Diff for "Mars.vs.Moon"

Mars.vs.Moon

Elon Musk "seems" obsessed with Mars, and creating a permanent self-sustaining human presence there.

This doesn't pencil out, but the !SpaceX giant-booster capabilities he is building and justifies with alleged Mars missions may be a cover story for his actual intentions. Many innumerate fools (and their money) will invest in "Mars", but not difficult-to-explain but vastly more profitable opportunities for future !SpaceX capabilities.

Worst case, if Musk doesn't have undisclosed but more-profitable alternative opportunities in mind, he will lose control of those !SpaceX assets, and others will put them to good use.

But what about Mars?

A Hohmann transfer from Earth to Mars takes about 260 Earth days. Because Mars orbit eccentricity is 0.0934, travel time varies by more than 20%, so "regular" trips to Mars must accommodate total travel times of years, a vast amount of EVERYTHING (air, food, water, medical and repair supplies) needed by passengers onboard a spacecraft. Plus the tools and skills to maintain all of this, in a harsh radiation environment that can damage critical assets with no hope of repair. Musk is making no investment in completely isolated, self-sustaining environment capabilities, so (besides big boosters) he is making none of the necessary preparations for a survivable visit to Mars, much less the ENORMOUS preparations required for a complete independent civilization on Mars.

Compared to that, typical travel time to the Moon is three days, and the mission opportunities are at least once per day per (rotating) Earth launch site.

A permanent lunar colony would be vastly easier to establish, though hydrogen and carbon are lacking. With cheap enough launch (such as space-solar-powered launch loops), those elements can be imported from Earth; over the very long term, the elements can be abundantly supplied by comets targeted precisely at "capture chambers" on the Moon.

A permanent Mars colony must deal with perchlorates, which kill people and machines. The entire planet must be detoxified before people can safely settle there. Mars must also be surveyed for a vast range of minerals and ores, necessary for the vast range of materials used by a modern civilization, and essential for a civilization far more dependent on machines than Earth civilization. We are still finding and developing new ore bodies on Earth, after millennia of exploration; on Mars, we must first learn what ores to look for and how to look for them, then develop new extraction and refining technologies adapted to the Martian environment. Hiroshima and Nagasaki after nuclear bombardment offered vastly better survival prospects.

Moon Versus Mars

The Earth's orbit around the Sun is nearly circular, eccentricity is 0.0167. With a semimajor axis of 149.6 million kilometers, perihelion is (0.9833*149.6M) = 147.1 million kilometers,and aphelion is 152.1 million kilometers, a variation of 5 million kilometers. The Moon's orbit is also slightly elliptical, distance varying from 363 thousand to 406 thousand kilometers, so "worst case" the Moon's distance from the Sun varies from 146.7 to 156.1 million kilometers, about 9%, compared to 20% for Mars. Insolation is square law, so the sunlight variation doubles, approximately 18% for the Moon and 40% for Mars.

Currently, the axial tilt of Mars is 25%, but lacking a large stabilizing Moon, that ranges over megayears from 0 degrees to 80 degrees. Over the very long term, a pole will sometimes experience hundreds of Earth-days of darkness and hundreds of Earth-days of perpetual sunlight overhead, while the equator cycles from Sun-near-horizon daily twilight to an approximately "normal" day. So, the "Mars" numbers below are for the current axial tilt of 25 degrees, similar to Earth's 23.5 degrees, but will not apply over megayears of time. Mars is unruly compared to Earth.

Mars is also DIM. At aphelion, it is 249 million kilometers from the Sun, compared to lunar aphelion of 156.1 million kilometers. If the Moon intercepts 1250 watts of sunlight per square meter at aphelion, the total illumination of the entire Moon (average radius 1740 km) on its Sun-facing side is 1250*π*(1.74e6)² = 1.2e16 watts. For Mars (average radius 3390 km) at aphelion ( illumination = 1366 W/m² * (149.6/249.3)² = 492 W/m² ), the total Mars illumination is 492*π*3.39e6² = 1.8e16 watts ... only 50% more sunlight than the Earth's "small" Moon. Given the Mars "worse-than-nothing" perclorate-laden atmosphere, the Moon seems relatively temperate.

OK, you interject, what about the Moon's poky-slow rotation, cycling between very hot and very cold?

That is a problem - solved by burying a habitat beneath a few meters of lunar regolith. Which we must do anyway, for cosmic radiation shielding on either Moon or Mars, neither having a thick atmosphere or a strong magnetic field like the Earth.

Keeping Up With The Sun, on the Moon

The Moon offers another clever opportunity. Imagine a railroad track circling the Moon's equator. Tidelocked to the Earth, one "lunar day" is 29.53 Earth days, 709 hours. The lunar equatorial circumference is 10917km (or 6784 miles for us backwards US-Americans). A rail vehicle travelling "westwards" around the Moon at 9.6 miles per hour will maintain its position relative to the Sun; that's slower than a child on a bicycle.

The track won't be level, but as my friend Bob Forward liked to say, that is a "mere engineering detail." Ramps, switchbacks, deflections to the north and south ... from coast to coast, the steepest grade on U.S. Interstate 80 is 6%, the highest elevation is 2630 meters and the total length is 4668 km, between Teaneck NJ (41°N 74°W 40m elevation) and San Francisco (38°N 122°W 16m elevation). That might be a proxy for a lunar bicycle path

A perpetual "rail-cyclist" can choose a starting and ending time of "lunar 6 AM" or "lunar noon", for any chosen real-time hours, and zero "moving-local" elapsed time. Saves the effort of resetting a lunar watch when moving between time zones. Spoilsports will set their watch to GMT, go faster for a while, then take time for sleeping and eating.

Bottom Line: Why Mars?

We will explore Mars. Mars may have sheltered life, billions of years ago. Mars life would have evolved very differently than Earth life, offering a "parallax view" of the spectrum of possible biochemistries. The fraction of surviving biomolecules surviving to the present will be very very small, and the search will require vast resources. But the value of a completely different "second biology" ... and the innumerable artificial biologies extrapolated from the "baseline" between those two biologies ... will be the most valuable scientific discovery ever. Unless we screw this up.

On the other hand, if a few manned missions "auger in" on Mars, with YEARS of food and excrement aboard, the "biosignal" of that multitonne impact will likely be billions of times stronger than a few rare surviving biomolecules. We would need vastly more than vast resources to find and prove the Mars molecules in a vastly larger cloud of shit. The cost of lives and treasure lost to that failed mission would be nothing compared to the loss to science and biotechnology of burying the ghostly remains of Mars biology in a cloud of EARTH SHIT.

It would be worse than using rare Gutenberg Bibles as fast food wrap ... more like destroying all knowledge of Christianity, and all the heroic efforts and saintly lives inspired by that, which agnostic me would give my life to preserve.

Musk's stated "second home on Mars" may also be a waste, but his effort can be repurposed for vastly higher value results. I really really hope that he already has better plans, and his "Mars talk" is misdirection that motivated employees and outfoxes his competition. If he doesn't have better plans, the competition will surely outfox him.