Why colonize Mars and not the Moon?

[|Glitch|]

Here's a thought: did anyone old enough on this forum anticipate the emergence of the internet, say, forty years ago?

I started using the Internet in 1979. So that was 38 years ago.

The point I wish to make is that the future remains generally unknowable, especially as it applies to technological advances. Therefore, proposing the setting up of a permanent colony on Mars using current technology is one hell of an ask.

We are not going to set up a permanent colony on Mars. Not with current technology, or technology we develop in the near future (within the next decade). There is no point and it would be prohibitively expensive. We may eventually develop the technology to protect astronauts from solar and cosmic radiation, but the only purpose for visiting Mars is for scientific research. Mars can never be made to be self-sufficient and life-sustaining, which means that it will continue to cost us (Earth-bound taxpayers) billions to send anything to Mars. It would be cheaper to establish a colony on the moon. It would also make more sense to have a lunar colony if the purpose was to construct spacecraft for future exploration. We would still have to supply them from Earth continuously, but since the moon is much closer than Mars it would be much cheaper and more frequent.

 

[lifeonmercury]

With regard to the suggestions made here about increasing Mars' mass for the purpose of allowing Mars to hold an atmosphere with sufficient air pressure and surface water... What about crashing both Martian moons into Mars along with 5,000 asteroids?

 

[|Glitch|]

With regard to the suggestions made here about increasing Mars' for the purpose of allowing Mars to hold an atmosphere with sufficient air pressure and surface water... What about crashing both Martian moons into Mars along with 5,000 asteroids?

That might work, but I don't think you would want to be living on the surface of Mars at the time. It would also be extremely expensive.

 

[|Glitch|]

Like going to the moon within this decade in 1961. And then Apollo happened. But we don't have to be there in 10 years. There is nothing wrong with landing on Mars in 2037.

That was different. We deemed that exposing our astronauts to 6 total days of solar and cosmic radiation was an acceptable risk. It could have ended very badly, but it didn't. We were damn lucky. Spending two plus years outside of Earth's protective magnetosphere is not a risk, it is certain suicide. We can at least wait long enough to develop some kind of radiation protection to ensure the astronauts at least reach their destination alive. That should not take very long. A manned mission to Mars by 2037 seems like a much more reasonable and realistic timeline.

 

[lifeonmercury]

I would think it'd be possible to drill down to the centers of Mars' moons and use controlled nuclear explosions causing them to break apart and fall onto Mars. Do that now and wait a few years for the dust to settle. Mars One could keep to its proposed timetable.

 

[|Glitch|]

I would think it'd be possible to drill down to the centers of Mars' moons and use controlled nuclear explosions causing them to break apart and fall onto Mars. Do that now and wait a few years for the dust to settle. Mars One could keep to its proposed timetable.

Phobos' mass is 1.0659 × 10¹⁶ kg and Deimos' mass is 1.4762 × 10¹⁵ kg. Even if we did violate the Outer Space Treaty of 1967, and use nuclear bombs in space, you would need a lot more than we have to move such massive objects. Furthermore, such large objects impacting Mars would have an effect on its rotation, and may even change its orbit.

 

[Dale]

That is offset by the lower delta_v requirements.

Are you saying that the delta v to Mars is less than the delta v to the moon?

 

[lifeonmercury]

Phobos' mass is 1.0659 × 10¹⁶ kg and Deimos' mass is 1.4762 × 10¹⁵ kg. Even if we did violate the Outer Space Treaty of 1967, and use nuclear bombs in space, you would need a lot more than we have to move such massive objects. Furthermore, such large objects impacting Mars would have an effect on its rotation, and may even change its orbit.

If the US, Russia, and China go all in on this, who's going to stop them and try to enforce that treaty?
Deimos is only 7 miles wide. I think we've got enough firepower to blow it to smithereens.
Mars currently has 38% of Earth's surface gravity. Any guesses at how much it would be after "consuming" Phobos and Deimos?

 

[Stavros Kiri]

MIT estimates they will have a solution by 2026.

I do not dissagree

 

[rootone]

The Moons of Mars are both very small.
Probably wouldn't change surface gravity by much more than1 or 2 percent if they were crashed on to it.

 

[Dale]

a six month trip to Mars today is certain suicide

I am skeptical about this claim. Do you have a reference for this?

 

[Algr]

Deimos is only 7 miles wide. I think we've got enough firepower to blow it to smithereens.

When we used to do underground nuclear weapons tests, how deeply were the nukes buried? How much Earth actually got moved?

I am skeptical about this claim. Do you have a reference for this?

It's mostly all the talk about the impossibility of packing that much food and water on a spaceship. We've experimented with gardens, but they are nowhere near guaranteed to work.

 

[Bandersnatch]

If the US, Russia, and China go all in on this, who's going to stop them and try to enforce that treaty?
Deimos is only 7 miles wide. I think we've got enough firepower to blow it to smithereens.
Mars currently has 38% of Earth's surface gravity. Any guesses at how much it would be after "consuming" Phobos and Deimos?

Blowing them apart would not automatically crash them onto the surface. You'd end up with a bunch of debris still hapilly orbiting the planet.
But more importantly, crashing both moons AND every single asteroid from the asteroid belt would increase Mars' gravity by less than 1%.

 

[|Glitch|]

I am skeptical about this claim. Do you have a reference for this?

Assuming the mission was planned during the solar minimum, and there were no gamma-ray bursts or solar flares directed toward the astronauts, NASA estimates a total exposure of 300 mSv for the journey to Mars, and a total exposure of 1 Sv for a 30 month (6 months going to Mars, 18 months on Mars, and 6 months getting back to Earth) mission duration. 250 mSv is enough to cause nausea, fatigue, and loss of hair. That is the best case scenario.

On its journey to Mars, the Curiosity rover provided crucial data on this and it was higher than expected. A round-trip manned mission to Mars would expose the astronauts to up to four times the advised career limits for astronauts of radiation due to galactic cosmic rays.

If they did manage to make it back to Earth alive, they would be dead shortly thereafter. If just one solar flare or a gamma-ray burst was directed at the astronauts, they would be dead within seconds.

Sources:
https://cosmosmagazine.com/space/how-much-radiation-damage-do-astronauts-really-suffer-in-space
https://www.wired.com/2014/04/radiation-risk-iss-mars/
http://www.space.com/21353-space-radiation-mars-mission-threat.html
http://www.livescience.com/56449-cosmic-radiation-may-damage-brains.html
http://blogs.agu.org/wildwildscience/2009/09/01/how-much-radiation-does-it-take-to-kill-you/

 

[Chronos]

Radiation exposure is a serious issue for manned space missions and a big reason NASA suspended moon launches. The sun is a dangerous and unpredictable adversary. The lunar mission astronauts were lucky not to be fried. Shielding remains a very serious issue for any space mission. A cursory review of NASA date will confirm this risk - and its worse than they suspected back in the 60's. They deemed it an acceptable risk for political reasons. It also appears to have shortened the lives of astronauts, who tend to be very healthy compared to the average person. See http://www.nature.com/articles/srep29901 for the disturbing details.

 

[DDH]

When we used to do underground nuclear weapons tests, how deeply were the nukes buried? How much Earth actually got moved?
.

The largest was 5 megatons, buried at 5,875 feet. The second question is irrelevant.
It isn't inconceivable to imagine a nuclear device with an exploding force exceeding 40 to 100 times as large. As the gravity pull of Deimos is so small, it's very probable that Deimos would be shattered into a large number of pieces. On the other hand, it's almost certain that not all parts would strike Mars.

 

[Stavros Kiri]

Any guesses at how much it would be after "consuming" Phobos and Deimos

Small change, but orbit perturbation I think is the problem. [I agree with the next 2:]

The Moons of Mars are both very small.
Probably wouldn't change surface gravity by much more than1 or 2 percent if they were crashed on to it.

Furthermore, such large objects impacting Mars would have an effect on its rotation, and may even change its orbit.

 

[Algr]

I think I missed something here, what is blowing up Phobos and Deimos supposed to accomplish? Wouldn't it be better to divert a large icy comet to hit mars?

 

[Stavros Kiri]

I think I missed something here, what is blowing up Phobos and Deimos supposed to accomplish? Wouldn't it be better to divert a large icy comet to hit mars?

Mass and gravity would also increase (but may need more than one large comet), potential feasible atmosphere, + !we got the water too!
Great idea! In fact that's how early Earth got it's water too and more (etc.) ... (e.g. minerals, aminoacids ... bla bla ... boom! life was created perhaps at the bottom of the oceans! ...).

Can do the same with Mars!

Since you had the idea perhaps can start a project or at least write a paper ...
[Then of course one would have to find the comets (-candidates) ...]

 

[Stavros Kiri]

I think it is unlikely that Mars can be made to have a breathable atmosphere either. Raising the Martian surface pressure to Earth's 100 kPa with Martian gravity means an air column 2.6 times higher than earth's, wrapped around a planet with half the diameter. Instead of a space boundary at 50 miles, Mars` would be at 130 miles.

You may be right, but the discussion here may have just found a solution (!?) [see previous 2 posts above] ...

 

[Stavros Kiri]

So you intend to toss asteroids at the planet while people are living there? That is rather reckless.

I' m sure they'll find a way ... (e.g. for protection) ... if that's the way to go.

 

[Stavros Kiri]

As Robert Zubrin sais, (~)"we are trying to solve a 22nd century problem with a 20th century mind ... It may not happen exactly that way, ... but it will happen! (by 23rd century, ... not 33rd !) ". ...

 

[mfb]

250 mSv is enough to cause nausea, fatigue, and loss of hair. That is the best case scenario.

250 mSv short-term exposure. Not 250 mSv over several months, which will just increase the cancer risk a bit.

The 1 Sv is with very pessimistic shielding estimates, and over even longer timescales.

http://www.livescience.com/56449-cosmic-radiation-may-damage-brains.html

The mice were exposed to their total radiation dose (higher than what is expected for astronauts) within minutes, not within months.

See my comparison in an earlier post: drinking a glass of wine per day for a year won't kill you, drinking 365 glasses in a row will do.

If just one solar flare or a gamma-ray burst was directed at the astronauts, they would be dead within seconds.

Stop posting nonsense.
Here is a NASA reference. If the astronauts would have walked around outside in spacesuits during the 1972 flare, they would have gotten a dose of 400 rem - potentially deadly within a few days, but not necessarily, and certainly not "within seconds".
No one would schedule a Moon walk with a solar flare appearing, however. Inside the spacecraft , the dose would have been 35 rem. Unpleasant, leading to a headache and increasing the long-term cancer risk, but not critical.
The Apollo modules were lightweight - modern spacecraft have better shielding. The dose would be even lower. No headache.

We had astronauts living in space for decades now. You seem to believe that the magnetic field of Earth does magic. It does not. It reduces the low-energetic component of cosmic radiation. It does not shield against gamma-ray bursts at all (because they are not charged particles), and it does not shield against high-energetic particles (multi-TeV range) either.

Mars can never be made to be self-sufficient and life-sustaining

I would be interested in a reference for that claim. How can you be so sure about that, especially as all the experts think otherwise?

Even if we did violate the Outer Space Treaty of 1967, and use nuclear bombs in space, you would need a lot more than we have to move such massive objects. Furthermore, such large objects impacting Mars would have an effect on its rotation, and may even change its orbit.

Treaties can be modified in international agreement.
The gravitational binding energy of Deimos is just 1.4*10¹⁶ J, or 3 megatons of TNT equivalent. The gravitational binding energy of Phobos is 4*10¹⁷ J, or 95 megatons TNT-equivalent. Nuclear weapons have enough energy to disintegrate the moons, if we want. I don't see the point of that, but it would be possible. Removing Phobos from its orbit could be interesting for a Martian space elevator in the distant future.
The effect on its rotation? Having everything impacting the surface would make the day ~1/3 second shorter.
The effect on surface gravity? Utterly negligible.
The effect on its orbit? Non-existent because the center of mass of the system does not change.

It also appears to have shortened the lives of astronauts, who tend to be very healthy compared to the average person. See http://www.nature.com/articles/srep29901 for the disturbing details.

They found a p<0.05 effect with a sample size of 7 after potentially looking at more than 10 categories. Congratulations. More here.

Are you saying that the delta v to Mars is less than the delta v to the moon?

Yes.
LEO -> Moon surface needs 5700 m/s.
LEO -> Mars surface with aerocapture needs ~4300 m/s, depending on the launch window.
The advantage of Mars is the atmosphere. Going back needs much lower delta_v starting from the Moon, of course. But even starting from Mars, a single stage rocket can work. The same rocket that landed on the surface, which means you just need to fuel it. And that is easier on Mars...

 

[Vanadium 50]

The gravitational binding energy of Phobos

Deimos and Phobos are held together not by gravity, but by chemistry. It's hard to calculate the exact binding energy, because we don't know much about the interior structure and composition, but a ballpark estimate is that you need ~400x more energy to dissociate Phobos and 1000x more to dissociate Deimos.

 

[Stavros Kiri]

The effect on its orbit? Non-existent because the center of mass of the system does not change.

Thanks for correcting us on that one! (simple mechanics! ...)

Just some minor "marsquakes" perhaps ...

 

[Stavros Kiri]

But what about gravitational equilibrium in the solar system? Also negligible? (i.e. the perturbation)

 

[mfb]

Deimos and Phobos are held together not by gravity, but by chemistry. It's hard to calculate the exact binding energy, because we don't know much about the interior structure and composition, but a ballpark estimate is that you need ~400x more energy to dissociate Phobos and 1000x more to dissociate Deimos.

Depends on how we want to disintegrate them. Your numbers would mean 40,000 MT for Phobos and 3,000 MT for Deimos. That is still possible. 400 and 30 Tsar bomba style (with the additional fission layer that got removed) nuclear explosions, respectively.

But what about gravitational equilibrium in the solar system? Also negligible? (i.e. the perturbation)

No matter what we do with the moons, it will have no notable effect on anything in terms of orbits. Mars has 60 million times the mass of Phobos and Deimos combined. If we bring the moons down (not trivial with angular momentum), the combined mass does not even change. If we shoot the moons away, the combined mass goes down by 1 part in 60 millions. Completely irrelevant.

 

[Stavros Kiri]

Depends on how we want to disintegrate them. Your numbers would mean 40,000 MT for Phobos and 3,000 MT for Deimos. That is still possible. 400 and 30 Tsar bomba style (with the additional fission layer that got removed) nuclear explosions, respectively.
No matter what we do with the moons, it will have no notable effect on anything in terms of orbits. Mars has 60 million times the mass of Phobos and Deimos combined. If we bring the moons down (not trivial with angular momentum), the combined mass does not even change. If we shoot the moons away, the combined mass goes down by 1 part in 60 millions. Completely irrelevant.

I meant more the forces from the sun and other planets to the moons etc. (that could affect the dynamics of the system - not trivial!) , not the mass itself! That could have been a problem, but may be also negligible. What do you think?

 

[Stavros Kiri]

May be use "small perturbation theory" (on the forces and orbits) ...
The result may be from negligible to ... disasterous (or even chaotic?) to the solar system ... . It depends. As I said, ... not trivial! ...

 

[Stavros Kiri]

Disturbing the equilibrium of a system can always be a problem ...