by ice (dark blue colors), except near the equator where winds and ocean currents push sea ice eastward onto the dayside where it breaks up and melts (pale blue to light yellow colors). Credit: NASA Nexus for Exoplanet System Science (NExSS) / NASA Goddard Institute for Space Studies (GISS).

Three-dimensional planetary general circulation models have been used to project climate change into future decades, but have matured to the point that they can probe habitability questions such as how a planet can become habitable under variations in stellar radiation and atmospheric chemistry. The NASA Nexus for Exoplanet System Science (NExSS) effort works on these matters in a cross-disciplinary effort to parse habitability in terms of the factors that make it happen, from host stars to protoplanetary disks and rocky planet atmospheres.

ROCKE-3D stands for Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics, now developing as a collaborative investigation within NExSS. At NASA GSFC, the Goddard Institute for Space Studies (GISS) developed ROCKE-3D to run global circulation model simulations deploying and manipulating past climates of Earth and other planets by way of analyzing climates and ocean habitats. The idea is to produce model spectra and phase curves for future observations. Let me quote from the GISS website:

Our project uses solar radiation patterns and planetary rotation rates from simulations of spin-orbit dynamical evolution of planets over Solar System history provided by our colleagues at the Columbia Astrobiology Center and at other institutions that are part of our NExSS team. In turn, the synthetic disk-integrated spectra we produce from the GCM will be used as input to a whole planetary system spectral model that emulates observations that candidate future direct imaging exoplanet missions might obtain…

Here you can see the direction of this work. What these teams are trying to do is model what future observatories may see when we become capable of directly imaging rocky exoplanets. We need to learn what kind of signals may be detectable as we allocate precious observing time to those targets most likely to repay the effort. Here theory about the kind of spectral details that life may produce is the foundation for later direct observational data.

Olson’s Oceans

Back to Olson, who wants to fold ocean dynamics into this effort and consider how they may be manifested on habitable exoplanets. Can features of ocean circulation that we cannot observe be inferred from atmospheric properties we can see? Olson’s work is an attempt to link ocean circulation with key planetary parameters, invoking the biological constraints differing ocean habitats may place on worlds around a variety of stars.

We can’t say how this work will develop, but there is the real prospect for the telescope design of future missions — think LUVOIR (Large UV/Optical/IR Surveyor) or HabEx (Habitable Exoplanet Observatory) — to be affected as we learn more about what we need to look for. Adds Olson:

“Our work has been aimed at identifying the exoplanet oceans which have the greatest capacity to host globally abundant and active life. Life in Earth’s oceans depends on upwelling (upward flow) which returns nutrients from the dark depths of the ocean to the sunlit portions of the ocean where photosynthetic life lives. More upwelling means more nutrient resupply, which means more biological activity. These are the conditions we need to look for on exoplanets.”

Immense effort is going into modeling planetary climate and evolution to guide our investigation of habitability. It will be fascinating to watch the trajectory of these studies as we begin to deploy advanced space-based resources to probe for biosignatures. My guess is that we will see early detections of potential biosignatures — these will receive huge press coverage — but we will not find anything that is unambiguous.

That may seem like a letdown when it happens, but ruling out abiotic mechanisms for possible biosignatures is equally a part of global circulation modeling, and this work will take time.


Comments on this entry are closed.

  • Alex Tolley August 27, 2019, 12:21

    This is an interesting idea. The major nutrient mixing is around the 2 poles due to the main currents, as well as local upwelling on the Chilean coast. The importance of upwelling is when nutrients are depleted by carbon fixation and/or zooplankton deaths pulling nutrients down out of the photic regions. The ocean currents are driven not just by solar radiation and planetary rotation, but also by the distribution of the continents. This last seems to make it difficult to do much work until these are known, perhaps by techniques other than direct imaging of the disk, but by interpretation of the planet’s albedo as it rotates.

    Knowledge of paleo ocean currents was lacking back in the 1970s when I studied oceanography, so it would be interesting to take a peep at what is known today. I haven’t seen any work using currents to explain impacts on extinctions such as the Permian, which might be moderated in the oceans if currents could remove the anoxic zones.

    As like was largely restricted to the oceans for most of Earth’s history, knowledge of how life responds to the ocean environment of its world might well provide an indicator to its likely signal, and more importantly its lack of signal, assuming life emerged on that world.

    This last is important because it seems to me that this work is predicated on abiogenesis as being common, rather than rare.

    • Ronald August 28, 2019, 4:49

      Yes, although, I think, oceanic conditions are only one aspect of (super) habitability, this is definitely interesting.

      I have been wondering whether ocean *depth* is also one of the factors of nutrient upwelling and oceanic productivity. After all, the shallow continental shelf seas are the most fertile. And in contrast the open ocean, with an average depth of almost 4 km, is sometimes called the ‘wet desert’ or ‘blue desert’. It is also sometimes known as the ocean paradox: the nutrients are down below, whereas the light is at the top layer.

      Total open ocean biomass on Earth is about 1 gigatonne (GT) of dry weight, that is much less than the world’s tundra’s or deserts. Per unit area it is less than the extreme desert.
      Total Net Primary Productivity (NPP) of the open ocean is, because of its huge area and high turnover of phytoplankton, comparable to that of the tropical rainforests. However, per unit area, NPP of the open ocean is similar to that of tundra or semi-desert.

      So, I have been wondering about an optimal ocean depth, shallow enough to allow for upwelling and high productivity, but at the same time deep enough to function as a global heat sink and climate buffer. 400 m?, 800 m?, 1200 m?

    • Laura August 31, 2019, 4:43

      Did you finally checked Ballesteros’ paper on exoseas? It seems there could be some kind of synergy with this work.

  • Gary Wilson August 27, 2019, 12:40

    In a galaxy of hundreds of billions of stars and possibly trillions of planets would somebody actually argue that there wouldn’t be planets more hospitable to life than our own? We might as well go back to thinking the solar system revolves around the Earth. We live in a suburb of a tiny section of a minute portion of one arm of one galaxy. Let’s assume every type of world possible exists out there surely? That would include planets that would make Earth look downright hostile to life in all probability (and probabilities are all we have at the moment).

  • Ronald August 27, 2019, 13:49

    Very interesting topic, of course, however, I want to make two points here:
    1) It reminds strongly of the concept of super-habitability, as proposed by Heller & Armstrong (2014): Superhabitable Worlds”. Astrobiology. 14 (1): 50–66.
    So, I am somewhat surprised that study wasn’t referred to.
    2) What I miss in the first place, is a good and clear definition of, and criteria for, ‘measure of habitability’.
    I could, for instance, think of 3 or 4:
    a) Biodiversity; measured as number of biological species, or something similar.
    b) Biomass; in weight per area.
    c) Productivity; e.g. Net Primary Productivity per area.
    d) Duration; tricky, how long can the living ecosystem of the planet persist.

    • Paul Gilster August 27, 2019, 20:17

      Good point, Ronald, as usual. For those not familiar with Heller and Armstrong’s work, see What Makes a Planet ‘Superhabitable’:


      from 2014.

    • Alex Tolley August 27, 2019, 20:52

      As most of the energy in an ecosystem is obtained from the sun, the constraints on primary productivity are the solar radiation and the efficiency of conversion by photosynthesis. Other factors do intrude – water, nitrogen, phosphorus availability as well as trace elements.

      Given the availability of adequate nutrients and solar radiation, the rate of carbon fixation will, therefore, be dependent on the biochemistry that has evolved. That should be independent of the physical and other features of a planet, even if exotic means of trapping energy via chemistry evolve.

      For any given ecosystem, the energy use is almost independent of the evolved species present. There are either a few large animals or many small ones. The depth of the food chain is also not important. IOW, ecosystems tend to maximize the available energy available from the converted sunlight.

      On Earth, phosphorus is generally the most limiting nutrient. The availability of nitrogen is rarely limiting, and it can be readily fixed from the atmosphere.

      If we could engineer a photosynthetic process in plants that was 10x more efficient, would that make much difference? I would suggest the limitation of phosphorus, and CO2 in the air would restrict the possible primary productivity of these plants to not very much more than exists today. Even in the ocean, where CO2 is far more abundant, phosphorus would restrict the amount of carbon fixation. Turnover might possibly be higher, but the biomass would still be dependent on available phosphorus.

  • Laintal August 27, 2019, 18:07

    Thanks Paul

    Its very interesting

  • Robin Datta August 28, 2019, 2:51

    As we extend our realm of “known knowns” into the “known unknowns” subliminal hints of the existence of “unknown unknowns” add hope and fear – two sides of the same coin – to the quest. It is convenient to think of a continuum from physics through physical chemistry, inorganic and organic chemistry, biochemistry, molecular cell biology, and on to multicellularity and biology-based intelligence, because that is the paradigm in which we exist. Sprouting or branching in variant directions beyond our ken could well produce results not yet imagined.

  • Ronald August 28, 2019, 4:23

    “We found that higher atmospheric density, *slower rotation rates*, (…) may enjoy a planet that is even more hospitable than our own”.
    With regard to slower rotation rates, I have always wanted a planet with a 32-36 hour day ;-)

    But seriously, this is interesting, as a contributing factor to (super)habitability.
    This does have some implications: for a terrestrial planet I would then expect such a planet to be somewhat older. Our day seems to grow about 1 hour longer per 200 My, so a 32 hour day will take another 1.6 Gy, a 36 hour day another 2.4 Gy. I a not sure, however, to what extent this is caused by momentum transfer to the moon or other factors, and therefore, to what extent this would also be true for other terrestrial planets.

    And then there is also the aspect of planetary rotation and magnetic field: if I remember well, a very well-informed contributor here (was it Ashley Baldwin? Or Alex Tolley?) described in a very interesting and comprehensive comment some time ago, that there is a maximum day-length (or inversely: minimum rotation rate), I think it was around 48 hours or so, beyond which the magnetic field drops precipitously.
    So, there is apparently some kind of optimum here, my 32-36 hour day? :-)
    And, this slower rotation rate/older planet would also necessitate a star with a longer stable main-sequence lifespan, e.g. something around G8/K0 or so, in the neighborhood of what Heller and Armstrong suggested.

    Can anybody here say something more about this? Ashley Baldwin? Alex Tolley?

  • Gary Wilson August 28, 2019, 13:26

    Would super habitability also depend on the lack of a pervasive sentient species which was determined to reduce the habitability of the planet? Do all sentient species have a tendency to reduce the biodiversity and habitability of their home? It’s an interesting question. Aren’t many alien invasion stories based on the idea of a sentient species having degraded their home planet and come seeking a “fresh start”? This planet was a paradise. Can we return it to that state?

  • Gary Wilson August 28, 2019, 14:42

    I was just out watering our own little patch of heaven and thinking. Would any Garden of Eden planet with a sentient species be technologically backward? Does the “invention” of the Scientific Method immediately set the inventor species on a road to environmental degradation? Is there a window of maturity that has to be passed through to get beyond habitat destruction and environmental degradation? It would be so interesting to have a data set of examples of sentient species and find out what actually does happen.

    • Alex Tolley August 28, 2019, 17:01

      Environmental degradation happened before our civilization acquired the scientific method. This often usually due to agriculture, although the Romans deliberately wrecked Carthage by salting the soil. But earlier, when we were hunter-gatherers, we had little capability of destroying the environment except by the use of fire and possibly by killing all the large mammals for food. Going back earlier in time, when we split from the apes, we know that apes do not destroy their environment, so I would argue that sentience isn’t the problem per se, but rather our ability to use powerful tools coupled with our short-term thinking that is rooted in our biological drive to survive and reproduce.

      At least now we have the knowledge about what we are doing. Unfortunately, the short-terminism is still a problem.

    • Robin Datta August 29, 2019, 1:24

      Intelligence finds ways to defeat limits to survival, growth and replication until it comes up against invincible limits. Sadly by that time the trampling over so many limits may have lain waste to so many of the systems that sustained it.

      It takes wisdom to grok when to desist from further depredation. And again sadly, the required depth of wisdom and the required degree of its prevalence in the population may, by their lack, constitute a Great Filter.

      • Gary Wilson August 29, 2019, 13:00

        I still remember reading The Limits to Growth as a teenager. It had a huge impact on me. I still recall thinking “are we going to change our behaviour based on these facts?” That was 47 years ago. I think I have my answer unfortunately.

        • Alex Tolley August 29, 2019, 16:06

          I read it too, as well as Ehrlich’s The Population Bomb. But they both proved wrong. Population because it did not anticipate the “green revolution” that hugely improved crop yields. The limits to growth because it did not understand conics and out response to scarcity as well as new technologies ( eg better fossil fuel extraction, and fiber optic cable to replace copper). There are limits if we restrict ourselves to Earth, but we can push those limits out a lot further.

          Countervailing forces like oil majors capturing governments retarded our change of energy sources. Fresh water is going to be a problem – even rainy northern England is forecast to run short of water within a couple of decades! The water wars are in full swing here in California. Who, back in the 1960s, thought that coastal cities would be inundated due to global heating? So there are limits, which we will find [partial] mitigation solutions for, but I don’t see the sort of collapse that Limits to Growth forecast. But you never know…

          I have read Donella Meadows’ “Thinking in Systems” which I thought was a good introduction to modeling systems that goes well beyond the simple techniques of LtG.

          • Gary Wilson August 30, 2019, 13:37

            I would argue neither Ehrlich nor the authors of The Limits to Growth had it wrong. They both had the timing wrong due to unforeseen technological advances. The general trends are both still there sadly. Far too many people using far too many resources and producing far too much pollution on the one hand and far too much greenhouse gas emission producing a rapidly changing climate on the other. The last century of a dominant human race? I tend to think so but timing is always tricky. Is that what we want though? Use it all up as fast as possible? Humans have very little time left to make the kind of dramatic changes necessary to allow for a long term stable home. I could list all of the problems accumulating but it would take several thousand words. I think people get the general idea. Or do they? Thanks for your comments by the way Alex and Robin.

    • Alex Tolley August 29, 2019, 13:28

      We have had at least one non-sentient species degrade the global environment – photosynthetic bacteria. These poisoned the globe by producing toxic oxygen, forcing the anaerobes to retreat to environments where oxygen was mostly absent. The aerobes that became out mitochondria have offered us a way to benefit from this degradation, although at a cost of producing free radicals that our human cells can only partially cope with.

      Suppose we humans do indeed effectively destroy the rich biological environment we live in? Would not our intelligent machines and robots perhaps create their own civilization on the ruins of ours? We may just be on the cusp of such a transition, although it may take centuries or millennia to reach its conclusion. If that were a natural transition for technological civilizations, then the Fermi question would still be valid, IMO. As a human, I am not advocating this transition (at least on Earth), but I do wonder in the cosmic scheme of things whether artificial, machine “life” so common in SciFy might not be the next state for biological technological life.

      From a “search for life” perspective, we may detect planets that are either living with no sign of technological civilization or planets with degraded or absent of life, but with abundant signs of technological civilization. The “transition state” of biological technological civilization may be very rare as it happens in the cosmic blink of an eye.

      • Michael Fidler August 30, 2019, 9:01

        Our planet was uninhabitable by advanced lifeforms for 85% of it’s history. Most habitable planets may be just the opposite, being inhabited by intelligent species for 85% of their history!

        I would suggest putting up cameras and instruments on islands far from air routes such as the French islands in the south Indian Ocean to monitor for extraterrestrial spacecraft.

        • Ronald September 3, 2019, 11:14

          “Most habitable planets may be just the opposite, being inhabited by intelligent species for 85% of their history! ”

          I wonder about that, and honestly I would doubt it, if it is a terrestrial planet similar to Earth in size, composition and age. I think that with regard to the origin and evolution of life on a terrestrial planet, there is a kind of clock-work mechanism at work, meaning that such a planet requires a certain amount of time to ‘ripen’ for higher life.
          In particular, the O2 sinks (particularly the crust) have to be saturated before the atmosphere can become O2 rich (the Great Oxygenation Event, GOE).
          It is then that Eukaryotic cells with mitochondria start making good sense and can originate, or at least dominate and diversify.

          So, I would expect that on any terrestrial planet the development of higher life (i.e. multi-celled Eukaryotic, specialized organs, sexual reproduction, etc.) does not start until at least 3 gy, if not more, of age.
          And after a certain amount of time the solar-type host star will become too hot, pushing the planet out of the Continuous HZ. For our own Sun this will probably happen in 0.5 to 1 gy, leaving our planet only habitable for thermophile bacteria.
          So, the period for higher life on a terrestrial planet is a window of opportunity, which depends in size upon the type of solar star, the cooler types, toward late G, early K, having the longest ‘higher life windows’. For such long-term stable solar stars plate tectonics of the planet may eventually become a limiting factor for higher life. Our Earth has enough radioactive decay left in its mantle for at least another 1.5 gy of plate tectonics. A slightly larger planet with more thorium in its mantle could keep this going even much longer.

          I could imagine a (slightly larger) terrestrial planet orbiting a G8 – K0 star, 6 gy old or so, having had an evolution of higher life since its own ‘Cambrian explosion’ of some 2 gy (instead of our measly 0.54 gy) and still having a future of another 2 gy.

  • Geoffrey Hillend August 28, 2019, 16:53

    An Earth twin has to be the gold standard for biodiversity. Pressure and rotation does not matter only when it comes to micro organisms like viruses, bacteria, etc. A larger atmospheric pressure can increase the greenhouse effect no matter what the chemical composition of the atmosphere which will increase average planetary surface temperature, and that can occur only with a larger gravity in the life belt around a star and that will eliminate animals and humans. A slow rotation will most likely indicate a lack of magnetic field since charted particles in an iron core have to move in circles to create magnetic field. Without magnetic field deflection, there is sputtering or solar wind stripping which amounts to atmospheric loss, or it’s escape into space.

    Proxima B is near to it’s star and we don’t know it that limits the size of a planets atmosphere if the Star grabs most of the gas from the protoplanetary disk of dust and gas. With most likely solar wind stripping, Promixa B still might have an atmosphere and a spectral signature of water vapor will certainly be indicative of oceans and surface water, but if there is no water in the spectra, then there will not be any surface water or oceans. It certainly will be news if water spectra are detected. We still have to have the other biosignature spectra like oxygen, and methane.

    The atmosphere of a tidally locked planet might have one big Hadley cell with the high pressure coming from the colder, night side and flowing towards the warmer day side. Colder air represents high pressure and warmer is air low pressure.

  • ljk August 29, 2019, 11:03

    I am going to go out on a limb and say Earth is not an oddball world because we simply know so little about the intricate details of our own galaxy…


    Yes, we know of thousands of exoplanets when we knew of almost none before 1990, but those are the low-hanging celestial fruit. Same goes for alien life, even moreso in fact because we don’t know of any beyond Earth.

  • Geoffrey Hillend August 29, 2019, 17:59

    If Earth twins are rare and oddball, then there still is over one hundred billion stars in our galaxy so rare could be one hundred to one thousand or more. It might be harder to find one, but one is all one has to find. We also don’t have any spectra of the super Earths and earth size exoplanets were already know. Also the idea that we don’t know yet that there is any life beyond Earth is still debatable depending on who is doing the observing.

  • Michael Fidler August 30, 2019, 8:43

    Larger rocky planets should have more volcanic activity and even if continents can not form in the deep oceans, seamounts should be common. This is probably where life originated, with plentiful smokers and volcanic activity. The recent find by NASA of a large pumice island could also transport life from different locations. What effect would a higher level of H2O have on the mantle and lithosphere and the mixing with magma? Higher pressure from the ocean may squeeze out the magma like toothpaste.

  • Geoffrey Hillend September 2, 2019, 16:01

    There does have to be some water in order to lubricate the plate movements to have tectonics in the lithosphere. I read somewhere online that If there is too much water like an ocean world, then there is too much water pressure and no plate movement is possible.

    • Michael Fidler September 3, 2019, 3:16

      Satellite reveals thousands of uncharted mountains in Earth’s oceans.

      March 20, 2019

      “Seamounts, typically formed by extinct volcanoes and rising anywhere from 3,000 feet to over 13,000 feet, are estimated to number at least 100,000 throughout the Earth’s oceans. Of the 350 or so that have been sampled, they’ve also been found to host extremely rich ecosystems for a wide array of marine species. As a result, scientists are eager to document as many as possible in an effort to protect these biodiversity hotspots from destructive fishing and deep sea mining practices.
      Researchers are looking ahead to 2021, when NASA’s SWOT satellite (Surface Water and Ocean Topography) is expected to launch aboard a SpaceX Falcon 9. Developed by an international group of hydrologists and oceanographers, the satellite will create the first global survey of the Earth’s surface water, with seamount detection as sensitive as 1 kilometer (3,200 feet) high.

      Together with the United Nations-backed Project Seabed 2030, a $3 billion effort to map the entire sea floor, it’s hoped that whatever mysteries we uncover will help inform future conservation policies.”


  • Michael Fidler September 3, 2019, 0:52

    The idea that plate tectonics is required for continents and the upwelling that they cause may not be necessary. The current that seamounts cause and the associated upwelling in the oceans already have large ecosystems on them. The latest count is at least a 100,00 seamounts in all the earth’s oceans and even deep ocean worlds may have static systems that produce large Hawaiian type seamounts. So plate tectonics may not be the only way advance life forms can develope on deep ocean worlds.

    Large impacts could also cause activity in the lithosphere of these supposedly dead deep ocean worlds!

  • ljk September 5, 2019, 9:33

    Could microbes be affecting Venus’ climate?

    Posted by Paul Scott Anderson in Space | September 3, 2019

    Unusual dark patches in Venus’ atmosphere – called “unknown absorbers” – play a key role in the planet’s climate and albedo, according to a new study. But what are they? That’s still a mystery.


    So let’s send some balloon missions there to sample those layers already.

  • Michael C. Fidler September 11, 2019, 4:59

    Water Vapor on the Habitable-Zone Exoplanet K2-18b.

    “Ever since the discovery of the first exoplanet, astronomers have made steady progress towards finding and probing planets in the habitable zone of their host stars, where the conditions could be right for liquid water to form and life to sprawl. Results from the Kepler mission indicate that the occurrence rate of habitable-zone Earths and super-Earths may be as high as 5–20%. Despite this abundance, probing the conditions and atmospheric properties on any of these habitable-zone planets is extremely difficult and has remained elusive to date. Here, we report the detection of water vapor and the likely presence of liquid water clouds in the atmosphere of the 8.6 M⊕ habitable-zone planet
    K2-18b. With a 33 day orbit around a cool M3 dwarf, K2-18b receives virtually the same amount of total radiation from its host star (1441 ± 80 W/m2) as the Earth receives from the Sun (1370 W/m2),
    making it a good candidate to host liquid water clouds. In this study we observed eight transits using HST/WFC3 in order to achieve the necessary sensitivity to detect water vapor. While the thick
    gaseous envelope of K2-18b means that it is not a true Earth analogue, our observations demonstrate that low-mass habitable-zone planets with the right conditions for liquid water are accessible with
    state-of-the-art telescopes.”

    First water world, could be a real black swan or our first look at the most common super earths.