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Moon vs. Asteroids/NEOs Near Earth vs. Mars : Lunar Polar is Best

For human settlement as well as potential financial profitability, sustainability, and growth, this page compares Earth's Moon vs. Near Earth Asteroids/Objects (NEA/NEO) vs. Mars for their relative merits across important factors. The lunar poles are assumed the location of choice on the Moon; nowhere else being considered on the Moon.

The goal is to achieve self-sufficient human colonization of space, in a secure, permanent way, at least. I would also have the goal of developing space resources to benefit Earth, but some people disregard this goal. Either or both ways, you can use the tables below to compare the different options of lunar polar vs. the best Near Earth Asteroids/Objects (NEOs) vs. Mars.

This is about finding the best location for the most economical, lowest risk, most sustainable, most profitable, and potentially highest growth location, with quickest payback, for investors with a reasonable amount of money and a sense of urgency.

This does NOT consider government funding. This comparison is not made for people who intend to rely on government funding for their space projects and who would otherwise not do anything without government funding. This comparison is made for purely private sector ventures. This is also not about "manifest destiny" in the far future. It focuses on the practical, now, instead of the overly imaginary.

Likewise, this does NOT consider scientific interests like telescopes, the search for primitive life, understanding the evolution of the solar system, etc. It also doesn't value just exploring new and different places for something new and different. In fact, it values the opposite, in that old and better known places are safer bets. Nor does it address the faithful's emotional desires to go stand or explore in some particular place for the human experience. All these things will later benefit from the success of a purely private sector venture, and a private entity could sell telescopes, tours, etc., but it's not the main basis of an initial private sector venture, the first steps.

(Nor is it just about what would be cool or interesting, nor about just doing something very different from what we've ever done before ... and I tire of hearing simplistic conclusions without much consideration ... especially by journalists who haven't bothered to do their research well or just don't care about much more than selling an attractive storyline.)

(I use NEO for "objects", not "asteroids", because many scientists consider "asteroids" to have originated in the inner solar system but not include comets from the outer solar system which were captured into the inner solar system during flybys. These captured comets are expected to have significantly more volatiles, which are crucial for both life support and space based industry.)

Based on the above, the following is a systematic comparison. Just to make clear, I did not start with any bias based on emotion or self-interest or some sort of vision to promote, this is simply looking for what is most likely to succeed. I have read many advocates promoting their preference like somebody selling a business product, by emphasizing the benefits of their destination and the disadvantages of alternatives, without pointing out contrary points or giving a balanced comparison. You are welcome to send comments to me for consideration.

This will start with a chart summarizing my analysis, and after the chart each row will be discussed.

Moon (lunar polar) vs. asteroids (NEOs) vs. Mars
color coding:
best
middling
disadvantageous

Familiarity with resources: Lunar polar NEOs (the selected best) Mars
Sampling and probes Apollo samples returned, many probes Probes of different objects Probes

Familiarity with resources:

To "live off the land" we need to send equipment to extract and process the local materials, and that equipment had better work well on the local materials if we expect people to survive there for long. We must have a sufficient knowledge of the local materials in abundance for sure, and in what forms for the right equipment to process those materials.

For the Moon, we have lots of Apollo samples from different locations which were brought back to Earth for detailed analysis, plus some Soviet Luna samples and a little bit from the Chinese. We have some small samples retrieved from some asteroids but not the ones we would mine. We don't have any samples retrieved from Mars, though we have sent many probes so have a fairly good idea. Asteroidal materials can be compared to meteorites, but there can be expected to be some differences between what will survive as a meteorite and be identified as one, versus what we may find on the ordinary surface.

A problem with asteroids / Near Earth Objects is that they can vary greatly between bodies, far more than between different areas on the surface of the Moon or Mars. We have not yet sent a probe to any economically attractive asteroid, only to uneconomical ones. It would be far more risky to send material processing equipment to an unprobed object, just based on its lower cost to go there and back. We can get some idea of an asteroid's composition by telescopic spectroscopy, but much more from a probe. There is considerable debate about whether samples need to be returned to Earth, or whether advanced prospecting probes would be sufficient.

The Moon is the best characterized, but just because it's green in the chart, that is just a relative ranking, with the returned Apollo samples helping the Moon's relative ranking. However, the lunar poles have yet to be visited on the surface, and all data on the poles is from probes in very low orbits (since the Moon has no significant atmosphere). The poles are expected to be mostly the same kinds of materials as other lunar samples but with volatiles mixed in which are easily extractable by just heating.

While we could send some general equipment to a lunar pole and it might work well, there would still be benefits to sending more probes to get a more detailed understanding of a particular site. However, we may not be able to afford to take too long, fall for prospective contractors who push for too much detail thereby needing excessive services to be paid for in the form of still more of their studies and more of their probes, or get too conservative and risk averse ourselves, as those can lead to getting bogged down and financial failure. This also applies to asteroids and Mars, of course.

Mission deployment costs: Lunar polar NEOs (the selected best) Mars
Research and development returned samples to work with zero G mining, variety of NEOs reasonable simulants
Deployment fuel Interorbital (IO) + landing Interorbital (IO) interorbital (IO) + landing
Deployment time days to weeks weeks to months months to years

Mission deployment costs

How much time and money is needed for each scenario, relatively speaking, before payback? The costs can be broken down into research & development in advance, and deployment of mining and manufacturing equipment.

Research and development

All scenarios require a lot, so these are just relative rankings, e.g., a green rank does not mean cheap. Research and development is facilitated by the existence of samples, which exist for the Moon due to the Apollo missions, though as mentioned before, information from surface probes and remote sensing by orbital probes and telescopes can also be used. The Moon and Mars are more consistent across their surfaces than asteroids / NEOs. Lack of experience in mining in nearly zero-g disfavors asteroids, but not too much. Experience with landers favors the Moon and Mars. It's assumed that no Mars launch rocket needs to be developed, and all astronauts going to Mars accept a one-way ticket, in order to minimize R&D costs for Mars in this analysis.

As noted in a later section, it's difficult to make a case for Mars as regards returning any goods or services to near-Earth space, so it's assumed here that nothing is returned from Mars, but for the Moon and asteroids near Earth, money can be made this way, which creates the need for an economical lunar launch system and interorbital vehicles to return materials for lunar and asteroidal mining scenarios. This adds to the R&D costs for the Moon and asteroids, a little more for the Moon. However, the vehicles for interorbital transport and landing can be reused for return missions, if refueled on site.

Deployment fuel (outbound from Earth)

Of course, once we arrive at any of these destinations, we can start making fuel propellants from local resources, and don't need supplies from Earth anymore, but the first mission will need to be fueled by Earth launched propellants.

Some asteroids near Earth have a very low outbound "delta-v" which offers minimal fuel to reach it and rendezvous and land upon it. The Moon is obviously a much lower delta-v object to reach than Mars, for the interorbital journey. For the final step, landing, the Moon is also much smaller so that less fuel may be needed for a fueled soft landing, but Mars has a thin atmosphere which can provide a lot of braking, though not all of the necessary braking for landing humans or a large amount of equipment. Mars' atmosphere is only about 1% of Earth's so it may be a very rough landing if atmospheric braking is heavily relied on, and a heavy parachute would also need to be accounted for.

Deployment time

Time is money, especially given overhead (staff, facilities, etc.), and if you've got competitors then it's advantageous to get your product to market more quickly. The Moon is just days to weeks away (depending upon vehicle -- human or cargo), all the time. "Near Earth" objects much further and with accessibility varying a lot, with "launch windows", but we can assume months. Mars is months away, at the best times, with "launch window" every 22 months (yes, almost 2 years). That's just for the outbound journey. Emphasis: The Moon is just days to weeks away, all the time.

Financial return, sustainability: Lunar polar NEOs (the selected best) Mars
Product return time days to weeks Weeks / months / years not economical, full stop
Product return cost Launch from moon + IO IO only but quite variable not economical, full stop

Financial return, sustainability

Mars' surface is simply not a location to export goods and services, except a reality TV program, and reality TV can also be exported from the Moon and asteroids. Here, we are looking at exporting goods and services, such as fuels and building materials for near Earth large scale space structures, industry, and colonization.

Product return time

We can launch stuff off the Moon and have it in a suitable high Earth orbit within days to weeks, all the time. Returning things from asteroids / near Earth objects would typically take months, and the return time is inconsistent due to the varying relative orbits, since the Moon goes around the Earth but asteroids/NEOs go around the Sun.

Notably, it has been suggested that Mars' two small asteroidal moons, Phobos and Deimos, might be attractive for mining. As noted before, Mars' distance from Earth varies, e.g., sometimes it's on the opposite side of the Sun, and of course at closest approach it's still tens of millions of miles/kilometers away, whereby the economical return time would range from months to years. Generally, we should compare these two moons to "near Earth" asteroids and objects, not to Mars the planet itself with its additional landing and launching costs.

Product return cost

Products must be launched off the Moon, which requires propellant extracted from the Moon, at least until an electromagnetic launcher is developed and deployed (being that electromagnetic launch is feasible since the Moon has no atmosphere and a low launch velocity). For this analysis, I assumed no electromagnetic launcher. (However, an electromagnetic launcher could significantly improve the economics of launching from the Moon, there has been research on these going back decades, and electromagnetic launchers are currently operational on military ships so it's not so far fetched as regards R&D and experience to date.)

While theoretically it may require less fuel to return material from an asteroid near Earth, it's important to keep in mind that the return delta-V and time of transit from near Earth asteroids varies greatly over time due to its orbit around the Sun. It would need to be a very special NEO to compete with the Moon for just return delta-V, all considered.

Resources: Lunar polar NEOs (the selected best) Mars
Volatiles High certainty already Unsure if unprobed High certainty already
Metals Free metal granules Granules and/or chunks Free unlikely, can manufacture
Glasses & ceramics High certainty already High certainty already High certainty already

Resources

Volatiles

Water, carbon, and nitrogen are vital for supporting life. Mars has these in great abundance, as do parts of the lunar poles.

Probes have indicated that Near Earth objects might typically be a lot drier than hoped decades ago. Some are extinct comets, but there is a lot of debate about the potential density of volatiles remaining in NEOs of cometary origin, and we don't have evidence of the abundance of volatiles in NEOs like we do for Mars and the lunar poles. It would be risky to go to a NEO assuming it has lots of volatiles which could be economically extracted in sufficient quantity. There needs to be research of the material deep under the surface of particular targeted NEOs, especially those believed to be captured comets.

Metals

Metals can be extracted from selected minerals on all bodies. However, free nickel-iron metal granules and chunks exist and are most abundant in asteroids, and highly abundant in lunar regolith, but not on Mars due to oxidation. This is the easiest and cheapest way to source some good metals.

Glasses and ceramics

Similar to how concrete is used on Earth, many structures can be built from the abundance of materials on the Moon, Mars, and asteroids, which can be made from minimally processed regolith and rocks, to produce fiberglass, glasses, and ceramics, without the need to consume any or significant amounts of volatiles. The Moon, Mars, and asteroids may be equivalent in this regard. "Cement" like used on Earth using volatiles is another matter, but should be unnecessary, though feasible with volatiles.

Potential exports: Lunar polar NEOs (the selected best) Mars
Volatiles Known from orbital probes Unsure if unprobed not economical, full stop
Metals Free granules or manufactured Free granules or manufactured not economical, full stop
Glasses & ceramics Abundant and easy Abundant and easy not economical, full stop

Potential exports

Exports are for selling to make money and make the business sustainable and grow.

Exports could be either finished products or feedstocks, and it may be assumed that they are to be delivered to high Earth orbit (whereby they could also be further distributed to low Earth orbit or anywhere). This topic gets a little bit complex due to the variety of products and services which could be provided by space resources.

Orbital space offers 24 hour solar power. Mars has nights of similar duration as Earth, but the Moon has nights lasting 2 weeks, though it has been argued that parts of the lunar poles have continuous or nearly continuous sunlight. Asteroids would have continuous sunlight off the surface in orbit, and asteroids usually have short rotation times so not much energy storage is needed.

Orbital space also offers more flexibility in manufacturing due to the option of zero gravity, and low gravity (centrifugal) processing, very large solar power arrays, and containerless ultra high temperature processing.

It has been argued that it may be more economical to launch material from the Moon to be processed in factories in orbit, and to not bother with the expense of landing a lot of the industry onto the Moon's surface, but instead build up giant factories in orbital space. Therefore, there would not be much need to launch final products, and launch of standard feedstocks would be simpler. This would be materials which have been processed to some extent on the Moon for higher quality feedstocks, such as standard billets or containers of uniform feedstocks, with pre-processing equipment on the lunar surface. Likewise, for asteroids, there's a similar analysis for returning processed feedstocks to industry in Earth orbit.

Volatiles

These can be primarily fuel propellants, life support elements, and industrial processing chemicals.

Water, liquid oxygen, liquid nitrogen, carbon, and various other chemicals can be produced from reasonably abundant sources in the lunar poles, and abundantly on Mars' surface, but how abundant they are on a near Earth object such as a dormant comet is questionable.

Metals

Metals for export include iron, calcium, magnesium, aluminum (on the Moon especially), titanium, and others, by basic industrial processing, whereby the three candidate sources could be considered roughly equivalent. Processing methods can vary. Here, it's mainly worth mentioning the exportable metals early in space development.

Significantly, there are free nickel-iron granules which also contain significant amounts of cobalt, platinum group metals, and other elements, which can be easily separated by crushing and magnets. These are fairly abundant on the lunar surface, and very abundant in many near Earth objects, but not abundant on Mars.

Glasses and ceramics

Most things on Earth are not made from metals, but instead from much cheaper bulk materials.

Basic dirt and rocks can be processed and used as bulk materials for various things by melting, and there are relatively simple pre-processing methods to separate minerals for particular characteristics (magnetically, electrostatic beneficiation, ...). Many space development scenarios use a lot of fiberglasses, ceramics, and glasses.

Power supply: Lunar polar NEOs (the selected best) Mars
Solar power 2 weeks/night, maybe polar points Continuous Further from Sun, 12 hour batteries
Nuclear May be recommended Not needed, small backup May be recommended

Power supply

In orbital space, we have 24 hour solar power in abundance, for both electricity and heat. Asteroids and industry in high Earth orbit can benefit from this.

The lunar surface has 2 week nights, which becomes problematic if we depend upon solar power and so would need a lot of energy storage. There are some locations on peaks within the lunar polar region which are continuously lit, and electric power could be beamed to places at night, though this all starts to get a bit complicated. Mars has nights similar to Earth's.

Otherwise, nuclear power sources can be used for electricity and heat, but again, this starts to get more complicated, especially for large scale industry during the nights.

In orbital space, solar arrays can be very, very large, and made of relatively thin materials. Large solar arrays can be built on the lunar surface since there is no wind and the gravity is low. On Mars, there are occasional winds and dust storms, and the gravity is higher.

(It's also possible to radio beam power from orbit based solar power satellites, such as from a space station in lunar polar orbit, and dedicated power utilities in orbital space would of course use beams instead of wired transmission, but this starts to get a bit further than the first steps.)

Human and robotic missions: Lunar polar NEOs (the selected best) Mars
Robot comm. round trip ~2.5 seconds Minutes, variable ~6 minutes to ~44 minutes
Radiation risk (flares, cosmic) Shortest trip, polar craters, tunnel in Long trip, tunnel in, go behind Long trip, tunnel in
Human deployment days to weeks Weeks / months / years long trip plus risky landing
Human emergencies days to weeks Weeks / months / years months at best, bigger rocket

Human and robotic missions

Humans are very expensive to send into space and maintain, so a high reliance on teleoperation and autonomous robots is preferred, especially in the early phase. Nonetheless, having versatile humans on-site can greatly help productivity and fix unforseen problems.

Eventually, we want human bases with high enough populations and advanced capabilities to become autonomous and give our species survival. However, we won't get to that point of take-off if our initial costs are too high and the project fails financially early on due to the high costs of deploying too many people too early.

Robot communications round trip

A lot of work will require teleoperation of robots. While theoretically, many things should be able to be done with autonomous robots, realistically we will do a lot of teleoperation, and for the sake of decent productivity and much quicker results, there is a great benefit to short round trip communications times.

We've heard a lot of hype about autonomous robots, going back to the 1960s, 1970s, 1980s, 1990, 2000s, and 2010s, and in so many cases it has fallen way short of optimistic projections. In reality, human teleoperation will be important, and productivity will be very sensitive to round trip communications times. This favors the Moon by far, over asteroids and Mars.

Radiation risk (solar flares, cosmic)

Humans in the space station in low Earth orbit are largely protected by the Earth's magnetic field against solar and cosmic radiation, but at all of the considered destinations -- asteroids, the Moon, and Mars -- the radiation is much higher. Mars and the Moon have practically no protective magnetic field, quite in contrast to Earth. It is assumed that once humans reach their destination, they will use local materials to create radiation shielding, so the 3 locations are considered equivalent.

Notably, Mars' atmosphere does not provide much protection. It is only about 1% that of Earth's. (The lack of a geomagnetic field at Mars allowed the solar wind to strip away the vast majority of its atmosphere.)

Different kinds of radiation are attenuated by different kinds of barriers -- such as bulk dirt vs. water ice. Therefore, there is some benefit to having an abundance of water onsite, because water is particularly effective against some kinds of radiation. However, for these cases, I've considered the 3 destinations fairly equivalent, because local materials can be used for shielding, though it takes considerable work.

Next, we consider the radiation threat to humans in transit between Earth and each of these destinations. For example, during the Apollo Project, this was a worry.

Human deployment

To send humans to any of the locations, we must consider the safety of the travel time, due to the radiation in space and potential solar flares. For a longer voyage, we may need more radiation shielding which would thus increase the cost of mass transportation, or else the astronauts accept risks.

During the Apollo Project, the missions were so short that NASA decided to take a small risk and go. If a solar coronal mass ejection towards Earth had occurred, then the mission would have been aborted and the spacecraft would have returned to Earth immediately. However, for longer transit times, especially to asteroids or Mars, there would be no such option, and either we would take higher risks or else we would be transporting a lot more shielding in the spacecraft in transit, even if it's in part storing a lot of water around the spacecraft.

Human emergencies

If there is an emergency which requires a human to return to Earth quickly, such as an illness or injury, or if there's a base disaster, then obviously the closer the better. Of course, this could be relieved if astronauts volunteering for these missions just accept that they aren't going to be sent back and they're going at their own risk, as many people have discussed, and that's fair enough. You may put as little or as much weight on this factor as you prefer. There are lots of astronauts willing to take risks, so I tend to not put much weight on this factor, but it still should be mentioned since it has come up in other discussions.

Conclusion

You may draw whatever conclusion you prefer, but my conclusion is that clearly the lunar poles are the best resources to go after in phase 1 of space industrialization and colonization. Notably, before volatiles were detected at the lunar poles, I was much more interested in Near Earth Objects (NEOs) for supplying volatiles and potentially more. That changed after the Clementine probe detected lunar volatiles apparently in abundance, and especially after Lunar Prospector confirmed it in good detail, after which I changed my mind decisively to focusing on the lunar poles. The general consensus in the greater professional space community has also shifted heavily to the lunar poles as the next major phase of space industrialization and colonization, due to the discovery of lunar polar volatiles. However, some entities stuck to NEOs, such as Planetary Resources, Inc., and of course there are die hards for skipping the Moon for Mars. The greater consensus is that developing the Moon first will give us greater capabilities in regards to Near Earth Objects and Mars later.

PERMANENT was largely created before the discovery of volatiles at the lunar poles, whereby both Near Earth Asteroids/Objects and the Moon were thoroughly covered, and I intend to continue covering significant updates in regard to Near Earth Objects, but the emphasis of PERMANENT is now the lunar poles, and especially the lunar south pole.

Fortunately, NASA has also clearly and resolutely gone in this direction, too, with the Artemis Program, and with an emphasis on infrastructure enabling the private sector to develop the Moon.


Same tables as above, but all together, and shorter without discussion:
Moon (lunar polar) vs. asteroids (NEOs) vs. Mars
color coding:
best
middling
disadvantageous


Lunar polar NEOs (the selected best) Mars
Familiarity with resources: Lunar polar NEOs (the selected best) Mars
Sampling and probes Apollo samples returned, many probes Probes of different objects Probes
Mission deployment costs: Lunar polar NEOs (the selected best) Mars
Research and development returned samples to work with zero G mining, variety of NEOs reasonable simulants
Deployment fuel Interorbital (IO) + landing Interorbital (IO) interorbital (IO) + landing
Deployment time days to weeks weeks to months months to years
Financial return, sustainability: Lunar polar NEOs (the selected best) Mars
Product return time days to weeks Weeks / months / years not economical, full stop
Product return cost Launch from moon + IO IO only but quite variable not economical, full stop
Resources: Lunar polar NEOs (the selected best) Mars
Volatiles High certainty already Unsure if unprobed High certainty already
Metals Free metal granules Granules and/or chunks Free unlikely, can manufacture
Glasses & ceramics High certainty already High certainty already High certainty already
Potential exports: Lunar polar NEOs (the selected best) Mars
Volatiles Known from orbital probes Unsure if unprobed not economical, full stop
Metals Free granules or manufactured Free granules or manufactured not economical, full stop
Glasses & ceramics Abundant and easy Abundant and easy not economical, full stop
Power supply: Lunar polar NEOs (the selected best) Mars
Solar power 2 weeks/night, maybe polar points Continuous Further from Sun, 12 hour batteries
Nuclear May be recommended Not needed, small backup May be recommended
Human and robotic missions: Lunar polar NEOs (the selected best) Mars
Robot comm. round trip ~2.5 seconds Minutes, variable ~6 minutes to ~44 minutes
Radiation risk (flares, cosmic) Shortest trip, polar craters, tunnel in Long trip, tunnel in, go behind Long trip, tunnel in
Human deployment days to weeks Weeks / months / years long trip plus risky landing
Human emergencies days to weeks Weeks / months / years months at best, bigger rocket


Copyright 2019 by Mark Evan Prado, but you may use this chart in presentations as long as you keep the PERMANENT logo on the bottom. You may also request a .jpg version of the table, or a PDF version of this page.

Details on topics above are of course discussed elsewhere on this website.




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