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 Konstantin Feoktsitov wrote that when he was 10 (~1936) he came to a sad realization. Since going into space was better than everything else, any effort he put into anything other than going into space was wasted effort, BUT by the time he got the Ph.D he would need to contribute to that program men would already be on Venus, so he would never be the first to anything[1]. I don't know Russian language sci-fi well enough to guess what the source for this (or maybe was it Tsiolkovsky? dunno), but that suggests to me that the Soviet interest in Venus wasn't just because the US had a stranglehold on Mars or anything like that, it was because Venus spoke to them in the same way that Mars did to Americans. Any Russian speakers can confirm?

[1]: He ended up as Sergei Korolev's right hand man, and was tasked by the Chief Designer himself with stripping all the safety devices out of the Vostok capsule so that it could hold three men [Vokshod]. When Feoktistov objected, Korolev told him if he did a good job, he'd get to take it into space, and Feoktistov accepted the challenge.

One reason could be that early soviet space probes had big issues with durability, generally caused by their unreliable pressurized & gas cooled (generally pure nitrogen at atmospheric pressure) electronics - US generally used much more reliable vacuum rated electronics).

For this the signifficantly shorter flight time to Venus is a big advantage, not to mention that a lander wont survive for long anyway, further reducing issues with probe longevity.

Russia got the first probe on Venus, so maybe it’s success being celebrated and reinforcing more interest.

I just saw an episode of the new BBC series Planets talking about this. One thing they mentioned was that it was seriously suggested even in the 40’s that there could be rainforests and a fertile surface underneath the cloud cover on Venus. Could see the mystery in particular being an interesting thing to grow up hearing about.

Here is a book from the soviet era, about Venus

https://www.goodreads.com/book/show/23302599

"Тайна утренней зари"/"The Mystery of the Dawn"/"Taina Luceafărului".

As for their space program, I do believe they had almost similar investment for Venus and Mars, just Venus was more approachable and the missions were more fruitful(?). They canceled some Mars and Venus programs in time. Some wikipedia page about USSR space program:

https://en.wikipedia.org/wiki/Soviet_space_program

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.

On the other hand, NASA’s (recent!) insistence that everything be justified in terms of the search for life is not shared by everybody.

I for example really don’t care at all about potential microbial life vs. extending the domain of earth’s life through permanent settlement and terraformation of both Mars and Venus.

The cloud cover on Venus is so thick it could contain life right now. The belief that it’s necessarily barren due to extreme conditions predates the widespread knowledge of extremophile earthbound life. If you gave me better than even odds that there is life on Venus I’d take them.

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.

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.

We don't need to cool it down. We could float a platform about 49.5 km above the surface of Venus, where the temperature and pressure nearly match the earth at sea level. To launch a probe, we could simply drop it from the platform.

This article about Venus is very enlightening: https://en.wikipedia.org/wiki/Atmosphere_of_Venus

my comment was in response to parent saying venus was a better candidate for colonization than mars.

but i am totally on board with exploring venus, although im not convinced the atmospheric issues are significantly lesser than the surface, just different (hurricane winds, sulfuric acid, etc)

How would we float a platform at that height?

By attaching it to a steel balloon filled with breathing gas, which can provide lift in the Venusian atmosphere.

Inside the baloon you get a really nice habitat with the correct Temperature, pressure and gas composition for humans to live in.

Other than a basically unlimited supply of CO2 however, what would the advantage be compared to a just a space station?

With Mars, you can mine building materials from the surface.

CO2 has carbon in it. Strip off the oxygen to breathe, the rest makes very strong building material.

Attach hydrogen, you get rocket fuel. Or plastic. Bind in some nitrogen, you can have proteins. There is probably silane lower down; send down a balloon to collect it, for silicon. Or all the way to the surface, to collect rocks.

Nuke power is totally practical there; no shielding needed, or worry about leaks; you just hang it a mile below your living-space balloons.

You can live there long term since there is gravity.

Also, there is a lot of protection from radiation, from the mass of atmosphere above you and the mass of the planet below you.

Is Mars' gravity too low for long-term habitation?

I know that we know that zero-G is a negative, but do we have any idea if it's a threshold that needs to be reached, a linear response to G-force that scales from untenable to fine, etc?

I would imagine that it's going to be a gradient. Just like any other form of exercise, the more effort you put in, the more positive effect. Humans would need to put in much less effort on Mars. Once we are spread across the solar system there will probably new exercise systems for 0 and .3 G environments.

I am also unsure about how it would affect the prenatal development as the way "layering" occurs is highly dependent on gravity.

The only way to really find out is to go there and live for a while :)

We can float things in the earth atmosphere at sea level. My completely ignorant prior is that we should be able to do it there too, if the temp and pressure are the same.

Much better: the air at normal pressure is much denser, so ordinary breathing air supports a balloon.

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. :-)

Send your mining robot below. It cools itself with phase change liquids, but also opens high pressure tanks to the 90 bar atmosphere. When you hoist it back, just plug those pressure tanks in to turbines connected to generators. That wouldn't be a huge amount of power, but maybe wildcat prospectors could operate like that in the early days.

Would it be enough energy to compensate for the work you'd need to do to lift the robot back up? Presumably there's some energy gained from sending it down but not enough to bring it back, especially since it is coming back heavier. I just don't know how to work the math on that.

Lisa, in this house we respect the laws of thermodynamics!

Why not use liquid oxygen as the phase change liquid? Then the gas could be caught in a bladder tethered to the ground. When it comes time to ascend, use it as a balloon?

There must be some way to exploit the temperature difference between the surface and 50km up, without mega-engineering.

Hmm, maybe some variant of a solar updraft tower where hot lower atmosphere gases are siphoned up to generate power and heat lifting balloons?

OK that's just opened my eyes a little. It sounds so obvious - if the atmospheric pressure is the same then yes we should be able to fly aircraft. Maybe not with the engines used on Earth but in principle at least. Slightly terrifying that a loss of power should result in a 50km drop to a crushing hot acid death, but probably not much worse in reality to smashing into rock like you would on earth. Very interesting comment - thanks!

> "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.

Have you heard of Murphy's law?

Floating above Venus provides the benefits of a gravity well, but there's the danger of sudden buoyancy loss.

Everything about exploring space and planets is a rebut to Murphy's law.

Very cool NASA video: https://www.youtube.com/watch?v=0az7DEwG68A

We don't need to cool Venus down, but in a few hundred years we might need to cool the earth, so learning how to do that on Venus might be a good idea.

Just because you are at sea level, you can't suddenly float stuff in the air. I like your optimism though. :) I was imaging a floating city like cloud city in star wars [0].

[0] https://www.starwars.com/databank/cloud-city

This is a bit more thought out than perhaps OP applied, several theretical investigations have been done into floating cities on venus and it more or less comes down to building blimps out of gasses like nitrogen and oxygen. Because the venus atmosphere is so dense, this would actually work.

I would love to read about those investigations. Do you have any pointers?

What if your float thing pops? Everyone sinks and dies??

Mars' atmosphere is 95.3% carbon dioxide, which means that the problem we have to solve is not "how do we inject craptons of greenhouse gas into the atmosphere" but "how do we stop the solar wind from stripping away the atmosphere," which is not a problem we have a clear idea as to how to solve.

Contrary to popular belief, the rate that solar wind strips Mars atmosphere is so ridiculously low that we can comfortably kick the problem of stopping it down the road a few hundred thousand years. If we manage to generate a habitable climate by terraforming with additional heat and atmosphere, adding a magnetic field becomes a very low priority.

Venus has more carbon dioxide in its atmosphere and has the added bonus of the surface being pressurized like you are deep sea diving....

Sure but we got to survive till we could clear carbon dioxide

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

I wouldn't say we know exactly how to heat up Mars. Without a magnetic field, any atmosphere we conjure out of the polar regions would escape into space. We are far, far closer to completely reversing the effects of climate change on Earth than we are to teraforming Mars.

Yeah, but I believe it takes ~10 million years for a Mars atmosphere to escape.

So it could be entirely feasible to treat the Mars atmosphere as a tire, that you "inflate" every now and then to keep the pressure constant.

That would be a very wasteful use of precious volatiles though.

But we could kick up a magnetic field with superconducting rings around the poles though.

Losing 0.00001% per year is not "very wasteful" to me.

There are ideas for putting up a magnetic field based on putting a contraption in whichever L1/L2... point is between Mars and the Sun.

Convert that into tonnes, and then calculate how much biosphere could be supported with that volatile weight. And once it is gone, it is gone. It’s not a renewable resource. You’d be trading away billions of years of future Martian biosphere.

Oxygen and nitrogen are hardly rare substances in the solar system, and probably not even on Mars. There are near infinite number of "tonnes" on Mars.

Besides, if the alternative is to leave Mars dead forever, I'd rather let it live for a billion years.

But maybe I don't get what your alternative is, if any?

Nitrogen and hydrogen are basically only really available via volatiles. They aren’t components of common minerals in the rocks.

The alternative is to spin up a magnetic field with superconducting magnets to protect that atmosphere from the solar wind.

well obviously we'd need orbiters that generate an artificial magnetic field my man!

http://www.nifs.ac.jp/report/NIFS-886.pdf

We do know how to cool Venus. Build a sun shade. It’s an old idea, and a simple idea, and there’s lots of engineering literature on how it can be reasonably accomplished.

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.

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.

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.

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 increases radiation. So in Venus orbit, you need more shielding than you need at low Earth orbit. On Mars, you need less.

There's another commentor suggesting floating in steel balloons. Um, weather is going to be rough. Really, really rough. The mass of building materials necessary to survive the storms strikes me as likely deal-breaker. Never mind the complete lack of light.

I don't know if everything is harder on Venus, but most of the first-order issues are substantially harder.

> death by cold is [...] the default problem in space

well, actually... you need lower-energy atoms for higher-energy ones to rub against to carry away the excess. there's not many atoms in vacuum, so the default problem in space is overheating. see eg. https://en.wikipedia.org/wiki/External_Active_Thermal_Contro... or https://en.wikipedia.org/wiki/Liquid_cooling_and_ventilation...

> you have to first survive the freezing trip to Venus. So you need heating and air conditioning. A lot. Of both.

the heating part is very, very wrong. the AC would be Atmospheric Control, see https://en.wikipedia.org/wiki/International_Space_Station#Sy....

> you need lower-energy atoms for higher-energy ones to rub against to carry away the excess.

Wat? Conductive and convective heat loss are certainly things, but heat radiates away too, and that is exactly how the systems you describe perform. The fact that the hull doesn't radiate much heat away itself isn't suprising, but all things being equal, the system still dies cold. Put the other way: if heat was truly the problem, is there any outcome where ISS melts, short of re-entry?

> s there any outcome where ISS melts, short of re-entry?

i don't think so. should the cooling system fail, the sources of heat (mechanical work, biological processes) would cease way before that.