[swombat]

For those eager to read ahead, they are very, very careful in this article not to imply in any way that this is definitely from any sort of living sources.

> Organic molecules, which contain carbon and usually hydrogen, are chemical building blocks of life, although they can exist without the presence of life. Curiosity's findings from analyzing samples of atmosphere and rock powder do not reveal whether Mars has ever harbored living microbes, but the findings do shed light on a chemically active modern Mars and on favorable conditions for life on ancient Mars.

Shame. I for one am looking forward to reading about actual life on Mars within my lifetime. Hopefully active life. We shall see.

[Thieum22]

It may be comforting that considering the Great Filter theory ( http://en.wikipedia.org/wiki/Great_Filter ) finding life on mars might actually be bad news.

[cLeEOGPw]

One of the so called "Great Filters" is our Moon. It is providing Earth's metal core with constant moving force and refreshing the dynamo and keeping our atmosphere and water not blown away by solar winds. Since the size of Earths satellite is far from ordinary, this instantly reduces chance of advanced life appearing elsewhere. And if the theory of the source of Moon is right, it formed after collision with object of a size of Earth, the filter is restricted by star systems with the planets within a certain range that had a collision with other planet in a way that left long lasting big object rotating around that planet and generating magnetic field preventing water and atmosphere from escaping. So just by applying only this "Moon filter", reduces the chances of advanced life in our own Milky Way to probably just few cases in whole galaxy. And add the probability of intelligent beings appearing on random planet that has life, it starts to seem pretty realistic that we are only ones not only in Milky Way, but also surrounding galaxies.

The conclusion is we better start working on colonization techniques, because chances are that the future of life in our galaxy is in our hands.

[Udo]

Earth's magnetic field is not powered by the moon. As far as we currently know, the dynamo effect is caused by the action of molten material against a rotating solid inner core. It's true that our magnetosphere keeps the atmosphere in, but having a magnetic field is far from uncommon or unexpected for a planet of Earth's size and composition. In fact, Mars - a planet lacking powerful moons - once had a magnetic field just like ours. The problem here is the size of the planet was not sufficient to keep enough heat inside for as long as ours has.

You might be conflating this with the theory that the Moon stabilizes the Earth's rotational axis and prevents it from wobbling too strongly, which would cause unpredictable summers and winters, kind of like the ones described in A Song of Ice and Fire.

Yes, the Earth-Moon system probably has some uncommon features, but let's not make the mistake to postulate that a world has to be precisely like Earth in order to support intelligent life. It's not at all obvious that our ecosystem represents the only possible solution for an environment that can produce intelligence. All we know is it is one solution.

> The conclusion is we better start working on colonization techniques, because chances are that the future of life in our galaxy is in our hands.

I agree!

[dredmorbius]

"Mars - a planet lacking powerful moons - once had a magnetic field just like ours."

I think the salient point here is "once had".

The Earths' core remains molten.

Some of that is latent heat of formation, some nuclear decay, some tidal stresses. I don't know the contributions of each. Contribution from Earth-Moon tidal stresses isn't insignificant though.

We _do_ know that tidal stresses can be hugely significant -- Io and Europa are thought to be heated (to differing degrees) by the stresses of orbiting Jupiter. Also one of Saturn's moons, Enceladus, which shows signs of volcanism with ice plumes.

The thought occurs to me that moons of a large gas planet could also harbor formation of life, though they'd have to be rather closer to their parent star than the Solar System's giants are.

[Udo]

Heat from radioactive decay and primordial heat are each thought to be about half Earth's internal energy budget - tidal forces from the Moon, even though they're strong enough the change the elevation of the surface by up to half a meter, do not factor in at a significant ratio as far as I know. Of course I'm only talking about the Earth-Moon system and the claim that without the Moon we would not have any atmosphere or magnetosphere.

> moons of a large gas planet could also harbor formation of life

Indeed, and the fact that there are at least two ways to convey energy to an ecosystem should increase the prevalence of life in general. Moons are an excellent spot for life, in some ways maybe even better than planets. They are more numerous, they can be cozy even outside of the Goldilocks zone, to some degree they can be protected by the magnetic field of their gas giant, they are never tidally locked to the star, and they might have a better chance for volatile chemicals on the surface than your average rocky planet.

Since the thread was originally about the Fermi paradox though, one has to wonder about the likelihood for bearing technological civilizations. How fruitful are ocean worlds for bringing forth tool users? Intelligence may in fact be common, but how conducive is this environment to science and engineering? We don't know.

> though they'd have to be rather closer to their parent star than the Solar System's giants are

If they're experiencing enough tidal stress, such as Europa is, they don't have to be close to the star at all.

[dredmorbius]

I was considering a land-based life-form.

I also suspect that while life could develop within, say, an ice-covered sea on an outside-the-Goldilocks-zone gas giant's moon, that the total available energy flux would likely not be sufficient to support a large or diverse population. Even absent the problems of developing a technological society in an aquatic (or analogous liquid) environment, total biomass, competitive pressures, diversity, and similar stresses which gave rise to humans and intelligence seem unlikely.

Instead I was considering a world with surface conditions similar to Earth, but itself the moon of a larger world.

I've also been reflecting on filters, and one thought that's been occurring to me is that many worlds may simply be subject to sufficiently frequent catastrophes that intelligent life never developed. In the case of humans on Earth, there was a planetwide catastrophe -- the Chicxulub impactor, 66 million years ago. Humans themselves split from their common chimp ancestors 2 million years ago. And complex life emerged about 500 million years ago, after first emergence at least 3.5 billion years ago.

There have been numerous perturbations of terrestrial conditions over that period, but it does suggest that over various intervals, certain degrees of stability are required. Asteroid impacts, nearby supernovae, climate disruption, widespread volcanism, orbital disruptions, variations in solar intensity, and other factors could all reset a nascent emerging life, complex life, intelligence or civilization. There are a lot of opportunities to get it wrong.

At the same time, various stresses also seem to have contributed to humans being, well, human.

[givan]

We have bacteria that live inside volcanoes or on the bottom of the ocean in extreme conditions, life adapts, without the moon life would only look differently there is no proof that without the moon life on earth would not be possible, looking at life in the universe from a human environment point of view is flawed.

[minikites]

But we only see complex life in a narrower range of much milder conditions. I bet there's lots of space microbes but I agree with the parent to this comment that complex, intelligent life is probably pretty rare.

[givan]

Milder conditions relative to our environment? this is subjective, where do you see complex life and how do you know that complex life requires "milder" conditions or that is rare if we only have ourselves as an example that happen to live in such an environment?

What stops bacteria that live in harsh environments to evolve even if probably slower? harsh meaning hard/impossible for ourselves or for life as we know on earth.

[minikites]

So where is everyone?

http://waitbutwhy.com/2014/05/fermi-paradox.html

> That would mean there were 10 quadrillion, or 10 million billion intelligent civilizations in the observable universe.

>Our sun is relatively young in the lifespan of the universe. There are far older stars with far older Earth-like planets, which should in theory mean civilizations far more advanced than our own.

I think intelligent life is pretty special/rare, given the evidence.

[dredmorbius]

NB: The collision genesis theory ("GIH" or Giant Impact Hypothesis) of the Moon's origin involves a body about the size of Mars, referred to as "Theia".

http://en.wikipedia.org/wiki/Origin_of_the_Moon http://www.nasa.gov/topics/solarsystem/features/moon_formati...

Otherwise, yes.

[madaxe_again]

The great filter theory is subject to our own filter bubble. As I see it, there are other possibilities -

Intelligent life doesn't want to be found - at least by us.

Intelligent life tends towards simulation, rather than expansion.

Further to the above, we are the only intelligent life in the simulation in which we reside.

Intelligent life is far more of an aberration than we realise.

Intelligent life is actually very dumb on a macro scale, and falls prey to Malthusian collapse, either by falling into a significant energy gap or by destroying their biosphere.

Intelligent life tends to succumb to dysgenic fertility, and ceases to be intelligent.

Therefore the discovery of life on other worlds means little for the Fermi paradox, as our model may grossly oversimplify or overlook one or more variables which lead to us, now.

Personally I think we're in a sim and we're about to lose the game, as we're staring down an energy deficit Malthusian collapse, uh, right now.

[roywiggins]

Three of your possibilities are "locations" for the Great Filter, as I read them:

> Intelligent life is far more of an aberration than we realise.

The filter is between "smart mammal" -> "human-level smarts." So there's lots of planets with lions, tigers and bears, but not talking dinos (or whatever).

> Intelligent life is actually very dumb on a macro scale, and falls prey to Malthusian collapse, either by falling into a significant energy gap or by destroying their biosphere.

The filter is between "21st century humanity" and "interplanetary/interstellar civilization." The universe is full of ruined planets, noticable because they've got transuranic elements floating around they shouldn't have.

> Intelligent life tends to succumb to dysgenic fertility, and ceases to be intelligent.

The filter is somewhere between "human-level smarts" and "interplanetary civilization." The universe is full of Morlocks.

We want the filter to be behind us. If it's actually "life is nearly impossible" then we're golden. Life on Mars 'pushes' the possible 'locations' of filter further forward (so life is probably common). If it's multicellular life, that pushes the filter further again, etc.

[swombat]

We're only "golden" until an unfortunate gamma ray blast occurs somewhere nearby and wipes out life on Earth in moments.

[exratione]

The important thing to realize about the Fermi Paradox is that all generalizations about behavior fail automatically as explanatory theories.

It only takes one small group within one species to generate a self-replicating probe, at which point all of the galaxy is visited in a few million years.

A solution to the Fermi Paradox has to explain why that event has never happened despite the fact that some element of our species will do exactly this at some point in the next thousand years. The laws of physics allow it, and our psychology is clearly up for it.

[fixedd]

The whole Fermi Paradox thing bugs me too, but in a different way. It assumes we have the capability of detecting the presence of other intelligent life.

The largest radio telescope we have (the 305 meter diameter Arecibo) would need to have it's sensitivity increased by around two orders of magnitude JUST to pick up our TV/FM/AM signals from outside the solar system. If we move into the narrowband signals then, depending on the source-strength, it could pick up signals at up to a few thousand light years... if it happened to be pointed in exactly the right direction at exactly the right time. So, our most sensitive instrument is only capable of measuring a fraction of a percent of a fraction of a percent of the galaxy.

I just straight-up don't believe that we're even remotely approaching the capability of asserting that the galaxy is sterile of higher life that's constantly dumping EM noise... and that's without assuming they've found ways to transmit data that we're ignorant of or that we've seen it and just haven't noticed it.

--

The other thing (and I feel a bit like a religious person saying this) is that we have exactly zero basis for asserting that the type of machine you're talking about haven't been here. Given that if one of these machines came here, and stayed, the Earth itself would annihilate all traces of it (especially on the surface) within short order we shouldn't necessarily expect to find evidence of a visit.

Taken to the extreme, you could even reason that all life on Earth could be the product of one of these machines.

[dhimes]

Not only is sensitivity an issue, but also frequency range. I feel quite confident that more technologically advanced civilizations will communicate at frequencies we are currently unable to demodulate. It's more efficient. Look how our frequencies have scaled on the order of a hundred years.

[swombat]

> Taken to the extreme, you could even reason that all life on Earth could be the product of one of these machines.

Hah, hilariously ironic. "Where is alien life in the universe? Are we the only ones?" continually bemoan the descendants of the organic probe sent to Earth to populate it with intelligent life.

[bsder]

> It only takes one small group within one species to generate a self-replicating probe

And what would that probe look like?

For it to be a useful to the sending civilization, it needs to go out, replicate, and send information back.

The first two are easy. Send out lots of meteorites with bacteria on them.

The third is not so easy. Creating a self-replicating machine which can then transmit back across interstellar distances or store information in its replication program and then send more of itself out is hard.

Or, you help life evolve and then wait for the results to reach the point where they can send out their own probes and signals...

[kamaal]

>>And what would that probe look like?

And more importantly why would anyone send anything to anywhere?

I never understand the argument people make about probes spreading across galaxies. If we assume they are at least as intelligent as we are, then purposelessly wandering in the universe would be least of their goals.

I can understand if probes have military goals. Like for example to evaluate threats to them. But like us here on earth, and with their technology would be carried out at a technical sophistication we have no remote capabilities of detecting currently.

[fixedd]

> And more importantly why would anyone send anything to anywhere?

You're assuming everyone is rational. For instance, if I were a future billionaire I'd totally do it... knowing I'd never see even a glimmer of return on the investment... just cause.

[rybosome]

> A solution to the Fermi Paradox has to explain why that event has never happened

How do you know that it has not? I'm not seriously asserting that it has, mind you. Just noting that there could be a swarm of radio-silent probes in the Kuiper Belt, in which case we would have no clue whatsoever.

[marcosdumay]

It didn't eat us.

One'd expect self replicant things to grow into every available ninche, however irrelevant it is. Thus there's no self replicant thing consuming our galaxy (or there is, but it's incredibly new).

[DennisP]

Maybe the first one prevents other intelligent species from arising, and the anthropic principle applies. We're the first, otherwise we wouldn't be here.

Another idea is that basic game theory and physics applies to everyone. It's virtually impossible to defend against attack by objects accelerated near the speed of light. The only way to be safe is to destroy potential threats before they destroy you, and be very very quiet.

[anigbrowl]

Or intelligent life doesn't leave the sort of markers we have been looking for up to now. I don't buy the sim theory at all and think it's a dreadful philosophical cop-out.

[aruggirello]

> Personally I think we're in a sim and we're about to lose the game

I agree with your last point; however, I believe this is actually a virtual school rather than a "sim".

[Florin_Andrei]

> Intelligent life tends towards simulation, rather than expansion.

Someone didn't take the Internet away from them when they were young, so they grew addicted to it. Bunch of navel-gazing nerds.

> Intelligent life is actually very dumb on a macro scale, and falls prey to Malthusian collapse, either by falling into a significant energy gap or by destroying their biosphere.

Looking at the Homo "Sapiens" species with a critical eye, I fear this is the most likely explanation.

[givan]

Great filter theory is pure speculation because this is the only thing you can have in absence of any data on the subject.

Beyond our solar system the best data we have are shadows blocking star light that indicate an exoplanet sometimes they are false alarms being just star (sun) spots, radio waves are something we use at this point in our very young civilization, there is no indication that this is a standard or efficient way of communication to associate missing radio data to absence of other civilizations.

In conclusion we have no data about life in the universe to jump to such conclusions or any conclusion, the only thing we can do is continue exploring and speculate on the question if there are advanced civilization capable of contact why aren't they contacting us?

[roywiggins]

Von Neumann probes could reach every star in the galaxy pretty quickly. A civilization with a few million years start on us should have their robotic friends here already, basking in our sun.

And there only has to be one civilization that 1) can and 2) does create such probes. If spacefaring civilization is common, it seems awfully unlikely that none of them have done so yet.

[pavelrub]

> it seems awfully unlikely that none of them have done so yet.

Based on what? How did you estimate the probability of a random intelligent civilization sending detectable (from Earth) Von Nuemann probes into the universe? For a probability of 1/1000 there could be hundreds of intelligent civilizations within our galaxy without any such probes, and the probability can be much lower than that.

[givan]

> it seems awfully unlikely that none of them have done so yet.

We don't know that, there is no way to detect that with our current technology unless one of the probes land on earth and the government/military agrees to disclose and confirm the information, maybe this already happened but nobody wants to see it because they are afraid of the implications http://en.wikipedia.org/wiki/Phoenix_Lights http://en.wikipedia.org/wiki/Belgian_UFO_wave

[maaku]

Great filter theory is nonsense. The period between intelligent life evolving and it taking over the universe at near the speed of light is so short, in cosmic time, that any civilization anywhere should expect to see an empty universe (in their light cone).

[Lost_BiomedE]

Before reading Power, Sex, and Suicide, I may have agreed.

http://en.wikipedia.org/wiki/Power,_Sex,_Suicide

It is a possibility that there is a relatively small window where single celled life has the opportunity to become multicellular life. As one amazon review summed it:

'After the origin of life, the next big step on the way to us was the origin of eukaryotes. These are all the organisms - including people, trees, mushrooms, and slime molds - who package most of our DNA into chromosomes in cell nuclei. Mitochondria, the "powerhouses" of eukaryotes, are descended from bacteria which took to living in a very close relationship with another type of one-celled organism; in fact they came to live inside the other. Nick Lane argues that this merger must have preceded the formation of the nuclear membrane.' *

The great filter is stronger and weaker in argument depending on where you place the filter, but the idea in general remains the same.

*more info here but less than the book, via an article in new scientist by the author: http://ronbarak.tumblr.com/post/25996121029/life-is-it-inevi...

[maaku]

I'm not sure what aspect of my post you are arguing against? I guess there could be different definitions at play here, but I was talking about a hypothetical developmental stage where most civilizations destroy themselves. E.g. nuclear war, climate change, etc.

Regarding how common life is in the universe, I wasn't talking about non-intelligent life. I fully expect that we will find signs of such life elsewhere in the cosmos in the next hundred years, either on Mars, Europa, Titan, Enceladus, or perhaps in the atmospheric spectra of some extra-solar planet.

No, I was talking about intelligent life, which if iot exists has a very short gestational period before transforming into lasting intelligence(s) expanding into the universe at close to physical limits. In particular the window between development of technology detectable from distant observation (e.g. radio) and a runaway singularity pushing that civilization's expansion rate to light speed limits is so small that regardless of the prevalence of intelligent life in the universe, we should expect to see an empty sky. Why? Because for most of the history of the cosmos we see an empty sky in our light cone. Then suddenly the most distant stars start to go dim with strangely shifted spectra, in an expanding wave that flows through visible star systems at >0.9c until it hits us, and ... well who knows what happens then.

The Fermi paradox is: "if there are so many intelligences, why can't we see them?" The transhumanist response is: "if we could see them, we'd be dead." By the anthropic principle we can only expect to exist in the time period where we are alive, not dead, so we should expect with very high probability to see an empty sky, and with very low probability the coming onslaught of darkness.

[lumpypua]

I agree with your overall statistical/singularity argument, but that's not reason enough to call a great filter nonsense. The biology of a great filter is at play along with the overall cosmological context.

"Power, Sex, and Suicide" argues that eukaryotic (and thus multicellular) life is basically a fluke—it is the great filter. The tumblr link Lost_BiomedE gave takes a while to get to that punchline but it's worth a read.

[maaku]

I should have said "the great filter explanation of the Fermi paradox is nonsense." There may be one or more great filters. There may be an early filter, or a late filter, or both. But that issue is orthogonal to why we see an empty sky. We see an empty sky because the amount of time between observing an extraterrestrial intelligence and being absorbed by it is so short that we should expect to exist in an empty-sky universe, regardless of how common life is.

One might then argue about the prevalence of extraterrestrial intelligence based on the age of the universe and the fact that our light cone apparently does not contain any other intelligent life. IMHO a sample size of 1 isn't that interesting however.

[lumpypua]

Power, Sex, and Suicide is one of the best books that has ever been written for the educated lay audience on biology. Great topics—the origin of life, sex, maad biochemistry. Seriously, if you're interested in biology and you have a decent background, read this fucking book.

[Houshalter]

Only if it's independently evolved, if it's a fork of life on Earth then it doesn't tell us anything about the probability of life elsewhere.

The great filter is very likely the evolution of multicelluar life and animals, which are unlikely to be found on mars. If we found living animals on mars I would be very concerned about the future of the human race.

[chc]

Why? Mars lost its magnetic field long ago, and most of its atmospheric mass followed behind. Whether animals had evolved there before these events happened doesn't really have any bearing on the cause or effect of those events.

[Houshalter]

If animals independently evolved on mars, it would mean the great filter is ahead of us rather than behind us.

[chc]

This seems like some kind of strange magical thinking to me. If animal-like creatures evolved on Mars and then all died because their planet's atmosphere and water dissipated early in its history, that tells us nothing about some "great filter" ahead of us. Our planet is large and geologically active and will most likely remain so until the sun engulfs it, so what would have killed any hypothetical life on Mars is not the same thing that will kill us.

[Houshalter]

If animals evolved independently on mars, it probably means the universe is full of life and that animals have evolved many times before on other worlds.

If so then we should expect many of those worlds to evolve intelligent life, and some of those worlds to still be around in the present day and colonizing, building stuff, or possibly even contacting us.

And yet there is no sign of any intelligent life out there despite intense scientific effort to search for it. This increases the probability of the hypothesis that most intelligent life goes extinct, which means we will probably go extinct.

[swombat]

Are you saying you're not currently very concerned about the future of the human race?

[omgitstom]

It matters what stage of life is found on Mars. Regardless, one data point even if it is our own solar system won't be enough for us to determine what/where the Great Filter or Great Filters could be.

[manachar]

> Shame

Poor word choice. There's no shame in being careful about the science and trying to represent it carefully in your press releases.

Many non-science types do not know that organic molecules can exist without life and will already be jumping to conclusions.

[aaroninsf]

I believe OP shares your sentiments, and that you mistake the usage here.

'Shame' as used here is shorthand for 'that's a shame,' which used colloquially to express disappointment colored with sympathy and understanding, does not imply that any of the nominal subjects is being criticized.

Source: I'm a native English speaker.

[Florin_Andrei]

Isn't 'pity' fairly similar, or is it more commonly used in British English?

[cbd1984]

'Pity' would be a Britishism in this context, yes.

[TallGuyShort]

I believe this is not the case in the US, at least in my experience. In South Africa people say "shame" to express pity for someone else (or even just when something is adorable) but when I say it hear I get weird looks :)

[pdabbadabba]

Native U.S. English speaker here: we do use the word "shame" as GP describes. We use "shame" both to say that someone should be ashamed and also to express general disappointment. (Though we would not use the word to talk about something that's merely adorable.) To my U.S.-English ears, swombat's use of the word "shame" seemed clearly of the "general disappointment" variety.

[tomrod]

In the U.S. don't we generally use "for shame" when berating?

[pdabbadabba]

Yes. But here the writer simply began a statement with the word "shame" and proceeded to give a sober explanation consistent more with disappointment than outrage. In this context, I think the better interpretation of the writer's sentiment is to read "shame" as, essentially, short for "it's a shame" rather than "for shame!"

[publicfig]

No, it is definitely a case in the US. In his sentence, you could expand it to "That's a shame" or "That's a crying shame", both idioms that can express that something is "unfortunate" or "disappointing", and does not always require a blame.

[ChristianBundy]

I'm a native English speaker and I was born and raised in the US (specifically the Pacific Northwest), and "shame" isn't weird at all.

It's used to express disappointment – with or without blame.

[TallGuyShort]

Thanks for the responses everyone. I've been in the US 15 years now and I'm still never 100% sure about dialect differences :)

[givan]

Mars and his satellites have many surprises, maybe we will find something extraordinary there during our lifetime.

We should go boldly where man has not gone before. Fly by the comets, visit asteroids, visit the moon of Mars. There’s a monolith there. A very unusual structure on this potato shaped object that goes around Mars once in seven hours. When people find out about that they’re going to say ‘Who put that there? Who put that there?’ The universe put it there. If you choose, God put it there..

Astronaut Buzz Aldrin

http://en.wikipedia.org/wiki/Phobos_%28moon%29#Proposed_miss...

[WalterBright]

Let's face it, like the canals, there is no life on Mars. 40 years of probes have come up empty. It's a sterile rock. We should be thinking in terms of terraforming it by seeding it with terrestrial life.

[ceejayoz]

40 years of probes haven't been testing for it. To my knowledge, the last formal attempt at actual detection of life (not conditions for life, but life) was the 1970s Viking landers. There's not even scientific agreement on the right way to search.

Meanwhile, here on Earth, we thought until recently that deep sea vents were sterile. If we didn't know life's limits here, we certainly can't claim to know them on Mars.