A Shield from Stellar Eruptions?

by Paul Gilster on July 28, 2011

We don’t know whether life can exist on a planet circling a red dwarf, but as reported in these pages frequently in the last few years, there have been studies showing that liquid water could persist on the surface of such planets despite the fact that they would most likely be tidally locked, with one side always facing their star. So the potential is there, but we also have to account for flare activity and the question of how life might adapt to it. Perhaps there are protective mechanisms that might shield such planets from the worst such eruptions, a possibility now raised by Ofer Cohen (Harvard-Smithsonian Center for Astrophysics).

Cohen and team have recently gone to work on planets of a far different kind — hot Jupiters crowded up in tight orbits around more Sun-like stars — but the work on gas giants is intended to lead on to a close look at red dwarf planets in similar proximity to violent stellar events. Until that study is complete, we can learn from their work on what happens when a coronal mass ejection (CME) hits a nearby planet. A CME pumps billions of tons of electrically charged hot gas into the Solar System, an event that can cause major disruptions to the Earth’s magnetosphere. It was a CME and ensuing geomagnetic storm that blacked out large regions of Quebec back in 1989.

Much tamer phenomena are likewise markers for solar activity, as anyone who has been fortunate enough to experience the Northern or Southern Lights already knows. My first encounter with the Northern Lights was in Iowa back in my college days, when the northern sky one night seemed to mimic a huge open window with gauzy white curtains being blown by the wind. It was an eerie, though not colorful, phenomenon, and I heard at the time that the lights were fairly rare at our comparatively low latitude. Years later in Iceland I would get the Northern Lights in technicolor one late October, a stunning display that had me standing speechless looking out over Reykjavik’s docks at the rippling and ever changing stream of colors.

Cohen’s work on aurorae shows that distant hot Jupiters should experience the same phenomena, though peaking at 100 to 1000 times the brightness of what we see on Earth. When a Coronal Mass Ejection hits a gas giant just a few million miles from its star, the planet would be subject to extreme forces, feeling the concentrated might of the blast. The immediate effect would be a weakening of the planet’s magnetic shield. And as CME particles reaches the planet’s atmosphere, the auroral lights would manifest themselves first as a ring around the equator that would, in the course of six hours, move up and down toward the planetary poles.

Image: This artist’s conception shows a “hot Jupiter” and its two hypothetical moons with a sunlike star in the background. The planet is cloaked in brilliant aurorae triggered by the impact of a coronal mass ejection. Theoretical calculations suggest that those aurorae could be 100-1000 times brighter than Earth’s. Credit: David A. Aguilar (CfA).

Remarkably, the hot Jupiter itself seems relatively well protected by its magnetic field. Cohen’s simulations show that the initial orientation of the planetary magnetosphere (which is elongated into a comet-like tail by the stellar wind) is almost perpendicular to the CME’s direction, with the result that the CME is modified in highly complex ways. But the key finding is that even in such extreme conditions, the planet’s atmosphere can be shielded from erosion. From the paper:

Despite its proximity to the host star, we find that the planet is well shielded from being eroded by the CME, even with a relatively weak intrinsic magnetic field of 0.5 G. We also find that the planetary angular momentum loss associated with a disconnection of part of the planetary tail is negligible compared to the total planetary angular momentum. Our simulation suggests that the planetary magnetosphere can be significantly affected by the CME event, and that the energization of the planetary magnetospheric-ionospheric system might be much higher than in the Earth. It also suggests a transition in the magnetospheric Alfvén wings [wedge-shaped structures of magnetospheric plasma] configuration during the event, as well as a rotation of the whole current system by 90°. However, our simulation cannot provide such detailed information about the planetary properties; investigation of these aspects of the interaction requires a detailed numerical model for the planetary magnetosphere.

So a hot Jupiter gets pummeled by a CME, but the power of its protective mechanism is surprising, and as Cohen points out in this CfA news release, “…even a planet with a magnetic field much weaker than Jupiter’s would stay relatively safe.” How to extend such findings in the direction of stellar activity on red dwarfs and the consequent effect on planets there? We have much to learn, but perhaps this team’s continuing investigation in that direction will clarify whether discovering a planet in a red dwarf’s ‘habitable zone’ really does flag a potential for exoplanetary life.

The paper is Cohen et al., “The Dynamics of Stellar Coronae Harboring Hot-jupiters II. A Space Weather Event on A Hot-jupiter,” accepted by the Astrophysical Journal (preprint).

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{ 33 comments }

Interstellar Bill July 28, 2011 at 16:56

Let’s not forget that a habitable planet tidally locked to a red dwarf
would be an extraordinarily static environment,
with none of the challenges likely to evoke the rise of even monkey-level intelligence:
No diurnal cycle, just a fixed sun in an unchanging sky.
Weather varying with position but very little with time, with no climate change.
No stars visible on the day side.
Worse yet, the dwarf spews hard radiation for the first 5-10 billion years of its trillion-year lifespan.
Topping it off is the dwarf’s relative lack of photosynthetically suitable wavelengths.
Don’t waste SETI time listening to red dwarfs.

FrankH July 28, 2011 at 19:00

Wouldn’t a tidally locked planet (or one in a resonant rotation, like Mercury) also have a weak magnetic field? Also, probably no or little tectonic activity.

Habitable (or at least life supporting) M-dwarf planets can join habitable moons around gas giants as the unicorns of exoplanet research.

Eniac July 28, 2011 at 23:28

Let’s not forget that a habitable planet tidally locked to a red dwarf
would be an extraordinarily static environment,
with none of the challenges likely to evoke the rise of even monkey-level intelligence:
No diurnal cycle, just a fixed sun in an unchanging sky.
Weather varying with position but very little with time, with no climate change.
No stars visible on the day side.
Worse yet, the dwarf spews hard radiation for the first 5-10 billion years of its trillion-year lifespan.
Topping it off is the dwarf’s relative lack of photosynthetically suitable wavelengths.
Don’t waste SETI time listening to red dwarfs.

None of these would have any bearing on the first appearance of life if it takes place deep underwater or underground, as we today suspect it did on Earth.

And frequent violent CMEs sound extraordinarily non-static to me, and plenty of a challenge. The variability of the star and the high temperature gradient from the day to night side are likely to make for more interesting weather, seasons, and climate change than ours.

We really have no idea what is needed to “evoke the rise of intelligence”, and to simply postulate that it is all of the things we have here on Earth is plain wrong. Intelligence comes from interaction with other life mostly, not from minor features of the environment such as whether there is a moon or stars in the sky.

Alex Tolley July 29, 2011 at 10:48

The assumption that the only life that counts is intelligent, surface living animals seems to be almost a trope for this kind of article. Much like early C20th visions of life on Mars or Venus.

As Eniac syays, life probably evolved under water, not in rook pools, and bacterial life on earth is quite plentiful in the lithosphere.

One can’t help imagining astronomers in some future starship approaching a rocky world, seeing no waving palm[-like] trees and declaring “It’s dead, Jim”, while ignoring the obvious [to a biologist] signs of bacterial communities.

Interstellar Bill July 29, 2011 at 12:43

Eniac, thank you for your attentive reply.

I didn’t want to seem as dogmatic as you think,
but please consider that intelligence is extremely costly
in both metabolic and genetic accounting,
requiring great advantage for it to arise.
In our case, paleontologists repeatedly cite Pleistocene climate-change challenges as an indispensible spur to human evolution.

Microbial life, in contrast, is tough enough to survive nearly everywhere,
so its occurence on a tidally locked planet would be no wonder.
What would be a wonder would be metazoans arising in the hard-radiation environment of frequent CMEs, so you’d have to wait gigayears, until the star ages into slow-rotating quiescence, before that happens.

And why would you expect anything but static weather on a nonrotating world? That would be the null hypothesis that has to be disproved. Climate modeling shows rising air at the hot substellar pole feeding upper-level air circulation across the terminator that finally sinks at the cold antistellar pole, with surface winds blowing back across the terminator. At any one locale you’d expect the same weather, 24/7. Life would be specialized for stellar colatitude (angle from the substellar point), but once settled-in you would expect lifeforms to undergo no further evolution. Just look at ants, which haven’t changed since the Cretaceous. Ecological equilibrium is the biological norm, with change happening only in response to big environmental alterations. Absent the KT bolide, dinosaurs would still be dominant.

By the way, it is well documented that there has been no ‘encephalization’ trend in mammalian evolution. Aside from the human line, no lineage has shown any intrinsic tendency to larger brains. Domestic cats, for example, only have two-thirds the brain volume of feral cats, after less than 10,000 years of domestication, showing that nature has no love for intelligence per se.

Rob Henry July 29, 2011 at 19:47

Since the first two comments above seem to fringe on faulty rare Earth type arguments, I feel obliged to reverse the situation. Say that we somehow come by the knowledge that nearly all life and intelligence inhabits red dwarfs, we would suddenly see many reasons why.

Red dwarfs are more common than other types of stars, but given the above mystic insight we can do rather better than that, by looking at where Earth’s biosphere does worst. Water badly limits growth in many parts of our lands and nutrient recycling is an even worse limiter of growth at sea. High insolation in the sub-solar point cause such heating that it might set up sufficient deep ocean convection to return nutrients from the ocean depths. The oceans might thus be far more productive than ours. Steady rain at the fringes of ice shelves might solve the problems for the land, their topsoil being created by the decomposition of waste from land based organisms that hunt the fertile seas.

Earth seems to have fluked the right balance of continental building and water inventory to facilitate the development of land based higher forms. Almost by rights a world with a high inventory of water should be a water world. Now think of that water world placed where the habitable zone implies tidal lock. The oceans would end up automatically ringed by ice, thus providing a good balance of “land” and sea.

Mass extinctions might be a net accelerator of the development of higher and more intelligent life. If this has been mediated through meteorite impacts on Earth, then we were lucky we weren’t wiped out completely by the biggest such event, but if this process was mediated by stellar flaring, the chance of total planetary sterilisation from one event is much lower.

The problem magnetic field creation is one of the areas that we know to the least of and our modelling of this is thus highly likely to need revision, so atmospheric spluttering might turn out to be a lesser issue.

In retrospect, the strongly increasing insolation, as expected from a sun of Sol’s mass, and the improbability of tidal lock that could mitigate the problem, looks like a fatal blow to the prospects of a long-term HZ around larger stars. Lets not waste and more SETI time on solar mass stars.

To me, the only problem listed that seems hard to nullify or convert into an advantage is the lower levels of photosynthetically useful light there

Rob Henry July 29, 2011 at 20:12

Interstellar Bill, I have news that could be cried out in the desert air where hearing could not latch it. Its true that large brains are expensive to make, and this is traditionally the reason why a vestigial organ slowly shrinks, but this is unlikely to be the main cause of the shrinking brain size in lines of domestic animals.

The truth is that brains are even more expensive to maintain. Every time there is a famine we feed our domestic animals just enough to survive, and we rigorously preclude any clever way to get more, this effectively causing a genocide of all the large brained ones.

This makes it even more striking that nearly all mammals find it worthwhile to maintain their current brain size – the incentive for this must be massive. It suggests that a small change in evolutionary incentive might be sufficient to drive their development to the next level.

Eniac July 29, 2011 at 23:37

Bill:

Why would you expect anything but static weather on a rotating world? After all, the rotation is even and predictable, with an exact period, like clockwork. Of course the weather would be the same every day, would it not?

In reality, there is plenty of irregularity that arises without irregular causes, variously known as chaos, turbulence or dynamic instability. There is no reason to think that those would not exist on a tide-locked world. More so, if anything, because of the more extreme temperature gradient. Of course, there is also libration, orbital excentricity, moons, and variation of stellar output to shake things up externally, if it really were needed.

The only thing permitting the notion of “static weather” on a tide locked world with an atmosphere is that we haven’t seen one yet. The recently observed storms on Saturn may well be doldrums compared to what we may find when we do.

I am sure after we do gain the abilitity to observe the atmospheres of tide-locked exoplanets, some will argue that intelligent life could never evolve in such a violent and unpredictable environment.

Adam July 30, 2011 at 20:33

It’s a truism which should be tossed into the bin of “things we thought we knew, but were wrong” – the idea that Red Dwarfs are deficient in biologically useful wavelengths and thus excluded from making oxygen for their atmospheres. When the tricky work of deriving the actual spectra is done, the level of Photosynthetically Active Radiation in the spectrum of a red dwarf’s light is comparable – if not equivalent – to what plant life on Earth has available…

Orig Life Evol Biosph. 1999 Aug;29(4):405-24.
Habitability of planets around red dwarf stars.
Heath MJ, Doyle LR, Joshi MM, Haberle RM.
Biospheres Project, London, U.K.

Abstract

Recent models indicate that relatively moderate climates could exist on Earth-sized planets in synchronous rotation around red dwarf stars. Investigation of the global water cycle, availability of photosynthetically active radiation in red dwarf sunlight, and the biological implications of stellar flares, which can be frequent for red dwarfs, suggests that higher plant habitability of red dwarf planets may be possible.

PMID: 10472629

…so I would respectfully suggest that overly dogmatic claims of the habitability or non-habitability of red dwarfs, and even cooler stars, be toned down a bit.

andy July 31, 2011 at 8:22

Looking at the evolutionary history on Earth I don’t see that our own planet is especially optimal for evolving technological intelligence either. Certainly evolution’s been going in all kinds of weird and wonderful directions but intelligence seems to be pretty rare.

And there’s always the possibility that the evolution of human-level intelligence came about as a result of sexual selection rather than being primarily driven by factors outside the species: i.e. it is a peculiarly metabolically-intensive alternative to large antlers on deer, the tail feathers of the peacock, or the various other bizarre display structures that animals use to attract mates.

Athena Andreadis July 31, 2011 at 12:08

Much of the “forget red dwarfs” lists seem a mix of rare earth/anthropic principle assumptions.

The expression “even monkey-level intelligence” is frankly odd. Monkey-level intelligence is significant. If the definition of intelligence is “using technology” we will sail obliviously past many a life-bearing planet.

Intelligence does not require a heavy genetic investment. The major surprise of the human genome was how few genes we have. Unless you mean maternal investment, which is also incorrect — that asymmetry is true for all mammals (the uncommonly high cost of human birth is a separate issue connected to bipedalism).

The temperature differentials on a tidally locked planet guarantee hurricane-force winds and models are only as good as their data input (given the distance to other systems, not fine-grained enough for categorical conclusions about weather).

Solar flares & coronal emissions may give rise to rapidly-evolving life in response to radiation and the stellar activity cycles. Photosynthetic wavelengths extend way past the green portion of the spectrum, complex non-photosynthetic life is patently possible and life need not develop or expand to the surface of its planet.

Domestic animals are bred for docility and bigger bodies (for milk, meat, wool, etc), a policy that constitutes an active anti-encephalization protocol.

There is no teleological component to intelligence, it’s as random as anything else in biology and, like everything else, it has been “invented” several time in terrestrial lifeforms. It just so happens that we were the first to go past a specific threshold, and attain a specific kind of language as well as technology.

Bottom line: we won’t know until we really know, and what we learn will surprise us.

Athena Andreadis July 31, 2011 at 12:27

Andy, intelligence is not driven by reflexes (which by definition bypass the cortex), although it can act as a potent aphrodisiac for a subset of humans (and a turn off in another). If intelligence were indeed a quasi-hardwired mating response, it would become the prerogative of one gender — although many people continue to believe that for humans as well, contrary to evidence.

Also, there is another hypothesis, with data backing it, that active selection is not in the domain of male flamboyance. Instead, both sexes start colorful/decorative and the females actively select against strong coloration and/or markings, to ensure higher viability.

andy July 31, 2011 at 17:17

Haha I knew posting that would get me into trouble… just to say I did not mean to imply that intelligence was the prerogative of one gender and my apologies if it came out that way. Nor was I suggesting that intelligence is an aphrodisiac, I am not THAT naive about social interactions despite being a male posting on a space blog… only that it could have evolved in that context and then got co-opted for other things (guess your point about reflexes negates that speculation though).

Eniac August 1, 2011 at 2:27

Athena is right, there is nothing teleological about intelligence. It just seems that way from our point of view. The fact that we are the only intelligent species on this planet says nothing about how rare or common the phenomenon is. It could be no other way. If there were none, we would not be here discussing this issue. There cannot be more than one, because we, as the first, preclude the emergence of others. Thus, as with any tautology, the existence of exactly one of us carries zero information.

One thing, though: the degree to which we are dominating all other species and the short time (in evolutionary terms) this took to develop do indicate that in terms of competitive advantage our sort of intelligence ranks at the top among evolutionary breakthroughs of all time.

“Only intelligent species”, of course, calls for a more concrete definition of what we mean by “intelligent”. In my view, the threshold Athena refers to that no other species has crossed and that led to the “brain race” is the ability to accumulate information. To learn and teach faster than we forget, so that each generation has a little more knowledge to start with than the previous. This has inexorably led to an accelerating avalanche of information, through morals and taboos at first, then stories, songs, and poems, then writing, then books, then mass media, and now the Internet. Technology is a useful byproduct and facilitator of this phenomenon, but not its essence.

Ronald August 1, 2011 at 11:23

The idea that the flares and CME’s of red dwarfs might promote evolution as an effective means of selective pressure is a tricky one: selective pressure as a driving force of evolution only works as long as the selective pressure isn’t too high and/or too abrupt. If it is it may actually lead to impoverishment or outright extinction (think of giant asteroid impacts, mega volcanic eruptions, super novae, very abrupt ice ages, …).
It is not unlikely that flares would effectively and repeatedly sterilize the surface areas of any nearby planet before (higher, surface) life gets a chance to gain a foothold.
So I really have my doubts about something as intense as red dwarf flares and the like as a positive evolutionary driving force, at least for anything beyond the bacterial level at the surface of such a planet.

Athena Andreadis August 1, 2011 at 16:34

Ronald, if the planet has sufficient water all these problems are largely negated. Don’t forget that many engineers have proposed a water shield for crewed starships, for the same reasons.

For the rest, we have a single sample, so extrapolations are fun but as good as fiction.

Avatar2.0 August 2, 2011 at 3:56

Liquid water on planets orbiting red dwarfs is another questionable assumption:
Frequent (on time scales relevant for biological evolution) flares and CMEs coupled with the low magnetic field (tidal locked planets) mean such planets have a rarefied atmosphere. Low-pressure atmosphere means water evaporates at low temperatures. On the day side of the planet, the constant heat from the sun will evaporate most water. On the night side, the lack of heat translates into water being frozen solid.
All this translates into little or no liquid water on planets around red dwarfs.

Rob Henry August 2, 2011 at 17:17

Avatar2.0, of all the know worlds in our system with liquid water, Sol contains the least. Are you sure that hydrogen might not be preferentially lost from the atmosphere? If so then we should get a fast built up of oxygen, replenishing the atmosphere from its vast oceans. In Earth’s case, a build-up of oxygen looks like the critical step in the development of higher life. Thus if life on red dwarfs can overcome the implied lowering of nitrogen inventory with time in this scenario, red dwarf planets would yet again stand as better SETI candidates than Earth, and all this due to the core processes in your objection!

Avatar2.0 August 3, 2011 at 5:19

Rob Henry, the lower the pressure, the lower the evaporation temperature of water – as in h2o evaporating, not undergoing electrolysis.
This is an universal physical law.

On worlds with low atmospheric pressure (such as planets orbiting red dwarfs), very little heat is needed in order to turn and maintain vater in gaseous form (and, on the day side of tidally locked planets, the sun provides the necessary heat).

And, of course, on red dwarf orbiting worlds, the atmosphere is periodically peeled away by flares and CMEs (much like happened with Mars’s atmosphere, despite our Sun being far better behaved than red dwarfs).
Meaning, in time, all gaseous water in the atmosphere (almost all water from the day side) will be lost into space.

As to the night side of red dwarf orbiting worlds, all water there will be forever frozen.

So – frequent hard radiation baths (to which carbon-based life is highly vulnerable), little water for life chemistry and for protection, little photosynthesis usable light.
Add to that the fact that no other substances known to science exhibit properties approaching the unique characteristics of carbon based organic compounds (which makes them ideal for life) – which means life based on other compounds will have severe disadvantages.

All this means that, despite our wishes, red dwarf systems are environments quite hostile to life. Life appearing there is highly improbable – and higher life, even more improbable.
We can speculate all day about improbable what-ifs that may permit life to appear there – they remain improbable what-ifs.

Athena Andreadis August 3, 2011 at 10:15

Avatar2.0, most commenters here are past HighSchoolScience101 and know about the privileged positions of carbon, water etc. as well as the issues of tidally locked planets with red dwarf primaries. Hell, some of us have written books on these topics. All scenarios of extraterrestrial lives remain wishful what-ifs until we have a confirmed independent sample. Full stop, except for SF stories and BS sessions around real and virtual fireplaces.

Rob Henry August 3, 2011 at 23:00

Avitar2.0, how high is the cold trap of the red dwarf planet you model, and how much do those uv flares effect the water at the top of the trap? What is the ratio of thermal loss of atmosphere to solar flare ablation? All these play a role in the final answer, thus the scenario you give is too simplistic, even as an overview.

Avatar2.0 August 4, 2011 at 8:43

Rob Henry
“All these play a role in the final answer, thus the scenario you give is too simplistic, even as an overview.”

Much like the scenarios presented by you, Rob Henry.
With one difference: even a simplistic overview on a forum such as this one shows that your scenarios are FAR from being as probable as you suggest (indeed, they’re quite improbable) – partly because they ignore a multitude of factors, some of which I mentioned in my previous posts.

andy August 4, 2011 at 16:55

Frequent (on time scales relevant for biological evolution) flares and CMEs coupled with the low magnetic field (tidal locked planets) mean such planets have a rarefied atmosphere.

I’ll just note here that GJ 1214b has managed to retain a substantial atmosphere despite being located closer to the star than the habitable zone. So has Gliese 436b.

Rob Henry August 4, 2011 at 19:32

Avitar2.0, we still have such paucity of information, and have to make so many assumptions to build these models, that to suggest any degree of certainty seem very brave, and more probably foolhardy.

Avatar2.0 August 5, 2011 at 4:48

Rob Henry
“Avatar2.0, we still have such paucity of information, and have to make so many assumptions to build these models, that to suggest any degree of certainty seem very brave, and more probably foolhardy.”

I agree – up to a point.
Certainty, of course, is out of the question, but one should be able to narrow the probability range of life’s appearance in the discussed systems.

About andy’s comment:
A comparative look at Mars and Venus seems to indicate that a lack of magnetic field is only one of the factors that influence atosphere loss (one which is more important in systems with frequent/powerful solar flares/etc).
Another important factor seems to be the mass of the planet – meaning, red dwarf orbiting super-earths should be able to retain their atmosphere.

Athena Andreadis August 5, 2011 at 14:48

“… but one should be able to narrow the probability range of life’s appearance in the discussed systems.”

Actually, no. Beyond the broadest conclusions (for example, life is unlikely to arise in hard vacuum), this is based on assumptions/preconceptions that will guarantee the desired outcome by tinkering with models not developed from direct data. We’re still uncertain of what happened on earth, and if what happened here is the sole possible route to the successful emergence of life. Rewind tape: we have one sample, and even the record of that is incomplete.

Rob Henry August 5, 2011 at 20:09

I apologise if, at times, my frustration is too targeted at individuals. It is all really aimed at a recognised flaw in scientific method that has been allowed to become institutionalized in the name of expediency. Today this fault is called the paradigm approach, and its one strength is that is allows us to build coherent stories to explain current scientific thinking. Without it neophytes could never come to grips, and we all presume that excessive research time would otherwise be spent unproductively. As long as we constantly remind ourselves that most of our perceived scientific knowledge will one day be completely revised, and much of if will be found to be wrong, this approach is tolerable. A good case can even be made that it is great at interpolating to models for scenarios that lie between phenomena that are already well measured. But when we interpolate to new ones AND believe them fact without testing… well isn’t that insanity by definition

Rob Henry August 6, 2011 at 3:05

Athena, just after speaking of the dangers of extrapolation I feel that the time is perfect for me to accept your challenge of finding requirements common to all life. I predict 3 unheralded features will turn out to be common to all life that has not been artificially created

1) All life will have a genetic information storage component that has a layer behind it with a net charge. I base this on the difficulty of reconciling looser approaches to genetic information storage with facilitation of improvement through natural selection. If evolved organism must keep their genome in a formally array, then the fidelity of copying must involve strong codon-anticodon bonding from the beginning, yet allow sheet/thread separation. Thus there must be distal repulsive forces that act over a greater distance than each codon-anticodon pair, and attaching a charge to a back-bone/sheet is the only way that I can imagine it done.

2) All solvents for chemically based life will be polar as a direct consequence of the above.

3) All life will turn out to sensitive to heat sterilisation. My logic runs as follows: genetic arrays must be one or two dimensional, so are only likely to evolve to specify one or two dimensional enzymes, yet practical considerations dictate that more efficient three dimensional active sites will be selected for. Thus enzymes will always tend to be elaborately folded, and such folding makes them heat sensitive.

Yes, insanity comes to us all!

Athena Andreadis August 6, 2011 at 13:25

Rob Henry,

1) There is no codon/anticodon pairing in DNA or RNA. You are thinking of translation. What happens in the double helix is pair bonding via hydrogen bonds and base stacking interactions. There is no a priori requirement for keeping the genome “in a formal array” and in fact the organization of terrestrial DNA (with its many, often cross-purpose requirements) has made several of the processes complex and cumbersome, as they require such actions local unfolding and absorption of the resulting torque.

2) The fact that polar solvents are more versatile than non-polar ones is plain-vanilla chemistry. Water is unique because of the density reversal of its solid/liquid components.

3) Terrestrial thermophiles survive to temperatures of 250 F and their enzymes fold just fine. At high enough temperatures, chemistry and physics dictate that bonds will be destabilized, starting with the weaker ones that are often crucial to biological molecules because they confer flexibility. So this falls under the “life won’t arise in hard vacuum” broad category. And, as with #1, there is no a priori requirement for genetic arrays to be one- (eh?) or two-dimensional. DNA and RNA are certainly not, they are just highly prolate.

Rob Henry August 6, 2011 at 17:08

Athena those are all great points, but some of them only address the faults in my terminology, that crept in to allow me to shorten my argument.

1) genetic information has two roles, information storage and replication. It is only keeping the fidelity of information above the “melting point” of its information that I cared of, and during this process it is much easier to produce an “anticode” to the code to be replicated than reproduce it directly. Even if it is done directly, there must be a phase of code-anticode or code-code pairing, and this is to where my comments were addressed.

2) The seeming usefulness of expansion when freezing to protecting biosystems worries me as possibly anthropocentric. Arguments in its favour sound very convincing, but water seems to be the most common solvent in our universe – so if this were true it would begin to look designed.

3) I really meant that every creature must have a narrow operating temperature range – ones that break this rule on Earth seem to have two sets of enzymes that are expressed at different temperatures – as is sometime suggested by a double peak to their growth rate v temperature. This narrow temperature range could be very high. Also your mention of the need for flexibility in enzymes, is telling as you will note that this textbook requirement is never invoked with other types of catalyst. This difference is simply due to the active cite construction, which in turn relates to the linearity of the precursor. I predicted that this situation will turn out to be universal.

Finally, the information in our genes is certainly held via the connection of data points over one dimension. The fact that they are twisted in 3D space is a difficulty has required much extra work for Earthly biology, but that is just a detail. The metabolic theory of abiogenesis would want it possible for enough information to be held in self-replicating subunits that are not attached to each other (ie not connected in the manner of subunits in a nucleic acid strands) as to allow primitive life to first form. Many think that this is a red herring, and that it will eventually be proved that this type of genome is not amenable to improvement through natural selection under any circumstances.

Nebula Gray September 2, 2011 at 9:46

Why does a tidally locked planet have to have an inefficient magnetic field? From what I’ve gathered, lower-mass M-dwarfs have their habitable zones near the 24-36 hour orbital radius. Earth generates a sufficient magnetic field by completing one revolution per 24 hours, so why would a planet in an orbit of similar length not generate enough magnetism? Or does a magnetic field have to be rotating relative to its star to repel flares?

Another thought occurs to me: Gliese 581 has three gas giants orbiting close to it. One of Jupiter’s moons retains a magnetic charge from the planet. Couldn’t planets like Gliese 581-g have their magnetic fields replenished as they pass through the bow shocks of inner giants? The most danger they would face would be when the gas giants were aligned on the other side of the parent star. Given the 1:2:4 resonance of Gliese 581′s gas giants, this wouldn’t be a problem for 581-g.

ljk September 19, 2011 at 11:29

Climate instability on tidally locked exoplanets

Authors: Edwin S. Kite, Eric Gaidos, Michael Manga

(Submitted on 13 Sep 2011)

Abstract: Feedbacks that can destabilize the climates of synchronously-rotating rocky planets may arise on planets with strong day-night surface temperature contrasts. Earth-like habitable-zone (HZ) planets maintain stable surface liquid water over geological time. This requires equilibrium between the temperature-dependent rate of greenhouse-gas consumption by weathering,and greenhouse-gas resupply by other processes. Detected small-radius exoplanets, and anticipated M-dwarf HZ rocky planets, are expected to be tidally locked.

We investigate two feedbacks that can destabilize climate on tidally-locked planets. (1) If small changes in pressure alter the temperature distribution across a planet’s surface such that the weathering rate increases when the pressure decreases, a positive feedback occurs involving increasing weathering rate near the substellar point, decreasing pressure, and increasing substellar surface temperature. (2) When decreases in pressure increase the surface area above the melting point (through reduced advective cooling of the substellar point), and the corresponding increase in volume of liquid causes net dissolution of the atmosphere, a further decrease in pressure occurs.

We use an idealized energy balance model to map out the conditions under which these instabilities may occur. The weathering runaway can shrink the habitable zone, and cause geologically rapid 10^3-fold pressure shifts within the HZ. Mars may have undergone a weathering runaway in the past. Substellar dissolution is usually a negative feedback or weak positive feedback on changes in pressure. Both instabilities are suppressed if the atmosphere has a high radiative efficiency.

Our results are most relevant for atmospheres that are thin and have low greenhouse-gas radiative efficiency. These results identify a new pathway by which HZ planets can undergo rapid climate shifts and become uninhabitable.

Comments: 30 pages, 6 figures, submitted to ApJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph); Geophysics (physics.geo-ph)

Cite as: arXiv:1109.2668v1 [astro-ph.EP]

Submission history

From: Edwin Kite [view email]

[v1] Tue, 13 Sep 2011 02:46:27 GMT (410kb,D)

http://arxiv.org/abs/1109.2668

katesisco October 11, 2011 at 15:05

All intelligence is local. Science Daily (10/11/20110 has an article that says a neuron that ‘learns’ changes from a high vibration to a lower one (from 30 to 27).
There is no reason to believe we are the apex intelligence on planet Earth. Take eels, for example. And again Science Daily says that octopi are believed to have made arrangements from the vertebrae of their food/opponent.
Intelligence may be tied to the compression Earth is experiencing due to the compaction of Sol’s hemisphere. If so, we may compare it to Flowers for Algernon.
This is the end of the 5000 y cycle, the year before the decompression event when the plasma focus releases as jets. The spirals in rock art–light can be polarized in spirals—-those blue spiral lights that titilated the world several months ago– only a year to go.

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