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Other than PR, what would a Mars manned mission provide that a moon-base and 'cargo flights to the moon' wouldn't? If the aim is to perfect human survival off-

by sago 10y ago

Other than PR, what would a Mars manned mission provide that a moon-base and 'cargo flights to the moon' wouldn't? If the aim is to perfect human survival off-earth, then surely the moon is a better goal. I know we've been to the moon, but only for a few hours. We're nowhere near the tech/cargo transfer needed to put a manned base on it. Are we going to put a few people on Mars, lose interest in that right away, wait another 40 years and then aim for Europa? [edit: Thank you all for the responses.]

jessriedel 10y ago
Although its obviously speculative, I'm pretty sure the expert consensus is that Mars is significantly more promising for self-sufficient human colonization than the Moon.
jrv 10y ago
I'm no expert at all, but three things come to mind: - Mars has a (thin) atmosphere, mostly made up of CO2 -> good for plant growth. The Moon has none. - Mars has gravity closer to Earth than the Moon. - Mars has lots of water, while the moon has possibly just a little? EDIT: found http://www.mars-one.com/faq/mission-to-mars/why-mars-and-not-another-planet http://www.mars-one.com/faq/mission-to-mars/why-mars-and-not..., which cites similar and more reasons (although Mars One seems to be pretty much a scam).
- bergie 10y ago
  The Martian atmosphere also makes aerobraking possible, meaning spacecraft arriving there need less delta-V. A Dragon2 can land in Mars, but not on the Moon because of this.
  - exDM69 10y ago
    Aerobraking is a benefit but is the Dragon really unable to land on the moon? The moon has less gravity (about half) and the velocity difference should be much smaller for a lunar intercept than a Mars intercept. Has anyone got numbers for this?
    - lmm 10y ago
      Dragon doesn't have enough delta-V to land on the moon. The plan for a Mars landing is to use it as a lifting body to keep it above the ground for long enough to shed most of its velocity.
      - exDM69 10y ago
        Yes, GP said that already but I'm after the numbers here. How much delta-v the Dragon has? And what are the approximate requirements for Moon vs. Mars landing?
        Symmetry 10y ago
        The Dragon 2 has about 1.6 km/s. Apollo had 2.47 km/s to land and 2.22 km/s to take off. Oh, and it would take on the order of 4.5 km/s to take off from Mars and maybe a few hundred to land.
        exDM69 10y ago
        Thanks! These numbers look reasonable to me. Can you provide a link to source (s)? I'd like to read some more...
      - dalke 10y ago
        I've read various statements which say that Dragon can land on the Moon, such as http://www.nbcnews.com/science/space/mars-ahead-spacex-unveils-dragon-v2-capsule-astronaut-trips-n118116 http://www.nbcnews.com/science/space/mars-ahead-spacex-unvei... : > Musk has said a fully loaded Dragon could even be sent to make a touchdown on the moon or Mars or https://www.nasaspaceflight.com/2016/04/spacex-debut-red-dragon-2018-mars-mission/ https://www.nasaspaceflight.com/2016/04/spacex-debut-red-dra... : > “With Dragon launched on a Falcon Heavy, it can go pretty much anywhere in the solar system, because that’s a heck of a big rocket,” he continued. > “Dragon, with the heat shield, parachutes and propulsive landing capability, is able to land on a planet that has higher entry heating, like Mars. It can also land on the Moon, or potentially conduct a Europa mission.” How does that fit with the statement "Dragon doesn't have enough delta-V to land on the moon"?
- robbiep 10y ago
  '- Mars has gravity closer to the earth than the moon' Depends on what you mean by close. 0.38 is closer to 16.7 than 1, but any improvement on that is important
  - Manabu-eo 10y ago
    If you are talking about human health, it might be that any gravity bellow 0.8g is almost as bad for human health as microgravity. It could be that any gravity above 0.1g is as good as 1g for human health. We simply don't know the format of that curve. We have no data on it even on rodents (the ISS module for that was scrapped). We only know that 1g is good and microgravity is bad. And that very high g is bad too.
danielvf 10y ago
First of all, going to Mars is hard. It makes going to the moon look easy. Most missions to Mars have failed - in fact, with fifty years of trying, the USSR and Russia has never had a successful Mars mission. A round trip to the Moon is a week, a round trip to Mars is four years in space. So if we could do humans on Mars, it would mean that we had learned far more than we used to know. It's like the difference between climbing a hill in your city, and climbing Mt Everest.
- sago 10y ago
  Doesn't that argue for doing the moon first? If you say "yeah we've not climbed any hills yet, but we're totally gonna try Everest" that might not show much common sense. And if the aim is to just try to do the hardest possible thing we can think of, why Mars and not, say Venus? I think difficulty is a red herring. The other suggested reasons (atmosphere, gravity, water) seem much better reasons.
  - danielvf 10y ago
    We've already been to the moon first though, several times. Mars is the next (huge) step forward in difficulty.
    - sago 10y ago
      We've visited for a few hours, this is about putting a colony on it. That's orders of magnitude more difficult. Why do something orders of magnitude more difficult on a planet orders of magnitude more difficult to reach? As I said, the other answers seemed to give credible suggestions.
      - deleted 10y ago
        [deleted]
gpm 10y ago
Musk is very clear that his plan is to establish a self sustaining colony, not another 'footprints' mission, and not a colony that needs to be sustained via continuous resupply. Mars has several advantages, you can pretty much google this and get better arguments then I'm able to make here. But here are a few key points. - Earth like day period, 39 minutes longer versus almost a month longer than earth. - More stable day-night temperature - More gravity - A weak atmosphere (versus none), and the capability to retain a earth like atmosphere. - Easy access to Water, and CO2. Important for growing plants and making rocket fuel amongst other things.
- johan_larson 10y ago
  I have to wonder what the heck a "self-sustaining" Mars colony would export to Earth to pay for all the stuff they need to import.
  - cjahsh 10y ago
    Just look at people living in the Arctic: everything is imported, basic necessities are expensive, and getting replacements could take weeks. Now imagine that you're on a different planet, and there are only a few firms that CAN resupply, and they'll only do it if you can compensate them sufficiently. Better hope the colony is built on a platinum and rhodium mine!
  - emiliobumachar 10y ago
    I think "self-sustaining" in the context means that if Earth dissapears, explodes, turns into grey goo, or otherwise becomes unavailable, the Mars colony stands a chance of surviving indefinitely. Yes, it's a hugely ambitious goal.
  - TeMPOraL 10y ago
    "Self-sustaining" by definition means able to survive indefinitely without importing anything from Earth.
    - nabla9 10y ago
bombless 10y ago
>Stephen Petranek: Your kids might live on Mars. Here's how they'll survive https://go.ted.com/Cy8v https://go.ted.com/Cy8v Water is easy to get on mars, so there's chance man can live independently on mars. I heard that NASA already found a way to make water from moon rock, but that sounds … magical
Manabu-eo 10y ago
One advantage of Mars to the Moon for a self-sustaining civilization that no-one mentioned is that it is MORE than a few hours away. Any moon base or future economy would be very dependent on earth, while Mars have more incentive to be independent and a real civilization backup.

by sago 10y ago

jessriedel 10y ago

Although its obviously speculative, I'm pretty sure the expert consensus is that Mars is significantly more promising for self-sufficient human colonization than the Moon.

jrv 10y ago

I'm no expert at all, but three things come to mind: - Mars has a (thin) atmosphere, mostly made up of CO2 -> good for plant growth. The Moon has none. - Mars has gravity closer to Earth than the Moon. - Mars has lots of water, while the moon has possibly just a little? EDIT: found http://www.mars-one.com/faq/mission-to-mars/why-mars-and-not-another-planet http://www.mars-one.com/faq/mission-to-mars/why-mars-and-not..., which cites similar and more reasons (although Mars One seems to be pretty much a scam).

bergie 10y ago
The Martian atmosphere also makes aerobraking possible, meaning spacecraft arriving there need less delta-V. A Dragon2 can land in Mars, but not on the Moon because of this.
- exDM69 10y ago
  Aerobraking is a benefit but is the Dragon really unable to land on the moon? The moon has less gravity (about half) and the velocity difference should be much smaller for a lunar intercept than a Mars intercept. Has anyone got numbers for this?
  - lmm 10y ago
    Dragon doesn't have enough delta-V to land on the moon. The plan for a Mars landing is to use it as a lifting body to keep it above the ground for long enough to shed most of its velocity.
    - exDM69 10y ago
      Yes, GP said that already but I'm after the numbers here. How much delta-v the Dragon has? And what are the approximate requirements for Moon vs. Mars landing?
      - Symmetry 10y ago
        The Dragon 2 has about 1.6 km/s. Apollo had 2.47 km/s to land and 2.22 km/s to take off. Oh, and it would take on the order of 4.5 km/s to take off from Mars and maybe a few hundred to land.
        exDM69 10y ago
        Thanks! These numbers look reasonable to me. Can you provide a link to source (s)? I'd like to read some more...
    - dalke 10y ago
      I've read various statements which say that Dragon can land on the Moon, such as http://www.nbcnews.com/science/space/mars-ahead-spacex-unveils-dragon-v2-capsule-astronaut-trips-n118116 http://www.nbcnews.com/science/space/mars-ahead-spacex-unvei... : > Musk has said a fully loaded Dragon could even be sent to make a touchdown on the moon or Mars or https://www.nasaspaceflight.com/2016/04/spacex-debut-red-dragon-2018-mars-mission/ https://www.nasaspaceflight.com/2016/04/spacex-debut-red-dra... : > “With Dragon launched on a Falcon Heavy, it can go pretty much anywhere in the solar system, because that’s a heck of a big rocket,” he continued. > “Dragon, with the heat shield, parachutes and propulsive landing capability, is able to land on a planet that has higher entry heating, like Mars. It can also land on the Moon, or potentially conduct a Europa mission.” How does that fit with the statement "Dragon doesn't have enough delta-V to land on the moon"?
robbiep 10y ago
'- Mars has gravity closer to the earth than the moon' Depends on what you mean by close. 0.38 is closer to 16.7 than 1, but any improvement on that is important
- Manabu-eo 10y ago
  If you are talking about human health, it might be that any gravity bellow 0.8g is almost as bad for human health as microgravity. It could be that any gravity above 0.1g is as good as 1g for human health. We simply don't know the format of that curve. We have no data on it even on rodents (the ISS module for that was scrapped). We only know that 1g is good and microgravity is bad. And that very high g is bad too.

danielvf 10y ago

First of all, going to Mars is hard. It makes going to the moon look easy. Most missions to Mars have failed - in fact, with fifty years of trying, the USSR and Russia has never had a successful Mars mission. A round trip to the Moon is a week, a round trip to Mars is four years in space. So if we could do humans on Mars, it would mean that we had learned far more than we used to know. It's like the difference between climbing a hill in your city, and climbing Mt Everest.

sago 10y ago
Doesn't that argue for doing the moon first? If you say "yeah we've not climbed any hills yet, but we're totally gonna try Everest" that might not show much common sense. And if the aim is to just try to do the hardest possible thing we can think of, why Mars and not, say Venus? I think difficulty is a red herring. The other suggested reasons (atmosphere, gravity, water) seem much better reasons.
- danielvf 10y ago
  We've already been to the moon first though, several times. Mars is the next (huge) step forward in difficulty.
  - sago 10y ago
    We've visited for a few hours, this is about putting a colony on it. That's orders of magnitude more difficult. Why do something orders of magnitude more difficult on a planet orders of magnitude more difficult to reach? As I said, the other answers seemed to give credible suggestions.
    - deleted 10y ago
      [deleted]

gpm 10y ago

Musk is very clear that his plan is to establish a self sustaining colony, not another 'footprints' mission, and not a colony that needs to be sustained via continuous resupply. Mars has several advantages, you can pretty much google this and get better arguments then I'm able to make here. But here are a few key points. - Earth like day period, 39 minutes longer versus almost a month longer than earth. - More stable day-night temperature - More gravity - A weak atmosphere (versus none), and the capability to retain a earth like atmosphere. - Easy access to Water, and CO2. Important for growing plants and making rocket fuel amongst other things.

johan_larson 10y ago
I have to wonder what the heck a "self-sustaining" Mars colony would export to Earth to pay for all the stuff they need to import.
- cjahsh 10y ago
  Just look at people living in the Arctic: everything is imported, basic necessities are expensive, and getting replacements could take weeks. Now imagine that you're on a different planet, and there are only a few firms that CAN resupply, and they'll only do it if you can compensate them sufficiently. Better hope the colony is built on a platinum and rhodium mine!
- emiliobumachar 10y ago
  I think "self-sustaining" in the context means that if Earth dissapears, explodes, turns into grey goo, or otherwise becomes unavailable, the Mars colony stands a chance of surviving indefinitely. Yes, it's a hugely ambitious goal.
- TeMPOraL 10y ago
  "Self-sustaining" by definition means able to survive indefinitely without importing anything from Earth.
  - nabla9 10y ago

bombless 10y ago

>Stephen Petranek: Your kids might live on Mars. Here's how they'll survive https://go.ted.com/Cy8v https://go.ted.com/Cy8v Water is easy to get on mars, so there's chance man can live independently on mars. I heard that NASA already found a way to make water from moon rock, but that sounds … magical

Manabu-eo 10y ago

One advantage of Mars to the Moon for a self-sustaining civilization that no-one mentioned is that it is MORE than a few hours away. Any moon base or future economy would be very dependent on earth, while Mars have more incentive to be independent and a real civilization backup.