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I suspect Americans will have to get used to a lot of things on Mars that are different from the USA. No guns is quite a logical decision; bullets could cause depressurization. The close spaces of colonies and the gossipy village-like atmosphere would be something our grandparents were used to, but most suburbanites would find alien. Inevitably there would be a more "socialistic" culture because of the greater needs to work together to provide basic necessities such as air. Any Martian colony could not afford to have unemployment or welfare, either, which will change the social structures in ways we can't imagine.
-- RobS
I wonder how much life on Mars would seem like confinement. In January in Chicago, I stay in the house all day, or I split time between house and office. I live in a relatively small area most of the time. Driving outside is nice, but one could do that on Mars in a rover. A walk outside the house is nice, but one could do that on Mars as well, just in a spacesuit.
I think confinement in a space ship for months would bother me. There is no place to "go"; outside is a boring, uniform vacuum, with no landmarks. But in previous centuries a typical European sailing ship confined 100 or so men to a space 100 feet long and 25 feet wide for months at a time. Men slept cheek and jowl in hammocks. Ceilings were barely 5 feet high; many men could not stand up below deck. Go tour the USS Constitution in Boston harbor some time to get a sense of what people have been doing to themselves for thousands of years. It's quite remarkable what people can do together and not just survive, but work together. And the crews of those ships were not screen psychologically; on the contrary, they were often the dregs of society!
I think I could manage fairly well on Mars in a hab, a greenhouse, and a pressurized rover, if I could go outside for a walk once a week or so. Oh, and I'd need my computer. Some people would need a television, and the Mars crews would probably have that, and the web and internet.
-- RobS
In the little bit of research I have done, I don't see any reason to assume that ambient Martian light is insufficient for plants. Corn grows when there'a a month of cloudy weather; it doesn't happen often, but every decade or so it happens. If you had a cylindrical greenhouse with its long axis oriented north-south, in the morning you could lower the insulation on the east side and let in the sunlight; the west side would still have its insulation blanket up, and if the insulation blanket were silvered, it would reflect additional light inside. In the late afternoon you could reverse the process, raising the insulation blanket over the east side of the greenhouse and lowering it on the west side. That would increase insolation maybe fifty percent, making it close to terrestrial normal.
As for the "dim" light bothering astronauts, I don't think anyone would notice. I remember in 1970 I experienced a 95% total eclipse of the sun (I wish I could have gone to the area of totality, but I was too young!). At the height of the eclipse I was experiencing about as much sunlight as Jupiter's moons receive; it was a bit errie, but barely noticable as a fainter background. Next time there is a partial eclipse of the sun in your area, go outside when about half the sun is covered. You won't even notice the drop in insolation. But when its about 95% covered it is noticeable; yet even then, its about like the brightness at sunset.
RobS
My guess is that the first mission or two probably should bring a nuclear reactor and hydrogen and make water from the imported hydrogen and atmospheric carbon dioxide. Extracting water from permafrost may be too difficult to do automatically. A drill could miss an ice pocket, or the drill bit could get stuck and you'd have to wait for an astronaut to show up and fix the problem. Systems using a front end loader to scoop up permafrost may encounter concrete-hard regolith and be unable to do enough scooping. Possibly a system that travels around, covering an area of ground with a metal hood, then heating it from above with microwaves, driving off the water, could extract enough, but then you'd have to bring the water back to the ship and transfer it. If a ship landed on a polar cap, a drill could go into the cryolith, insert heat, and extract the water, but at the possible danger of undermining the vehicle by making a cave underneath it! These problems would be easier to solve with astronauts running around and fixing things or improvising on the spot.
-- RobS
Fascinating discussion about constructing domes. Zubrin's *Mars Direct* assumes that concrete is not necessary, though. One can bury the skirt of a hemispheric dome with regolith and that is enough to counteract the atmospheric pressure. The key is to find the right regolith. For example, there are several former lakebeds that have been located from orbital photography. Their composition is probably layers of fine clay with water-ice still present at depth. Such lakebeds would provide ready water supplies (you'd drill a well and add reactor heat, for example) and uniform, soft materials for excavation. Presumably one could erect a dome in such a material simply by using construction equipment to excavate a circular trench of adequate size, place the dome and its skirt, then backfill. If you want more stability, one could drive steel pylons into the lakebed. All that could be accomplished using machines driven by men without spacesuits.
Air will initially leak out of the dome by perculating through the clay underneath. But you could inflate the dome with Martian air for a few months and add water vapor. The water would perculate into the ground and freeze up the cracks, eventually producing a block of ice underneath the warmed ground. The domes might be leaky, but photosynthesis possibly would produce oxygen faster than the leaks, too. If one surrounded a dome with other domes, the growing colony would only leak air at its periphery, and many domes, surrounded by other domes, would produce surplus oxygen for maintaining the colony's supply.
Terraforming might weaken such domes, but if the temperature on Mars rose enough to weaken permafrost, it would only be after the atmosphere thickened significantly anyway. Under those circumstances the domes would need less mass to hold them down and the differential pressure would be less, leading to smaller leaks.
Since terraforming will most likely take centuries, the earliest domes can always replace concrete with a water and clay mixture if anything strong and hard (and airtight) is needed. Injecting water into the ground around a dome, forming an ice curtain, may be the best way to prevent subsurface air leaks.
-- RobS
One of the references to the area one needs for a closed life support system is this:
http://members.aol.com/dsfportree/ex84k.htm
That's a paper in Portee's fascinating "Romance to Reality" website that is well worth cruising through.
You can also hit a bunch of references if you do a Google search on "lunar wheat." A strange combination, but it pulls up a series of websites about growing wheat on the moon (which would apply to Mars as well).
-- Rob S
I quite agree with Byron that people will probably never live on Venus, and terraforming it is probably too difficult and expensive. But I think remote exploration of the planet from orbit--rather like the current exploration of the Antarctic--is probably of scientific value, especially considering that Venus is almost exactly the same size as earth and may have had oceans in its first billion years or so. For all we know, life may have evolved on Venus first, then was seeded onto Earth and Mars as a result of impacts. We could all be Venusians! Whether that can ever be determined, however, is unclear.
I do see two possible economic uses of the planet: (1) harvesting deuterium from the atmosphere (though it may not be cheap enough to be economical); and (2) it might be a good place to send earth-crossing asteroids. We could crash them there if we wanted to get rid of them, or we could engineer close passes to Venus--grazing the atmosphere--to put them in Venus orbit. Their materials could be harvested and sent back to Earth in small enough chunks to be safe. I suspect (2) is doubtful, though, because we can harvest materials from the asteroids where they are. I doubt there is an economic advantage to concentrating a half dozen or so at a time in Venus orbit and working on all of them with one mining team. The only advantage would be to create a subsidy for Venus exploration; it would be safer to explore Venus from orbit if you were inside a cocoon of several meters of rock and dirt to absorb cosmic rays, and then you might as well haul in an asteroid, build a base out of it, explore Venus, and do some mining at the same time.
As for Europa, it will be very hard to explore it directly by humans because it is imbedded in Jupiter's van Allen belts, and thus is bathed in very lethal levels of radiation. Ditto for Io. Callisto is outside of the radiation belts. Ganymede is inside, but has a magnetic field of its own that may deflect the radiation enough to make the surface safe (I don't know).
Someone asked whether Venus's temperature would change if its rotation rate were speeded up. I don't think so.
-- RobS
The surface temperature estimates of 60s and 70s are misleading. If you go to a beach on a sunny day, you quickly discover you do not want to walk around barefoot unless the sand is wet, because in direct sunlight it gets up to 130 or 140 degrees and it hurts! But the air never gets that warm (thank God). Same on Mars. The surface may warm up to 60F but the air temperature is permanently like Chicago in January; quite a bit below freezing.
But insulation changes the situation drastically. An airtight bubble of plastic will maintain higher temperatures easily. Even a sheet of plastic laying on top of the ground on Earth--not air tight--raises the surface temperature about ten degrees F. I threw a sheet of plastic over my bathtub-sized fish pond in my back yard in northern Indiana last winter. The pond never froze, even though the air temperature hit zero, and one geranium survived the winter under the plastic. I suspect four or five layers of transparent plastic will maintain room temperature during the day, and if you cover the greenhouse at night it'd do okay all night, too.
-- RobS
The closed cycle hydroponic systems being designed for spaceships only need 10-20 square meters per person to recycle waste and feed them a simple diet. I think the calculations for the orbiting colonies were about 50 to 100 square meters per person for agriculture. So I suspect a Martian greenhouse could feed people on 100 square meters per person, especially if supplemental lighting were used. Of course, all of this assumes very careful tailoring of water and nutrients for each species.
-- RobS
Two things to remember about dirigibles on Mars: (1) since the atmosphere is 1% as dense, the dirigibles need 100 times the volume to achieve the same lift, wich means they need about 5 times the height, width, and depth of a terrestrial dirigible; and (2) hydrogen burns in CO2, so a lightning strike could cause a Hindenberg-style disaster, though probably rather slowly.
-- RobS
The weights for the hab and ERV given in *Case for Mars* are a bit misleading because they don't include the aerobrake, landing engine, and landing fuel. But those weights have been included in the plans. Of the 140 tons in low earth orbit, 40.6 tonnes can be put in Mars orbit and 25.2 tonnes on the surface for the piloted option (page 89). The difference between 40.6 and 25.2 tonnes is the mass of the aerbraking system, engines, and fuel.
I agree that a redesigned "Mars Direct 2" plan would be nice to have. But politically, I suspect it is a waste of time. Mars Direct 1 exists to give everyone a rough idea of what can be done. A Mars Direct 2 design will similarly become out of date before anything can actually fly, and will cause people to compare the two and debate their relative merits. What's needed now is effort to find the money, and that means acquiring experience and building trust. Once those exist, you can revise Mars Direct to build something that will actually fly.
-- RobS
NASA is testing robotic construction and they've shown it's possible from Earth (though maybe not for Mars, where the time delays are much longer than on the moon). But assuming you can deploy one-meter-square panels on the surface using a rover and that each one makes 100 watts of power for 8 hours a day, and each panel weighs 4 kilograms, and you can wire them together remotely (which would be pretty tricky!), you'd need 1,000 such panels, weighing 4,000 kg, to generate 100 kw of electricity. That's the weight of the Mars Direct reactor, but it makes 100 kw of power 24 hours a day, not 8 hours a day. Also, 4 kg per panel may be too low; 8 kg may be more accurate. That might be enough power to refuel an Earth Return Vehicle over 18 months. That's all you need, because then the astronauts land and set up another 1,000 square meters of panels, and they makes sure all the wiring is done right. They then have almost as much power as a single reactor to draw off of. During a dust storm it would be reduced to maybe a quarter or a fifth as much for maybe as long as six months, so you'd have to design your human outpost to run on just a few kilowatts of power.
If I have the mass figures right, it might work. But no one yet knows how to deploy and assemble 1,000 square meters of solar panels by robotic rover dealing with a half-hour time delay. A reactor would definitely be simpler.
-- RobS
Phobos and Deimos are marvelous intermediate stations on the way to Mars. Since they are probably made of carbonaceous chondrite (which is several percent water) they probably can be sources of rocket fuel. Ultimately it is probably best to design a reusable one-stage Mars shuttle that goes from the Mars surface to Phobos (delta vee, 5.5 km/sec or 12,300 mph), where it can refuel and head to earth or return to the Martian surface. If you want to export items from Mars--fossiliferous rocks to sell on Earth, or gold nuggets--it would be easiest to fly them to Phobos, accumulate a supply there, then fly up another small batch, refuel with Phobosian fuel, load on board the previous cargos, and head for Earth.
Phobos and Deimos take less delta-vee to reach than the surface of the Earth's moon (delta-vee, 4.3 km/sec, versus 5.5 km/sec), so they might ultimately prove to be as cheap or cheaper a source of hydrogen and oxygen for low earth orbit than the poles of the moon. The lunar poles are unlikely to have very much carbon dioxide or nitrogen; the former is abundant in carbonaceous chondrite and the latter is available.
So it may be cheapest to design a reusable one stage shuttle from the beginning of Mars exploration. At first it would rendezvous with a fully-fueled Earth return vehicle sent from Earth, but if astronauts spent a week visiting Phobos every time they were on their way down or on their way back up--twice every two years--facilities on Phobos could gradually be developed and expanded.
--RobS
I have done some thinking about Venus exploration, and suspect at some point it will be worthwhile remotely from Venus orbit (where communications times are milliseconds, rather than minutes). The Mars Direct architecture will provide humanity with the equipment to go to Venus orbit and continued development of earth orbiting stations will give us the ability safely to put a staffed station in an elliptical Venus orbit (one that would only take a few thousand miles per hour of delta-vee to head back to the earth).
The key to robotic exploration of Venus may very well be solar-powered "high-flier" airplanes that would fly for years above the cloud cover. With solar panels on the tops and bottoms of the wings--to catch the reflected sunlight off the clouds and the light coming directly from the sun overhead--the planes could get up to four times the solar energy per square meter as a solar panel in earth orbit. Such planes could fly fast enough to stay perpetually in sunlight (the atmosphere circulates around Venus at a high altitude at about 250 mph, if I recall).
Solar powered planes would provide continuous meteorological data. They could also send microwave beams of power through the clouds to robotic stations on the Venus surface, which would rely on the microwave power to run air conditioning units! Even electronics fry at the temperatures measured on the Venus surface. Robotic surface stations could probably be equipped with metal balloons filled with hydrogen gas to lift them up, let them float somewhere else, then land again (or they could use propellors powered from beamed energy from above; the surface winds are very light, just a few mph).
Throughout one Venus day, a surface station could drift from place to place on the Venus surface or just above it, photographing, taking samples, measuring the chemical composition of rocks. As the Venus day at a particular spot on the surface came to an end, that would probably spell the death of the station unless microwave power could be sent down from space. A very small, battery-powered airplane could come down from the high-flier to the surface station, hook onto a basket of rock samples, and fly it back up to the high flier, where heavier equipment could carry out more detailed chemical analysis.
I suspect a sample return mission would be possible using a high-flier. The samples would be brought up to the high flier from the surface by small battery-powered aircraft or balloons. The high flier could contain in it a small multiple-stage rocket. Possibly the high flier could slowly extract water from the Venus atmosphere--it has water, but not a huge amount--and using solar power, slowly make methane and oxygen, just like the Mars Direct system does. If the high flier flew at an altitude of 40 to 60 miles, it would be in a zone with a lower atmospheric pressure and temperature than the surface of the earth. Over a year or so, the high flier's rocket could accumulate a few tons of propellants. The samples would be transferred to the rocket's cargo area, the rocket would be released, and it would fly to orbit, where either the human crew would retrieve it or it would rendezvous with another rocket. There are designs right now for 6000-kg solid-fueled rockets to fly 100 kg from the Earth's surface to low earth orbit. I suspect from a high-flier, 100 kg could be put into a low Venus orbit by a smaller rocket than that.
As the technology for surface exploration improved, perhaps a station in Venus orbit with a dozen people would be needed to run the surface probes.
Another possibility is a small reusable minishuttle that would descend to a high flier, rendezvous with it and dock for months, refuel using the high flier's water extraction system, then fly back to orbit. Remember that several percent of Venus's water is deuterium; it's far more common in Venus's atmosphere than Earth's or Mars's. Possibly the deuterium could be harvested and flown to orbit cheaply enough to be resold on Earth (where it is worth $10,000 per kilogram).
I don't see people ever landing or even flying regularly into the Venus atmosphere; it's not necessary. But I do see them running things real-time from Venus orbit. We'll see.
-- RobS
Micrometeoroids are not a problem on Mars; the atmosphere stops them. I think the smallest craters on Mars are about 100 meters across, which means anything less than about a meter or two in diameter is broken up by passage through the Martian atmosphere.
As for melting any permafrost, this could be a problem. Near the Martian equator the top few meters of regolith probably have very little water in them, so putting a heated dome on top would not result in mud. The liquid water would slowly vaporize and escape into the atmosphere. I suspect a bigger problem, though, would be freezing of the soil inside the dome, because the regolith right now probably has an average temperature of about forty or fifty below zero. You could balance out the problem by putting inside your dome the right amount of soil. Let us say the heat in the interior of a dome were such that the top meter of ground would be thawed by it. Then you install your dome, fill it with a bit more than a meter of soil, and let the top meter thaw out from the heat above. The dome's plastic "ground cloth" would be permamently frozen in place underneath, impermeable to water and gas transfer.
As for cosmic and solar radiation, the Martian atmosphere, according to *The Case for Mars,* provides adequate shielding for growing plants and provides considerable shielding for humans. I suspect the best design for a Martian "town" would be to build the housing and work space into the dome edges, so that they would be under at least two or three meters of regolith for radiation and shielding and insulation, but to have windows opening into the dome for light and easy access to the vegetation areas. If beds and other heavily frequented areas were a few meters back from the windows, they would be very low radiation environments, but would still benefit from the light and airiness of the dome.
People could even have porches and patios to their housing. You'd just want to have a roof over the porch or patio with a few meters of dirt on top of the roof to protect you from cosmic and solar radiation. You could sit in your lawn chair and look out on the corn and vegetables growing in the middle of the dome.
-- RobS
Most of the articles I have read about nuclear thermal engines propose to use them from low earth orbit up, not for launch to earth orbit. Most people are assuming that chemical engines will be used for the foreseeable future to get things to low earth orbit.
Another nuclear engine worth remembering is the gaseous core nuclear engine. Apparently the uranium or plutonium fuel is maintained as a gas inside the engine and is separated from the hydrogen propellant by keeping the former inside a spinning vortex. There are computer simulations indicating gaseous core engines are possible, but no one has built one yet. The Isp, if I remember right, is 2,000 to 3,000 seconds; in other words, 40,000 to 60,000 mph. Now THAT'S fast! I don't know what thrusts are contemplated, but nuclear engines are capable of fairly high thrusts compared to other engines because of the compact nature of the energy source and the fact we are using heat, not electricity (and thus are able to use the entire power output of the engine).
I have seen articles about these engines on the web, but I don't remember where.
-- RobS
The other useful kind of asteroid is the chondritic type, which is rich in water. It could be mined to create hydrogen and oxygen for rocket fuel, probably more cheaply than hauling the fuel from the Earth's surface.
I suspect within twenty years most of the mining will be automated, though a human crew may need to visit every few years to set up new equipment, repair broken equipment, and possibly haul away broken things that can be repaired and reused cheaply. The fuel for the human crew can probably be made from the asteroid; even nickel-iron asteroids may have some water.
I am less certain how quickly we will move asteroids to earth orbit for processing. The dangers of an asteroid accidentally hitting the Earth and wiping out a city would be too great, and even if it could be reduced, the fear would remain.
-- RobS
I'd like to broaden out this topic a bit, to the problems of petty crime. Once there are enough people on Mars, an option for some circumstances would be sending the person to a remote outpost. This would work for some crimes--theft, for example--or hurting others (fistfights). It might even work for some psychological problems; sometimes isolation can be useful. In some cases there would be privileges that could be taken away. I suspect it will be impossible to ban alcohol from Mars--the Russians have it on all their flights, I gather--but one could take away drinking privileges for transgressions. Or if the coffee is getting short, one could take away the coffee drinking privilege!
I think petty crimes (including fights) are a much more serious problem than insanity. Even friends can become enemies under the wrong circumstances of isolation and intense interaction in tight quarters. As you may have heard, NASA has made little effort to test people for compatibility. The MIR space station had many difficult moments when crewmembers argued. The American and Russian crews on Mir were poorly integrated together (I suspect ISS is better). There were serious problems in understanding because of language difficulities. Any international Mars flight could face serious cultural differences as well. If a Mars team is chosen this way--the US gets to choose one, Russia one, France one, Canada one, Japan one--the result could be a bunch of people thrilled to be going to Mars, but not particularly liking or understanding each other.
-- RobS
It will be interesting to see what happens when someone plans to build something permanent on the moon or Mars. Then these issues will have to be resolved. The moon may be the first test case, because the areas at the poles where there is permanent shadow and ice are not vast--large, but not vast--and areas with perpetual sunlight (mountain peaks) are very small and rare. Whoever wants to tap the resources of the lunar poles will have to claim mountain peaks for themselves. I suspect by then some sort of legal arrangement will be made.
Once there are people on Mars--even a few--there will be people to set up and police land claims, and that means that thousands of people *on Earth* will be able to buy plots of Martian land and obtain legally binding title. This is important because the Mars fans who join the Mars Society and otherwise dream will at least be able to buy a piece of Mars. They'll eventually be able to rent a rover to explore their land remotely (the controls could be handled remotely with cheap software and a DSL web connection). They may even be able to get samples flown back from their land. For all these services they will have to pay, and they might even have to pay a small annual land tax as well.
If this becomes popular, there may be far more Mars land owners on Earth than on Mars. On could imagine that the Mars government would have to accommodate their interests and rights, possibly by given then voting rights of a sort (perhaps for one chamber of a Mars legislature).
--RobS
The difficulties with contamination are two, I think: (1) even if the danger of contaminating the Earth with dangerous lifeforms is a billion to one, NASA cannot ignore it; the US government would be liable; (2) fear, an emotion one can never underestimate and can destroy even logical plans.
-- RobS
Air breathing chemical launch systems hold out a huge potential for making launches cheaper. A launch from the Earth's surface to low earth orbit requires 8 or 9 times as much fuel as payload (structure plus cargo). Hydrogen-oxygen rockets are usually about 5/6 oxygen and 1/6 hydrogen (that includes extra hydrogen to lower the molecular weight of the exhaust and increase its velocity). The big problem is that after you get to 5,000 mph or so, it takes more energy to slow the air in order to use it to burn the fuel than you get back. Hypersonic burning of fuel is theoretically possible and will probably be developed in the next few decades. Once it comes along, the weight of launch vehicles could be cut to maybe a quarter of what they are now; maybe even less. Once the technology becomes mature, low earth orbit should be reachable for $100 per kilo or less. It's a matter of time and a lot of research and development funding.
-- RobS
Pyramid-shaped mountains are not hard to create naturally. Faults tend to cut bedrock into straight surfaces, and erosion tends to follow fault lines because that's where the rock is weak. Prevailing winds can facet natural surfaces as well. In the desert one can find "ventifacts," which are rocks with flat surfaces. The flat surface forms on the upwind side of the rock where windblown sand causes abrasion. If the rock gets rotated somehow, it can have two or three facets. A change in the direction of the prevailing wind (seasonally or from climatic change) can do the same thing to a mountain.
These processes do not produce smooth surfaces, like a classic pyramid. But poor resolution can make a bumpy surface look smooth.
As for the face, I don't know anyone in planetary science who takes it seriously as a possibly artificial structure. At other lighting angles it does not look like a face at all. It's a bumpy, complex mountain surface that at the right angle looks like a face, just like the "Old Man of the Mountain" in the White Mountains of New Hampshire. You have to stand in exactly the right place on the highway to see the Old Man of the Mountain; walk fifty feet up or down the road and the side of the mountain looks rough and random. It's a big tourist attraction.
--RobS
There's an interesting article on SpaceDaily.com that says the cost of tourism in low Earth orbit will go UP before it goes down because of supply and demand. The Russians can send only two tourists a year to the ISS; one on each Soyuz flight. But they already have three tourists lined up and fourth in the wings. They charged Shuttleworth 20 million after saying the second tourist would get a slightly cheaper rate (he didn't). Apparently the Russians give their space program only a quarter of the money it needs, so they have a high incentive to attract paying customers.
I think at the Aeronautical Encyclopedia website I read an excellent series of pages about the Burans. Each Buran has its own page. Only the one that flew into orbit is complete. There's a 90% complete one in Moscow, and the other two (I think) are even less complete.
--RobS
On the issue of a rail gun, I am not too worried about it being viewed as a potential weapon. Anything launched from the moon toward Earth--including a manned vehicle--has the potential to serve as a weapon. But the Earth's atmosphere protects us from anything small--that is, less than tens of tons--pretty well. So any kind of launcher that throws, say, a ton of lunar materials into space at a time cannot serve as a weapon against Earth because of the shielding effect of the terrestrial atmosphere.
I agree with others that an electromagnetic launcher is probably the best way to get stuff off the moon and back to the Earth. The moon has libration, which would tend to move the surface around under a lunar elevator or tether, complicating their effectiveness. A tether possibly could compensate by changing its orbit, but I think a lunar elevator might have a harder time of compensating.
-- RobS
I think it is easy to criticize NASA if you aren't involved in it. Perhaps one can get to Mars and spend much less money than NASA does. But NASA must do what it does at a minimal risk to human life, and reducing the risk to human life is immensely expensive. NASA also has to deal with everything from improving aircraft safety to flying probes to Pluto. Mars is not and should not be its only focus.
For that matter, Mars should not be our only focus--and I say that as someone who went into planetary science because of his love of Mars and who writes sci fi novels about Mars to this day. We have to return to the moon some time, and the chances are good it will be before we go to Mars; the moon's hundreds of times closer, after all, and its water is potentially more valuable than anything we can haul back from Mars any time soon.
We Mars lovers must remember that to many people, Mars is just cold, icy ball of distant rock. The difference between the moon and Mars often boils down to emotions, with some people loving each world more. If one strips away the emotion, one ends up with lots of question marks; does Mars have life? Can it tell us something about the evolution of Earth? Can we ever terraform it? But there are equally pressing question marks about the moon; can it provide humanity with cheap rocket fuel? Can it provide materials for building solar satellites? Can it provide a platform for immense radio telescopes? Can it fuel fusion reactors with helium 3? Can it become a tourist destination? The answer to the last question is: the moon can be a tourist destination more quickly and cheaply than Mars.
My point is, we cannot preclude lunar exploration. It will not be an either/or question; it will have to be moon and Mars. It will PROBABLY mean we will return to the moon before humanity sets off for Mars.
There is no doubt that NASA can do things more cheaply than it does. But I would not expect that privatization of space can do it much, much more cheaply.
-- RobS