Why colonize Mars and not the Moon?

[mfb]

We know all 500 km objects up to the orbit of Neptune. Everything undiscovered larger than that would need a very eccentric orbit.
We know most 1 km objects in the inner solar system.

In terms of mass-extinction impacts within 1000 years, long-periodic comets are the main threat. Every other object in the inner solar system is known well enough.

For longer timescales, Chiron is the most interesting object larger than 100 km. It is currently in an orbit between Saturn and Uranus, but that orbit is not stable over astronomical timescales. It might fly through the inner solar system within a million years. Smaller objects like 1996 AR20 could fly through the inner solar system much earlier. Not within 1000 years, but within 100,000 there is a reasonable probability.

1. We need cheaper access to space. SpaceX is trying.

They are not just trying. They have the cheapest rocket on the market already.

First to the Moon. Then to other moons and asteroids. Best places to study Mars is from base on martian moon. Distance is so short that telerobotics is possible. Single Mars base or robots can only study small area. Moon base can control robots everywhere. Moon is needed for radiation protection of the crew. We need significantly less fuel to go from Earth to martian moon than to the Moon (both with soft landing). But because of longer travel time we need to practice with Moon base first.

A base on the surface can control rovers all over the Martian surface as well. The surface provides better radiation protection than the moons. In terms of fuel to get there, the surface is similar to the moons, as you can use the atmosphere to slow down in both cases. Getting back is much easier from the moons of course. The moons don't provide relevant gravity, however - long-term stays there are problematic. If you don't want to land on the surface, better stay in a spacecraft in orbit and make artificial gravity there.

 

[lifeonmercury]

I get it that Mars has an atmosphere and the Moon doesn't. I don't understand why this matters though. The low air pressure and high carbon dioxide levels would make the Martian air unbreathable. Do scientists really think they can eventually transform the Martian atmosphere so that people can be outside without a spacesuit?

 

[ikihi]

Some people on this forum have no imagination. Almost anything is possible to achieve with the right amount of will power and funding.

 

[jkn]

Number of such objects inside the orbit of Neptune = 3.
Number of such objects that get within 100 million miles of Earth = 0

Correction: Number of known such objects that get within 100 million miles of Earth = 0. We might even have unknown planet!

I admit it is very unlikely event. There are unknown number of events which could destroy life from Earth. All hopefully very unlikely (evidence: Life exists). An event destroying our civilization is much more likely (evidence: SETI has not found anything). Anyway life has been here about 3000 million years. It has only 1000 million years left.

 

[anorlunda]

Anything is possible to achieve with the right amount of will power and funding.

PF is dominated by scientists and engineers who are more reality based than that. We can all imagine FTL travel. Would you disparage those who believe that we will never achieve that?

 

[Vanadium 50]

Some people on this forum have no imagination.

And some people on this forum have no knowledge. Are you willing to argue that we could be missing a continent on Earth because of lack of imagination?

 

[Vanadium 50]

Number of such objects in interstellar space

If it's in interstellar space, it's not a threat until it gets closer. That has a time scale of centuries.

 

[Sankar Raman]

It is more sensible to build habitable space ships near earth. As the numbers expand we can consider colonizing Mars or ths satellites of Jupiter and Saturn. To start with we should promote a massive population explosion. 7 billion is too small, at least 30 billion is needed. Near outer space can easily sustain 15 billion to start with.

 

[jkn]

We know all 500 km objects up to the orbit of Neptune. Everything undiscovered larger than that would need a very eccentric orbit.
We know most 1 km objects in the inner solar system.

In terms of mass-extinction impacts within 1000 years, long-periodic comets are the main threat. Every other object in the inner solar system is known well enough.

For longer timescales, Chiron is the most interesting object larger than 100 km. It is currently in an orbit between Saturn and Uranus, but that orbit is not stable over astronomical timescales. It might fly through the inner solar system within a million years. Smaller objects like 1996 AR20 could fly through the inner solar system much earlier. Not within 1000 years, but within 100,000 there is a reasonable probability.

They are not just trying. They have the cheapest rocket on the market already.A base on the surface can control rovers all over the Martian surface as well. The surface provides better radiation protection than the moons. In terms of fuel to get there, the surface is similar to the moons, as you can use the atmosphere to slow down in both cases. Getting back is much easier from the moons of course. The moons don't provide relevant gravity, however - long-term stays there are problematic. If you don't want to land on the surface, better stay in a spacecraft in orbit and make artificial gravity there.

If SpaceX rockets keep on exploding once a year, they are not cheapest. So no success yet.

A base on surface needs satellites to control rovers all over Mars. Moon base needs satellites only if they want continuouss acces for all rovers. There is no point to land if work can be done without.

Martian moons provide same radiation and meteorite protection as Mars. Perhaps they need to dig slightly deeper. But that's easy because nothing weights much.

Using rotating structure to replace gravity is easier on moon than on orbit. Build circular tunnel deep enough. Then build maglev track inside it. Then a train going around. On orbit very strong structure is needed to provide centripetal force. Moon rock does it for free. Moons also give

Yes aerobraking to Mars saves fuel. It has also destroyed many probes. How many failures while landing to the Moon?

 

[jkn]

I get it that Mars has an atmosphere and the Moon doesn't. I don't understand why this matters though. The low air pressure and high carbon dioxide levels would make the Martian air unbreathable. Do scientists really think they can eventually transform the Martian atmosphere so that people can be outside without a spacesuit?

In very long time scale yes. How fast would it leak to space? Could we prevent leak by creating artificial magnetic field? In short time scale atmosphere gives easily O2 and C. It can also create dust storms preventing solar energy production for weeks. So Mars base needs nuclear reactor.

Base on pole of Mercury would be interesting. Unfortunately not practical target with chemical rockets.

 

[mfb]

I get it that Mars has an atmosphere and the Moon doesn't. I don't understand why this matters though. The low air pressure and high carbon dioxide levels would make the Martian air unbreathable. Do scientists really think they can eventually transform the Martian atmosphere so that people can be outside without a spacesuit?

The atmosphere is a convenient source of carbon and oxygen. Melting the ice caps could lead to a larger pressure, rising temperatures and making spacesuits unnecessary (you would just need an oxygen mask). And in the very long run, it is possible to make a breathable atmosphere.

If it's in interstellar space, it's not a threat until it gets closer. That has a time scale of centuries.

The free-fall time from 50 AU is about 80 years, with some initial velocity an object can come to the inner solar system in less than 50 years. Not so much warning time for a comet that could potentially kill all life on the surface of Earth.

It is more sensible to build habitable space ships near earth. As the numbers expand we can consider colonizing Mars or ths satellites of Jupiter and Saturn. To start with we should promote a massive population explosion. 7 billion is too small, at least 30 billion is needed. Near outer space can easily sustain 15 billion to start with.

A massive population explosion is the worst thing that can happen. We don't have the technology or the resources to have billions living in space. A larger population means we'll fight even more over resources on Earth. There is not even an advantage of such a huge population, apart from slightly more R&D capabilities.

If SpaceX rockets keep on exploding once a year, they are not cheapest. So no success yet.

2 failures in 29 attempts is roughly the industry average of 5%. Commercial satellites are insured, and insurance rates for Falcon 9 are similar to other rockets. It is the cheapest rocket (in its payload range of course).

A base on surface needs satellites to control rovers all over Mars. Moon base needs satellites only if they want continuouss acces for all rovers. There is no point to land if work can be done without.

We have those satellites already, and even if we wouldn't, they are cheap compared to a manned base. Controlling rovers only a few minutes per day is stupid if you can control them all day.

Martian moons provide same radiation and meteorite protection as Mars. Perhaps they need to dig slightly deeper. But that's easy because nothing weights much.

Microgravity makes construction harder, not easier. And it makes it much slower.

Build circular tunnel deep enough. Then build maglev track inside it. Then a train going around.

Okay, now we are certainly in the science fiction range.
The moons are not solid rocks, you have to stabilize every tunnel you want to dig. And maglev trains ... yeah, okay. No.

On orbit very strong structure is needed to provide centripetal force.

A long string and a counterweight. Which is something like a 100 times cheaper than a maglev tunnel on a moon.

Yes aerobraking to Mars saves fuel. It has also destroyed many probes. How many failures while landing to the Moon?

Aerobraking didn't destroy any probe so far. One probe got lost when it entered the atmosphere while not being designed for it. A few probes crashed while trying to land. So what? We had many successful missions to the surface already. We didn't have any missions landing on a Martian moon so far (3 were launched to land on Phobos, but none of them reached it).

How fast would it leak to space? Could we prevent leak by creating artificial magnetic field?

Leaking would be a process that takes millions of years, and we can create an artificial magnetic field. It would be possible (but extremely expensive) even with current technology.

Dust storms reduce the solar power output by ~50%, maybe a bit more. Inconvenient, but not fatal for a colony. You can store a lot of energy via methane and oxygen with reasonable conversion efficiencies.

 

[jkn]

If it's in interstellar space, it's not a threat until it gets closer. That has a time scale of centuries.

Interesting question is: When would we notice it? Dino killer was 10 km (20 km?). It would destroy our civilization, if not all of us. Would you survive, if you had to collect, hunt and grow you own food? How long before impact would we see it? New Horizons went to Pluto in 10 years. Interstellar object could come in much faster. If it comes from Kuiper belt or from Oort cloud, it would be slower. Even then I doubt we could find it more than few years before impact. Not enough time to do anything.

 

[jkn]

...
2 failures in 29 attempts is roughly the industry average of 5%. Commercial satellites are insured, and insurance rates for Falcon 9 are similar to other rockets. It is the cheapest rocket (in its payload range of course).We have those satellites already, and even if we wouldn't, they are cheap compared to a manned base. Controlling rovers only a few minutes per day is stupid if you can control them all day.Microgravity makes construction harder, not easier. And it makes it much slower.Okay, now we are certainly in the science fiction range.
The moons are not solid rocks, you have to stabilize every tunnel you want to dig. And maglev trains ... yeah, okay. No.A long string and a counterweight. Which is something like a 100 times cheaper than a maglev tunnel on a moon.Aerobraking didn't destroy any probe so far. One probe got lost when it entered the atmosphere while not being designed for it. A few probes crashed while trying to land. So what? We had many successful missions to the surface already. We didn't have any missions landing on a Martian moon so far (3 were launched to land on Phobos, but none of them reached it).Leaking would be a process that takes millions of years, and we can create an artificial magnetic field. It would be possible (but extremely expensive) even with current technology.

Dust storms reduce the solar power output by ~50%, maybe a bit more. Inconvenient, but not fatal for a colony. You can store a lot of energy via methane and oxygen with reasonable conversion efficiencies.

5% failure rate is not good enough for manned missions. Even Space Shuttle was better. I guess insurance companies assume new launcher is not better than industry average, so their insurance has not risen. If this explosion / year continues, they are in trouble.

Controlling rovers only a few minutes per day! How do you get that? Even Phobos is 6000 km above Mars. Rovers near poles need satellite link.

I doubt that microgravity makes construction very hard. We have not done anything in such gravity. I don't know if micro gravity is correct term. It's used in Space Station. Perhaps milli gravity would be better. It is not possible to jump to escape velocity from Deimos. Running at escape v with space suit is also impossible. So gravity is not useless. Cubic meter of solid rock would weight about one kg. Tunneling machinery on Deimos would look very different than on Earth. Perhaps martian moons are too unstable to build on. Even then we need lot of mass radiation protection. Best source for that is moons.

Maglev trains are in use already. What is problem here? Structure of moons might be a problem. Stabilizing it is not an enormous problem. Gravity is low -> pressure against tunnel wall is low. Rather thin wall is enough. I repeat: we need Moon base to provide materials for expansion. Lifting everything from Earth is not possible.

A long string and a counterweight. Now you forget cosmic radiation. Lot of mass is needed to block it. Perhaps humans can tolerate it few months during trip to Mars. But for longer time protection is needed. String cannot support rotating radiation shield. Rotating part must be light. Heavy shield must not rotate.

Not aerobraking directly. How about heat shield and parachute separation failures? Moon lander can have antennas, solar panels and landing legs in position before landing. Mars lander must open up after heat shield and parachute separation. Lot of moving parts that could fail.

Do we know that dust storm reduce the solar power output by ~50%? Has any probe been active during planet wide dust storm?

 

[Sankar Raman]

"
"We don't have the technology or the resources to have billions living in space."
Yes we do. To start with we can mine the asteroids and comets.
Further a distributed space colony is the safest against any disasters. Of course a global cooperation is needed to implement space colonization.
We have to develop Robotics to mine asteroids as well as even Venus for energy resources. Space travel will become as common as Air Travel today!

 

[mfb]

5% failure rate is not good enough for manned missions.

It is the failure rate for unmanned missions. If the missions would have been manned, the crew would have been fine in both cases. In the second explosion it wouldn't even have been in the rocket.
The failure rate (=crew died) for manned spaceflight so far is about 1%: 315 launches, 4 crews died.

Controlling rovers only a few minutes per day! How do you get that? Even Phobos is 6000 km above Mars. Rovers near poles need satellite link.

Fine, a few minutes were too pessimistic. You are still limited by the condition that the moon has to see the rover, and that the rover needs sunlight at the same time. Anyway, the point is irrelevant, as satellites are easy: you would want them even if you stay on a moon to cover the time where the moon is over the night side. The crew will have access to rovers basically 24/7 (as we have now already).

Experience with very low gravity: We built MIR and the ISS. Gravity on the tiny moons is irrelevant compared to inertial forces for most steps.

Jumping to escape velocity on Deimos is impossible thanks to the space suit, but jumping for 1 minute with every step is bad enough. Free-fall time for 1 m height is ~25 seconds, for a final velocity of just ~7 cm/s.

Even then we need lot of mass radiation protection. Best source for that is moons.

Or Martian regolith. It is literally just lying around in unlimited amounts. Ice would also be possible, potentially doubling as water reservoir for a station.

Maglev trains are in use already.

Yes, on Earth, constructed by an army of highly skilled workers, with tons of specialized materials constructed by even larger armies. Add even more people and a heavy tunnel boring machine for the tunnel. How many kilotons of material did you plan to ship to Mars for the first few astronauts? No, you cannot quickly build a superconductor factory on a moon - all that stuff has to be shipped.

Pressure against the wall would be coming from the train, no gravity involved.

A long string and a counterweight. Now you forget cosmic radiation.

No. Take material from the moons ;). You don't need any fancy assembling. Have some (inflatable?) empty containers, fill them with stuff from a moon, go back to a Mars orbit (negligible delta_v), attach them to the station.

Where do you see the problem with the string? With two equal masses rotating, something like 200 m of string should be fine. At that length, existing fibers just need 0.1% of the station mass as cable mass (safety factor of 2 included already). You can support 1000 tons of station plus shielding with a single ton of cable.

Opening antennas and so on wouldn't be a large problem for a manned missions, humans can fix things if they get stuck.

Do we know that dust storm reduce the solar power output by ~50%? Has any probe been active during planet wide dust storm?

Spirit and Opportunity, 2007. 750 Wh/sol -> 490 Wh/sol for Spirit. Dropped later to 260-300, probably due to dust accumulation. You can clean the solar cells of a Mars outpost.
There is an additional nice effect: those dust storms occur close to perihelion (with a causal relation), where Mars receives 40% more sunlight than during aphelion. The first 30% decrease in sunlight are "for free" - you need that contingency for aphelion anyway.
Older publication: http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources30.pdf - Figure 6. You need a really serious storm to get below 50% irradiance. The direct component can become negligible, but scattered light is sufficient.

"We don't have the technology or the resources to have billions living in space."
Yes we do. To start with we can mine the asteroids and comets.

Total amount of matter mined from asteroids and comets so far: Less than 1 gram. I wouldn't call that "asteroid mining".
Not even the most overoptimistic proposals for space exploration would lead to billions of people in space within our lifetime.

 

[PAllen]

Is it possible to estimate the order of magnitude probability of a 500 km interstellar object getting anywhere near Earth in the next e.g. 100 million years? I have no idea how to quantify this; my intuition suggests many orders of magnitude less than other possible extinction scenarios.

 

[rootone]

That's about the size of Vesta, the second biggest asteroid known in the solar system, and a lot bigger than many planetary moons.
Since these are clearly visible we can safely assume there are no undiscovered bodies of that size any closer than Neptune.
Beyond Neptune there are a number of minor planets, (Pluto having been now reclassified as such.)
That region is not yet well explored, but indications are that it probably is mostly empty.
The Oort cloud is hypothesised to exist way out beyond Neptune and may be the origin of occasional large comets that arrive in the inner solar system.
However Jupiter steers most of these away from Earth and even if it didn't, the Earth really is a very small target, much more easy to miss than to hit.

 

[lifeonmercury]

How would the Mars settlers communicate with Earth during periods when the two planets are on opposite sides of the sun?

 

[rootone]

One or more satellites could be parked in an orbit around the Sun from where both Earth and Mars are contactable at these times.
It would act as a relay for signals, (so slightly greater transmission times, but that's better than no signals)

 

[1oldman2]

Interesting question is: When would we notice it? Dino killer was 10 km (20 km?). It would destroy our civilization, if not all of us. Would you survive, if you had to collect, hunt and grow you own food? How long before impact would we see it? New Horizons went to Pluto in 10 years. Interstellar object could come in much faster. If it comes from Kuiper belt or from Oort cloud, it would be slower. Even then I doubt we could find it more than few years before impact. Not enough time to do anything.

As an example, today on January 9th 1247 GMT we had a two day "heads up" as an asteroid estimated at 11 to 34 meters passed at a distance of half way between the Earth and the Moon, certainly no "dino killer" but this highlights the advanced warning problem we face. Of course the size and Albedo make a huge difference in detection time but there's a lot of surprises in store for us out there in space.
http://www.space.com/35257-asteroid...-2-days-after-discovery-commentary-video.html

 

[lifeonmercury]

Will the Mars One mission establish the settlement near Mars' equator? Apparently the temperature there can get well above freezing.

 

[Jeroen537]

Before speculating on colonization of Mars, a note of caution. It may be that travel to Mars, let alone living on Mars, is simply no feasible option for humans.

Recently, Nature published a paper on the risk of cosmic radiation for the Central Nervous System (CNS). A summary of this and related research can be found at http://www.sciencealert.com/mars-bound-astronauts-risk-long-term-brain-damage-and-chronic-dementia. This document also contains a link to the Nature paper.

So far, no believable countermeasures to stop cosmic radiation from inflicting damage to passengers on a spaceship have been suggested, and in view of the enormous energy of cosmic radiation these may well prove unattainable. The possibility of repairing damage to the CNS on the fly is pure speculation at this point.

So, fun as it is to dream about space colonization, it is far from certain that it will ever be possible.

 

[Joshua_T]

It seems to me that the most common reason for wanting to colonize Mars is in case of an extinction level event on Earth. If all that you are trying to do is protect the human race, why not spend the money and resources developing ways to counter any extinction like event here on Earth?

It could be things like medical technology to prevent disease, anti-asteroid systems to counter asteroids, or even make orbital nuclear defense systems to defend against aliens (I doubt they exist but its good to be prepared). All of this would be a lot cheaper and happen in a much shorter time than colonizing and terra-forming Mars.

I really like Musk's work and its a great idea to colonize another planet, but I don't think that its the most practical way of protecting the human race.

Think of the Earth as a military base that you are trying to protect against a major scale attack. Wouldn't it make more sense to spend all of the resources that you have on making sure that it can withstand any attack rather than making a smaller base in the mountains as a backup in case the first is destroyed?

 

[mfb]

Is it possible to estimate the order of magnitude probability of a 500 km interstellar object getting anywhere near Earth in the next e.g. 100 million years? I have no idea how to quantify this; my intuition suggests many orders of magnitude less than other possible extinction scenarios.

500 km: extremely unlikely.
10 km: Quite likely. We have impacts of that size on average every 50 million years.

However Jupiter steers most of these away from Earth and even if it didn't, the Earth really is a very small target, much more easy to miss than to hit.

Jupiter steers as many towards Earth as it steers them away - apart from the few that hit Jupiter. It makes the orbits unstable over long timescales, so something either hits or gets kicked away after a while.

One or more satellites could be parked in an orbit around the Sun from where both Earth and Mars are contactable at these times.
It would act as a relay for signals, (so slightly greater transmission times, but that's better than no signals)

Transmission times are not the main issue. A relay satellite reduces bandwidth massively. You can't use "small spacecraft communicates with large Earth-based dish" any more, you need spacecraft - spacecraft communication over interplanetary distances. Better than no signal, but transmission will be limited to the most urgent things during opposition. This is just a 2-3 weeks period every 26 months, luckily.

Will the Mars One mission establish the settlement near Mars' equator? Apparently the temperature there can get well above freezing.

Mars One is a PR stunt, nothing more.

Recently, Nature published a paper on the risk of cosmic radiation for the Central Nervous System (CNS). A summary of this and related research can be found at http://www.sciencealert.com/mars-bound-astronauts-risk-long-term-brain-damage-and-chronic-dementia. This document also contains a link to the Nature paper.

Experiments with mice. The radiation levels for a trip to Mars are higher than in low Earth orbit, but the mission to Mars (one way flight time) is significantly shorter than the longest trips to orbit.

 

[UsableThought]

So far, no believable countermeasures to stop cosmic radiation from inflicting damage to passengers on a spaceship have been suggested, and in view of the enormous energy of cosmic radiation these may well prove unattainable.

I know nothing of the topic, but on the lowest possible level of "doing a quick Google," I find multiple hits from credible sources saying that yes, as of now it's a hard problem (and one that has been known about for many years), but nothing saying it is an insoluble problem.

E.g. see this Space.com article from 2015 which lists the 5 winning submissions for shielding/mitigation sent into a NASA prize competition for the public; the submissions don't adequately solve the problem but apparently suggest further avenues for research; and this of course is in addition to whatever else is being researched by government and/or industry: http://www.space.com/29512-mars-mission-radiation-nasa-challenge.html

Also, this 2016 Smithsonian article on the problem quotes "radiation expert Ron Turner, a senior science adviser at NASA's Institute for Advanced Concepts in Atlanta," saying that the most efficient solution might simply be a quicker trip to Mars to minimize exposure: ""The best bang for the buck is advanced propulsion, not shielding." http://www.smithsonianmag.com/science-nature/radiation-remains-problem-any-mission-mars-180959092/

 

[Al_]

It's certainly a good question, but I think there are two main reasons that people have fixated on Mars rather than the moon:
(1) Mars has a day/night cycle very close to Earth. The moon has a 4 week day/night cycle. During the two week night, it gets extremely cold, and solar power is not available for generating energy.

There is almost permanent sunlight available at the Lunar poles. Some long power cables to connect PV panels placed at different spots, and you have 24/7 power.

(2) Mars has a ready supply of water, which is essential for any human colonization. The moon might have water in permanently shadowed craters at the poles, but this has not been proven. Elsewhere on the moon is extremely dry, so water does not appear to be available.

The Moon has water, http://www.jpl.nasa.gov/news/news.php?feature=3887 and Nitrogen, and everything else. Just a bit deeper down. It also has caves. Great places for a base.
We would need to prospect the Moon just as much as Mars, and controlling robots from Earth is much easier with a 3 second delay than with the 20 minutes it takes on Mars.

 

[Gary Weller]

I'd like to see an outpost created on the Moon as a stepping stone to Mars or elsewhere. Perhaps mining the moon for whatever ingredients we can to build a larger ship that would have far less trouble launching. Of course I understand that the Moon doesn't have everything we need, not even close, but it's still a good start.

 

[Al_]

Before speculating on colonization of Mars, a note of caution. It may be that travel to Mars, let alone living on Mars, is simply no feasible option for humans.

Recently, Nature published a paper on the risk of cosmic radiation for the Central Nervous System (CNS). A summary of this and related research can be found at http://www.sciencealert.com/mars-bound-astronauts-risk-long-term-brain-damage-and-chronic-dementia. This document also contains a link to the Nature paper.

So far, no believable countermeasures to stop cosmic radiation from inflicting damage to passengers on a spaceship have been suggested, and in view of the enormous energy of cosmic radiation these may well prove unattainable. The possibility of repairing damage to the CNS on the fly is pure speculation at this point.

So, fun as it is to dream about space colonization, it is far from certain that it will ever be possible.

Personally, I wouldn't want to spend that long in space without a LOT of radiation shielding. It's really expensive to lift that much shielding stuff up from Earth, but if you take the raw materials from the Moon, it uses far less fuel. It might even be possible to launch it from the Moon by a magnetic launcher. I bet that Mars will eventually be colonised from the Moon, not from Earth! But, why would anyone want to hide themselves away down a deep gravity well like Mars, when they could stay free and make use of all those huge resources easily transportable from the small bodies with no real gravity?

 

[Al_]

I'd like to see an outpost created on the Moon as a stepping stone to Mars or elsewhere. Perhaps mining the moon for whatever ingredients we can to build a larger ship that would have far less trouble launching. Of course I understand that the Moon doesn't have everything we need, not even close, but it's still a good start.

I disagree - the Moon does have everything we need. Just a little bit underground. It's a huge moon after all!
It's way easier to go to the Moon with a bucket and a shovel than to go to Mars with a bucket and a trowel.

 

[PAllen]

500 km: extremely unlikely.
10 km: Quite likely. We have impacts of that size on average every 50 million years.

But wouldn't those 10 km impacts be almost all from objects already in the solar system? What I am wondering is the question you raised in passing: is there any way to guess, even if we can't know, about how often a substantial interstellar object passes close to earth?