6 ms·

This article really makes me wonder why mars is such a focus of space exploration right now, when Venus seems to be a much more interesting target: - close

This article really makes me wonder why mars is such a focus of space exploration right now, when Venus seems to be a much more interesting target: - closer (or so I believe, and according to [1]) - more atmosphere to do stuff with - more natural resources to collect - more energy to collect Granted the conditions are rough down there (pressure, temperature), but are they really rougher than those found on Mars. Different, granted, but harder? Also, depending where you place yourself in the atmosphere, conditions might actually not be that bad. Is landing a long lasting robot on Venus really harder than doing it on Mars? [1] https://sciencing.com/mars-venus-closer-earth-4940.html https://sciencing.com/mars-venus-closer-earth-4940.html

jacobush 7y ago
On Mars, you need to heat from severe arctic temperatures (and sometimes not at all, in mid summer) and you need some sort of pressure dome. (But you don't need 1 atmosphere.) On Venus you need some way to pump away a heat making lead melt. So... yeah, definitely much more harsh. We don't even have the technology for such heat pumps, even though I guess they are theoretically possible. You'd need exotic materials and a nuclear plant I assume. I the atmosphere though of Venus though, it gets very interesting. Apparently it's about 1 (Earth) atmosphere pressure at a temperature of about 20 Celsius (70 F), so we could have floating cities! (But the cities would have to be resistant to sulfuric acid and we would have to bring our own water.)
- roywiggins 7y ago
  Probably the best bet for Venus surface exploration is some kind of high-temperature integrated circuit. There's already some work on that sort of thing for the innards of jet engines and the like.
  - jacobush 7y ago
    Agreed! I was thinking what you would need for a manned mission. But definitely, electronics operating at that temperature is very interesting and maybe not impossible. I have heard random ideas about mechanical contraptions, too. I wonder about power though. An electronic design could maybe run on some sort of non-rechargeable battery which could deal with the temperature. But if you wanted serious power, a molten-salt reactor would be very interesting. It would I guess "only" be extremely expensive, but maybe not impossible. The interesting thing is that you basically don't need any safety because the reactor is inert and not radiating until you start it. All in all though, I think blimps at various depths are more practical.
  - Robotbeat 7y ago
    Yup. I did some work on that for a Venus lander when I was an intern, which is published here: https://ntrs.nasa.gov/search.jsp?R=20150002090 https://ntrs.nasa.gov/search.jsp?R=20150002090
- pharke 7y ago
  I'm not sure you'd need to bring your own water, the sulfuric acid is produced in the upper atmosphere when sunlight splits carbon dioxide into carbon monoxide and oxygen which then react with water vapour and sulphur dioxide. We could harvest that water vapour and CO2 to produce oxygen, water, and rocket fuel. We've got lots of experience with sulfuric acid and resistant materials are rather common place plastics (including teflon) and stainless steel. I have no idea why there hasn't been more of an effort to get a flying robotic probe to Venus. I think it would be mindblowing to have high res pictures and video of the upper atmosphere with a bright sun over head and an endless sea of clouds.
roywiggins 7y ago
The longest lasting robot on Venus was Venera 12, which lasted 110 minutes. Venus is hard because it melts electronic circuits. On Mars, you just need a heating element to stop yourself freezing. (if you can make something work in a vacuum, it will probably work just fine on Mars. And we have lots of experience working in vacuum!)
- gene-h 7y ago
  The Venera landers stopped functioning because the solder in their circuits melted. Higher temperature solder could have been used preventing this problem, but the key issue is that silicon no longer functions as a semiconductor at these temperatures. Silicon carbide still works as one though and we're now starting to see silicon carbide electronic circuits and foundry processes to make them.
JumpCrisscross 7y ago
> closer (or so I believe, and according to [1]) Venus is physically closer, but that isn't the best measure of "closeness" for propulsive space travel. The right metric is delta-v, "a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver" [1]. Ignoring aerobraking, it takes almost 5x the energy to get to Venus compared to Mars [2]. (Side note, to drive the point home: it's easier to boost objects out of the Solar System, from Earth, than to send them into the Sun.) [1] https://en.m.wikipedia.org/wiki/Delta-v https://en.m.wikipedia.org/wiki/Delta-v [2] https://www.dailymail.co.uk/sciencetech/article-2679107/Mind-interplanetary-gap-Space-subway-map-reveals-travel-planets-moons-solar-Tube.html https://www.dailymail.co.uk/sciencetech/article-2679107/Mind...
- travisporter 7y ago
  Actually, I found that it is not as drastic as 5x on this site. https://space.stackexchange.com/questions/2156/does-a-mission-to-venus-orbit-require-less-propellant-than-a-similar-mission-to https://space.stackexchange.com/questions/2156/does-a-missio...
  - JumpCrisscross 7y ago
    > it is not as drastic as 5x on this site Those are deltas-v from low-Earth orbit to low-Venus and low-Mars orbits, respectively. Going from low-Venus orbit to the Venusian surface costs as much as getting from Earth to low-Venus orbit plus getting from Earth to Mars almost 3x over [1]. [1] https://www.dailymail.co.uk/sciencetech/article-2679107/Mind-interplanetary-gap-Space-subway-map-reveals-travel-planets-moons-solar-Tube.html https://www.dailymail.co.uk/sciencetech/article-2679107/Mind...
    - Retric 7y ago
      Only if the atmosphere was non existent. In practice getting to the surface is free, launching again is the problem. This becomes more pronounced as you simply don’t need to enter orbit. Even if that’s the goal, bouncing off the atmosphere is still useful.
    - 7y ago
Robotbeat 7y ago
Not having ground is pretty dang tough. And Venus, since it doesn't have a very accessible ground, doesn't have many natural resources at all: only what the atmosphere provides. Nitrogen, CO2, maybe some hydrogen if you can wrench it from sulfuric acid. Mars has/had a hydrological cycle and thus not only has accessible raw minerals, but many are concentrated to a useful degree. There's water ice, gypsum, salts, metals, clays, etc. Mars has abundant iron-nickel meteorites on its surface. As far as landing a long lasting robot on Venus, ABSOLUTELY it's easier to do it on Mars. Every robot landed on Venus has died within a couple hours because the heat is so great. You need an insane power source whose cold side is hot enough to melt lead and glow a dull red in order to produce enough energy to refrigerate your vehicle. This is possible but extremely difficult to do. There aren't a lot of materials that work at the 450 Celsius. VERY few plastics (Kapton for short duration), and even a lot of metals have problems. And the pressure is insane, too. It's like being in a supercritical CO2 autoclave. And on the surface, there's almost no sunlight and the windspeed is very low. The only feasible powersource really is nuclear (radioisotope and fission) for long-term use to run a refrigeration cycle. It's possible to use high temperature electronics, but the power requirements for those are extremely high and you're stuck with extremely simple digital circuits. Think 1940s/1950s electronics. Mars is just fantastically easier. Floating in the clouds of Venus isn't so bad, but again, no ground. I love the idea of sending a lot more stuff to Venus. But Venus is a hellscape on the surface and so you're stuck floating or flying indefinitely for long-duration things unless you pay a really high engineering price.
- avar 7y ago
  > And on the surface, there's almost no sunlight and the windspeed is very low[...] Ignoring other issues with Venus (heat, pressure, acid...) "wind" turbines on the surface seem completely viable. The wind speed is low (reaching ~2.8 m/s on the surface) but the pressure is 90 atmospheres[1], or 67 kg/m^3, compared to ~1.225 kg/m^3 on Earth. If you plug that into a wind power calculator[2] you can see that with a conservative 1.4 m/s surface wind you need a 1 meter radius fan blade to get the same power as a 7-8 meter radius blade on Earth. So wind power on the surface seems completely viable, aside from the small engineering issue that your turbine would melt into a pool of metal in seconds with current technology. 1. https://en.wikipedia.org/wiki/Atmosphere_of_Venus https://en.wikipedia.org/wiki/Atmosphere_of_Venus 2. https://rechneronline.de/wind-power/ https://rechneronline.de/wind-power/
Symmetry 7y ago
I highly recommend reading the Selenian Boondocks series on Venus ISRU. There's a lot of useful stuff there, it's relatively easy to extract in gas phase processing, but you're still missing a few things. Also, at the right altitude Venus is one of the more pleasant locations in the solar system. Like, wander around outside with goggles and a breathing mask pleasant. But the Venusian surface is death and it really is very challenging to land a rover there. Better to deploy flying robots than rovers for now. https://selenianboondocks.com/category/venus/ https://selenianboondocks.com/category/venus/
- ur-whale 7y ago
  >https://selenianboondocks.com https://selenianboondocks.com Wow, this site is really nice, thanks for sharing.
crazydoggers 7y ago
Good questions, and good responses as well! I don’t think you should get downvoted for asking relevant questions. Mars is definitely easier to visit, easier for robots, and much easier for humans to explore. However, I think Venus is a treasure trove of data for planetary, weather, and climate scientists. For example, the mysterious solar absorber in the upper atmosphere mentioned in the article; might it be something that has applications here on earth for solar power? I would love Venus to hold as much of a sway in the public imagination as Mars does at the moment.
avar 7y ago
Venus's surface pressure is 90 atmospheres, the same as at a depth of 1 km down in the Earth's ocean. Even if the temperature on the surface was comfortable for humans in short sleeves it would still be in insane logistical challenge to do anything on Venus's surface. But it's not, it's also hot enough to melt lead down there.
gkfasdfasdf 7y ago
This idea is explored in an episode of the excellent PBS Space Time: https://www.youtube.com/watch?v=gJ5KV3rzuag https://www.youtube.com/watch?v=gJ5KV3rzuag In short, Venus has many advantages over Mars.
elsonrodriguez 7y ago
Echoing other comments here, but what it comes down to is that the only habitable part of Venus is its atmosphere, which means a natural difficulty in producing raw materials to produce more habitat. You could figure out some clever way to produce carbon structures from the atmospheric gasses, or even plastics with great patience (there's some hydrogen in the atmosphere). However on Mars you can just build a mud hut for starters, then build up to some native martian concrete and steel. Venus is great for a scientific outpost, but Mars is better suited to a self-sustaining colony.
- skykooler 7y ago
  > You could figure out some clever way to produce carbon structures from the atmospheric gasses Isn't that how trees work? Setup some filtration unit to remove the sulfuric acid, pump the CO2 over tree saplings, and as output you get wood plus a source of fresh oxygen.

jacobush 7y ago

On Mars, you need to heat from severe arctic temperatures (and sometimes not at all, in mid summer) and you need some sort of pressure dome. (But you don't need 1 atmosphere.) On Venus you need some way to pump away a heat making lead melt. So... yeah, definitely much more harsh. We don't even have the technology for such heat pumps, even though I guess they are theoretically possible. You'd need exotic materials and a nuclear plant I assume. I the atmosphere though of Venus though, it gets very interesting. Apparently it's about 1 (Earth) atmosphere pressure at a temperature of about 20 Celsius (70 F), so we could have floating cities! (But the cities would have to be resistant to sulfuric acid and we would have to bring our own water.)

roywiggins 7y ago
Probably the best bet for Venus surface exploration is some kind of high-temperature integrated circuit. There's already some work on that sort of thing for the innards of jet engines and the like.
- jacobush 7y ago
  Agreed! I was thinking what you would need for a manned mission. But definitely, electronics operating at that temperature is very interesting and maybe not impossible. I have heard random ideas about mechanical contraptions, too. I wonder about power though. An electronic design could maybe run on some sort of non-rechargeable battery which could deal with the temperature. But if you wanted serious power, a molten-salt reactor would be very interesting. It would I guess "only" be extremely expensive, but maybe not impossible. The interesting thing is that you basically don't need any safety because the reactor is inert and not radiating until you start it. All in all though, I think blimps at various depths are more practical.
- Robotbeat 7y ago
  Yup. I did some work on that for a Venus lander when I was an intern, which is published here: https://ntrs.nasa.gov/search.jsp?R=20150002090 https://ntrs.nasa.gov/search.jsp?R=20150002090
pharke 7y ago
I'm not sure you'd need to bring your own water, the sulfuric acid is produced in the upper atmosphere when sunlight splits carbon dioxide into carbon monoxide and oxygen which then react with water vapour and sulphur dioxide. We could harvest that water vapour and CO2 to produce oxygen, water, and rocket fuel. We've got lots of experience with sulfuric acid and resistant materials are rather common place plastics (including teflon) and stainless steel. I have no idea why there hasn't been more of an effort to get a flying robotic probe to Venus. I think it would be mindblowing to have high res pictures and video of the upper atmosphere with a bright sun over head and an endless sea of clouds.

roywiggins 7y ago

The longest lasting robot on Venus was Venera 12, which lasted 110 minutes. Venus is hard because it melts electronic circuits. On Mars, you just need a heating element to stop yourself freezing. (if you can make something work in a vacuum, it will probably work just fine on Mars. And we have lots of experience working in vacuum!)

gene-h 7y ago
The Venera landers stopped functioning because the solder in their circuits melted. Higher temperature solder could have been used preventing this problem, but the key issue is that silicon no longer functions as a semiconductor at these temperatures. Silicon carbide still works as one though and we're now starting to see silicon carbide electronic circuits and foundry processes to make them.

JumpCrisscross 7y ago

> closer (or so I believe, and according to [1]) Venus is physically closer, but that isn't the best measure of "closeness" for propulsive space travel. The right metric is delta-v, "a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver" [1]. Ignoring aerobraking, it takes almost 5x the energy to get to Venus compared to Mars [2]. (Side note, to drive the point home: it's easier to boost objects out of the Solar System, from Earth, than to send them into the Sun.) [1] https://en.m.wikipedia.org/wiki/Delta-v https://en.m.wikipedia.org/wiki/Delta-v [2] https://www.dailymail.co.uk/sciencetech/article-2679107/Mind-interplanetary-gap-Space-subway-map-reveals-travel-planets-moons-solar-Tube.html https://www.dailymail.co.uk/sciencetech/article-2679107/Mind...

travisporter 7y ago
Actually, I found that it is not as drastic as 5x on this site. https://space.stackexchange.com/questions/2156/does-a-mission-to-venus-orbit-require-less-propellant-than-a-similar-mission-to https://space.stackexchange.com/questions/2156/does-a-missio...
- JumpCrisscross 7y ago
  > it is not as drastic as 5x on this site Those are deltas-v from low-Earth orbit to low-Venus and low-Mars orbits, respectively. Going from low-Venus orbit to the Venusian surface costs as much as getting from Earth to low-Venus orbit plus getting from Earth to Mars almost 3x over [1]. [1] https://www.dailymail.co.uk/sciencetech/article-2679107/Mind-interplanetary-gap-Space-subway-map-reveals-travel-planets-moons-solar-Tube.html https://www.dailymail.co.uk/sciencetech/article-2679107/Mind...
  - Retric 7y ago
    Only if the atmosphere was non existent. In practice getting to the surface is free, launching again is the problem. This becomes more pronounced as you simply don’t need to enter orbit. Even if that’s the goal, bouncing off the atmosphere is still useful.
  - 7y ago

Robotbeat 7y ago

Not having ground is pretty dang tough. And Venus, since it doesn't have a very accessible ground, doesn't have many natural resources at all: only what the atmosphere provides. Nitrogen, CO2, maybe some hydrogen if you can wrench it from sulfuric acid. Mars has/had a hydrological cycle and thus not only has accessible raw minerals, but many are concentrated to a useful degree. There's water ice, gypsum, salts, metals, clays, etc. Mars has abundant iron-nickel meteorites on its surface. As far as landing a long lasting robot on Venus, ABSOLUTELY it's easier to do it on Mars. Every robot landed on Venus has died within a couple hours because the heat is so great. You need an insane power source whose cold side is hot enough to melt lead and glow a dull red in order to produce enough energy to refrigerate your vehicle. This is possible but extremely difficult to do. There aren't a lot of materials that work at the 450 Celsius. VERY few plastics (Kapton for short duration), and even a lot of metals have problems. And the pressure is insane, too. It's like being in a supercritical CO2 autoclave. And on the surface, there's almost no sunlight and the windspeed is very low. The only feasible powersource really is nuclear (radioisotope and fission) for long-term use to run a refrigeration cycle. It's possible to use high temperature electronics, but the power requirements for those are extremely high and you're stuck with extremely simple digital circuits. Think 1940s/1950s electronics. Mars is just fantastically easier. Floating in the clouds of Venus isn't so bad, but again, no ground. I love the idea of sending a lot more stuff to Venus. But Venus is a hellscape on the surface and so you're stuck floating or flying indefinitely for long-duration things unless you pay a really high engineering price.

avar 7y ago
> And on the surface, there's almost no sunlight and the windspeed is very low[...] Ignoring other issues with Venus (heat, pressure, acid...) "wind" turbines on the surface seem completely viable. The wind speed is low (reaching ~2.8 m/s on the surface) but the pressure is 90 atmospheres[1], or 67 kg/m^3, compared to ~1.225 kg/m^3 on Earth. If you plug that into a wind power calculator[2] you can see that with a conservative 1.4 m/s surface wind you need a 1 meter radius fan blade to get the same power as a 7-8 meter radius blade on Earth. So wind power on the surface seems completely viable, aside from the small engineering issue that your turbine would melt into a pool of metal in seconds with current technology. 1. https://en.wikipedia.org/wiki/Atmosphere_of_Venus https://en.wikipedia.org/wiki/Atmosphere_of_Venus 2. https://rechneronline.de/wind-power/ https://rechneronline.de/wind-power/

Symmetry 7y ago

I highly recommend reading the Selenian Boondocks series on Venus ISRU. There's a lot of useful stuff there, it's relatively easy to extract in gas phase processing, but you're still missing a few things. Also, at the right altitude Venus is one of the more pleasant locations in the solar system. Like, wander around outside with goggles and a breathing mask pleasant. But the Venusian surface is death and it really is very challenging to land a rover there. Better to deploy flying robots than rovers for now. https://selenianboondocks.com/category/venus/ https://selenianboondocks.com/category/venus/

ur-whale 7y ago
>https://selenianboondocks.com https://selenianboondocks.com Wow, this site is really nice, thanks for sharing.

crazydoggers 7y ago

Good questions, and good responses as well! I don’t think you should get downvoted for asking relevant questions. Mars is definitely easier to visit, easier for robots, and much easier for humans to explore. However, I think Venus is a treasure trove of data for planetary, weather, and climate scientists. For example, the mysterious solar absorber in the upper atmosphere mentioned in the article; might it be something that has applications here on earth for solar power? I would love Venus to hold as much of a sway in the public imagination as Mars does at the moment.

avar 7y ago

Venus's surface pressure is 90 atmospheres, the same as at a depth of 1 km down in the Earth's ocean. Even if the temperature on the surface was comfortable for humans in short sleeves it would still be in insane logistical challenge to do anything on Venus's surface. But it's not, it's also hot enough to melt lead down there.

gkfasdfasdf 7y ago

This idea is explored in an episode of the excellent PBS Space Time: https://www.youtube.com/watch?v=gJ5KV3rzuag https://www.youtube.com/watch?v=gJ5KV3rzuag In short, Venus has many advantages over Mars.

elsonrodriguez 7y ago

Echoing other comments here, but what it comes down to is that the only habitable part of Venus is its atmosphere, which means a natural difficulty in producing raw materials to produce more habitat. You could figure out some clever way to produce carbon structures from the atmospheric gasses, or even plastics with great patience (there's some hydrogen in the atmosphere). However on Mars you can just build a mud hut for starters, then build up to some native martian concrete and steel. Venus is great for a scientific outpost, but Mars is better suited to a self-sustaining colony.

skykooler 7y ago
> You could figure out some clever way to produce carbon structures from the atmospheric gasses Isn't that how trees work? Setup some filtration unit to remove the sulfuric acid, pump the CO2 over tree saplings, and as output you get wood plus a source of fresh oxygen.