The Goldilocks zone???

maninasia

Yes I'm for real. Please don't put words in my mouth, I don't believe life can only exist in the goldilocks zone, but many commentators do if you read the articles than constantly quote it. I mean we already have examples of moons in our solar system that are PRIME candidates for life 'as we know it' that are not in the goldilocks zone. This is not even going into life 'as we don't know it', which could well exist on the gas giants or in the oort cloud.

And after your long and quite well written post I believe you can see the difficult in defining what exactly is the 'goldilocks zone' and it's constantly moving goalposts and abritrary neccessity for liquid water at the surface of a planet.

Yes goldilocks has some validity to Earth, but even in our solar system the best candidates for Earth like life (animal critters using some of the posters definition above) outside of Earth would not be included in the 'goldilocks' definition (liquid surface water, planet), kind of ridiculous don't you think?

Finally I'd argue although we know a lot more than decades ago we still understand very little about our own solar system and what has happened, how extensive oceans and atmospheres were on Mars etc., why they have changed. We haven't even done any proper tests for direct evidence of bacterial life on Mars, which seems to be odds on that microbes exist under the subsurface.

As for what determines the viability for life to take off or take hold other factors may be just as important as the position of the Earth in regards to the sun (within reason of course). I mean maybe plate tectonics is the key, ever think of that? Interestingly apart from Earth only some moons are known to have active plate tectonics.

http://pubs.usgs.gov/gip/dynamic/unanswered.html

slade_x

maninasia wrote: »

Yes I'm for real. Please don't put words in my mouth, I don't believe life can only exist in the goldilocks zone, but many commentators do if you read the articles than constantly quote it. I mean we already have examples of moons in our solar system that are PRIME candidates for life 'as we know it' that are not in the goldilocks zone. This is not even going into life 'as we don't know it', which could well exist on the gas giants or in the oort cloud.

The possibility that life can exist outside of the habitable zone isnt in question here. the easiest way to find an earth like planet of our own is to base the search on it

maninasia wrote: »

And after your long and quite well written post I believe you can see the difficult in defining what exactly is the 'goldilocks zone' and it's constantly moving goalposts and abritrary neccessity for liquid water at the surface of a planet.

Earth is the only planet like this that we know of with complex life, specifically an intelligent species like us. Its not about every nuck and cranny where life may or may not exist. that doesnt narrow down the search

maninasia wrote: »

As for what determines the viability for life to take off or take hold other factors may be just as important as the position of the Earth in regards to the sun (within reason of course). I mean maybe plate tectonics is the key, ever think of that? Interestingly apart from Earth only some moons are known to have active plate tectonics.

And here's the problem, right now a search for any (any at all) life including life not like our own, given all the numerous different factors you would have to account for even in just this galaxy, is impossible. The habitable zone is not a parameter for any and all forms of life. It is a simplistic above all practical approach to finding an earth like planet.

Narrowing the search parameters increases the odds of success otherwise you are looking absolutely everywhere for any and all different types of that proverbial needle in a haystack. so where do you start in that scenario? im sure a directive of "practically" everywhere for "practically" anything would be practical for those who have taken on the challenge.

Factors like plate tectonics and all the others that may or may not be involved will not come into play unless we are within the neighbourhood of where to look. we are very limited on where and how we can look, hence the obvious approach

when mailing items, a courier looks at the parameters in a given order starting with Country (obviously the most important to look at FIRST) > county > town > neighbourhood > name or number of the destination. is basically what you are suggesting is to start off with the most arbitrary of all; the number and work your way from there? in which case i really dont like your odds of narrowing in on exactly where you are looking for. The unfortunate reciever will never get their mail.

maninasia

I get the point but fundamentally I disagree with the premise that you start with this narrowly defined region, as I can already see from our solar system that moons are more prevalent , more diverse and also more active geologically. If you are looking for an EXACT or VERY SIMILAR planet to Earth yes why not...but let's not confound it with an unscientific blanket 'habitable' statement approach.

Let's say the REAL habitable space is more than 50% of our solar system...not very useful as an addressing system now is it for finding life?

It is already well known the best habitable place candidate for Earth like species (using the Earth animal definition) is probably Europa or Encephaledus in our own solar system.

http://en.wikipedia.org/wiki/Enceladus_(moon)
http://en.wikipedia.org/wiki/Europa_(moon)

Venus-fail. Mars-fail. Earth's moon-fail (interesting that one, it is the solar system's largest moon, but it only has very small amounts of water).

So you can argue the other way and the supposed goldilocks zone is not really such a 'just right' place at all..at least for liquid water. In fact maybe large bodies liquid water have a better chance of existing further out as moons of gas giants as their surface will have frozen over...I don't know.

Rubecula

maninasia wrote: »

I get the point but fundamentally I disagree with the premise that you start with this narrowly defined region, as I can already see from our solar system that moons are more prevalent , more diverse and also more active geologically. If you are looking for an EXACT or VERY SIMILAR planet to Earth yes why not...but let's not confound it with an unscientific blanket 'habitable' statement approach.

Let's say the REAL habitable space is more than 50% of our solar system...not very useful as an addressing system now is it for finding life?

No this is not right Jupiter alone is larger than the rest of the solar system combined so 50% habitable is way off

It is already well known the best habitable place candidate for Earth like species (using the Earth animal definition) is probably Europa or Encephaledus in our own solar system.

http://en.wikipedia.org/wiki/Enceladus_(moon)
http://en.wikipedia.org/wiki/Europa_(moon)

Venus-fail. Mars-fail. Earth's moon-fail (interesting that one, it is the solar system's largest moon, but it only has very small amounts of water).

Earth's moon is not the largest in the solar system that honour goes to Ganymede, by a massive margin over our moon too.

So you can argue the other way and the supposed goldilocks zone is not really such a 'just right' place at all..at least for liquid water. In fact maybe large bodies liquid water have a better chance of existing further out as moons of gas giants as their surface will have frozen over...I don't know.

Sorry to be pedantic.

Bohrio

maninasia wrote: »

I get the point but fundamentally I disagree with the premise that you start with this narrowly defined region, as I can already see from our solar system that moons are more prevalent , more diverse and also more active geologically. If you are looking for an EXACT or VERY SIMILAR planet to Earth yes why not...but let's not confound it with an unscientific blanket 'habitable' statement approach.

Let's say the REAL habitable space is more than 50% of our solar system...not very useful as an addressing system now is it for finding life?

It is already well known the best habitable place candidate for Earth like species (using the Earth animal definition) is probably Europa or Encephaledus in our own solar system.

http://en.wikipedia.org/wiki/Enceladus_(moon)
http://en.wikipedia.org/wiki/Europa_(moon)

Venus-fail. Mars-fail. Earth's moon-fail (interesting that one, it is the solar system's largest moon, but it only has very small amounts of water).

So you can argue the other way and the supposed goldilocks zone is not really such a 'just right' place at all..at least for liquid water. In fact maybe large bodies liquid water have a better chance of existing further out as moons of gas giants as their surface will have frozen over...I don't know.

Just remember that the habitable zone is not the same as planet habitability, habitable zone refers to the stellar conditions needed to maintain carbon based life.

There is a part of my post that you probably didn’t read (likely my fault as it was a bit long, sorry )

The concept generally does not include moons, because there is insufficient evidence and theory to speculate what moons might be habitable on account of their proximity to a planet."

for example, some scientists believe that comets carry some sort of life in them.

Things such as plate tectonics have more to do with planet habitability (planetary conditions required to maintain carbon-based life) but again this doesnt apply to moons.

Also, Ganymede is the largest moon in the solar system (not our moon) and is also covered in ice. In fact, scientists theorize that there could be a salt water ocean underneath its 200 km ice crust. But then again, Ganymede is a moon, not a planet so the habitable zone "concept" does not apply here.

Maybe a good analogy will be, for example, this one.

Let's say I like to fish (havent done it in 20 years but let's just pretend I do) and I move to a different country, a place I have never been before, I brought all my fishing gear and one day I decide I want to go fishing. Normally, I would go to a lake or a river because I know, based on my experience, that fishes live in the water.

In your case, you would (and please dont take this the wrong way this is just an example) go to a random cave hoping to find water in it and maybe, if you are lucky, a fish!

Remember that habitable zone refers to liquid water on the surface of the PLANET, not underneath a thick crust of ice.

maninasia

Rubecula wrote: »

Sorry to be pedantic.

Don't know what you are on about for Jupiter, the 50% number does not refer to planets but to a volume of space in the solar system or a percentage of the number of bodies in the solar system, anyway it is just a number to illustrate a point.
As for the moon, I stand corrected.

maninasia

Good post again but this bit...

'plate tectonics have more to do with planet habitability (planetary conditions required to maintain carbon-based life) but again this doesnt apply to moons.'

Why? (apart from the obvious answer that a planet is not a moon)

Anyway, we can start to see how Goldilocks zone has way too many loose parameters..now it is morphing to Planetary Habitable zone and liquid water on the surface. But doesn't it strike you as very abritrary and in fact irrelevant?

To explain, most of the Earth's surface is covered with ocean, most of the life exists in the ocean, not on the surface, and oceans have been frozen solid or have had large parts covered with solid ice for periods of millions of years (snowball earth). It doesn't really matter if the surface is frozen or not!

I can see that it makes sense that if we found a very Earth like planet in the same orbital zone that it may have a higher chance to harbour life like ours. Sure. Just let's not get obsessed about that and miss the much bigger picture. Don't devote too many resources to that and restrict the search parameters too tightly.

Bohrio

maninasia wrote: »

I can see that it makes sense that if we found a very Earth like planet in the same orbital zone that it may have a higher chance to harbour life like ours. Sure. Just let's not get obsessed about that and miss the much bigger picture. Don't devote too many resources to that and restrict the search parameters too tightly.

I think the last part of your post sums it up.

I see now where you are getting at. A few years ago we thought it was impossible for carbon based life forms to exist outside this "habitable zone". Today, our search for life (no matter how basic) has taken us to places where, 30 years ago, we would never dare to look.

We are learning as we go I guess.

Also, remember that snowball earth is a hypothesis (doesnt mean i dont believe in it). Back then, temperatures on earth were not, apparently, as extreme as they are in, for example, Europa where temperatures can drop to as low as -220 degrees Celsius.

And it took a lot for Earth to get out of it.

”The carbon dioxide levels necessary to unfreeze the Earth have been estimated as being 350 times what they are today, about 13% of the atmosphere.[54] Since the Earth was almost completely covered with ice, carbon dioxide could not be withdrawn from the atmosphere by release of alkaline metal ions weathering out of siliceous rocks. Over 4 to 30 million years, enough CO2 and methane, mainly emitted by volcanoes, would accumulate to finally cause enough greenhouse effect to make surface ice melt in the tropics until a band of permanently ice-free land and water developed;[55] this would be darker than the ice, and thus absorb more energy from the sun — initiating a "positive feedback".”

Scientists also believe that back when earth was covered in ice, these ice sheets may have delayed or prevented the establishment of multicellular life. With this, I am not saying life can't exist in Europa (or other places), some people, have theorize that cosmic rays hitting europa's surface are converting some of the ice into free oxigen which could be absorbed into the ocean below, this particular theory says that, if this continues like this in a few millions years, Europa could not only be crawling with anaerobic microbial life but even more complex life forms such as fish… (http://www.universetoday.com/42303/europa-capable-of-supporting-life-scientist-says/), but again this is just a theory.

Just put it this way, so far, we have not been able to prove the existence of life anywhere else but earth. We are doing our best but, so far, we can only theorize. If we can’t prove the existence of life in our solar system imagine how hard it will be to prove it on another solar system, several light years away.

BULLER

maninasia wrote: »

Good post again but this bit...

Don't devote too many resources to that and restrict the search parameters too tightly.

I think you're just arguing for the sake of arguing! The goldilocks zone is hardly a massive search restriction. There are possibly hundreds of millions of planets in goldilocks orbits around stars in our galaxy and as telescopes get bigger we'll start to be able to detect them. The fact of the matter is that this is where earth like planets are, and hence life. I would hazard a guess that the chances of life on a goldilocks zone planet towards something outside this zone like the moon Europa wouldnt even be comparable.

maninasia

I'm arguing because I personally detest poorly thought out theories. What the goldilocks theory is is simply 'confirmation bias', a well known psychological effect.
http://en.wikipedia.org/wiki/Confirmation_bias



'The fact of the matter is that this is where earth like planets are, and hence life' Massive assumption.... Haven't seen much complex life on our moon or on Venus lately, have you? Plus how do you define goldilocks zone, we have been debating that (well at least I have ).

'I would hazard a guess that the chances of life on a goldilocks zone planet towards something outside this zone like the moon Europa wouldnt even be comparable.'

Why? From your example of one? From the example of one from our poorly understood and researched solar system? Over 10 years ago we didn't even know there was a huge amount of microbial activity and diversity in the subterranean environment, atmosphere and oceans of Earth. That's our home planet and we didn't have a clue.
Have we actually done any direct tests for bacteria on Mars even? Have we sent any probes to really look for life in the gas giants and their moons?
There is a multiple of moons than planets on our solar system (and probably most solar systems), 168 known moons . So we have about 20 TIMES the number of moons to planets. This also matters if you think that objects in the solar system sometimes face random extinction events, more lifeboats for life.

Moons are more diverse and geologically active than planets in our solar system. That means that they present a wider range of possible habitats for life to spawn or to colonise successfully. Apart from Earth only moons have active tectonic activity in our solar system. We have at least three moons with liquid water and one planet with liquid water in our solar system.

http://www.physicsforums.com/showthread.php?t=114464
http://www.funtrivia.com/askft/Question113202.html

That's a minimum 3 to 1. DO we know if life exists in those moons, no, because we have never even looked! We literally don't have the foggiest idea.

Where are most moons located in our solar system, OUTSIDE the goldilocks zone. Who cares if a moon is not a planet, you think a lifeform can tell the difference or cares? Get my point?

So yes finding Earth like planets is interesting but it is just one part of the puzzle.

Bohrio

maninasia wrote: »

That's a minimum 3 to 1. DO we know if life exists in those moons, no, because we have never even looked! We literally don't have the foggiest idea.

But we are looking... we just can't find any.

So far, all we know is based on theories, all the links you have shown us are just theories. We dont have the technology to do any better.

Europa's ocean (if there is any) is covered by a crust of ice 120 km thick (againt another assumption), with our current technology there is no way we can get through that ice, there is also ice in our moon and the best we could do was to shoot a missile into the ice and wait for those particles to hit out atmosphere so we could then analize them...

Who said we are not looking, we are looking everywhere, so I feel!

maninasia

Well NASA is looking but it's a slow process and technologically challenging. That said they could have conducted more direct biological tests on Mars if they had really wanted to or taken a risk. They are quite risk averse, especially if you think they haven't done any direct testing for organic molecules on Mars since the Viking program in 1975! The results of the Viking probe are still ambiguous, even according to the scientist that was in charge of that part of the experiment.

Read this article which gives some insight.
http://www.space.com/9504-search-life-mars-top-priority-robot-probes-scientists.html

They formed an assumption from a very limited amount of data that was flawed but fit into some primitive scientific theories of the time.

'After the Viking missions, the general consensus was that cold, radiation, hyper-aridity and other environmental factors ruled out the chances for microbial activity on or near the surface of Mars. This assumption based largely on how Viking's instruments did not detect organic compounds that would have indicated Martian life has been reinforced by each follow-up mission since then' (I don't get the reinforced bit, later missions have shown how perclorate is present which degrades organic molecules and also that methans is being replenished in the Martian atmosphere).

They pumped incredible amounts of cash into the space station and shuttle, each shuttle launch cost approx 450 million USD and each shuttle, four in all, cost a billion USD. That's not a total waste but they could have put together some awesome robotic life seeking probe missions for the cost of each launch. The space station cost anywhere between 35 billion to 100 billion USD!

Bohrio

maninasia wrote: »

Well NASA is looking but it's a slow process and technologically challenging. That said they could have conducted more direct biological tests on Mars if they had really wanted to or taken a risk. They are quite risk averse, especially if you think they haven't done any direct testing for organic molecules on Mars since the Viking program in 1975! The results of the Viking probe are still ambiguous, even according to the scientist that was in charge of that part of the experiment.

Read this article which gives some insight.
http://www.space.com/9504-search-life-mars-top-priority-robot-probes-scientists.html

They formed an assumption from a very limited amount of data that was flawed but fit into some primitive scientific theories of the time.

'After the Viking missions, the general consensus was that cold, radiation, hyper-aridity and other environmental factors ruled out the chances for microbial activity on or near the surface of Mars. This assumption based largely on how Viking's instruments did not detect organic compounds that would have indicated Martian life has been reinforced by each follow-up mission since then' (I don't get the reinforced bit, later missions have shown how perclorate is present which degrades organic molecules and also that methans is being replenished in the Martian atmosphere).

They pumped incredible amounts of cash into the space station and shuttle, each shuttle launch cost approx 450 million USD and each shuttle, four in all, cost a billion USD. That's not a total waste but they could have put together some awesome robotic life seeking probe missions for the cost of each launch. The space station cost anywhere between 35 billion to 100 billion USD!

First, Mars is inside our solar system's habitable zone. I thought you wanted people to look beyond that "area". I have heard of numerous projects involving mars, even manned missions.

Nevertheless, at this moment, there is no money at all. So those type of missions are out of the question. We wont even go to the moon much less visiting Mars or Jupiter.

So I dont really see a problem here. We are looking for life everywhere and we are not restricting this search to the habitable zone as you seem to believe.

So I think I am lost now, I thought that the main problem for you was that people were not looking for life outside this habitable zone?

Bluehair

Newbie to the forum and enjoying the debate here.

It would seem reasonable to question the science or indeed the usefulness of the Goldilocks/Habitable Zone but what is the alternative for investigative purposes?

Unquestionably life can exist, and possibly evolve, in a range of conditions far outside the parameters of the 'zone'. This should be investigated further and as far as I'm aware is the subject of much research these days especially on the likes of extremophiles which will hopefully teach us a great deal about the potential for life in a range of conditions.

Presumably though our desire is to suggest, based on observation in our own solar system, that life in other solar systems is either more or less likely to develop in that solar system. All we can say is, again based on observation in our own solar system combined with a reasonable understanding of its' history, that we haven't seen much in the way of life bursting out of anywhere else except Earth thus far.

Let's be fair though. We aren't even at the infancy stage of understanding how/when/where life develops. Theories such as the 'Habitable Zone' are useful only insofar as they themselves are learning tools as we advance ourselves in this arena. Lets not forget too that 'theories are analytical tools for understanding, explaining, and making predictions about a given subject matter'. Ultimately as far as the evolution of life on a given planetary body is concerned we understand very little, can explain even less and are a long way from being able to make reasonable predictions!

maninasia

http://www.newscientist.com/article/mg21028124.800-alien-life-may-huddle-under-hydrogen-blankets.html

More ideas regarding life on planets outside the goldilocks zone.

Capt'n Midnight

Mahatma coat wrote: »

Like when they describe something as a Class - M Planet in StarTrek. what are the paramaters and how much wiggle room is there?

IIRC M means it has oxygen , so has to be in the zone

It's in a book upstairs somewhere





Venus / Mars are worth looking at too for the effects on atmosphere,

Venus has lost most of the hydrogen. Had it a moon like we do would it still have oceans ?

If mars had been heavier would the green house effect been ok there ?

Also look up "snowball earth" to see how we nearly got shut down a while back

The sun is getting brighter over billions of years so the zone moves out, but our planet has kept pace by mechanisms like clouds and glaciers and the really big on of having life. Life means chalk deposits on the sea floor. These when subducted power volcanoes which means we get cool stuff like venus / mars don't (have they found venusian vulcanism yet ?)

maninasia

Glad to see some points here which show the story is a lot more complicated than it first appears, we don't have much clue as to why Earth maintained such a diversity of life for so long along with it's atmosphere but Mars didn't (although odds on that Mars has microbial life). Was it because of Mars size, that it's volcanism shut down early, that it didn't have life established so it couldn't create a 'gaia' effect, did the distance from the sun play a part or not, was the relatively huge moon a big factor, was there a cataclysmic impact? Really a lot of unknowns.


If I'm right the newest 'best candidate' yet for life is outside of the Goldilocks zone (now I know that is also a factor of the size of the planet making it easier to detect)!
http://www.spacedaily.com/reports/Climate_scientists_reveal_new_candidate_for_first_habitable_exoplanet_999.html

maninasia

This is pretty cool...free floating planets, possibly very common.

http://www.spacedaily.com/reports/Bennett_team_discovers_new_class_of_extrasolar_planets_999.html

maninasia

Huge bodies of liquid water found near surface of Europa.

http://www.wired.com/wiredscience/2011/11/lake-europa/

Bohrio

maninasia wrote: »

Huge bodies of liquid water found near surface of Europa.

http://www.wired.com/wiredscience/2011/11/lake-europa/

already posted here

http://www.boards.ie/vbulletin/showthread.php?t=2056452902

no need to reopen a thread thats over 5 months old mr! Specially when it has nothing to do with it

Cú Giobach

maninasia wrote: »

Huge bodies of liquid water found near surface of Europa.

http://www.wired.com/wiredscience/2011/11/lake-europa/

Not really relevant in a thread about liquid water on the surface of a body is it. There's lots of subsurface water around, that's quite a different beast.

maninasia

Not relevant. A hue body of liquid water 1.8 km from the surface? How is 'sub-surface' water a different beast? How about oceans on Earth, at a rough guess 99.9999999999999999999999999 is subsurface water right?


Funny how it was found outside the goldilocks zone eh? It has EVERYTHING to do with the goldilocks zone as it looks like they will have to revise their definitions soon.

Cú Giobach

maninasia wrote: »

Not relevant. A hue body of liquid water 1.8 km from the surface? How is 'sub-surface' water a different beast? How about oceans on Earth, at a rough guess 99.9999999999999999999999999 is subsurface water right?

It's different because it's not on the surface of Europa, it's a little bit nippy out there.
Coming up with your own definition of "surface" now?

Funny how it was found outside the goldilocks zone eh? It has EVERYTHING to do with the goldilocks zone as it looks like they will have to revise their definitions soon.

Funny? Not in the slightest, we have understood how such a thing is not just possible but practically inevitable for quite some time now.
Why on earth would we have to change our ideas of where we believe liquid water could remain stable on the surface of a body because we found water beneath the surface of one outside such an area, that's not very logical now is it.

Bohrio

maninasia wrote: »

Not relevant. A hue body of liquid water 1.8 km from the surface? How is 'sub-surface' water a different beast? How about oceans on Earth, at a rough guess 99.9999999999999999999999999 is subsurface water right?


Funny how it was found outside the goldilocks zone eh? It has EVERYTHING to do with the goldilocks zone as it looks like they will have to revise their definitions soon.

It is not relevant because the habitalbe zone as far as I know only refers to planets, not moons. And still refers to liquid water on the surface.

Remember that this "zone" refers to earth like planets. Like Mars billions of years ago when it apparently had liquid water on its surface.

Anyway, I know there is no point in explaining this again, it is pretty clear to me that you have your own definition of what the goldilock zone is... and there is no way we can make you change your mind.

namloc1980

Bohrio wrote: »

It is not relevant because the habitalbe zone as far as I know only refers to planets, not moons.

Why can't the habitable zone refer to moons?

Bohrio

namloc1980 wrote: »

Why can't the habitable zone refer to moons?

From what I read sometime ago moons are susceptible to their planets own gravitational forces, among other things.

Planets such Jupiter or Saturn can have a very strong effect on their moons (for example Io's volcanic activity).

Of course I could be wrong... I am often wrong!!!

namloc1980

Bohrio wrote: »

From what I read sometime ago moons are susceptible their planets own gravitational forces, among other things.

Planets such Jupiter or Saturn can have a very strong effect on their moons (for example Io volcanic activity).

Of course I could be wrong... I am often wrong!!!

If a planet is in its star's habitable zone then by definition so would its moons. Imagine if Jupiter was in the habitable zone, then in theory Europa would be an ocean world.

Bohrio

namloc1980 wrote: »

If a planet is in its star's habitable zone then by definition so would its moons. Imagine if Jupiter was in the habitable zone, then in theory Europa would be an ocean world.

I think it will depend on other things such as atmospheric pressure, the planets magnetic field, gravity, etc.

For example, Mars has ice water on its surface. It is believe that most of mars is ice covered by a thin layer of red dust (saw that recently on a documentary somewhere) but, even though Mars is still inside the habitable zone, the water remains solid, this is apparently due to planet having a very low atmospheric pressure (i think)...

So for liquid water to exist you need more than just being inside this area.

Going back to Io. When first discovered scientist could not believe that Io was "alive". They couldnt explain how a moonlike Io could be volcanicly activite. Then it turned out that the reason for this was that the planet was pulling the moon towards him, creating some sort of friction, etc etc...

namloc1980

Bohrio wrote: »

I think it will depend on other things such as atmospheric pressure, the planets magnetic field, gravity, etc.

For example, Mars has ice water on its surface. It is believe that most of mars is ice covered by a thin layer of red dust (saw that recently on a documentary somewhere) but, even though Mars is still inside the habitable zone, the water remains solid, this is apparently due to planet having a very low atmospheric pressure (i think)...

So for liquid water to exist you need more than just being inside this area.

Going back to Io. When first discovered scientist could not believe that Io was "alive". They couldnt explain how a moonlike Io could be volcanicly activite. Then it turned out that the reason for this was that the planet was pulling the moon towards him, creating some sort of friction, etc etc...

That doesn't mean you can just exclude moons from the Goldilocks theory. Look at Titan. It has a dense atmosphere with a higher surface pressure than Earth and it has large bodies of liquid methane on it's surface. There's no reason why there couldn't be a Titan like moon around a planet in the habitable zone of a star somewhere with water instead of methane.


Lakes on Titan

Bohrio

namloc1980 wrote: »

That doesn't mean you can just exclude moons from the Goldilocks theory. Look at Titan. It has a dense atmosphere with a higher surface pressure than Earth and it has large bodies of liquid methane on it's surface. There's no reason why there couldn't be a Titan like moon around a planet in the habitable zone of a star somewhere with water instead of methane.


Lakes on Titan

Titans temperature is on average -220 degrees. Despite the fact that the pressure is higher than earth is way too cold. This is the reason why that gas is in a liquid state. This is what the habitable zone is all about. Planets outside this habitable zone are way too cold to sustain liquid water on their surface. There are many things that have to come into play before they can sustain liquid water. What the habitable zone is saying is that, the most likely place to find it is in this area. Remember it refers to Earth like planets, none of the moons and planets out there are earth like, habitable zone is used when searching for earth like planets on neighbouring solar systems.

When I said moons do not follow this principle the same way planets do it doesnt mean that if a moon is inside the habitable zone it wouldnt be a candidate for life, I meant that a moon outside the habitable zone is not the same as a planet outside the habitable zone but if a moon and a planet are inside this zone then both should be suitable for life. Is just that the two examples you put were probably not the most appropiate, thats all.

I believe life can be found outside this zone, I think everyone here does, and I think it might be possible to find liquid water outside the habitable zone, but for this to happen it must be due to a combination of many extraordinary things. But to find an Earth like planet outside the habitable zone... I dont think so tbh