Dont know if there is already a thread for this
Dont know if there is already a thread for this
We are discussing this one on this thread
but if you like, we could use this thread for a discussion of the chances it holds life.
The good news is, it is around the right temperature, assuming it has the right mix of gases in the atmosphere.
The bad news is, it is probably at least 10 times as massive as the Earth, so it won't be very Earth-like. Perhaps there is life present, but it will be nothing like life on our planet. It might hold a population of prebiotic replicating molecules, a population of algae or bacteria that may or may not resemble those on Earth; it might have a population of fish-like creatures, or low, strong, high-gravity-adapted land animals. If the atmosphere is dense enough it could have a population of flying or 'air-swimming' creatures.
Or something else entirely, or nothing. It certainly does not hold anything resembling a human.
do we know how higher gravity would affect bacteria growth -- does higher gravity necessarily preclude the genesis of cells?
I dont think they know the actual size yet, and so we dont know radius, so we cannot calculate gravity yet.
I wonder when they can start attempting to characterize if it has an atmosphere?
If by "higher gravity" you mean 2-5 times Earth's, it does nothing to bacteria. Microbial culture have been grown in cetrifuges at hundreds of gravities.
Large animals, especially on land, are a different matter.
Radius is the only thing they know, and it is known with quite some confidence; 2.4 x the radius of Earth.
Assuredly bacteria would not be affected by high gravity, but other factors in the environment would dictate whether bacteria evolve at all. If it is a waterworld the local environment might be too dilute to allow abiogenesis. On the other hand abiogenesis might happen elsewhere in the system and life could be transferred to this planet and thrive. Or the local microbiota might not resemble Earth species at all.
Other possibilities; a living ocean, full of specialised forms that cooperate together to form a superorganism; or a mechanical ecosystem, formed from organic self-replicating probes sent there millions or biollions of years ago. There are many others.
Roughly speaking, height limits would be proportional to gee level, for land plants and animals. There are plenty of primates three times shorter than us. So an alien with similar proportions to us is possible--just one third the scale.
The fact that the planet is more massive than Earth could mean that it holds one or two moons.
Primates originally evolved as tree-climbing frugivores. In an ecology adapted to an environment with 2.5 to 3 gees, tree-climbing frugivores would be quite remarkably different to Earth examples. Trees themselves would be very different; so, indeed would fruit. At the end of such a chain of difference, it is possible that one might end up with some sort of stunted humanoid, but the possibility seems very remote.
And one third the encephalisation, unless it devotes absurd amounts of energy to supporting the head and blood supply thereto.So an alien with similar proportions to us is possible--just one third the scale.
Why are we assigning evolutionary paths on a world we just heard of and know very little about it.
First question is, how old is the system? If it's only a billion years old, you're not going to find much there most likely but bacteria.
I'm not assuming; I'm speculating. Different thing.
Why? The encephalisation could be the same, given the alien is 1/3 the height of a human. The pressure difference from head to toe is the same. The required support material scales properly.And one third the encephalisation, unless it devotes absurd amounts of energy to supporting the head and blood supply thereto.
I assume high gravity - 3-10 gee wouldnt affect bacteria, but it would animal and plant life for sure. If it were only 3-4 Gee then I could see it having similar but smaller flora and fauna. Of course it would likely be nothing like earth life in form factor. but, who knows?
it would be great to analyze it for an atmosphere!!
Encephalisation is the mass ratio of brain matter to total body mass, so an alien with similar proportions to us would have the same encephalisation.
Basically, I was just taking the easiest approach toward an example of a hypothetical 3gee alien similar to a human.
Have you ever read about the scaling laws that make "giant ants" impossible? Well, those scaling laws work in reverse also. The same laws which make a scaled up ant impossible also make a scaled down human possible for a high gravity world.
But still, there are limits. One third scale is fine, because there are plenty of primates that size. But if we start talking 10 gees or more, we're starting to stretch things.
Yes, it is. But would a human with a brain with 1/3 the volume of an earthly human brain be equally sapient? The lateral compression would reduce its function, I think. The encephalisation quotient rule probably doesn't work when comparing the brains of creatures from different gravity regimes.Encephalisation is the mass ratio of brain matter to total body mass, so an alien with similar proportions to us would have the same encephalisation.
To me, a small primate 1/3 of human height does resemble a human. An alien with a humanoid body and proportions, would also qualify as resembling a human.
Hmm; so we might get some short, relatively dumb humanoid bipeds, but probably not fully sapient humanoids.
I'm more inclined to a belief that a sapient lifeform on a high gravity world would be some sort of centaur, perhaps using manipulatory organs developed from mandibles. Or a cone-like being with muscles that anchor to the peak of the cone for strength. The high gravity would favour small animals, for many reasons; they are stronger with respect to their size, and have faster reactions to deal with the speed of falling objects. Only in water could a creature grow to any great size.
Another problem with high-grav worlds is the probable persistence of hydrogen in the atmosphere. Any oxygen produced by photosynthesis would combine and form water. Not really a problem if anaerobic metabolism systems can support complex organisms; this recent discovery suggests that may be possible.
Maybe, but 3x gravity isn't all that extreme.I'm more inclined to a belief that a sapient lifeform on a high gravity world would be some sort of centaur, perhaps using manipulatory organs developed from mandibles. Or a cone-like being with muscles that anchor to the peak of the cone for strength. The high gravity would favour small animals, for many reasons; they are stronger with respect to their size, and have faster reactions to deal with the speed of falling objects. Only in water could a creature grow to any great size.
Still, extreme gravity could have interesting implications on flight and projectile weaponry. Flight and gliding are out of the question, but simple falling is a potent weapon. Sloth-like beings hanging from tree limbs or cliff sides could target victims below using rocks or shells or darts. Hanging lets the creature rely on tension for support, eliminating the balance problems of bipeds and upright quadrupeds.
It started when a discussion of exoplanet habitability brought to my attention the fact that Earth itself wasn't human habitable for most of its history due to insufficient oxygen levels. For billions of years, oxygen levels were limited by geological absorption. So what happened once that was saturated? Boom! Oxygen levels rise, and complex life explodes.
That said, hydrogen gas is a highly reactive energetic molecule. I suspect that a hydrogen atmosphere could serve the same basic role as an oxygen atmosphere for "aerobic" equivalent life. Just with the roles of oxidizer and fuel reversed. This couldn't have happened here on Earth, because Earth wasn't big enough to hold onto its hydrogen gas. But maybe it could happen on a super-earth or mini-neptune.
Last edited by IsaacKuo; 2011-Dec-07 at 08:58 AM.
Kobold (yes, its one of mine). I have no problem anticipating that humans may one day be modified to thrive in high gravity; but I think a high gravity superearth would probably be such a different environment to Earth that humanoids would be unlikely to evolve there.
IsaacKuo saidIn Rare Earth (Brownlee, Ward) the authors make the case that Oxygen is required for complex animals due to the energy requirement and (I seem to recall) development of skeletal structures, etc. We just don't have any other examples of complex animals which developed in anarobic conditions. Of course, that just might be LAWKI and there are ways we havent dreamed of....It started when a discussion of exoplanet habitability brought to my attention the fact that Earth itself wasn't human habitable for most of its history due to insufficient oxygen levels. For billions of years, oxygen levels were limited by geological absorption. So what happened once that was saturated? Boom! Oxygen levels rise, and complex life explodes.
Maybe biological density is proportional to the gravity well in which it evolves in. Gullivers Travels goes to space!
I'm excited by this , so IF the star is about sun size, I would calculate the ratio of K-22b's effective temperature to the earth's by the formula:
(T(K22b) / T(earth) = cube root (365 days/290 days) = 1.08, or about 273 Kelvin ( 0 celsius), which comports closely to NASA 's estimate of 22 celsius.
So the effective temp. of this planet would only be 8% higher than earth. Of course, this has nothing to do with surface temperature which is largely dependent on the density and composition of the planetary atmosphere, compare and constrast the sister planets earth-Venus.
oh, I did that kind of fast,
what I did was keep the solar output of K-22b's star equal to sun's for this estimate. Then I first from Kepler's 3rd law estimate the ratio of earth's distance from star to K-22b's by raising the period ratio (365/290 days) to the 2/3 powers. That give the distance of earth from star as 1.17 as K-22b's from its star, that part would be easy. Then use the usual formula for effective temperature using Stefan's law where the energy output of the planet is proportional to the fourth power of the temperature. If earth is 1.17 times as far as K-22b is, then by inverse square law it would get 1/(1.17)(squared) = .73 as much solar irradiance per square meter as does K-22b. So the effective temp. of earth should be the one-fourth power of 0.73 = 0.92 as high as K-22b's. Thus K-22b's effective temp. would be 1/0.92 = 1.08 , which we can get easier by algebra as cube root of the period in days ratio.
But the effective temp. of earth can easily be determined , I think even wikipedia shows that and it is 255 Kelvin. So I would quickly estimate K-22b's effective temp as 1.08 X 255 = 275 Kelvin.
The average temp. of the earth's surface at bottom of troposphere is a whole other matter, because of course that involves variables such as atmosphere. NASA got a estimate of 295 Kelvin for K-22b so my rough calc. is in the ballpark.
That's great, thanks. I actually forgot the radiation bit. So you're assuming an equilibrium temp, and therefore equating incoming with outgoing. Got it.
The problem is that our assumptions are based on our own planet specifically around essentially one system of biochemistry. Different ratios of materials in the environment lead to different chemistry solutions. Would alien life forms use a calcium based support structure? With different chemistry on hand maybe they wouldn't. Is the structure we are familiar with the strongest possible that could be grown by an organism? Depending on the availability of different chemicals, I have doubts that it is.
And evolutionary drive... perhaps there hasn't been evolutionary pressure to develop a skeletal system that much stronger than we have seen so far. If animals don't die because of skeletal breakage before bearing young a significant percentage of the time, there isn't pressure to possess a stronger skeleton. Perhaps there have been stronger skeleton developments, but maybe they came with disadvantages in our environment but would be worth the trade offs in another. There is a flawed assumption of evolutionary "progress" that creates the impression that evolutionary outcomes are overall ideal and thus across the board "best". Nonlethal mediocrity is a valid situation though.
I wouldn't expect to see something like a T-Rex on a high gravity world. But if I have no basis for comparison from all of THAT planet's factors, I can't honestly be surprised either.
If this planet is more massive than Earth then the surface air pressure should also be higher. Doesn't that increase the boiling point of water? If "habitable zone" is defined as a liquid water zone then the zone should depend on the mass of the planet also. I would say the more massive the planet is the further away from the sun will its habitable zone be.
I saw this release a few days ago. I'm not that excited about Kepler-22b. It's 600 light years away. Until we figure out a way to fold space-time, we aren't going to be traveling there to confirm whether or not if this planet can support life. I was much more intrigued by the discovery of planets in the Gliese 581 system that could possibly contain life. Gliese 581 is only 20 light years away. There's a chance of us actually being able to view this system in our lifetimes.