Alternate explanations for Venus

[Dinwar]

The problem with the 'greenhouse effect' explanation is that the average surface temperature of Venus is far higher (both day and night sides) than the black body radiation would explain (which places a limit on the average temperature of a body). You would need to explain why the average surface temperature (and associated atmospheric temperature) is so much higher than a perfectly absorbtive solid physical body. The high pressure of the atmosphere would enable it to radiate more of the surface heat into space because of its improved conductivity.

Okay. What's your alternative?

So the high surface temperatures are not simply the result of greenhouse effects, but you don't need geothermal heating to explain it either.

There's a simple test: See if there's active tectonics on Venus (far as I recall there's not, but I'll differ to anyone with actual evidence as opposed to vague recollections). If there's no active tectonics the heat source won't be close enough to the surface to make a difference, and this not only becomes unnecessary but it also becomes impossible (or, perhaps more accurately, it will contribute such a small aomount to the heat budget that it may as well be zero).

 

[Damien Evans]

Well, it used to be fantasized to have strange and exotic life under them clouds. I suppose we were all a little disappointed at the news that it makes Hell look like a cool place.



I think the conditions at the poles are not much hotter than the hottest locations on Earth where we find life. So life on Venus is not entirely ruled out, just very unlikely.

Hans

I'm not sure of a place with 400 degrees C, sulphuric acid rain and a crushing atmosphere on earth that has life.

IOW, No.

 

[Dinwar]

I, on the other hand, know of lithophiles, bacteria which live entirely encased in rock. They found 'em in the deep South African mines, the ones that go about 2 miles bgs. Concepts such as "breathing" don't really apply to them; they transfer materials between themselves and the rocks. You'd basically need to melt the planet to kill them. Turning it backing hot and raining sulfur on the surface is irrelevant to them.

There's also extremophiles that live in extremely high-temperature environments, and in extremely high-pressure environments. Not sure if we know of something that does both (I'm not sure how hot hydrothermal vents in the deep ocean get), but it's not unreasonble to assume they do.

Provided Venus was a tad more hospitable a few million years ago, it's not unreasonable to suspect that there's something alive there now. It's equally reasonable to assume not, but right now it's too close to call.

 

[kchiefs]

I've encountered someone who doesn't buy the conventional explanation for why Venus has such hellish conditions. It apparently upsets him for some reason.

So has anyone ever heard of any alternate explanations? Would someone like to speculate wildly and irresponsibly? Might there really be mermaids, sexually aroused women and jungles down there that the landers missed?

My favorite theory is that Venus is a star that didn't fire. Love that one.

EDT: and apparently that's jupiter not venus. I guess I really don't know why someone would doubt the conditions of Venus.

 

[lomiller]

Basically every gas becomes opaque at some depth to at least some segment of the visible/IR spectrum.

I was doing a hypothetical thought experiment, there is no need for us to use a gas that actual exists. That said transparency to visible light isn't actually a requirement. Lapse rate will even out the temperature gradient no matter where the energy is absorbed so it doesn't actually need to be absorbed at the surface and the atmosphere doesn’t need transparent to visible light for the conclusions to hold.

All you really need to know, therefore is how much light is not reflected I.E. absorbed either at the surface or on it’s way though the atmosphere. The other thing you need to know is how hot the surface needs to get before the top of the atmosphere can emit as much IR as there is non-reflected sunlight. A planet will warm/cool until it reaches this equilibrium point.

Assuming the reflectivity of the planet doesn’t change significantly incoming energy is effectively a constant leaving only outgoing IR to warm/cool the planet and this is a function of how opaque the atmosphere is to IR, and greenhouse gasses are any gas that is opaque to IR.

 

[Damien Evans]

I, on the other hand, know of lithophiles, bacteria which live entirely encased in rock. They found 'em in the deep South African mines, the ones that go about 2 miles bgs. Concepts such as "breathing" don't really apply to them; they transfer materials between themselves and the rocks. You'd basically need to melt the planet to kill them. Turning it backing hot and raining sulfur on the surface is irrelevant to them.

There's also extremophiles that live in extremely high-temperature environments, and in extremely high-pressure environments. Not sure if we know of something that does both (I'm not sure how hot hydrothermal vents in the deep ocean get), but it's not unreasonble to assume they do.

Provided Venus was a tad more hospitable a few million years ago, it's not unreasonable to suspect that there's something alive there now. It's equally reasonable to assume not, but right now it's too close to call.

Yeah, but it wasn't. Additionally, there's circumstantial evidence that the entire surface may have melted around 250 mya.

 

[lomiller]

They can create a localized temperature (such as in parts of the surface) somewhat above the black body temperature, but not the entire planet.

Incorrect. Greenhouse gases create *global* surface temperatures that are higher then the planets black body temperature.

As the atmosphere heats, it too becomes a radiator (and effectively part of the surface) and a dense atmosphere can effectively cool by convection. It's not a limitless process, it can only locally tilt the equilibrium so much before other factors work to equalize things.

This seems to fall under "that's not even wrong" It should be obvious that no planet can cool from convection. Planets "cool" by long wave IR escaping out the top of the atmosphere.

Greenhouse effects occur when you get a rather extreme difference in heat absorption between the surface and the atmosphere, and the surface re-radiating additional energy as infrared. when the radiant energy striking the surface is not not strong (as in Venus) you will not get that differential.

Eh? Greenhouse gasses are gasses that are opaque to IR, since they reduce the likelihood of an IR photon escaping the top of the atmosphere the planet warms until sufficient extra IR photons are produced to allow the same number to escape.

 

[MG1962]

Yeah, but it wasn't. Additionally, there's circumstantial evidence that the entire surface may have melted around 250 mya.

Do you recall where you may have read or seen that. I'd be interested in what they have to say

 

[Gr8wight]

I've encountered someone who doesn't buy the conventional explanation for why Venus has such hellish conditions. It apparently upsets him for some reason.

So has anyone ever heard of any alternate explanations? Would someone like to speculate wildly and irresponsibly? Might there really be mermaids, sexually aroused women and jungles down there that the landers missed?

I blame the Goonhogo.

 

[Ziggurat]

I was doing a hypothetical thought experiment, there is no need for us to use a gas that actual exists. That said transparency to visible light isn't actually a requirement. Lapse rate will even out the temperature gradient no matter where the energy is absorbed so it doesn't actually need to be absorbed at the surface and the atmosphere doesn’t need transparent to visible light for the conclusions to hold.

Actually, complete transparency makes the adiabatic lapse rate irrelevant. You get an adiabatic lapse rate when you get vertical convection, and to get any significant vertical convection you need to gain heat from below and lose it from above. You can gain heat at the ground from direct thermal contact, but you can only really lose it at the top from radiation. And if you're completely transparent, you don't radiate.

All you really need to know, therefore is how much light is not reflected I.E. absorbed either at the surface or on it’s way though the atmosphere. The other thing you need to know is how hot the surface needs to get before the top of the atmosphere can emit as much IR as there is non-reflected sunlight. A planet will warm/cool until it reaches this equilibrium point.

Sure, but you need to know how much atmosphere you have to calculate that second part. That's my point: more atmosphere means a hotter surface temp. Composition matters too, but if Venus had the amount of atmosphere we have, even with the composition it currently has, it would be a lot cooler than it is now.

 

[Ziggurat]

Incorrect. Greenhouse gases create *global* surface temperatures that are higher then the planets black body temperature.



This seems to fall under "that's not even wrong" It should be obvious that no planet can cool from convection. Planets "cool" by long wave IR escaping out the top of the atmosphere.

The surface of a planet most certainly CAN cool by convection. Below the point at which the atmosphere becomes opaque to IR, that can easily be the dominant cooling mechanism. That convection brings warm gasses up to high altitudes where it can then radiate heat into space, but the transfer of heat from the ground to the upper atmosphere very much involves convection. And since we're talking about surface temperatures, it's wrong to exclude convection from the discussion.

 

[Travis]

My favorite theory is that Venus is a star that didn't fire. Love that one.

EDT: and apparently that's jupiter not venus. I guess I really don't know why someone would doubt the conditions of Venus.

This person seems to be rather certain that it doesn't matter what type of gasses are in an atmosphere in regards to how much heat it can trap.

 

[brodski]

It apparently upsets him for some reason.

Does he tend to rant about Al Gore a lot?

 

[Travis]

Does he tend to rant about Al Gore a lot?

Yes. Says he should be in prison for some reason.

 

[Zeuzzz]

Its quite obviously the Venicians who have mastered weather control and are conspiring to stop silly humans like ourselves ruining their planet by making it as inhospitable as possible for us.

 

[This is The End]

BTW I frequently come across people attempting to use Boyles laws to claim that increasing temperature will increase atmospheric pressure. It WILL NOT. The classic gas laws apply to a closed chamber. Atmospheric gas pressure is caused entirely by the weight of a column of gas. If the gas is heated, it expands farther into space (unless it redistributes in the case of local heating) but it will NOT increase pressure just because the temperature increased.

Are you taking gravity into account? Are you saying that increasing the temperature will not increase atmospheric pressure at all? Zero increase in pressure no matter how much of an increase in temperature?

 

[MRC_Hans]

Are you taking gravity into account? Are you saying that increasing the temperature will not increase atmospheric pressure at all? Zero increase in pressure no matter how much of an increase in temperature?

Interesting question. Now, basically a temperature increase will create a taller column of air, with a correspondingly lower density (since it is the same mass of air), so the pressure will be the same. However, there is such a thing as the free air gradient of gravity, that is, as you move away from a body, its gravitaional pull will diminish.

So if the density (but not the mass) of the atmosphere is reduced, the top layers will be in lower gravity, so, all else alike, an increased temperature should result in a slightly reduced pressure.

Hans

 

[whatthebutlersaw]

In middle school I asked our teacher how the idea that extraterrestrial life would necessarily come from Mars came from, and she told us that in our own solar system, the planet closest to the conditions on earth was Mars. Although adding that it still was damn far off, of course, and that this was why writers liked to use it. As an aside she explained that Venus was more like Earth, than Mars, in terms of size, mass, density and gravity and that it probably was an equally good candidate for life.

Maybe your relative was told the same thing by their middle school teacher? I have noticed that a lot of people put a lot more faith in their middle school teachers than in professors of the same subjects.

I have friends and acquaintances who will not be convinced that certain concepts that were simplified to be teachable in middle school are actually more complicated once you reach a post grad level. Everything their grade school teacher said is gospel truth and knowledge never changes with more information.

Venus is sometimes referred to as the "Greenhouse Planet" as it has been believed that the reason for the hot conditions is a runaway greenhouse effect. Maybe your relative has heard this and envisioned the kind of hothouse that grows tomatoes in March?

 

[brodski]

Yes. Says he should be in prison for some reason.

That’s ‘cos Alg’ore (to give him his transliterated Venusian name) is leading the vanguard of an invasion. His first task is to ensure a more hospitable environment for his fellow Venusians.

 

[Dinwar]

Yeah, but it wasn't. Additionally, there's circumstantial evidence that the entire surface may have melted around 250 mya.

I'd also be interested. 250 ma? Sounds like someone's looking for evidence that the Permian Mass Extinction was caused by asteroid impacts. I'm not saying that you're wrong, just that this sends up a warning flag in my mind.

I have friends and acquaintances who will not be convinced that certain concepts that were simplified to be teachable in middle school are actually more complicated once you reach a post grad level. Everything their grade school teacher said is gospel truth and knowledge never changes with more information.

I've found that a lot of psuedoscience can be explained this way...