Astronomers Calculate How To Spot Life On an Alien Earth

KentuckyFC writes: "One of the main goals of the space program is to spot an Earth-like planet orbiting another star. And by Earth-like, astronomers mean a planet with liquid water, gaseous oxygen and even chlorophyll, or a light-harvesting molecule like it. The biosignatures of these molecules were all observed during the first Earth fly-by in 1990 when the Galileo spacecraft measured the light reflected off Earth as it flew past on its way to Jupiter. But if these biosignatures exist on more distant exoplanets, could we spot them today? Now astronomers have calculated how good the next generation of space telescopes will have to be to pick up these biosignatures of life. They say that gaseous water should be relatively straightforward to pick out and that oxygen will be more challenging. But the spectral signature of chlorophyll-like molecules will be much harder to spot, requiring significantly more sensitivity than is possible today (either that or a great deal of luck). That suggests a plan, they say. The next generation of space telescopes should look for water and oxygen on exoplanets orbiting nearby stars and only then begin the time-consuming and expensive task of looking for chlorophyll on the most promising targets. One spacecraft that might do this is the Advanced Technology Large-Aperture Space Telescope or ATLAST that is currently scheduled for launch in the 2025-2035 time frame."

Comments

But should we go.

[jellomizer]

If a planet has life on it. If we visit it, how much damage will that cause. I mean just the bacteria on our skin that is normally helpful, my thrive and kill off all the life on the planet that may not have such defenses.

Re:But should we go.

[Travis Mansbridge]

Soon we may need another habitable planet whether the locals like it or not.

Re:But should we go.

[Anonymous Coward]

If a planet has life on it. If we visit it, how much damage will that cause. I mean just the bacteria on our skin that is normally helpful, my thrive and kill off all the life on the planet that may not have such defenses.

It works both ways. The alien environment could be deadly for us (think about alien bacteria).

Re:But should we go.

[newcastlejon]

That assumes the wayward bugs can metabolise anything on an alien world. Things like basic sugars, which I would assume are simple enough to be common, probably. But infecting a totally alien organism? Probably not.

Take staph. aureus for example. It can survive on humans of course, and a few domestic animals (maybe due to their long association with people) but apart from those I understand that it isn't common in other species. A bacteria that can easily cross species lines is one thing, but making the jump to an alien biology is quite another. Then again the biology might not be so alien if they're looking for worlds where the native plant life just happened to evolve chlorophyll.

Re:But should we go.

[marcello_dl]

Come on, don't be negative: a new inhabitable world is much like an inhabitable new continent, and we already showed how our civilization is able to preserve the ecosystem we invade. Just ask the real Americans.

Re:But should we go.

[Intrepid imaginaut]

Even if we're biologically similar enough there's no huge need to send down anything but highly sterilised drones. Plus, you can learn an enormous amount just from low orbit observation, especially if you're sufficiently advanced to get there in the first place.

Re:But should we go.

[i kan reed]

Bacteria evolved to eat the completely artificial substance of nylon. I'd rate the scenario as "plausible"

Re:But should we go.

[meta-monkey]

These are the kinds of questions that absolutely fascinate me about exobiology. If we discover life on another world (maybe even in our solar system) and it turns out to be completely different from life as we know it, that would be amazing, to study a completely different biology. If we find this life and is just like us, that would be equally amazing, because it would hint at common origins or common processes to the formation of life everywhere. Even if we find no other life, that's amazing, because it shows how unique we truly are.

Basically, every discovery or lack of discovery regardless of outcome in exobiology is amazing. You can't go wrong with that science.

Re:But should we go.

[Anonymous Coward]

Link for the interested: https://en.wikipedia.org/wiki/Nylon-eating_bacteria

Re:But should we go.

[CrimsonAvenger]

Just ask the real Americans.

I take it by "real Americans" you mean those guys who came over from Asia before the Vikings came over from Europe?

Re:But should we go.

[Dcnjoe60]

If a planet has life on it. If we visit it, how much damage will that cause. I mean just the bacteria on our skin that is normally helpful, my thrive and kill off all the life on the planet that may not have such defenses.

It doesn't matter because the reality is we couldn't get there, anyway.

Re:But should we go.

[Charliemopps]

That's while the nylon was surrounded by a world rife with food for the bacteria and countless varieties of pathogens. Evolution works on chance and brute force. The chance that any given mutation can happen is exceedingly low, but given the countless numbers of bacteria a nylon eating bacteria becomes an almost inevitability. What are the chances that a bacteria that can live on humans will survive long enough on an alien world to find a material is can metabolize? I think it really depends on just how similar that world is to ours. I have a feeling we're going to find out there's lots of life out there, but it's absolutely nothing like what we thought it would be.

That said, this is still a worry. Even if the chances are low, the outcome could be genocide... of either them or us.

Re:But should we go.

[Anonymous Coward]

Just ask the real Americans.

I take it by "real Americans" you mean those guys who came over from Asia before the Vikings came over from Europe?

QFT. I'm sick of having some smug bastard tell me I'm not a real American (or that I'm an immigrant) even though I was born here. The atrocities against the aboriginal population of the Americas were terrible but I'm not to blame, nor do they have any more intrinsic right to live here than I do.

Re:But should we go.

[InsultsByThePound]

He means Sarah Palin. Now proceed to your scheduled waterboarding baptism. Yee-haw, muddafukka.

Re:But should we go.

[CreatureComfort]

I think it all depends on how tasty that alien life is...

Re:But should we go.

[Anonymous Coward]

And the path of destruction continues..

Re:But should we go.

[morgauxo]

LOL... as if we could!

Re:But should we go.

[Anonymous Coward]

It's complete speculation if Earth microbial life could infect alien life. It's much less speculative that there would be competition between the two. However there's no way to determine in advance which biome would be more competitive. Plausibly, an unpredictable mix of winners and losers would emerge. Most likely on a species by species basis, with little regard for origin.

There's one other thing we could reasonably expect. There ought to be a "home world advantage." Life that evolved on a world should reasonably be better adapted to local conditions than life arising from offworld. Again though, just because that seems reasonable, there's no good way of knowing or predicting the accuracy of that.

It's even possible that alien life could co-inhabit a world with Earth life with little conflict. If the species were sufficiently different, with different survival factors, resource competition might be near zero. Do I really believe that is a likely outcome though? No

Re:But should we go.

[Anonymous Coward]

How disappointed would everyone be if it turned out that after finding a few thousand worlds with life on them, that the preponderance turn out to be variations on the same theme, and that out of all the worlds where life could develop in theory, the ones where it does, and lasts long enough to be observable at a distance end up suggesting that only one basic formula (organic, carbon-based chemistry) gives rise to anything we'd recognize as life, and it turns out further that only worlds with certain specific characteristics of mass/density, average and extrema of watts/meter^2 of light falling on them, etc., wind up being a suitable place for life to evolve and hang on long enough to evolve into sufficiently complex forms to be of any real interest to us... what if, in short, we find that every exo-earth actually very closely resembles OUR Earth?

I'm not saying they will or would, only asking how disappointing would it be to all of you if when we finally find that one ball of rock that not only has liquid water, has oxygen in its atmosphere, has developed carbon-based life, and has done so sufficiently long enough ago that we here on Earth, let's say hypothetically 10 million light years away, has also developed trees, things that like to live in/swing between trees, that these things climbed down from said tree-like organisms, started to use and fashion rocks into more complex shapes, starts to evolve language, just at the right time so that within maybe 50 or 100 years of discovering the world in question, we get a first "S" beamed from that world? Followed by a rudimentary image broadcast of some kind of national games... followed by 50 or so years of horrific garbage, war footage, reality television, an alien sort of fascism creeping over the world, and a last desperate, "hear us now, universe... as we stand on the brink of planetary self-destruction, don't do as we..." and the signal is lost.

That would really bum me out, but it wouldn't surprise me a bit. Yeah, I guess I'm a glass-half-empty kinda guy... (actually, I see the half-empty glass as infinitely more full than it will be when it is inevitably knocked over onto something expensive and very sensitive to water...)

Re: But should we go.

[Anonymous Coward]

Its in our nature...

Re:But should we go.

[marcello_dl]

Successful troll is succesful.

Well, I am a descendant of the guys who helped put an end to the western Roman empire, so what? I don't imply I am in any way guilty or I have no rights to stay where I am, too. Vae victis.

It still means that a newly discovered planet will end up like this one because the people who are devastating this one are still in charge.

Chlorrophyll makes a big assumption

[i kan reed]

Isn't chlorophyll tuned to the easiest bands of energy that come from our sun and don't get scattered by our atmosphere? Wouldn't a slightly different stellar color or atmospheric makeup dramatically change how stellar energy would be chemically captured?

Re:Chlorrophyll makes a big assumption

[Dimwit]

It's not so much a big assumption as it is a starting point. There is probably a biosphere somewhere in the Universe that uses a red or yellow pigment for photosynthesis. The problem is that detecting it at a distance is much harder, because while we might see the spectral signature we couldn't be sure that it's life.

Looking for a biosphere that is very similar to that of Earth makes it much more likely that we'll be able to detect that it is in fact "life" and not something else. While we may miss 99% of the life in the Universe with this approach, if/when we do detect it, our confidence will be much higher.

Re: Chlorrophyll makes a big assumption

[Graymalkin]

Hence the line about "light gathering chemicals like it". There's a few different chemicals that can be used by organisms in photosynthesis. Chlorophyll is simply the most popular on the surface of the Earth. Other pigments are optimum for regions that receive different light spectra than the surface. On worlds whose stars had different spectral maxima than Sol these pigments would likely be more abundant in photosynthetic life.

Re:Chlorrophyll makes a big assumption

[dpilot]

ISTR that chlorophyll is essentially a "voltage doubler", basically for red light. (Leaves are green because they use the red, and discard/reflect the green.) If you consider red to be between 600nM and 700nM, then a little more UV than we get might deliver enough content between 300nM and 350nM to be used directly for photosynthesis. I wonder how much UV would be needed to bypass the doubler, and if that would be too much for life, in general. Of course that would mean a hotter sun than ours, and I've more recently heard more about searching around red dwarves, where the leaves would more likely look black.

Re:Chlorrophyll makes a big assumption

[Anonymous Coward]

ISTR that chlorophyll is essentially a "voltage doubler", basically for red light. (Leaves are green because they use the red, and discard/reflect the green.) If you consider red to be between 600nM and 700nM, then a little more UV than we get might deliver enough content between 300nM and 350nM to be used directly for photosynthesis. I wonder how much UV would be needed to bypass the doubler, and if that would be too much for life, in general. Of course that would mean a hotter sun than ours, and I've more recently heard more about searching around red dwarves, where the leaves would more likely look black.

I asked a biology professor why leaves aren't black. I mean, it stands to reason that absorbing more of the spectrum would improve efficiency, right? He said leaves are green because green wavelengths would damage chlorophyll. I haven't further corroborated this, but it was interesting to consider.

Re:Chlorrophyll makes a big assumption

[i kan reed]

I find your re-framing reasonable and helpful. Thank you.

Re:Chlorrophyll makes a big assumption

[morgauxo]

Actually it isn't.

Re:Chlorrophyll makes a big assumption

[i kan reed]

This is a statement I wish were clarified.

Re:Chlorrophyll makes a big assumption

[Anonymous Coward]

Yes, right here on earth yellow and red pigments are used for photosynthesis

http://en.wikipedia.org/wiki/Photosynthetic_pigment

Re:Chlorrophyll makes a big assumption

[Anonymous Coward]

Leaves are black, if your eyes aren't sensitive to wavelengths shorter than green side of the yellow/green line. Remember the whole spectrum we see is a tiny little sliver of the entire electromagnetic spectrum. If you could see the ENTIRE THING, (between some reasonable stopping points, i.e., very low frequency radio to gamma rays), you'd find almost nothing existing that's black. Almost every solid, and probably most liquids likely reflect SOMETHING.

Your question is kind of analogous to a situation where you have an FM radio receiver that's stuck on 108 MHz, and as you wander the landscape with it, you wonder why so few places have radio stations. You could wander, listening to static even though if you could tune down to 88 to 107 MHz, you'd pick up about a dozen stations almost anywhere you go. Then there's a whole bunch modulated by their input signals' amplitude, between about 0.54 MHz, and 1.6 MHz, that you wouldn't notice either. Leaves are green simply because the most successful, (energy efficient, cost effective to make, etc.,) method of energy harvesting forsakes absorbing green light. If leaves were black they could be let's say 2/3 the area, and do the same job, but what if a molecule that could absorb all that costs 10 times as much energy to make? Or perhaps it would cost less, but to get to a protein that could be used to make it, one has to go through too many steps that are cost prohibitive or counter-productive and tend to reduce survivability of the organism developing them? They'd never make it even half-way along that path, so they never reach the end of it.

Or, just maybe, there is a molecule that would make the leaves black, make them indestructible, make them insanely efficient, but also make them smell and taste irresistible to all animal life? You know, it turns out that the magic blackophyll tastes like a mixture of crack and powdered sugar? As a plant, you evolve THAT, you get EATEN in a heartbeat. Reflecting green was a compromise and judging from how much members of Kingdom Plantae cover the solid parts (and even some of the liquid ones) of the Earth's surface, it's a pretty successful compromise, too!

If anything could out-absorb what's already around, they'd eventually out grow, out harvest, out reproduce, and out compete the green plants, and the green ones would become rarer and rarer until they were all gone. That implies why plants are green, (most are, anyway...) it's because that's what works best on Earth.

Damn it, must I do everything?

[Anonymous Coward]

I have a very obvious shortcut that would cut this time in half. Skip the oxygen / water search, go straight to chlorophyll. If you find chlorophyll, you may assume there is oxygen and water present as well. Why waste all this money and time adding extra steps to the process? Oh, yeah, I forgot, S-T-R-E-T-C-H that funding out... milk it, milk it...

Re:Damn it, must I do everything?

[sadness203]

Except it's way easier to search for Water and oxygen than Chlorophyll.

Suppose it take 5 unit of time to confirm if there's oxygen
Then it take 5 unit of time to confirm if there's water vapor.
And then it take 100 unit of time to confirm if there's Chlorophyll.

You can analyze 10-20 candidates instead of just one.

And like somebody else said, Chlorophyll is one candidate, in other conditions, another chemical could be used.

Re:Damn it, must I do everything?

[Anonymous Coward]

It really doesn't matter. It's like that unbelievably sexy girl at the beach: you can look all you want, but since you'll never have her, why do that to yourself? With this, even if we find, water, oxygen, chlorophyll, and the unmistakable chemical signature of entire oceans filled with beer, it's irrelevant and a waste of time and money since we'll never be able to go there. Let's use this money to help undo the damage we're doing to the one little blue marble we *do* have access to and are cooking out of existence.

Re:Damn it, must I do everything?

[Anonymous Coward]

It really doesn't matter. It's like that unbelievably sexy girl at the beach: you can look all you want, but since you'll never have her, why do that to yourself?

That may be (almost certainly is) true for you, but that doesn't mean it's true for everyone.

Re:Damn it, must I do everything?

[Anonymous Coward]

We understand that's the lie you tell yourself to justify not leaving you mom's basement.

Meanwhile the rest of us are dating the hot chicks and will go about populating the rest of the universe without you.

That bad genetics are a dead-end is tautological.

Would it?

[thechemic]

If a 500LB spacecraft was flying at the speed of light, could it penetrate Uranus?

More like Borophyll!

[Anonymous Coward]

Obligatory Adam Sandler reference.

ATLAST

[Anonymous Coward]

The intro is misleading. ATLAST has not a single dollar pledged to it. It has no "scheduled" launch date. It does have a lot of people thinking about it (and a very similar project, HDHST), but for now it exists purely in dreams and on paper.

Re:ATLAST

[Trapezium Artist]

Absolutely right: I was going to point out the same thing. It's many, many years away from any possible launch ...

For reference, the James Webb Space Telescope (or NGST as it was then) was beginning to be picked up as a serious prospect by NASA, ESA, and the Canadian Space Agency in the late 1990's. It's due for launch now in 2018.

(This is not meant as a criticism: I've been closely involved with JWST since 1998 and know how hard it has been in terms of technology, programmatics, and politics to get the good state it's in today, namely mostly built and now entering the comprehensive integration and test phase.)

So, very crudely, I'd say that something like ATLAST might be launched after 2035, if it gets picked up as the highest priority in the next US astronomy decadal survey.

I just love scanning for lifeforms.

[hort_wort]

Lifeforms... *bleep blup bleep bleep* you tiny little lifeforms... *bleep blup bleep bleep* you precious little lifeforms... *snipsnapsnap clap* where are you? *dootootootootoo bleebleeblue*

Re:I just love scanning for lifeforms.

[Anonymous Coward]

Data should have had his positronic brain crushed for that bit. Vile!

But did they take the other story into account?

[wonkey_monkey]

Have they read this article?

Proposed Indicator of Life On Alien Worlds May Be Bogus

(disclaimer: I haven't read either of them. Just thought it was mildly amusing to have these two articles come along within days of each other)

Mars First

[Anonymous Coward]

What would any of these tests say about Mars? And the other planets in our own solar system? If from such a close vantage point they say "no way", yet we will continue to try to find life on them. So how could we put much trust in them when observing from such crazy distances? They would say "this is just one of many tests". I'm pretty sure that many of the exoplanets found would be similar to Venus, Mars, Jupiter, etc. Fun to imagine things about, but tiny chance of anything meaningful.

Re:Mars First

[Anonymous Coward]

It is debatable that Earth would even be easily visible. Mars almost certainly would show little of anything in terms of it's atmosphere. Carbon Dioxide mainly. Venus would have a much heavier CO2 signature, Earth, if distinguishable would be mainly Nitrogen and O2. As far as deforestation, Any technological civilization closer than 60 light years would know that the CO2 on Earth is increasing, and the Chlorophyll is decreasing.

Something I have always wondered about the Transit method and the Doppler shift method of detecting extra-solar planets is, how come we never hear about extra-solar planets that have longer orbital periods than Mars? I know it was because of Hot Jupiter s being easy to detect with the Doppler method and the fact that we would have to be watching those stars for something like 12- 30 years to get a transit from planets with the same Mass and Orbital radius signature of a Jupiter or Saturn. This is ok though because we are not interested in those types of planets because the assumption is that they most likely do not have any life (other than stuff like the possible sub surface ocean of Europa or other water ice covered , tidally heated oceans of the outer solar system)
I just wonder, on the long orbital period planets, does this mean that we are going to just ignore these planets?

I am willing to bet that there are places to look for life that we haven't even thought of, some of the planets we think are Earth-like aren't, and there are some that we gloss over, but that are definitely abodes for life (such as Gas Giant planets in the habitable zone of their host star, but that harbor Moons that could be analogs to Star War's "Yavin" or Avatar's "Pandora". I realize this is a numbers game, but in any numbers game there are usually surprises due to the fact that nature is not just stranger than we suppose but stranger than we can suppose.

Will It Still Be Habitable?

[Zamphatta]

Every time I read something like this, I wonder if any habitable planets we find will still be habitable by the time we can get to them. If we find a habitable planet just a relatively close 10 light years away, then we're already seeing it as it was 10 years ago. Something could've changed there by the time we're seeing it. It's probably unlikely there'd be THAT much change in just 10 years, but then you have to figure it'd take us thousands of years to reach it with our current technology 'cause we can't even go 1% the speed of light yet. I haven't done the math, but wouldn't that take thousands of years just to get 10 light year away? So even a habitable planet 10 light years away would be well beyond our reach for the foreseeable future.