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Fraser
2007-Jul-12, 09:32 PM
If aliens visited our Solar System, it would only take them a moment to figure out which planet is the one with all the life on it. That's because our atmosphere has a high percentage of oxygen in its atmosphere. ...

Read the full blog entry (http://www.universetoday.com/2007/07/12/if-theres-oxygen-theres-life/)

EDG
2007-Jul-13, 01:14 AM
What about photodissociation of water vapour on a panthalassic world with a thick atmosphere? Wouldn't that produce a lot of O2?

Fraser
2007-Jul-13, 02:14 AM
That was one of the ideas, but they found that a world like that would be outside the habitable zone of the star, so it wouldn't be a candidate.

thothicabob
2007-Jul-13, 02:22 AM
or what about nitrogen and carbon dioxide in the atmosphere? seems to me those'd be at least as, if not more, important than simply finding oxygen?

Then again, i bet those old "I Love Lucy" broadcasts from 30-40 years ago would probably do as much to indicate something's going on. Of course, it would take a closer look to determine if anything intelligent was the cause, and if so, then a great deal of whatever it is that's analogous to head-scratching and asking themselves, "wtf?" (or it's alienese equivalent) to figure out if it's safe to approach us or not...

Hmm. Come to think of it, there has to be SOME reason we've not been contacted by now...

(let's leave aside the likelihood there's no one near enough to hear us for now). ;o)

cityonthemoon
2007-Jul-13, 02:57 AM
or what about nitrogen and carbon dioxide in the atmosphere? seems to me those'd be at least as, if not more, important than simply finding oxygen?

Then again, i bet those old "I Love Lucy" broadcasts from 30-40 years ago would probably do as much to indicate something's going on. Of course, it would take a closer look to determine if anything intelligent was the cause, and if so, then a great deal of whatever it is that's analogous to head-scratching and asking themselves, "wtf?" (or it's alienese equivalent) to figure out if it's safe to approach us or not...

Hmm. Come to think of it, there has to be SOME reason we've not been contacted by now...

(let's leave aside the likelihood there's no one near enough to hear us for now). ;o)

I'm not sure aliens would want to visit. I would think they have enormous telescopes(size of their solar system) that can probably view the earth like a CIA spy satellite. :)

EDG
2007-Jul-13, 03:27 AM
That was one of the ideas, but they found that a world like that would be outside the habitable zone of the star, so it wouldn't be a candidate.

Um. Why would that make a difference? It could be outside the "habitable zone" and still be habitable - in terms of temperature at least. The water vapour and thickness of the atmosphere could increase the temperature a lot via the greenhouse effect, plus the pressure at the base of the atmosphere would probably be high enough to keep the water liquid at the surface.

The problem is that the traditional definition of "habitable zone" is becoming more and more irrelevant as a definition as time goes on. We know we have oceans under the ice shells of satellites orbiting gas giants in the outer system, and it's possible that they could have life in them... yet they're well outside the traditional "habitable zone".

EDG
2007-Jul-13, 03:28 AM
or what about nitrogen and carbon dioxide in the atmosphere? seems to me those'd be at least as, if not more, important than simply finding oxygen?

You can get both of those gases from volcanic eruptions - life isn't required to produce them.

m1omg
2007-Jul-13, 08:21 AM
or what about nitrogen and carbon dioxide in the atmosphere? seems to me those'd be at least as, if not more, important than simply finding oxygen?

Then again, i bet those old "I Love Lucy" broadcasts from 30-40 years ago would probably do as much to indicate something's going on. Of course, it would take a closer look to determine if anything intelligent was the cause, and if so, then a great deal of whatever it is that's analogous to head-scratching and asking themselves, "wtf?" (or it's alienese equivalent) to figure out if it's safe to approach us or not...

Hmm. Come to think of it, there has to be SOME reason we've not been contacted by now...

(let's leave aside the likelihood there's no one near enough to hear us for now). ;o)

The signals are so weak that you will not recieve them on Mars...and our newest TV signals are ruined in noise beyond Pluto...comeon, you cannot recieve TV from another country let alone star...

And Panthalassic planets, why not a candidate?
HZ is different for them they must be very far from the Sun to be comparabily warm otherwise they will be supercritical hell.

Mercyless
2007-Jul-13, 10:34 AM
Greetings

It was with sadness that i found out that the Terrestrial Planet Finder Mission was cancelled... This was one of the missions that i was keeping an eye on... The budget excuse does not convice me... Oh well, that's life

Best regards to you all
Mercyless

eburacum45
2007-Jul-13, 11:58 AM
The proposal seems to suggest testing for both O2 and O3;
from here
http://arxiv.org/abs/0707.1557

We conclude that with a balanced hydrogen budget, and for planets with an active hydrological cycle, abiotic formation of O2 and O3 is unlikely to create a possible false positive for life detection in either the visible/near-infrared or mid-infrared wavelength regimes.

a water world in the habitable zone would pass the first test but not the second (according to A. Leger et al, who described that class of planets in some detail).

m1omg
2007-Jul-13, 03:24 PM
The proposal seems to suggest testing for both O2 and O3;
from here
http://arxiv.org/abs/0707.1557


a water world in the habitable zone would pass the first test but not the second (according to A. Leger et al, who described that class of planets in some detail).

But if there is life...

thothicabob
2007-Jul-13, 04:21 PM
The signals are so weak that you will not recieve them on Mars...and our newest TV signals are ruined in noise beyond Pluto...comeon, you cannot recieve TV from another country let alone star...

And Panthalassic planets, why not a candidate?
HZ is different for them they must be very far from the Sun to be comparabily warm otherwise they will be supercritical hell.

Aww, man...! Sure, go ahead, ruin my fun. Crush my dreams. Grind my fantasies to a pulp under the Heel of Reason. So, by extension, I suppose I have to also conclude that neither are aliens recieving and re-broadcasting (assumedly without permission) episodes of the Three Stooges, Gilligans's Island, or Batman, either. Dang it! Now, not only is my entire world view turned topsy-turvy, but my summer's ruined, to boot! (I used to like to spend the warm nights gazing up at the stars, wondering which, among all those up there, have intelligences that can appreciate this creative output and are willing to share it with each other. Now, I can't.).

Seriously, though, this discussion seems to be moving from the ease with which some postulated visiting aliens would recognize our little blue marble as the planet 'with all the life on it' towards a discussion of habitable planets around stars in general...

I think that the earth would be a beacon for any entity passing through our neighborhood with the interest and ability to check out our solar system; just a cursory visual glance would show a dynamic planetary environment - visual evidence of water abundantly visible in all three forms would be one clue, doiable without any sort of spectrographic analysis. I also think there are other processes which can generate an atmosphere with a lot of oxygen. I'd think it would be more the specific composition of the atmosphere (oxygen mixed in with all the other gases present) that would be a more compelling confirmation that biological processes are ongoing; it's a combination I believe that cannot happen naturally WITHOUT life present. I can be wrong - I'm not planetary scientist - this is just my understanding.

As far as the general question goes, I think we're learning both that there are quite likely more environments even within our own system where life could conceiveablly gain a toehold, and, once achieved, could flourish, and also that even a suitable planet in a habitable zone around a star is not guaranteed to harbor life. Biogenesis requires a LOT of things, the most important of which are time and a relatively stable environmental environment but with enough dynamic complexity that facilitates/encourages the sorts of changes necessary for organic life to organize and evolve without getting sterilized every so often. Earth, I suspect, is a fortunate planet, in this sense. This all said, I suspect that whenever and whereever conditions are suitable, life not only can, but will arise. The big issue is how far it can go - and that's just open to so many variables; while "life" may be common in the universe, advanced life is likely a completely different question. The environment itself could place an upper limit of the degree of complexity possible, for starters.

But enough already. I need to use some to figure out how to spend the rest of the summer now...

m1omg
2007-Jul-17, 08:51 PM
Sorry:cry:

thothicabob
2007-Jul-17, 08:55 PM
Sorry:cry:


S'okay. I'll get over it.

Someday.

:cry:

m1omg
2007-Jul-17, 08:56 PM
S'okay. I'll get over it.

Someday.

:cry:

:cry: I am really sorry:(

thothicabob
2007-Jul-17, 09:17 PM
:cry: I am really sorry:(

And I really believe you! :)

See? I'm over it already! Someday sometimes comes sooner than one expects!

m1omg
2007-Jul-17, 09:22 PM
And I really believe you! :)

See? I'm over it already! Someday sometimes comes sooner than one expects!

:)

BigDon
2007-Jul-18, 07:47 AM
I thought the big biomarker gasses were the simultanious existence of oxygen and methane? Which shortly becomes water vapor and CO2 unless replenished continiously?

Or am I off the mark here?

m1omg
2007-Jul-18, 10:29 AM
I thought the big biomarker gasses were the simultanious existence of oxygen and methane? Which shortly becomes water vapor and CO2 unless replenished continiously?

Or am I off the mark here?

Yes you are right.
The existence of methane on Mars in the aeas with the highest humidity and absence of sulfur dioxide what will indicate volcanic origion gives hope to that maybe life is there!

Well, it was proven that under 1 mm of martian soil there will be radiation level low enough to protect microorganisms from deadly radiation.
Peroxide could be blessing because peroxide+water forms a mixture that will froze at -50 Celsius and so it could remain on Mars liquid and it is hydroscopic that is useful on such a dry planet.
It is not so harmful as you may thought because one bacteria on Earth uses it in it's metabolism; http://en.wikipedia.org/wiki/Acetobacter_peroxidans .

Maybe even formaldehyde is on Mars what is another implication for life on Mars;
http://en.wikipedia.org/wiki/Life_on_mars#Formaldehyde_on_Mars

If we will contruct more precise spectrometer and detect ammonia, the life is certainly there;
http://en.wikipedia.org/wiki/Life_on_mars#Ammonia_on_Mars

Conditions on Mars are not so bad after all.

thothicabob
2007-Jul-18, 04:09 PM
Makes one wonder what could be lurking in the hypothesized voids in some areas under the Martian surface. I'm not sure that conditions even there would be favorable for very complex life to form, but any life would be interesting. That there's little to no sign of life on the surface, however, while not a total strikeout for life in general, I think could indicate that likely not much higher single-celled life or some wierd form of plant/lichen/fungi would exist even in the most protected/favorable areas.

If life is found there, and it turns out to be RNA/DNA based, and understanding that there's still only a statistical sample of '2', would that tell us that: a) that's a possibly common path for life to follow, or would it be more likely that: 2) there's been some transferance of biomatter between earth and mars?