Drake Equation??? Humbug!!!!!

lunarmark · 2004-07-01 07:25:37

indeed it doesnt need a liquid core for a planet to have a magnetic field, [but] there is a big diffrerence between a token weak magnetic field and a magnetic field capable of diverting away radiation/ions. The earth has quite a strong magnetic field compared to most other planets, I firmly believe that in the absence of a magnetic field, deep rock/water shielding is about the only other way of protecting life forms - hardly an ideal enviroment for intellient life.

I cant imagine any chemical based life form surviving for very long anywhere near a gas giant like Jupiter.

The radiation in space is so strong it even discolours the rocks . (Even on our moon (which enjoys some protection from earths magnetic/electric field), the soil is white on newer impact ejecta, and grey/black on older soil).

Atmosphere and magnetic field, are in my view a must for life.

Cassini will tell us a whole lot more about this subject, I cannot wait for the results it will be amazing!

Actually the more I think about it, what the Cassini probe tells us will have more effect on the Drake equation than anyhting in a long while, magnetic readings, rock structure, dust composition and the surface of Titan - its like christmas!!!

ERRORIST · 2004-07-01 09:38:49

Does the Drake Equation account for fossils?????

lunarmark · 2004-07-05 02:55:49

In what context?

ERRORIST · 2004-07-05 08:40:36

Any senerio???

lunarmark · 2004-07-06 02:47:20

well, fossils would be around both on an 'extinct planet' that had life, and a planet that currently has life, so I cant see as it would effect the equation in any way.

if we said roughly how many planets contain fossils, then it would be all the planets that once had and currently have any sort of life, so likley there are many worlds with a fossil record, I am just not convinved that there are many worlds with intellegent life like ours that can actually communicate! the numbers are too small, unless something happens to greatly increase the odds of life forming we are still in the single figures for worlds like ours.

I heard on the news recently that our solar system might only have been formed the way it is because there was a binary star system right next to our presolar disk, which influenced the formation of our solar system, yet more potential evidence that we live on quite a rare planet!?

chat · 2004-07-06 05:01:27

lunarmark,

If we are looking for some other species to communicate with, i think the numbers will be only a few 100 in the entire universe.

If the earth is a normal place and even a 1 in a million happening, and life took a normal route on earth to create intelligence.
Then finding another species will probably never happen.

In a 4+ billion year planet life span, we have been here able to communicate for 75 years.

Adding those 2 odds together makes a very small number.

Roughly 1 place has intelligent species in existence at this time in 1million billion.
Or roughly 1 place in every 5000 galaxies have a species able to communicate with us.

The universe will probably have life everywhere it can be, but finding something like us that can talk back existing now will be a long search.

And if that 1 in a million is more like 1 in 100 million then we are probably alone, or as close to being alone as possible.

Unless the moons are happening places

P.S. Titan is shaping up to be that methane lake and snow storm and rain place
Can't wait for the view

lunarmark · 2004-07-06 05:26:13

Chat,

I agree, that's about my conclusion, the odds are just too high with current understanding (unless we suddenly find 50 earth like planets on our doorstep!).

The fact of the matter is, we have never recieved any contact from aliens (unless you believe the crack-pots so one can only conclude that we are cetainly in a quiet spot if not alone.

Personally I get worried when equations like the Drake predict just a few dozen possibilities, you only have to get the theory slightly wrong to make a massive difference to the total.

So on that basis we should continue with things like SETI but not expect to 'make contact' EVER.

Titan is indeed shaping up to be a fascinating place! the very latest pictures are superb, its looking remarkably like Earth in someways, so the 'Titan is like a primitive earth' theory might prove to be true after all!

It certainly is the most interesting moon/planet in the entire solar system besides our own, much more going on than mars thats for sure!

Arn't we just so lucky to live at the time we do? with all these great discoveries happening.

Certainly with all the wars and stuff going on in the world, its comforting to know that mankind hasnt gone completley mad!

chat · 2004-07-06 17:39:22

lunarmark

It wouldn't shock me to see Titan be much more earth like than we think.

If Titan does have liquid methane that doesn't freeze, and it rains methane, and has been like it is now for billions of years.
Then we might be shocked to find a totally alien set of life forms there.
Wouldn't that be a world shaker to find life on Titan.

I agree that the odds don't look great with our current understanding of solar system mechanics, and life span of humans vs the earthspan, and techspan vs humanspan.

Lets hope we are wrong and earth like planets and moons are everywhere.
Or Titan like places that have life might be the rule, and we are the exception.

I think the answer to how frequent earth like places exist will come in the 10 to 50 year time frame.
Once we can see fuzzy pictures of earth sized places, the answers will come fast.
We just have to make sure we look in the orbits of other gas planets also

I think SETI is a must, if we are alone then that is what we are.
But if we stop listening we are less than alone, we are lost.

We might listen for 500 years to static, only to discover that radio wasn't the way to communicate, or the nearest signal was 501 years away.
Or tomorrow a signal arrives and alters our thinking.
Either way we best have our ears open.

lunarmark · 2004-07-07 02:48:43

Titan will be very interesting, especially when you think it will be only the second planet we have visited with a decent atmosphere (excluding mars - it being a near vacuume).

I have to say, my thoughts are that planets tend to be a little more dull than they first seem, earth looks green and lush from space, but if you landed in the Sahara... you'd think it barren.

So I am not expecting to see pictures of a methane beach, with waves lapping directly in front of the camera. More likley it will be a moon cratered landscape a cross between Mars and a foggy day in Scotland ! and all we will see is a misty rock if we are lucky. But there is just that chance that we will see 'Somthing Wonderful' as Aurthur C Clarke said in '2010' ...

:;):

chat · 2004-07-07 17:39:18

lunarmark,

Well as long as we don't see a bagpipe band in the mist

I will be happy to see the probe just make it to the surface and take any picture, but if that first picture is plaid in color them I'm declaring titan Scottish

lunarmark · 2004-07-08 06:26:32

Aye laddie, titan i'll be misty alreight. We Dunnay know what yer will face when wee git there.

Certainly will be a change to see somewhere else like scotland, - only warmer ! <sarcastic moi?>

lunarmark · 2004-08-26 09:39:30

For info...

They have just discovered an exo planet with earthlike orbit (14 times bigger but in a similar orbit) Nowhere near being a gas giant.

http://news.bbc.co.uk/1/hi/sci/tech/3599496.stm]new earthlike exoplanet click here

Now this has implications!

SpaceNut · 2004-08-26 12:24:45

Rather than looking for planets and then wondering if life might be there. How about say how large can our planet be in the inhabitable zone from the sun and still support life.

lunarmark · 2004-08-27 04:10:02

Gravity would be the deciding factor, if a planet was too big it would have such a gravitational pull, that it would not allow life (as we know it to evolve). 14 times the gravity would be quite extreeme, I suspect that even water based life would have it's problems..

The other thing about a larger planet is that it would still be very geologically active, and a planet 14 times the size of Earth would be [very] volcanic...

Just right for starting life... But intelligent life might take too long to evolve before the star goes unstable, just a thought.

lunarmark · 2004-09-01 06:54:17

It seems that even a 'bigger earth', is bad news for life...

Extracted from a post by Sterling Webb,

Imagine an "Earth" exactly twice the diameter of our Earth: ~16,000 miles across. It would have four times the surface, eight times the volume, and 12 times the mass. It's surface gravity would be 3 times greater. The escape velocity from the surface would 2.45 times greater.
Because it would have 12 times the water but only four times the surface, the average ocean depth would be about 9000 meters! The pressure at the depths of these oceans would be about 3000 atmospheres. The highest mountains possible would be about 4000 meters, so if you were the greatest mountain climber on the 'SuperEarth', standing on the top of SuperEarth's highest mountain, you would have 5000 meters of water above you!

So No continents. The SuperEarth is a WaterWorld!

On our Earth, the crust is about 30 kilometers thick, but the lithosphere (rocks that stay stiff and not slushy and
slippy) is about 75 kilometers, so the Earth's lithosphere contains all the crust and the top part of the mantle.

The crust of the SuperEarth would be about 90 km thick, but the lithosphere would only be about 30 kilometers thick. This means that it would be very difficult to sink pieces of crust and equally difficult to bring deep basalt magmas to the surface.
On the other hand, the SuperEarth's silicate crust would be recylced very rapidly with lots of local vulcanism and "hotspots" and have a very similar composition everywhere. The only weathering that would be possible would be chemical, because all the volitiles are released into the oceans rather than the atmosphere.

The only question we can't answer is how hot or cold a SuperEarth would be, since that depends on the distance to its Sun. Too far away and the oceans turn to ice, even 'heavy Ice' which sinks. Too close and the oceans boil away, creating a SuperVenus. Even that is problematical, since it's hard to strip the atmosphere and oceans away from a planet that has an escape velocity of 27,400 meters per second!

So a bigger Earth is not just a bigger Earth. Knowing that somebody will ask how big a bigger Earth has to be before there's no land at all, just oceans, the answer is: somewhere between 2-1/2 and 3 Earth masses is the point where the median ocean depths equal the height of the highest possible mountain. Glub, glub!

chat · 2004-09-02 06:30:22

lunarmark,

It's tough to imagine an earth at 2x or 2.5 x it's size.

I would imagine that a planet much larger than earth would have very different atmospheric conditions.
Water might not exist for long on such a planet due to the increased internal heat produced from the planet.

The product of a larger earth i believe would be a larger Venus.
Conversion of water into co2 and loss of hydrogen would make a larger earth just like Venus.

A larger Venus sort of planet at 2 to 5 au might be a good candidate for life though, so those larger earth type of planets might end up hosting life at further distances.

Our Venus at 2 to 5 au would probably be a good candidate.

The 1 AU area seems so limiting for life, when you factor in moons, thicker than earth atmospheres, larger than earth planets and internal flexing of distant objects.
It makes for a much wider search area for life sustaining places.
When we have the tools to look at other solar systems we best look at everything we see.

chat · 2004-09-04 04:46:59

lunarmark,

After a bit more thought on the 2x earth, i think it all comes down to location and initial thickness of the atmosphere.

A 2x earth at 1au becomes a nasty Venus sort of planet.
But a 2x earth at a few au distances becomes a giant titan with its hydro carbon soup.
At 2 or maybe 3au the 2x earth stays as a wet earthlike world.

It seems to show that the range of earthlike worlds is very limited to 1 to say 3 au distance to maintain an earthlike place with life.
Even without a moon finding one in such a limited location will be rare, and one with a good sized moon at the right location a 1 in a billion shot.
Still thats 250 in our galaxy

Those moons are looking more like the universes places for life, and the earthlike places the freaks.

Shaun Barrett · 2004-09-04 08:43:52

Hi Lunarmark!
Who is this Sterling Webb person? I can't place him.
And why, in the case of his hypothetical planet exactly twice the diameter of Earth, should the mass be 12 times greater when the volume is only 8 times as great? Why does the average density of the hypothetical planet have to be 1.5 times Earth's average density?
Even if the planet is 12 times the mass of Earth, must it necessarily have 12 times the amount of water? What if it formed in a different and drier part of its proto-stellar system?
If the crust of this SuperEarth is 90 km deep but the lithosphere is only 30 km deep, then the lower 60 km of the crust is 'slushy' and deformable. How can crust be 'slushy' and deformable and still be called crust? And, if Earth's lithosphere (stiff and non-deformable) is 75 km deep, while SuperEarth's is only 30 km, why should it be harder to exchange material between the depths and the surface in the case of the SuperEarth?

It seems to me more likely that the SuperEarth's mass will be about 8 times Earth's and its surface gravity will be about twice that of Earth. SuperEarth should be more volcanically active but not necessarily to the point of making life difficult. Besides, what if SuperEarth is significantly older than Earth and its volcanism has died down to more terrestrial levels?
Earth's crust is able to sustain a differential of some 16 km between the deepest ocean trench and the highest mountain peak. SuperEarth, with twice the surface gravity, should be able to sustain a differential of some 8 km. With 8 times the water and 4 times the surface area, the average ocean depth might be twice that of Earth, or about 7.5 km. According to these rough figures, there should be significant percentage of SuperEarth above sea-level, even if you go by averages alone.
But averages can be misleading and percentages confusing. Here on Earth, 70% of the surface is water-covered and 30% is dry land. On SuperEarth, even if 92.5% of the surface is water-covered, its dry land area will be equal to the dry land area on Earth because SuperEarth is so much bigger.

Maybe I'm wrong but it just looks as though Sterling Webb is choosing the worst case scenario in every factor examined. The possibilities are more varied than he seems to suggest. He assumes SuperEarth's average density is 1.5 times Earth's, while I took it be equal to Earth's. What if it turned out to be closer to Mars' average density? SuperEarth's mass would then be some 5.67 Earth masses and its surface gravity 'only' 1.42 times that of Earth. Its crust might then be expected to sustain a topographical differential in height of over 11 km, which could easily result in maybe twice the actual area of dry land on SuperEarth as on Earth.
Quite a different picture.

MarsDog · 2004-09-05 01:43:19

Other life will also watch and listen, but likely not reveal itself, except to attack.
First contact might be Pluto sized, crashing into, and sterilizing Earth.
-
If we saw violent Alien Television news, it would be prudent to sneak up,
and destroy the Aliens, as a preventative war (something like the Middle East war).

chat · 2004-09-05 03:54:12

Shaun,

I believe a 2x earth with a 1 bar atmosphere at 1 au orbit with a sun similar to ours has no chance of having life.
The extra solar heat retention and internal heating will slowly make a 2x Venus.

Since we know so little about the density of planet arrangement we can only guess at what happened in our solar system.

So many factor come into play on a 2x earth to try and understand what would happen.

1. sun type.
2. earth 2x distance from it.
3. initial atmosphere of earth 2x
4. density of earth 2x
5. water quantity of earth 2x

If we guess at earth 2x having to be at a mars sort of orbit with similar water and atmosphere as earth then the density should be more like mars.

Beyond the 2.5x size we start to get so much internal activity that no matter where you put it in orbit, it either becomes a Venus sort of world or a titan sort of world.

It does show that earth like world are very limited in orbit and size they can be.

Good point about the extra water still leaving the extra amount of land.

Shaun Barrett · 2004-09-05 18:33:55

Hi Chat!
It looks like you and I are using the same criteria to justify two opposing standpoints!
You're saying there's too much variability in the possible physical parameters for life on a SuperEarth (linear domensions 2x) to be likely, which is probably true, but I'm simply saying that the parameters could be just right and life could develop on such a planet.
All I'm saying is there's no obvious show-stopper, in my view, which precludes all possibility of life.

You say in your last post that a 2x Earth, with a 1 bar atmosphere, at 1 a.u. around a Sun-like star, will experience extra solar heat retention. I've been thinking about that but I can't see why it should be so. Can you enlighten me on this point?
Another point I'd like to bring up, concerns the extra volcanism. This SuperEarth has 8x the volume but only 4x the area, so one might expect volcanism to be twice as common at the surface. Presumably, this means outgassing of about twice as much CO2 per unit area, which might be expected to increase the greenhouse effect, as compared to Earth. However, we've accepted the possibility, for argument's sake, that SuperEarth may well have 8x the volume of water but only 4x the surface area, compared to Earth. This, we decided, should lead to a greater percentage of SuperEarth being water covered - perhaps 90% or more. That volume of water, together with its greater surface area, should be very efficient at mopping up atmospheric CO2 and sequestering it away as carbonate rocks, which makes me think SuperEarth might tend to have a lower concentration of that gas in its air than we have here on Earth. While this dearth of CO2 would be offset to some extent by the generally higher humidity on SuperEarth (water vapour being an effective greenhouse gas in its own right), I can imagine our hypothetical planet, at 1 a.u., being somewhat cooler than Earth ... not warmer.

chat · 2004-09-06 04:41:54

Shaun,

I agree if we keep throwing the dice the 2x earth will end up in the right orbit and have the right makeup to sustain life.

I was doing more of a thought process on where such a planet must be to be in the right place.
And i agree, its tough to get a handle on what a 2x earth would be like.

At 1 au the 2x earth should receive 2x the amount of sunlight due to its size, as compared to earth.
Not a big factor on the planet itself, but a big factor on the atmosphere if its similar to earths.

The additional co2 production from volcanism might be mopped up by the more robust system.

That is a good point i hadn't given much thought to, and might allow a larger earth to be in a wider and narrower orbit for sustaining life.

My initial thought was at 2x light an additional 3% co2 and additional water vapor, the 2x earth slowly overheats.

But factoring in the more robust system on earth2x, those sort of planets might be better candidates for life than earth.

Gennaro · 2004-09-06 09:34:04

I just feel bad for the guys living on a 2x Earth. How are they going to achieve spaceflight?

John Creighton · 2004-09-06 09:57:44

I just feel bad for the guys living on a 2x Earth. How are they going to achieve spaceflight?

antimatter

chat · 2004-09-06 15:26:19

Gennaro,

With that much Earth will they ever need to go to space?
Texas on earth x2 will take one long drive to get through *lol*

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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Re: Drake Equation??? Humbug!!!!!

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