Join 3,512 readers in helping fund MetaFilter (Hide)


"A novel metric of habitability"
September 20, 2010 10:16 PM   Subscribe

Amid news of new extrasolar planet discoveries, including a system with a possible 7 planets, Greg Laughlin and Sam Arbesman have released a paper that will be published next month in the open-access journal PLoS One. "A Scientometric Prediction of the Discovery of the First Potentially Habitable Planet with a Mass Similar to Earth" (pdf of full paper) boldly predicts that: "the fi rst potentially habitable planet will be discovered, in this case, as early as May 2011, and likely by the end of 2013." NASA's Kepler mission is set to release data on hundreds of candidate planets early next year. The mission has discovered 7 so far. (Pre-vio-usly)
posted by IvoShandor (23 comments total) 13 users marked this as a favorite

 
While this is exciting and all, I find their sole parameters of planetary mass and surface temperature to predict earth-like planets to be a too simple to do any good. Seems like there are many other parameters that would need to be met for a planet to be habitable. This isn't my field, am I missing something?
posted by Maude_the_destroyer at 10:25 PM on September 20, 2010


Sure, there's lots of things that can predict whether or not a planet is habitable, but estimating the mass and surface temperature (sans atmosphere) is the best science can do right now. It's pretty amazing how much mileage they can get out the current data, which is all based on the wobbling light of distant stars.
posted by Kevin Street at 10:31 PM on September 20, 2010 [1 favorite]


Awesome! Let's go!

Oh...the closest one is still 38 parsecs away? Better go to Mars and unearth those Prothean ruins, then.
posted by danb at 10:33 PM on September 20, 2010


So, are we going to get to work on a generation ship, then? We'd better hurry, as we won't have the mineral resources to easily produce one in 100 years or so.
posted by shii at 10:48 PM on September 20, 2010


Of all the features of earth, its mass is one of my favorites.
posted by LobsterMitten at 11:03 PM on September 20, 2010 [5 favorites]


Yeah. I remember hearing how exciting it was that there were a couple of new planets discovered. Now there are actually hundreds. The technological advances being made in planet finding are really amazing.

I've heard they have a new telescope (I guess it's a new space telescope) that's going to look for 'glints' of light off planets surfaces to look for oceans or liquid bodies. Pretty awesome. You can see an example of glint here, illuminating a methane lake on Saturn's moon titan. Now imagine doing that on planets far outside our solar system.

Pretty amazing.
posted by delmoi at 11:50 PM on September 20, 2010 [3 favorites]


While this is exciting and all, I find their sole parameters of planetary mass and surface temperature to predict earth-like planets to be a too simple to do any good. Seems like there are many other parameters that would need to be met for a planet to be habitable. This isn't my field, am I missing something?

No, you're right, but the one catch is that "habitable" generally has a fairly specific meaning in exoplanet research, which boils down to "capable of having liquid water on the surface". (The classic definition is pretty much due to Kasting et al. 1993.) In essence, no one's really come up with a way for life to exist without liquid water, so it's taken as a necessary (though not sufficient) condition for life. This sets temperature constraints (can't freeze all the water off or boil it out) and mass constraints (once you get too big, you may be Neptune and no longer really have a surface; too small and you can't hang onto an atmosphere).

On the other hand, since no one is too clear what biosignatures of life would look like if they exist---in particular, what molecules we'd see in the atmosphere, and in what concentrations---there generally aren't too many additional constraints on "habitable".

Disclaimer: I work on exoplanets, but in instrumentation, not astrobiology. I'm familiar with this but it's not a specialty.

On preview: delmoi, are you thinking of this? This is definitely still theoretical work--their example is JWST with an external occulter. JWST won't go up until 2014 at the earliest, and occulters are still at the level of laboratory tests and some preliminary fabrication. (Also, space-based direct direction was de-emphasized this decade in the Decadal Survey in favor of technology development and possibly a downselect near the end of the decade, so I wouldn't expect too many pictures of Earth-mass planets until past 2020.)
posted by Upton O'Good at 12:15 AM on September 21, 2010 [5 favorites]


My Very Earnest Mother Just Sent Us New Planets.
posted by subgear at 12:40 AM on September 21, 2010 [2 favorites]


38 parsecs away.

Dammit, don't show me the candy if I can't HAVE the candy.
posted by BitterOldPunk at 3:09 AM on September 21, 2010 [1 favorite]


My Very Earnest Mother Just Sent Us New Planets.

There's an extra word there.
posted by empath at 5:11 AM on September 21, 2010 [1 favorite]


Of all the features of earth, its mass is one of my favorites.

Yes, that's what keeps me here.
posted by PlusDistance at 5:12 AM on September 21, 2010 [9 favorites]


Great, now I'll have to find another place to hang out offworld. I swear, you get comfortable in a place and then it's all in the NYT Style section and PLoS One and ruined.
posted by The Whelk at 5:22 AM on September 21, 2010 [1 favorite]


Actually, only six. One has been reclassified to a "dwarf planet."
posted by KirkJobSluder at 6:15 AM on September 21, 2010


BitterOldPunk So it'd be better if it was only two or three parsecs away? Either way we don't have an interstellar transport system and unless we can find some loopholes in physics we're unlikely to ever be in the business of sending canned apes across interstellar distances.

Which doesn't detract from the cool factor of any of this, IMO.

We're beginning to get actual data and it appears to be backing up what we'd guessed using the principle of mediocrity: solar systems like our own are probably not that uncommon. Which brings us back to Fermi's Paradox. We've always assumed, principle of mediocrity, that other stars have planets, that its not entirely rare to have planets in the Goldilocks zone meaning that they can potentially develop life as we know it. So where the heck is everyone?

There is nothing we know of that prevents von Neumann machines from being constructed, nor from strapping one such to a rocket and sending it on a trip to the nearest star system, there to construct, say, six identical ships which are sent off, etc. Likely such technology will be within our grasp in the next hundred or two hundred years if not earlier. Even if we can't, for some unforeseen reason, make antimatter to fuel truly efficient engines and push the probes up to 10% or more of C, there are other ways to push a probe up to at least 3% or so of C, and that adds trip time but what does a von Neumann probe care about trip time?

Which brings us, again, to Fermi. Where the heck are all the von Neumann probes that should be cluttering up our solar system along with every other solar system in the galaxy? If we can imagine such things, surely others can as well? If solar systems like ours aren't too dreadfully uncommon, if planets in the liquid water zone aren't too horribly rare, you'd think there might be life out there, and probably even intelligent life.

Are we unique, which may be possible but seems unlikely given that every bit of evidence gathered so far is in line with the principle of mediocrity?

Are there unforeseen difficulties with von Neumann type machines? Or with interstellar travel?

Are all the other intelligent species we presume exist just stay at homes who can't be bothered to build even a single von Neumann probe (because that's the lovely part about von Neumanns, you only have to build the first after that it takes care of the rest)?

Maybe all the other intelligent life is more aggressive than us and kills itself off in horrible atomic/biological/whatever wars before they gain the technical ability to build von Neumann probes?

I don't expect to live long enough to see any physical travel between our system and any neighboring solar systems. I have my doubts that mind uploading will be possible before I die, though it'd be nice if I'm wrong on that one. But I do hope that, before I die, we have big enough telescopes and good enough analysis to resolve Fermi's paradox, because it really is puzzling to me.
posted by sotonohito at 7:25 AM on September 21, 2010 [1 favorite]


On the other hand, since no one is too clear what biosignatures of life would look like if they exist---in particular, what molecules we'd see in the atmosphere, and in what concentrations---there generally aren't too many additional constraints on "habitable".

A big one is a large concentration of O2 and O3 in the atmosphere. Oxygen is very reactive, it wants to party with everybody, so if you have a large percentage of free oxygen in the atmosphere, something has to be generating it in large quantities.

So far, the only thing we know that does that is life. So, any discovery of a planet with near earth mass, surface temperatures, and lots of O2 & O3 in a dense atmosphere is a major discovery -- it's either life on another planet, or a whole new way to keep that much oxygen hanging around.

To be honest? Life is the easier answer to that posit.
posted by eriko at 8:03 AM on September 21, 2010


Are there unforeseen difficulties with von Neumann type machines? Or with interstellar travel?

Its entirely possible that interstellar travel is essentially impossible within the limits of the average evlotuionary development track of an intelligent speicies. Evidence suggests that we are fast approaching the limits of (1) the carrying capacity of our Earth (2) the extent of our easily available resources for further technological development and (3) our physical capacity for coping with the complexity of our own advanced society. Assuming that humans are the average, the fundamental bottleneck preventing interstellar travel could easily be just escaping the home planet, to say nothing of future bottlenecks whose feasibility we cannot even reasonable assess from our current position, such as a breakthough in passing the lightspeed barrier.

Without a major shift in world priorities towards outward interstellar expansion or at the very least extraction of mineral resources from our solar system, we may run out of energy or raw materials on Earth before reaching the point where we can begin asteroid mining, much less think about interstellar distances. And even a cursory look at the state of world politics and the average person's understanding of even elementary physics suggests that there are more pressing concerns (such as a coming worldwide water shortage or rising sealevel or peak oil or economic stagnation or WW3 or just the new season of Dancing With the Stars) that are highly likely to prevent a purposeful shift towards space in the near future.

For all we know our only window to interstellar travel is closing right now as we speak, as we approach peak oil and peak rare metals within the next 50 or so years. If we are the average, we can assume that any other advance species that makes it to this point would face thier own resource and political and collective action challenges on thier purple sky methane/water world, and it may be that a sollution really isnt possible. Although here's hoping for a cold fusion breakthrough to prove me wrong.
posted by T.D. Strange at 8:35 AM on September 21, 2010


I put the odds of a breakthrough in relativity that permits FTL travel to be extremely low given that we've observed that theory under a huge range of energies and conditions from CRTs to energetic supermassive black holes.
posted by KirkJobSluder at 8:44 AM on September 21, 2010


T.D. Strange Well, there's certainly no denying that we have pressing social/resource problems, and that getting a significant workforce off planet is an essential first step. Personally I think establishing an off planet presence (not interstellar, but at least to Luna and moving slowly into the belt and other regions around our solar system) is our only real hope as a species in the long run, but that's a different topic of discussion.

As far as local energy resources go, it is rather depressing. Oil gave us a boost and we acted as if it would last forever rather than using it to bootstrap ourselves into more sustainable energy usage patterns.

I should clarify that by "interstellar travel" I don't mean in terms of humans on starships. I'm increasingly convinced that starships are a dead end paradigm. I'm speaking only in terms of boosting hardware up to low end relativistic velocities (3%-10% of C) and accepting that it won't get anywhere for centuries. Shipping humans across interstellar distances seems as if it may well be, if not truly impossible, at least never economically feasible. Heck, shipping anything across interstellar distances in a reasonable amount of time may well be truly impossible, but "can't do it in a reasonable amount of time" is different from "can't do it". Again, if we're dealing with von Neumanns, who cares if it takes them 500 years to cross a mere parsec or two?

KirkJobSluder Most likely, yeah. I still hold out hope that we'll find a loophole, but I agree that it seems so unlikely that we might as well just work on the assumption that FTL is impossible. Heck, even getting much above 10% or 20% of C is likely to be so impractical we never do it even assuming all the energy problems are solved.
posted by sotonohito at 9:35 AM on September 21, 2010


Again, if we're dealing with von Neumanns, who cares if it takes them 500 years to cross a mere parsec or two?

If youre designing a selfreplicating starship, yes, the timeline doesnt matter, except to the extent that the ship has to be able to survive the first transit and replication. But that solution has no impact of the survival of the human race, if the only thing that can sucessfully tranverse the galaxy is a probe, sure that solves the paradox, but with no benefit for us. At that point the definiation of "life" is redefined as "a self replicating probe". Thousands of years after the fact, humanity's probes may "colonize" the whole universe, but no one will learn about it or be around to reap the benefits. To me that is not even worth pursuing. A much more worthy goal in the same vein would be a hibership or somekind of generational colony ship, at least then some actual humans may live to see another world, but again even talking about probes or ships is jumping ahead of several potentially insurmountable obstacles.
posted by T.D. Strange at 9:57 AM on September 21, 2010


Again, if we're dealing with von Neumanns, who cares if it takes them 500 years to cross a mere parsec or two?

Curiosity is great and all, but what economic good is an interstellar round-trip that lasts a millenium? What kind of organization could possibly be confident enough in its own stability to justify such a long-term investment?

It's one thing to send out probes and find out what's going on out there, but to me the point is not just to find out, but to go there, to integrate the rest of the galaxy into our neighborhood, and functionally speaking that means commerce.

Maybe the answer to the Fermi paradox is simply that there's no money in it.
posted by Mars Saxman at 10:01 AM on September 21, 2010


Realistically, I think the human race is stuck on this planet. If life from Earth gets to the galaxy, it's going to be artificial life, posthumans, or constructs that can handle deep time. We not only benefit from a fossil fuel glut, but a billion years of ecosystem development as well.

It's not a pleasant thought, but I don't see any way around it.
posted by KirkJobSluder at 11:01 AM on September 21, 2010


I think the tragically paranoid inductive reasoning version of the Fermi Paradox goes like this:

The first civilization in the galaxy appears. They say, "Surely we cannot be the first." They look around and find that nobody is talking. The question arises, "Why are we the only ones?" Someone says, "Because something is killing everyone who speaks up." Then they get quiet. No more broadcasting, just transmission by wire and laser beam. The civilization turns introspective.

The second civilization in the galaxy appears. They say, "Surely we cannot be the first ..."

It ends with thousands of deathly silent civilizations huddled around their cooling stars, shivering from the cold and from the fear, hushing themselves, waiting for the wolves to appear.
posted by adipocere at 11:19 AM on September 21, 2010 [2 favorites]


Exoplanetary astronomy is incredible. What we are able to accomplish from ground-based observation is amazing enough to add an extra sense of frustration to delayed orbital projects that are far more sensitive, such as the Terrestrial Planet Finder.

My life has straddled (so far) the knowledge that was true in the vast majority of human history, in which it was unknown if other stars in the universe had any planets (we knew they were theoretically possible, even likely, but had no evidence for their existence) to the point at which we are measuring the wind speed on planets that are 150 light years from us.

I also find it deeply ironic that the greatest probability for us finding intelligent life elsewhere in the galaxy, at least in the short term, is the detection of pollution in the atmosphere of their home planets. We are almost at the stage of being able to detect large exovolcanoes: not visually, but by using spectroscopy to detect molecules like sulfur dioxide. Once we're able to do that, it should only be a matter of time until we are able to refine our detection methods to find the hints of industrial pollutants, such as petrochemicals. After all, our own atmosphere is at the stage at which we need to erect towers in the remotest depths of the Amazon rainforest to collect the last gasps of pure, uncontaminated air. A civilization can "go quiet" all it likes with fibre-optic and low-power communication systems, but it would take centuries to cleanse the air of its industrial inheritance (assuming that an industrial age is something that a civilization "passes through", rather than being its death-knell).
posted by Bora Horza Gobuchul at 12:03 PM on September 21, 2010


« Older Bollywood Radio, the classics l Top 40 Countdown, ...  |  Beloved author Terry Pratchett... Newer »


This thread has been archived and is closed to new comments