tag:blogger.com,1999:blog-7494544263897150929.post7275381667868879975..comments2024-03-28T00:36:19.403-07:00Comments on Rocketpunk Manifesto: Goldilocks PlanetRickhttp://www.blogger.com/profile/16932015378213238346noreply@blogger.comBlogger107125tag:blogger.com,1999:blog-7494544263897150929.post-29358681170534995902010-12-26T04:11:12.506-08:002010-12-26T04:11:12.506-08:00ttc street car route car photo rally car snow cove...ttc street car route car photo rally car snow cover car steering works auto de mediuAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-40826540029654085692010-11-03T12:58:49.274-07:002010-11-03T12:58:49.274-07:00Interestingly, these models don't support the ...Interestingly, these models don't support the common claim that the substellar point would be so hot it turns into a "desert". The major factor forming Earth's deserts is not heat, but rather the prevailing winds blowing all clouds away from the horse latitudes.<br /><br />In the simple tidally locked model, winds blow toward the hot pole, meaning that as long as temperatures remain below boiling, it'll be more like a rainforest than a desert.<br /><br />In the chevron model, the entire pattern is actually offset from the pole, but it still looks like the rainiest region would be the warm chevron. There is no substellar desert, although the rainforest regions are far removed from the inner pole by a distance of 15% the planet's diameter (60% of the distance to the terminator!), lying in directions 45 degrees from the equator in each direction.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-21642179377491095702010-11-03T00:14:11.153-07:002010-11-03T00:14:11.153-07:00Here's some new research on tide-locked climat...<a href="http://www.wired.com/wiredscience/2010/11/gliese-581g-climate/" rel="nofollow">Here</a>'s some new research on tide-locked climates (that's an article, the actual paper is <a href="http://arxiv.org/abs/1010.4719" rel="nofollow">here</a>, Figure 1 and Figure 5 are the most readable bits).<br /><br />It seems that when cooling rates are fast, temperature follows the behavior you'd expect - hot on the pole directly under the sun, growing colder in all directions outward. Prevailing winds seem to largely go from cold to hot, but not quite in a straight line and they look rather chaotic - although the cold-to-hot trend is still pretty consistent across the entire planet (as opposed to Earth, where one third of the planet has poleward rather than equatorward winds). It's a little hard to be entirely sure how straight the winds are because the Mollweide projection they're using, while very good for non-tidally-locked planets where climates tend to be distributed by latitude, also isn't exactly the most intuitive for a planet dominated by inner and outer poles rather than north and south poles. Still, to a first approximation, "winds blow from the dark side to the light side" will do. (Presumably these are surface winds and the air makes its way back to the cold side in higher-altitude winds that aren't shown?) On a real planet, geography and stuff will influence things anyway.<br /><br />When they tweaked the model for slower cooling rates where atmospheric transfer plays more of a role, though, they got a weird <a href="http://www.wired.com/images_blogs/wiredscience/2010/10/gliese581g-climate.jpg" rel="nofollow">phone-shaped</a> distribution, with the hottest parts being surprisingly close to the terminator, and the next hottest parts lying on a chevron between these. The entire arrangement is skewed to the western side of the lit hemisphere. Prevailing winds are deflected around this phone, appearing to circle counterclockwise around the northern warm spot and clockwise around the southern warm spot. Far from the chevron figure, the winds are plain clean westward ones.<br /><br />Unfortunately, they don't state what influences these cooling rates, what reasonable ranges we can expect, or how they might justify the vast difference in cooling rate they had to put into the model to produce this chevron.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-58197310660812578172010-10-27T06:33:41.728-07:002010-10-27T06:33:41.728-07:00i think the new planet sounds a little like a piec...i think the new planet sounds a little like a piece of space junk flied into the orbit of this star.but it can be possible to have a new planet in that orbit.i would like to go, but it would take hundreds of years to get there.cant live that long!!!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-7729032071902849062010-10-15T11:31:14.283-07:002010-10-15T11:31:14.283-07:00Jim Baerg:
Consider putting the present day earth...Jim Baerg:<br /><br /><i>Consider putting the present day earth in tide lock with the subsolar point in the middle of the Pacific Ocean. All the continents would get glaciers a few km thick on them which would lower sea level by a km or 2. This would expose a fair bit of land in the shallower parts of the Pacific.</i><br /><br />Papers I've read on heat transport by atmospheres of tide-locked planets indicate that this mechanism will be kind of iffy. Mainly because heat transport is so efficient that with an earth-like atmosphere the temperature on the dark side will be just about freezing. A thicker atmosphere puts the temperature above freezing. My understanding is that this is different from earth because earth's Hadley cells insulate different parts of the atmosphere from each other, preventing efficient heat transport. Of course, these simulations were fairly crude, and even our most sophisticated climate models (famously) are not always accurate at reproducing the climate.<br /><br />Link:<br />http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-45MFXSB-37&_user=2741876&_coverDate=10%2F31%2F1997&_alid=1499890508&_rdoc=1&_fmt=high&_orig=search&_origin=search&_zone=rslt_list_item&_cdi=6821&_sort=r&_st=13&_docanchor=&view=c&_ct=1&_acct=C000058656&_version=1&_urlVersion=0&_userid=2741876&md5=a08f438ea7240802a603dbd923d3b61d&searchtype=a<br /><br />Summary:<br />http://www.treitel.org/Richard/rass/tidelock01.txt<br /><br />This neglects heat transfer by the oceans, which would be likely to increase the dark side temperature further if oceanic currents go from the day side to the dark side (which might not be the case if all the land is on one side and all the ocean is on the other).Lukehttps://www.blogger.com/profile/09617890536562434320noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-91871252941355838562010-10-15T09:12:12.521-07:002010-10-15T09:12:12.521-07:00Jim Baerg:
"However since it has been taking...Jim Baerg:<br /><br /><i>"However since it has been taking millenia for isostatic rebound to undo the depression produced by the ice sheet over Hudson Bay, my suggestion that melting part of the darkside icecap might have such an effect still stands."</i><br /><br />Yes, and spinning a 19 zettaton planet using the tug of a thin section of its crust would take less than a millenium?<br /><br /><br /><i>"Consider putting the present day earth in tide lock with the subsolar point in the middle of the Pacific Ocean. All the continents would get glaciers a few km thick on them which would lower sea level by a km or 2. This would expose a fair bit of land in the shallower parts of the Pacific."</i><br /><br />Hey! I hadn't thought of that! Good observation!<br /><br />Problem solved, then :) Yay!Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-58096865233328886782010-10-14T19:10:17.202-07:002010-10-14T19:10:17.202-07:00I know I was the one who brought up the idea of te...I know I was the one who brought up the idea of tectonics producing a bump that would shift the stable orientation of a tide locked planet, but on further thought I realize that <a href="http://en.wikipedia.org/wiki/Isostasy" rel="nofollow">Isostasy</a> would probably prevent that from happening. However since it has been taking millenia for isostatic rebound to undo the depression produced by the ice sheet over Hudson Bay, my suggestion that melting part of the darkside icecap might have such an effect still stands.<br /><br />Re: continental drift putting all the continents on the dark side. That might not be all that bad.<br />Consider putting the present day earth in tide lock with the subsolar point in the middle of the Pacific Ocean. All the continents would get glaciers a few km thick on them which would lower sea level by a km or 2. This would expose a fair bit of land in the shallower parts of the Pacific.Jim Baergnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-54353316731376961362010-10-14T10:07:35.225-07:002010-10-14T10:07:35.225-07:00I think a premise behind the proposed Terrestrial ...I think a premise behind the proposed Terrestrial Planet Finder was that it would be able to detect light reflected from planets using a telescope at least 100x more precise than Hubble.Seannoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-41680222620888810532010-10-14T09:43:16.749-07:002010-10-14T09:43:16.749-07:00On the note of detecting planets - how far away ar...On the note of detecting planets - how far away are we from snapping photos of nearby terrestrial exoplanets? There are already several direct pictures of gas giants... They're larger than Jupiter, some of them just on the limit between planet and brown dwarf, but somehow we do have pictures of exoplanets 129 light years away.Elukkanoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-37944338377329370662010-10-13T10:06:02.088-07:002010-10-13T10:06:02.088-07:00KraKon:
"Is Gliese a tectonically dead plane...KraKon:<br /><br /><i>"Is Gliese a tectonically dead planet?"</i><br /><br />We don't know! We haven't seen it!<br /><br />I expect heavier planets to stay tectonically active longer, which counts in Zarmina's favor. However, I don't know how spin rate affects things. There's also the possibility of tidal heating to consider.<br /><br /><br /><i>"The only way to have an ocean deep into the hot side of the planet is for it to rain constantly to replace losses by evaporation."</i><br /><br />Umm... no. I don't know if you were aware of this, but water has a tendency to flow. As long as the ocean is high enough to flow over obstacles, its elevation will even out planet-wide, regardless of rain levels.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-87191518321303277462010-10-13T03:26:24.480-07:002010-10-13T03:26:24.480-07:00Continental drift?
I think tectonic activity and...Continental drift? <br /><br />I think tectonic activity and hot spots extruding lava are much more important factors in continental drift than whatever tidal influence the sun has on the planet...Is Gliese a tectonically dead planet?<br /><br />Ocean planet:<br /><br />I see problems with that. The only way to have an ocean deep into the hot side of the planet is for it to rain constantly to replace losses by evaporation. To rain constantly, you need big constant clouds. As pointed out to me before, big clouds constantly overhead means that sunlight doesn't reach you, but it alse means massive runaway global heating. Maybe climatic cycles where clouds slowly gain ground on the hot side, until they cover the whole planet, trigger Venus like conditions underneath, leading to the dissipation of the clouds (no more evaporation on the hot side as sunlight doesn't go through) and the regression all the way to an equilibrium point...<br /><br />"The geologic time scales we're discussing here have not allowed crusts to be completely flattened,"<br /><br />They can only be flattened long after the planet becomes a cold, hard rock, and then a few billion years. Erosion is a million times faster!KraKonhttps://www.blogger.com/profile/16247562094101986439noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-24878648779355935502010-10-12T21:48:35.722-07:002010-10-12T21:48:35.722-07:00Well, planets that young aren't going to have ...Well, planets that young aren't going to have life now, but presumably there are young planets out there right now that are going to develop life someday...Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-11681784905105291662010-10-12T20:30:20.714-07:002010-10-12T20:30:20.714-07:00Welcome to a couple of new commenters!
Our curren...Welcome to a couple of new commenters!<br /><br />Our current detection methods, especially radial velocity and transit, are biased toward close-in planets, both in producing stronger signatures and producing them on a faster time scale.<br /><br />Currently, distant planets are detectable mainly when young, because they are hot enough to be detectable directly in the IR, and because they can distort circumstellar dust rings in a detectable way.Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-22207462634712263082010-10-12T18:11:50.527-07:002010-10-12T18:11:50.527-07:00Luke:
"It is easy to show that the gradient ...Luke:<br /><br /><i>"It is easy to show that the gradient is always perpendicular to the equipotential, and the force is the gradient of the potential (with a minus sign), so if the surface deviated from the equipotential surface, there would be a gravitational force pushing it sideways until it settles into the equipotential surface."</i><br /><br />An intuitive way to see this is: Stuff rolls downhill. Therefore, in order for stuff to not feel like rolling anywhere, there has to not be a hill.<br /><br /><br /><i>"I am not sure how much my proposed mechanism can shift things around."</i><br /><br />I recommend remembering that if gravitational-centrifugal-tidal effects held perfect sway, then all planets would be perfectly smooth with no mountains anywhere. (I.e., the surface would follow those equipotentials you mentioned.) Overall, I think a planet (several thousands of kilometers of rock and iron) can flatten a crust (several tens of kilometers of rock and water) faster than the crust can meaningfully tilt the planet. The geologic time scales we're discussing here have not allowed crusts to be completely flattened, so I doubt a continent will have very significant effects on a planet's axial tilt before tectonic drift causes the continent to up and move somewhere else again.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-53263723833434736972010-10-12T17:41:42.040-07:002010-10-12T17:41:42.040-07:00Milo:
However... I just realized something. While...Milo:<br /><br /><i>However... I just realized something. While the planet will be more elongated along the axis pointing toward/away from the sun, so will the seas.</i><br /><br />Quite. This was one thing that always bugged me about GDW's otherwise excellent Aurore sourcebook (for ther 2300 AD game). Aurore was a tide-locked planet, with huge sub-stellar mountains due to the tides. In general, the surface of the world will follow the gravitational equipotentials (or orbital-gravitational-centrifugal equipotentials, for adding in additional inertial forces). It is easy to show that the gradient is always perpendicular to the equipotential, and the force is the gradient of the potential (with a minus sign), so if the surface deviated from the equipotential surface, there would be a gravitational force pushing it sideways until it settles into the equipotential surface. So, on a perfectly fluid world, even though the sub-stellar point will tend to bulge toward the sun, it will never seem like it is uphill.<br /><br /><i>this means that the land elevation above or below sea level should not be influenced by whether you're at the poles or the terminator. So much for that.</i><br /><br />It works the other way around, I think. At least according to my proposed mechanism, any large concentration of mass which would naturally occur anyway (such as a continent) would cause a torque that shifts the planet's axis so that the mass is at the sub-stellar or anti-stellar region of the planet. This is opposed to mechanisms that have the tides shape a planet by deforming their hydrostatic equilibrium shape into something that rises above the sea at the sub- or anti-stellar regions (the tides will raise the land into a hump, but they will also, as you noted, raise the seas as well).<br /><br />I am not sure how much my proposed mechanism can shift things around. After all, you don't find earth's equator shifting so that large land masses lie along it, and this would involve a very similar mechanism.Lukehttps://www.blogger.com/profile/09617890536562434320noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-66304777063329645812010-10-12T13:36:11.418-07:002010-10-12T13:36:11.418-07:00I actually didn't think it through, but it'...I actually didn't think it through, but it's true: to detect an exoplanet with a Neptune like orbit, Kepler would need to observe its star for at least 328 years.<br /><br />Furthermore, since Neptun's size is only the 200.000 part of its orbit, that would be the approximate chance that it would pass between its star and our position, making it detectable by Kepler in the first place, assuming that the alignment of orbits between star systems is evenly distributed.Stephan Berlinnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-69152154264066324172010-10-12T13:33:41.588-07:002010-10-12T13:33:41.588-07:00This is not a problem, though. Constant climate c...This is <i>not a problem</i>, though. Constant climate change is a fact of life. Just look at Earth's evolutionary history. Life adapts - as long as there's something to adapt <i>to</i>. The danger is if there's nowhere left to evacuate to - if the planet shifts into a position where life would have trouble achieving high biodiversity <i>even if that position were stable</i>. (Good for biodiversity: a patchwork of land and sea in different temperature zones, supporting multiple biomes. Good for biodiversity: coastlines, which result in rainier land and sunnier sea. Bad for biodiversity: deep oceans with no coastline in sight. Bad for biodiversity: all water getting locked up on the frozen side.)<br /><br />Of course, Earth has a non-life-supporting era too, back during Snowball Earth. Fortunately, such extremes are rare enough that we had time to go from invertebrates -> fish -> tetrapods -> amniotes -> mammals -> primates -> humans (and many other branches) before another similarly extreme condition arose. However, all-land-in-one-hemisphere is a condition that arises somewhat more often.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-60844109344994772482010-10-12T13:33:25.452-07:002010-10-12T13:33:25.452-07:00Thucydides:
"I would guess that situation wo...Thucydides:<br /><br /><i>"I would guess that situation would apply whenever the land masses get together and form or reform a supercontinent like Pangaea. At other times, continental drift would have very little effect on the planet's orientation."</i><br /><br />I think that if anything, it is more likely that tidal pull would influence continental drift, not the other way around.<br /><br />Like Luke says, this is really something someone would need to simulate with some rather accurate computer models to be sure... We haven't even worked out how much <i>normal</i> continental drift you'd get in a very slowly rotating planet.<br /><br />However... I just realized something. While the planet will be more elongated along the axis pointing toward/away from the sun, <i>so will the seas</i>. (Remember, these are <i>tides</i> we're talking about.) Since I'd expect them both to get pulled by the same amount (over really long time scales where rock's rigidity can be overcome), this means that the land elevation <i>above or below sea level</i> should not be influenced by whether you're at the poles or the terminator. So much for that.<br /><br /><br /><i>"Mars has had some pretty dramatic shifts in the past, which may explain the change from "warm/wet" to the current "cold/dry" climate."</i><br /><br />I think this is more a result of Mars losing its tectonic activity, and consequently, it's atmosphere. With its atmospheric pressure dropped below the triple point of water, it will forevermore remain dry, regardless of temperature. Unless you can put back the atmosphere.<br /><br />Tectonic activity influences your atmosphere due to effects like a magnetic field (which protects against solar wind stripping your atmosphere) and volcanic outgassing (adds new air to replace losses), but I'm afraid I can't tell you the details (how important each is, what affects each's rates, etc.).<br /><br />Precession of the axis would only cause local changes as the north and south poles move. There would still be north and south poles, and so climates would move with them.<br /><br /><br /><i>"The big danger to any native life on Gliese 581g may be precession of the axis, which will shift the hot and cold poles and move the habitable zones as well. [...] How this will work on a tidally locked planet is unclear to me; the gravitational forces holding the planet in a tidal lock will be pretty strong, but perhaps the actions of the other planets in the solar system might have soe effect?"</i><br /><br />If you can tilt the axis enough so it's not perpendicular to the ecliptic, then this will introduce seasonal effects to the planet. Within the polar circle, you would experience actual day and night cycles, with day during summer and night during winter (independantly of which side of the planet you're on - although that would still affect temperature). Below the polar circles, light and darkness would be based only on which side of the planet you're on, like on a proper tidally locked planet (independantly of whether it's summer or winter - although that would still affect temperature).<br /><br />If you shift the axis relative to the planet's geography, but the tidal lock is stronger than your precession and restabilizes it so this new axis is still perpendicular to the ecliptic, then all you've done is shift the geography a bit relative to the poles (which return to their normal place). Although the underlying mechanics are different, effectively this is just continental drift.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-6345567535991627112010-10-12T11:26:07.401-07:002010-10-12T11:26:07.401-07:00I would guess that situation would apply whenever ...I would guess that situation would apply whenever the land masses get together and form or reform a supercontinent like Pangaea. At other times, continental drift would have very little effect on the planet's orientation.<br /><br />The big danger to any native life on Gliese 581g may be precession of the axis, which will shift the hot and cold poles and move the habitable zones as well. Mars has had some pretty dramatic shifts in the past, which may explain the change from "warm/wet" to the current "cold/dry" climate. How this will work on a tidally locked planet is unclear to me; the gravitational forces holding the planet in a tidal lock will be pretty strong, but perhaps the actions of the other planets in the solar system might have soe effect?Thucydideshttps://www.blogger.com/profile/09828932214842106266noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-8051361777476302982010-10-12T10:56:07.263-07:002010-10-12T10:56:07.263-07:00Milo:
To me, the worst-case scenario is that the ...Milo:<br /><br /><i>To me, the worst-case scenario is that the light side is either 100% land or 100% water, or at least has so little land and water that it limits biome opportunities on there.</i><br /><br />I'm going to do some wild speculating here - without modeling the dynamics, I don't know if it will work. But basically, consider the tidal forces operating on the planet. They tend to pull in out into an ellipsoidal shape, with the long axis pointing at the star. This orientation is stable - perturbations that knock the long axis away from parallel to the radius vector from star to planet results in a restoring force that brings the long axis back into the preferred orientation. So, suppose you have a large continent somewhere on our planet. This introduces a dyssymmetry in the distribution of mass. Tidal forces will tend to exert a torque on this extra continental mass sticking away from the planet's core, to either pull it toward the sub-stellar point or the anti-stellar point. If the torque is strong enough (and this is the point I am unsure about) you will end up with the largest continental land masses sitting on either one of these two extremes. This could leave us with a permanent warm side land mass for life to evolve on.<br /><br />This is not enough to publish in a peer reviewed journal, but could suffice for fiction.Lukehttps://www.blogger.com/profile/09617890536562434320noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-6401071586870020112010-10-12T09:47:12.313-07:002010-10-12T09:47:12.313-07:00KraKon:
"Life develops in the marshes just a...KraKon:<br /><br /><i>"Life develops in the marshes just above the terminator, where water levels are kept low because of the heat, yet humidity is at saturation point thanks to giant rainforest clouds above it. The evolutionary pattern would be entirely amphibian for a long period of time, protecting themselves from the direct sunlight under a few cm of water."</i><br /><br />...You need to protect yourself from direct sunlight, when you're at the terminator and have heavy cloud cover?<br /><br /><br /><i>"And if we have enormours winds, wouldn't that translate into a massive sandy desert on the hot pole, blowing sand all over the place?"</i><br /><br />Actually, I think the enormous winds are... umm... overblown. Many articles claim climate simulations that gave more Earthlike windspeeds, at least at the lower troposphere, which is what really matters. You could still have some storms, but so do we.<br /><br />I admit bias, since this is how I like it. Earthlike wind strengths to facilitate life, non-Earthlike wind directions and patterns so that life is exotic.<br /><br /><br /><i>"Flash idea:<br />Underwater life forms use nutrients carried by sand blown from the hot pole that land on water and dissolve for the benefit of aquatic plants. Still doesn't solve the sunlight problem through..."</i><br /><br />Well, remember my suggestion that what little life exists on the dark side would depend on plankton and runoff from the light side. These could be aeroplankton, too, which could provide a way to supply nutrients <i>on top</i> of the ice sheets covering the dark side's ocean.<br /><br /><br /><i>"Probably something we are wholly unable to predict."</i><br /><br />We can't fully predict the course evolution will take, of course. We can't even confidently say anything about our <i>own</i> planet's evolution that isn't backed by fossils. But we can still try to recognize the broad strokes.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-69583737276389401972010-10-12T09:46:41.204-07:002010-10-12T09:46:41.204-07:00KraKon:
"If we have a tidally locked planet ...KraKon:<br /><br /><i>"If we have a tidally locked planet with lots of water and convinient heat distribution through a thick atmosphere, I see the worst case scenario where half the planet is ice, the terminator a sea of meltwater, then anything above quickly transitions from saturation-point humidity to arid desert. In other words, the only land to set foot on is well beyond the water you need."</i><br /><br />It's not clear to me what you're postulating here. How much land/water?<br /><br />To me, the worst-case scenario is that the light side is either 100% land or 100% water, or at least has so little land and water that it limits biome opportunities on there.<br /><br />Let's take the 100% water case. The problem isn't that land animals could never evolve, since the fish could just wait a few eons for continental drift to bring in a continent before they try to crawl onto land. (Remember, we're talking about red dwarf planets. They have time to spare.) The problem is that land animals would have trouble evolving <i>very far</i>, since when in some later era the continents all drift back to the dark side, everything on land has practically nowhere to go, and so goes extinct. Some "land animals" could survive by going back into the ocean, like dolphins, but next time land appears they'll have to reinvent legs practically from scratch. And land plants will be gone too, don't forget that. On Earth, changing conditions from continental drift renders some organisms extinct, but enough survive to preserve major evolutionary innovations and repopulate the land.<br /><br />So you won't get <i>advanced</i> land life. You could get tetrapods, but you won't get tetrapods that evolve into amniotes that evolve into synapsids that evolve into mammals that evolve into primates that evolve into humans.<br /><br />Conversely, if you have more land than water, then most sea life will periodically go extinct. This is even worse, since life starts in the oceans - although hopefully microbial mats can adapt to land life early on. It's probably only later when you get complicated multicellular life that these extinctions really put a crimp in your evolution. Basically, picture today's oceans if all fish had gone extinct at the K-T event, and cetaceans ended up evolving to take all their niches.Milonoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-29717406217207245602010-10-12T04:25:51.576-07:002010-10-12T04:25:51.576-07:00Working backwards:
"Those were all planets w...Working backwards:<br /><br />"Those were all planets with an orbit extremely close to their star, naturally, as only they could make three or more passes in eight or less months."<br /><br />You mean there will never be a chance for us to detect, say, an exo-Neptune. Despite it being a big and mighty gas giant, it's cold and only passes betwwen us and its star <b>once every 164 years !</b><br /><br />"I don't know if tectonic effects can actually change a planet's orientation by a meaningful amount"<br /><br />I think that depends on the mass ratios of the two bodies (say Pluto/Charon), and the viscosity of the planet's composition. A hot planet with a large liquid core could absorb most of the tectonic effect through compression of fluids. A cold rocky planet would bear the brunt of the gravitational tensions and variation.<br /><br />"In fact, that could be a serious problem for evolution on tidally locked planets. On Earth, there have been eras where most of the land was in one hemisphere, with the other one being almost entirely ocean."<br /><br />Reminds of how much water Earth actually has... <br /><br />"On a tidally locked planet, if most of the land happens to have ended up on the dark side, where does land-based life evacuate? Or if you have less than 50% sea cover, than what if most of the sea gets shifted onto the dark side?"<br /><br />If we have a tidally locked planet with lots of water and convinient heat distribution through a thick atmosphere, I see the worst case scenario where half the planet is ice, the terminator a sea of meltwater, then anything above quickly transitions from saturation-point humidity to arid desert. In other words, the only land to set foot on is well beyond the water you need. <br />Flash idea:<br />Life develops in the marshes just above the terminator, where water levels are kept low because of the heat, yet humidity is at saturation point thanks to giant rainforest clouds above it. The evolutionary pattern would be entirely amphibian for a long period of time, protecting themselves from the direct sunlight under a few cm of water. Life would tardively develop from there into fish-like forms that exploit the vast expanses of colder water towards the terminator, or landforms that can support the heat for a little while or burrow to stay underground...<br /><br />And if we have enormours winds, wouldn't that translate into a massive sandy desert on the hot pole, blowing sand all over the place? <br />Flash idea:<br />Underwater life forms use nutrients carried by sand blown from the hot pole that land on water and dissolve for the benefit of aquatic plants. Still doesn't solve the sunlight problem through...<br /> <br />"So how much tectonic activity should we expect anyway? Would the planet's slow rotation reduce tectonics? Would tidal heating be a factor, like it's commonly cited for gas giant moons?<br /><br />"There are other sources of instability, like volcanism/meteor impacts changing greenhouse levels, new life forms evolving or migrating in from another region and forcing ecosystems to adapt to their influence..."<br /><br />Probably something we are wholly unable to predict.<br /><br />On planet-wide storms.<br /><br />As the planet doesn't rotate, there won't be any atmospheric cells powered by the planet's rotation. This seriously hinders storm formation as these cells force hot wind up a cold front...<br /><br />Maybe a planet wide cloud cell, going from one pole to another, powered only by convection? It'll die out at the poles though...KraKonhttps://www.blogger.com/profile/16247562094101986439noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-66300479543261855652010-10-11T14:37:49.010-07:002010-10-11T14:37:49.010-07:00Properties of the Kepler mission
To my understand...Properties of the Kepler mission<br /><br />To my understanding, Kepler detects exoplanets by registering recurring "dips" in the stars observed brightness.<br /><br />A certain number of dips is needed for detection: you can figure that would be at least two for a first estimate, at least three for a verified match.<br /><br />Kepler has been active only since May 2009. The first detected planets were published in January of 2010. Those were all planets with an orbit extremely close to their star, naturally, as only they could make three or more passes in eight or less months.<br /><br />Gliese 581g, again, is a planet with a close orbit, but not so close as the planets from the first batch, as more time was available to detect it.<br /><br />So, as Keplers mission time proceeds, more planets with an orbit similar to Earth will be detected; as Milo wrote above, that is not because those are more common; but it's also not precisely about sensitivity of equipment! It's about the time needed for the detection of planets with certain orbits, dictated by the properties of the Kepler mission. We just need some more patience.<br /><br />On the downside, planets with an orbit more far from their star will have a lower chance of passing between their star and Kepler, thereby decreasing the chance of detection. This would explain what I perceive to be a "slow down" in published detections over the year 2010.Stephan Berlinnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-2782850090981807712010-10-11T09:38:47.902-07:002010-10-11T09:38:47.902-07:00"On Earth, there have been eras where most of..."On Earth, there have been eras where most of the land was in one hemisphere, with the other one being almost entirely ocean."<br /><br />Like the present era. The Pacific ocean takes up most of one hemisphere.<br /><br />"I don't know if tectonic effects can actually change a planet's orientation by a meaningful amount (I thought that was largely the result of orbital perturbration from other objects in the solar system?), but you would definitely need to do more than melt a few meters of water on the surface of the crust."<br /><br />The Antarctic ice cap is a few km thick. I don't see any reason for the darkside ice cap on a tide locked planet to be much thinner.Jim Baergnoreply@blogger.com