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Momentum is building to explore Venus

nature.com

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Re: Momentum is building to explore Venus

#151

Post by willtim »

autokad wrote: post #118
mandevil wrote: post #91

Earlier quoted context omitted.

The Soviet Union always put more attention on Venus, and the US more on Mars. From what I can tell this dates back to before there were actual space programs, so I strongly suspect this has to do with the science fiction in the respective languages. For example in H.G. Wells 1898 War of the Worlds, the bad guys are from Mars, Edgar Rice Burroghs John Carter series is about Mars, etc. whereas engineer cosmonaut Konsta…

i think the primary reason for US interest in mars is due to the fact that it is much more likely that mars #1) previously contained life and #2) we will be able to find evidence of #1 on mars, vs venus.

I'm not sure there is consensus that Mars is much more likely to have had life. As the article states, Venus had liquid water for 3 billion years versus 400 million for Mars.

Re: Momentum is building to explore Venus

#152

Post by jbay808 »

User23 wrote: post #143
SaberTail wrote: post #54

I'm glad Venus is getting more attention. Mars seems to get the most attention as a place to visit, but we seem to ignore Venus. Venus has a few things going for it that I think make it a better choice for permanent human habitation than Mars. * Venus has nearly Earth-like gravity (8.9 m/s² instead of 9.8 m/s²) * The atmosphere 50 km above the surface is the right temperature for liquid water, and has a similar atmos…

I’m going to go out on a limb and guess that Venus’s high temperatures might be determined by solar radiation and the inverse square law and that its atmosphere is on the consequence side of the expression. That said I entirely agree we should be exploring it!

That's a pretty tenuous limb to go out on.

If that were the case, why is Venus hotter than Mercury, despite being farther away from the sun and having an albedo of 0.75? (Mercury's is about 0.1).

In fact, with its high albedo Venus reflects so much sunlight that it absorbs even less solar energy than Earth does, but despite that, it's hotter than mercury. I am pretty sure that's all due to its atmosphere, and I think every planetary scientist would agree.

Re: Momentum is building to explore Venus

#153

Post by Dylan16807 »

gdubs wrote: post #19
empath75 wrote: post #12

So I had two thoughts while reading it: Is it possible that in the 3 billion years that it had liquid water, Venus evolved advanced life that managed to trigger runaway greenhouse warming? Secondly, is Venus’s atmosphere a worst case scenario for global warming here or is there something that would prevent it happening?

I've often wondered the same thing! A little while back two NASA scientists published a paper on how you would detect the existence of a previous advanced society on Earth. Apparently, over a long time scale it's actually fairly difficult. Not at all my area, but it doesn't seem like we can actually answer that question you posed. It's fascinating. Carl Sagan's COSMOS might be the first time I'd ever heard about Glob…

> A little while back two NASA scientists published a paper on how you would detect the existence of a previous advanced society on Earth. Apparently, over a long time scale it's actually fairly difficult.

Depends on how you define advanced. Anything in geostationary orbit is basically there for the life of the solar system.

Re: Momentum is building to explore Venus

#154

Post by jbay808 »

modzu wrote: post #63
SaberTail wrote: post #54

I'm glad Venus is getting more attention. Mars seems to get the most attention as a place to visit, but we seem to ignore Venus. Venus has a few things going for it that I think make it a better choice for permanent human habitation than Mars. * Venus has nearly Earth-like gravity (8.9 m/s² instead of 9.8 m/s²) * The atmosphere 50 km above the surface is the right temperature for liquid water, and has a similar atmos…

well you said it: we know exactly how to heat up mars (greenhouse gases) but its not so clear how to cool down venus. also mars has water.

Carl Sagan once proposed an interesting concept of terraforming Venus by floating some kind of bacteria in its atmosphere. The bacteria would be constantly drifting down to the surface and dying, but with no predators and ample resources, multiplying quickly enough to replace the losses, and small enough to be kept aloft by air currents. Gradually they would transform the carbon back into solid mass, and bring the atmospheric pressures and temperatures down to earth levels.

Later on in his career he decided against that scheme, but with our progress in biotechnology, it might be the only feasible approach.

https://en.m.wikipedia.org/wiki/Terraforming_of_Venus

Re: Momentum is building to explore Venus

#155

Post by jbay808 »

hsnewman wrote: post #4

I've always wondered why we don't seed it with some biology that can eat the components of the Venusian atmosphere (ie: sulfuric acid, carbon dioxide) to make a more habitable planet over time.

You might already know this, but Carl Sagan proposed exactly that plan.

https://en.m.wikipedia.org/wiki/Terraforming_of_Venus

It would probably require more advanced bioengineering and understanding of ecology and extremophiles than we currently have, but it might still be the only feasible plan.

Re: Momentum is building to explore Venus

#156

Post by User23 »

jbay808 wrote: post #152
User23 wrote: post #143

Earlier quoted context omitted.

I’m going to go out on a limb and guess that Venus’s high temperatures might be determined by solar radiation and the inverse square law and that its atmosphere is on the consequence side of the expression. That said I entirely agree we should be exploring it!

That's a pretty tenuous limb to go out on. If that were the case, why is Venus hotter than Mercury, despite being farther away from the sun and having an albedo of 0.75? (Mercury's is about 0.1). In fact, with its high albedo Venus reflects so much sunlight that it absorbs even less solar energy than Earth does, but despite that, it's hotter than mercury. I am pretty sure that's all due to its atmosphere, and I think…

Maybe because Mercury is much smaller and thus absorbs far less solar radiation and has a far greater surface area to volume ratio allowing it to radiate heat more efficiently?

Venus's atmospheric composition is a consequence of its placement relative to the sun, mass, and volume.

Re: Momentum is building to explore Venus

#157

Post by [deleted] »

killjoywashere wrote: post #150
29athrowaway wrote: post #139

Earlier quoted context omitted.

Venus is closer to Earth.

Given a choice of death by fire and death by cold, death by cold is easier to mitigate against, and is the default problem in space. To survive Venus, you have to first survive the freezing trip to Venus. So you need heating and air conditioning. A lot. Of both. On Mars, you only need the heating systems that got you to Mars. Similar problem for radiation: going to Mars leads to less radiation. Going to Venus increas…

[deleted]

Re: Momentum is building to explore Venus

#158

Post by jbay808 »

User23 wrote: post #156
jbay808 wrote: post #152

Earlier quoted context omitted.

That's a pretty tenuous limb to go out on. If that were the case, why is Venus hotter than Mercury, despite being farther away from the sun and having an albedo of 0.75? (Mercury's is about 0.1). In fact, with its high albedo Venus reflects so much sunlight that it absorbs even less solar energy than Earth does, but despite that, it's hotter than mercury. I am pretty sure that's all due to its atmosphere, and I think…

Maybe because Mercury is much smaller and thus absorbs far less solar radiation and has a far greater surface area to volume ratio allowing it to radiate heat more efficiently? Venus's atmospheric composition is a consequence of its placement relative to the sun, mass, and volume.

Can you explain how volume comes into play?

Solar energy absorption is proportional to surface area, and radiative dissipation is also proportional to surface area.

By the way, Mercury is tidally locked, with a hot side facing the sun all the time. Even that hot side is not as hot as Venus.

There is no question, if you were to strip Venus' atmosphere away, it would cool down tremendously and probably be not much warmer than Earth, or even cooler depending on what albedo it ends up with.

This isn't even an open question or a mystery or an active area of study, by the way. This is very solidly known. I was hoping that by pointing out well-known but surprising facts like that Mercury is colder than Venus, and Earth absorbs more sunlight than Venus, it would encourage you to question your previous standpoint. But if you want to really challenge this point, then please at least do a little more to measure the strength of the limb you are standing on.

Atmospheric composition is not in general a function of mass, volume, and distance to a star, by the way. Due to feedback loops, planets can have multiple stable equilibria, and a history-dependent climate and atmosphere. That is why the concept of terraforming even makes sense. A planet with the size, mass, and location of Venus (or Earth...) can be made into a snowball or a fireball depending on albedo and greenhouse effects, and transitioned from one to the other.

Re: Momentum is building to explore Venus

#159

Post by darkpuma »

hathawsh wrote: post #90
stickydink wrote: post #80

Earlier quoted context omitted.

How would we float a platform at that height?

Most methods of flying things through Earth's lower atmosphere should apply well to Venus at 50 km: balloons, planes, helicopters, etc. To gather energy for rotors, maybe we could siphon heat from below to power a generator or other type of converter. Just playing with ideas. :-)

> "Most methods of flying things through Earth's lower atmosphere should apply well to Venus at 50 km: balloons, planes, helicopters, etc."

The kind of flying logistics needed to operate a station like the one proposed is something that hasn't been demonstrated on Earth, so doing it on Venus seems like one hell of a stretch. The closest match is the airship aircraft carrier experiments, which did not go well. If it can't work reliably on earth, how can it work reliably above Venus?

I think it's one of those things that looks great on paper but in reality has a ton of trouble. I think airships are like that on Earth and on Venus.

Re: Momentum is building to explore Venus

#160

Post by User23 »

jbay808 wrote: post #158
User23 wrote: post #156

Earlier quoted context omitted.

Maybe because Mercury is much smaller and thus absorbs far less solar radiation and has a far greater surface area to volume ratio allowing it to radiate heat more efficiently? Venus's atmospheric composition is a consequence of its placement relative to the sun, mass, and volume.

Can you explain how volume comes into play? Solar energy absorption is proportional to surface area, and radiative dissipation is also proportional to surface area. By the way, Mercury is tidally locked, with a hot side facing the sun all the time. Even that hot side is not as hot as Venus. There is no question, if you were to strip Venus' atmosphere away, it would cool down tremendously and probably be not much warm…

I honestly appreciate the lecture.

How does volume come into play? Well because the higher the surface area to volume ratio of a spheroid body is, the more efficiently it interacts with its surroundings, in this case by radiation.

That said, you haven't said a thing to support the position that Venus's atmosphere is the causal factor, and not a consequence of solar inputs. There's no reason to believe we can learn anything about the Earth's atmosphere from Venus than there is we can from Mercury.

Look this isn't that hard. Venus has the atmosphere it does because it used to absorb far more sunlight than it does now which caused the increased albedo.

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