Jonathan Vos Post*
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Abstract Since Caltech/JPL observations suggest possible water ice at the north and south poles of the planet Mercury, it is now feasible to consider a new class of human exploration missions to these sites, and three classes of robotic precursor missions that would precede human exploration (impact/ orbital spectroscopy, lander, sample-return). Mercury polar ice could provide neutrino detection opportunities and would provide in situ resources for refueling spacecraft for return to Earth.

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I. Introduction and Background Recent astonishing radar observations of the planet Mercury by Bryan Butler (grad student at Caltech), Dr. Raymond Jurgens and Dr. Martin Slade of NASA/JPL, suggest that the innermost planet Mercury may have patches of ice at its poles.1,2,3,4 These observations have been confirmed and explained.5 If this ice really exists, it enables most exciting new class of inner Solar Systems human expeditions possible.6,7,8 To confirm the presence of ice, map its extent, and select human landing sites, a series of robotic precursor missions are suggested. At least two discovery-class missions alreay proposed would help verify Mercury polar ice.9 This paper suggests a modification of one such already proposed mission, as well as the requirements for a more sophisticated robotic lander class of missions and robotic sample-return class of missions. -------------------------------------------------------- Copyright 1993 by Jonathan V. Post. Published by the American Institute of Aeronautics, Inc., and Space Studies Institute with permission * President and C.E.O. Mercury is a deadly world -- over 800 degrees Farenheit at the equator, during the closest approaches to the Sun every 88 days. This takes place at perihelion (36 million miles = 46 million kilometers) and doesn't last long, because of Mercury's swift orbital velocity (35 miles/sec = 56 kilometers/sec). But despite the broiling equator, it stays chilly at the poles. How cold?,As cold as 125 degrees Kelvin (minus 148 C., minus 235 degrees Farenheit) at the poles. How is this possible? Well, there are only three ways you can heat a body from outside: radiation. conduction, and convection. You can heat by radiation, as the Sun does to Mercury's equator -- but the solar rays strike slantingly and more weakly the closer we get to the poles. Brutal sunlight always smashes straight down on the equator, hot enough for metallic tin and lead to flow like water, over 800 degrees Farenheit during the closest approaches to the Sun every 88 days. By the same geometry, sunlight skims across frozen poles, blinding light with negligable heat. You can heat by conduction -- yet as fast as heat conducts to the poles from the core and the equator, it radiates away into the black sky. You can heat by convection, but there is virtually no air on Mercury to blow its sultry breath upon the poles. Mercury has an extremely thin atmosphere dominated by -- in order of abundance -- atomic Oxygen, atomic Sodium, Helium, atomic Potassium, and atomic Hydrogen; as we have known only since the 1985 work of A. Potter and T. Morgan.10 The pressure, measured in quadrillionths of Earth's atmospheric pressure, is so low that you might more accurately think of individual air molecules travelling like bullets on parabolic paths. When they hit, they are almost immediately launched again by thermal energy. But when they hit at the cold poles, some of the molecules freeze fast to growing patches of ice. At Aphelion, its furthest orbital position from the Sun, Mercury is 43.4 million miles = 69.5 million kilometers away from the solar furnace. This cooler spell lasts longer than the perihelion hot-spell, because consistent with Kepler's Law, the planet is moving more slowly, with a more sedate orbital velocity of 23 miles/sec = 37 kilometers/sec. The big difference between perihelion and aphelion gives Mercury the second greatest eccentricity of any planet orbit (e = 0.206, compared to Pluto's e = .250). The surface is basically rough like the Moon, since albedo (reflecting power) is very similar to the Moon, about 0.06 for Mercury. Since perihelion and aphelion differ by 17 million miles, the difference in received radiation may be about 50%. At closest approach to the Sun, Mercury receives 12 times the radiation intensity that Earth does; at the greatest distance from Sun, only 6 times as much. Early remote temperature measurements by E. Pettit, using a bismuth/bismuth-tin thermocouple at the focus of a telescope, gave readings of 400 degrees C. at Mercury's equator during perihelion, 340 degrees C. at mean distance from Sun, and 285 degrees C. at aphelion. At the equator, in the middle of the night, surface temperature is about freezing, according to later observations from radio telescope at Parkes, New South Wales, Australia. Infrared observations from Mariner 10 reduced the estimate of equator nighttime temperature to 90 degrees Kelvin, 90 degrees above absolute zero. What the JPL and Caltech scientists discovered, and annouced 1,2 in November 1991, is that there are ice patches at the north pole (and presumably at the south pole) of Mercury. Water ice! Some critics, including experts at JPL 12 think that the radar observations, instead, show metallic evaporites such as tin, copper, zinc, and metal sulphides. These critics think that ice on Mercury is as likely as a "snowball in hell." Let's summarize some of the arguments and counter-arguments. Pro: It looks like ice, and is cold enough. Con: other materials are equally reflective, and cold is not the issue. Pro: But if it's cold enough, ice can accumulate. Con: No, because cosmic radiation such as ultraviolet would evaporate any ice faster than it could form. Pro: But even a thin layer of dust on top would screen out the ultraviolet. Con: That's yet another hypothesis; by Occam's razor, your model is slashed to ribbons. Pro: Our model has enough parameters to robustly account for thick deposits of ice beneath a thin dust layer. Con: Your model has too many parameters; you can make it have any property you want to fantasize... And so on. In this paper, we assume the ice hypothesis, if only because it's so much more fun. We examine three types of robotic precursor missions to the icecaps of Mercury, and one type of human exploration mission. II. Robotic Precursor Missions Before people visit the poles of Mercury, robotic precursor missions must blaze the way. In 1974 and 1975 roughly 45% of Mercury was mapped by the Mariner 10 spacecraft at an average resolution of 1 kg/pixel, with less than 1% mapped at resolutions between 100 and 500 meters. 13 JPL published a pre-phase A mission study of a pluasible Mercury orbiter mission with two spacecraft carrying 11 science instruments to be launched by a Titan IV/Centaur.14 Under the current budgetary situation at NASA, this type of remote sensing of Mercury is far too expensive, and efforts were refocused on light weight production spacecraft with fewer instruments, Delta II launch, and low cost university mode management. A consortium of Caltech, JPL, and TRW have proposed 9 MIRROR: Mercury Imaging & Radar Ranging Orbital Reconnaissance, a discovery mission concept. This would provide global visual coverage at 100 meters resolution, with selected areas at 1 meter or better, and two-color wide angle imaging at lower resolution. It would use a radar spectrometer to probe the ice. MIRROR would precisely locate and map the extent of the Mercury polar ices. The spacecraft would have a dry mass of 244 kg, with 480 kg of propellant, and could be launched towards Mercury polar orbit in August 1997 or July 1999 by a Delta-II rocket. The following concept is a first-cut modification of MIRROR to provide chemical analysis of the Mercury ice from orbital observation of "artificial meteorite" strikes at the poles. A light weight spacecraft, perhaps modified from a TRW Eagle Class 3-axis spacecraft with a dual mode propulsion system, would be launched during either of two launch windows: (1) 1-21 August 1997, or (2) 19 July-9 August 1999, on a 4.9 year trip to Mercury. Upon final arrival at Mercury on, respectively, (1) 8-9 July 2002, or (2) 21-22 June 2004, the Isp=315 bipropellant engine fires at 450 Newtons to place the spacecraft into an elliptical 12-hour Mercury polar orbit with 200 km altitude periapsis at the equator and 17,560 km apoapsis (7.2 Mercury radii). Since the Delta II does not have the delta- V to launch the spacecraft directly to Mercury, a multiple-slingshot heliocentric E-VVMM-M transfer orbit is employed. With the 1997 launch, this involves an unpowered Venus swingby on 25 November 1998, a 300 km altitude powered Venus swingby with 0.234 km/s delta-V on 7 June 1999, a deep space 0.243 km/s set-up delta-V on 26 August 2000, a deep space 0.042 km/s set-up delta-V on 17 December 2000, an unpowered 200 km altitude Mercury swingby on 10 July 2001, a deep space 0.270 km/s set-up delta-V on 6 September 2001, and Mercury polar orbital insertion on 10 July 2002 with a v-infinity of 3.476 km/s. For the 1999 launch, a slightly more elaborate EE-VVMMM-M ecliptic heliocentirc multiple-swingby transfer orbit would be employed. Instead of the optical CCD Line Scan Telescope of MIRROR, which would be the spare Mars Observer Camera, our spacecraft would substitute an infrared CCD camera and spectrometer developed for SDI observation of cold payloads, the precise parameters of which are highly classified. Sometime before the Mercury orbital insertion, the spacecraft would release a cluster of 5 "artificial meteorites" -- golf-ball- sized 1 kg spheres each of different dense metal rare on Mercury (Tungsten, Uranium- 238, Platinum, Gold or the like). These are spring- or pyrotechnically-released so as to separate from the spacecraft, not interfere with the spacecraft's orbital insertion, and be aimed to violently impact near the North Pole of Mercury. There being essentially no Mercurian atmosphere to slow them down, these spheres impact at various points, nearly simultaneously, at velocities approximately equal to Mercury's escape velocity of 3.476 km/s plus the approach velocity at the time of spacecraft separation. For back-of-the envelope purposes, let's estimate this impact velocity at 5.00 km/s. Each "artifical meteorite" at that velocity, with each weighing 1 kg, carries a kinetic energy of 1/2 mv2 = 0.5 kg (5x103 m/s)2 = 0.5 kg (25x106 m2/s2) = 1.25 x 107 kg m2/s2 = 1.25 x 107 Joules. Since 1 J = 0.2389 calories, each impact carries approximately 2.986 x 106 calories. Since it takes 1 cal to heat 1 g of water by 1o C, and 80 cal to melt 1 g of water ice at 0o C, and 498 cal to vaporize 1 g of water at 100o C in a vacuum, then it takes roughly 148 + 80 + 100 + 498 = 826 cal to heat 1 g of ice from -148o C to 0o C, melt it, heat it to 100o C, and vaporize it. Hence, if all the energy of each impact was used to vaporize ice, each "artificial meteorite" would vaporize 2.986 x 106 cal/(826 cal/g) = 3.615 kg of ice. In actuality, some of the impact would shatter ice, some would send fragments flying, and some would heat the water to a considerably higher temperature, i.e. into ionized gas (plasma). So, if all 5 spheres hit ice, we would get 5 bright flashes, each with a different spectrum. One would be of water with a trace of tungsten, one of water with a trace of gold, one of water with a trace of platinum, and so forth. Additional impurities in the ice would show as traces of other volatiles, such as carbon monoxide, methane, ammonia, hydrogen cyanide, cyanogen, and the like. The orbiting infrared CCD spectrascope could easily determine which of the 5 impacts struck ice, and what the chemical consituents of the ice were at each of the impact points. If the spectrascope were even more sensitive, we could release the same mass as a shotgun blast of 5000 1-g ball-bearings, and get a pretty good resolution chemical mapping of the polar caps. As described in my Space-92 paper 8 there is a scientific experiment which could exploit the existence of deep pockets of ice on Mercury (or in the ice caps of Mars) for detecting solar, cosmic, or terrestrially- generated neutrinos. That's certainly not the only thing to do with planetary or interplanetary ice. We can extract water from the ice in comets or asteroids and use it to fuel really big spacecraft 15,16, or we can electrolyze the water into hydrogen and oxygen, use the oxygen for astronauts to breath, and use the hydrogen to build hydrogen-ice spacecraft for interplanetary or even interstellar missions 17, 18, 19, 20, 21. All of these concepts are sufficiently speculative to interest the science fiction community 22, 23. More expensive and ambitious than the proposed impact/orbital spectroscopy mission described above would be a soft-lander to analyze the icy material at a Mercurian pole. Variations of this would include a "hopping" lander, which would analyze the chemistry at one site, hop parabolically to another site, analyze it, and repeat until depleted of hopping capability. The low gravity of Mercury might make a hopper superior to a crawling robot for examining multiple sites, especially if the ice itself can be made into water reaction mass to propel the hopper. More expensive and ambitious than the lander, hopper, or rover would be a full- fledged sample-return mission, in which cryogenically preserved samples of Mercury ice (with their microstructure intact) would be returned to Earth by an ascent vehicle utilizing hydrogen/oxygen bipropellant extracted from the in situ ice by solar-powered melting, distillation, and electrolysis. As Muhleman has put it 9, "the existence of ice in these permanently shadowed regions near the poles has great importance for planetology. The total sources of water molecules from the planet's outgassing and meteoric and cometary impacts accumulate at such a small rate that the ice must be extremely old, perhaps the age of the solar system. Thus, that ice must contain a chemical record of the history of the inner solar system in the way that comets are thought to be a record of the outer solar system. Mapping the extent of the ice is the next logical step toward eventually returning ice samples." The head of NASA, Administrator Daniel S. Goldin, has expressed considerable enthusiasm for the Mercury sample-return cocept, as described in section IV below. But what are the trade-offs between human and robotic exploration of Mercury? For Moon, Mars, and Mercury, a sufficiently advanced autonomous robotic capability would preclude the need for human or human-tended surface sites, perhaps allowing an earlier deployment of inner Solar System neutrino array experiments. My colleagues and I in one of the better departments at Rockwell, led by Daphne Zeilingold 24, wrote a 200+ page report on planetary robotics which concluded that: (1) tele-operation at these distances isn't fast enough, due to speed-of-light communication delays; (2) contemporary and near-future robots are far too primitive and unreliable to do the job; (3) truly autonomous robots of the Asimov positronic-brain variety are likely to be available only after the earliest opportunities to return to the Moon and send people to the nearest planets; but (4) "supervised robotics" can tremendously improve mission safety and productivity on the Moon and planets. In supervised robotics, one person on Mercury can give general orders to a team of semi-autonomous robots, make sure they're doing their tasks well enough, and update those orders as necessary. Hence, exploration of the poles of Mercury is not a case of people OR robots, but an evolutionary change in the optimum combination of people AND robots. III. Human Expeditions If the ice is real, it should be possible to send a human expedition to Mercury, not long after the first exploration of Mars. Using nuclear thermal propelled rockets, as Bob Zubrin explains 25, 26, 27, 28, it should be possible to travel to Mercury and land near the north or south pole. Explorers will face far more hazardous conditions than on the Moon or Mars; they must deal with the problems of heat, cold, bizarre near-vacuum atmosphere, Mercury- quakes, solar ionizing radiation, and the like. Ultimately, they can refill the fuel tanks with water distilled from in situ ice. They can now make it home as passengers of the first interplanetary "steamship." Mercury is some 4878 kilometers in diameter, with uncompressed density 5.43 grams per cubic centimeter, so it has only 5% the mass of Earth. Takeoff is therefore easier than from Mars, since Mercury's escape velocity = 2.4 miles/second, which is why there is so little atmosphere in the first place. Travel between Mercury and Earth can be hastened by Venus gravity assists, as in the robotic mission scenarios described in Section II above. Astronauts would face the challenge of long-duration microgravity (which "fat slobs" can handle better than aerobically-fit low-blood pressure athletes, as I have pointed out elsewhere 11), and would require more radiation shielding than an equivalent Mars mission, but would otherwise use similar infrastructure. At the pole, conditions for human will be bizarre. A swollen sun hangs on the horizon. Elevation angles will never change, long jagged shadows will only rotate like clock hands across the broken arctic plain. Mercury's axis is a fraction of a degree from perpendicular to its orbit, so there are no Earth-like seasons, no sunrise or sunset at the poles, only the slow rotation and the swinging closer to and further from the furnace sun. Our 12-step program for the human Mercury mission, in its crude outline, is simple. (1) Land -- admittedly, this is harder than on Mars because there is no appreciable atmosphere against which to "aerobrake." (2) Lucky man or woman first sets foot on surface, plants flags, is photographed, makes short but transcendental speech. (3) Deploy and shield a "work shack" where astronauts can assemble equipment in shirt-sleeve conditions. (4) Deploy an ice purification and distillation plant. (5) Shovel ice into the plant, cracking if necessary with thermal shock or explosives, beneficiating (sorting, screening, preprocessing) if necessary. (6) Transfer distilled water into fuel tanks for ascent and return to Earth. (7) Perform surface science explorations and experiments, now that your "avenue of retreat" is open and you can concentrate on issues beyond survival. (8) Melt the required number of holes deep in the polar ice, perhaps with electrical heaters powered by the ship's nuclear reactor and generators. (9) Plant those Cerenkov radiation- detecting phototubes. (10) Startup and calibrate the now- emplaced neutrino telescope. (11) Sightsee, accept politically required phone message from President, stow all samples securely onboard, and say "we shall return." (12) Go home, recover, enjoy ticker-tape parade, accept awards, appear on talk-shows, get tenured professorship at prestigious university, write memoirs, appear on late- night infomercials, wonder what you'll ever do again one tenth as dangerous and exciting as the trip to Mercury. How can there be ice on Mercury at all? Similarly to the Ralph Leighton/Bruce Murray hypothesis 29 that ice might have collected in deep dark craters at the poles of the Moon. Mercury has a femtobar atmosphere dominated by atomic oxygen, vaporized atomic sodium, helium, ionized potassium, and hydrogen. Atoms are spread so thin that pressure isn't the right way to think of the gas, more like a swarm of ballistic atoms, rarely colliding, blasted loose from rock, flying on long parabolas, thermally blasted into suborbital trajectories again. But when volatiles, including water molecules, land at the poles, they stick -- frozen fast -- in ragged patches and in the shaded bowls of craters. The human expedition outlined here would land on the deepest polar crater, where the ice baked from rock or splashed from comet impacts had built up over millions of years to as much as half a kilometer thick , according to my conversations with Prof. Muhleman. This mission is predicated, as mentioned before, on the interpretation of radar images. JPL's 70 meter antenna at Goldstone, California, beamed 500,000 watts of radio waves at Mercury for eight straight hours in August, 1991. The radar echo whispered down on 36 kilometers of prarie outside Socorro, New Mexico. The 27 antennas of the Very Large Array, each 25 meters in diameter, picked up the signals, attenuated to the power of a buzzing fly. Martin Slade of JPL and Caltech grad student Bryan Butler collected the signals and processed them into images, under Goldstone operations supervisor Raymond Jurgens and experiment designer Professor Duane Muhleman. There was an extremely bright structure at the one visible pole. "Could be sodium salts," said Muhleman, "or some pathologically rough landscape that just happens to be at the North Pole, but we regard these alternatives as farfetched." It is even possible to get people to Mercury with Apollo-era chemical propulsion, and just possible to bring them home thanks to the slightly more complicated option refueling on site from water electrolyzed into tanks of hydrogen and tanks of oxygen. This article emphasizes possibility, not probability or priority. The possibility, based on existing data, is excitingly genuine. Nuclear thermal rockets have been emphasized in this scenario, but hybrid architeures including solar sails 30, 31, magnetic sails 32, or other more exotic propulsion techniques might also be considered. Other long-term speculation on the evolution of the space program 33, and on non-electromagnetic modes of communication in the Search for Extraterrestrial Intelligence 34, are beyond the scope of this paper. Concluding the case for Mercury: (1) if there are indeed patches of ice at the north (and presumably south pole), as suggested by radar imaging, and (2) if the ice at some location fills a crater to a depth of several hundred meters, perhaps half a kilometer, and (3) if propulsion is available (ideally a nuclear thermal rocket) which can refuel from purified Mercury ice, then (4) a human and/or robotic expedition to the pole of Mercury may be feasible, and could deploy a modified AMANDA-type neutrino experiment. Even if the ice patches are thinner, robots and humans could exploit ice to enable refueling for round- trips between Earth and Mercury. In a final speculative note, Arthur C. Clarke, upon reviewing my earlier publications, suggests 35 that large human populations may now be possible on Mercury. "Thank you for your material on the Mercury and Mars missions -- I still can't believe that there really is ice on Mercury, but if it's true, this could be of enormous importance. It might even make Mercury (or bits of it) easier to terraform than Venus!" IV. NASA Administrator Response Daniel S. Goldin, NASA Town Meeting, 3 December 1992, California State University at Dominguez Hills At a NASA Town Meeting, in front of a live audience estimated at over 600 people, and a spill-over audience elsewhere on campus by closed-circuit TV, and simultaneously live on NASA Select TV, the top NASA Administrator endorsed the principles advanced by two National Space Society activists: Jonathan V. Post's published proposals for robotic and human missions to the icy north and south poles of Mercury, and Dr. Robert Zubrin's "Mars Direct Architecture." What follows are excerpts from a transcription of that meeting, prepared from an audio recording by Dr. Thomas McDonough (Instructor at Caltech, NSS & OASIS member, and Director of the SETI program for the Planetary Society). 2nd Question from Audience: "My name is Jonathan V. Post. I worked on Galileo [to Jupiter], on Magellan [to Venus], I was Mission Planning Engineer on Voyager for the flyby of Uranus, I planned the flyby of [Uranian moon] Miranda. I'm a co-author with Ray Bradbury, a co-author with the late [Nobel Laureate] Dick Feynman, co- broadcaster with the late Isaac Asimov, co-editor with Arthur C. Clarke, and 17 months ago I was laid off from Rockwell International... Audience: 10+ seconds of laughter and applause... Post: "... I'm sure other people will ask questions involving the 100,000 aerospace jobs lost in the Los Angeles area, 80,000 of which were lost within the last 2 years. But looking ahead, let me ask a positive technological question. Scientists at Caltech and JPL have recently demonstrated the likelihood of ice at the north and south poles of the planet Mercury. Dr. Robert Zubrin has published a lot of papers on the so-called Mars Direct Architecture, a way of getting human beings to and from Mars sooner, faster, and cheaper. It seems to me that the same infrastructure that can and should get human beings to Mars and back could also get human beings to the north and south poles of Mercury, refuel from the water that's available there, and bring them back. Is it not worth having a precursor mission to bring a sample back from the poles of Mercury as well as the precursor mission to Mars that we saw earlier in the video, and have a Unified Inner Solar System Manned Exploration Program that includes the Moon and Mars and Mercury? Thank you. NASA Administrator Daniel S. Goldin: Okay. Let me see if I can dissect that as a thought. First, let me say that your question is right on. Any nation, if they want to spend a half-trillion dollars and blast astronauts off and get to Mars, then that's not the answer. I think that what we have to do is try and find clever ways of doing it. Let me help the people in the audience understand the implication of what you said. The fellow Zubrin, at the Martin [Marietta] Company, has come up with a concept where he proposes sending a robotic spacecraft to Mars, and Mars has an atmosphere of Carbon Dioxide. And what he'd like to do is have a machine on Mars that converts that Carbon Dioxide with a little feed Hydrogen into Methane, which is a fuel, and into Oxygen. And to send that robotic spacecraft to Mars and for a year or so to build up a whole big propellant supply so that if we launch a [manned] mission to Mars, we have to take much less weight there. We have a much less expensive vehicle. And as a result, we could perhaps do it sooner. In that sense, his concept is wonderful... but let me tell you the problem. Before we even think about sending human beings off to Mars, which is an engineering feat, we first have to understand how human beings can live and work in space. And let me explain what I mean by that. When you go out into space, we don't understand how to stop bone loss. A mission to Mars can take on the order of 1 to 2, even 3 years. We can't afford bone loss. We don't know what happens to the human immune system after exposure to long-time zero gravity and then coming into a partial gravity. We don't know whether the body can heal itself. What if a bone breaks -- will it ever heal? We don't understand the interaction of cosmic radiation with human tissue. And we don't even know the mapping of the radiation in the places we'd have to go. So before we go spend tens of billions of dollars and go launching off on another massive program, let's collect our thoughts, understand it, retire the risk on technology, send robotic precursor missions there, and YES -- LET'S SEND ROBOTIC PRECURSOR MISSIONS TO MERCURY. You know, we have been to the planets; we've sent [robotic missions to] all planets but one; we've sent humans to the Moon 6 times;but we've never brought back a piece of any planet. WHY DON'T WE BRING BACK SOME OF THE ICE ON THE POLES OF MERCURY? In fact, it's within our capability within 10 years from now to launch spacecraft that cost tens of millions to hundreds of millions, instead of spacecraft that cost hundreds of millions to billions, and as a result we don't do it very often. We could launch a spacecraft to Mars in 10 years, and have university students, professors, entrepreneurial companies all over the country and the world participate. When you have such a robust program, we could then begin to collect the data, we could get Space Station Freedom up, understand how humans can live and work in space, develop all the technology... And then maybe, for tens of billions of dollars, WE CAN PERFORM YOUR [human] MISSION. AND YES, MAYBE WE SHOULD REFUEL ON MERCURY. Or perhaps we go to the Moon and with another device, another chemical reaction, get Oxygen, put it in the Libration Point, near the Moon, and go up, get the Oxygen, go to Mars, generate the fuel on Mars [Zubrin's approach], then come back. Go to the asteroids, mine the asteroids, and it will be wonderful. That's a long-winded answer. Thank you. Audience: [applause] [other questions and answers][additional Goldin reference to the originality of Post's proposal, and the specific inference of extracting hydrogen and oxygen from Mercury polar ice, in tape cassette changeover gap probably after question by Irwin Horowitz, and thus missing from this transcript] Goldin: "... which also gets to another issue with the gentleman over here [points to Jonathan V. Post]. We have to go help the Russians because if we don't we could be spending another set of Trillion dollars fighting another war. On the other hand we have to balance that against all the wonderful people that are being laid off in our aerospace industry. And that's why we have a very deliberate program.... [other questions and answers follow] ... Just to say that we're going to solve all our problems by spending half- a-trillion dollars launching off to the Moon and Mars is not an acceptable answer. What we have to do is ... "clean up our act." Our [NASA] credibility with the U.S. Congress is not at an all- time high.... We'll have a great vision, I guarantee you, and with ideas from [Dr. Robert] Zubrin and this fellow here [points to Jonathan V. Post] we'll get there! V. References 1 John Noble Wilford, "Photographs by Radar Hint of Ice on Poles of Mercury", New York Times, 7 November 1991, p.A14 2 Muhleman, Duane O.; Jurgens, Raymond; Slade, Martin A.; and Butler, Bryan J.; Proc. American Astronomical Society's Division of Planetary Science, Palo Alto, CA, 6 November 1991, in press 3 Martin A. Slade, Bryan J. Butler, Duane O. Muhleman, "Mercury Radar Imaging: Evidence for Polar Ice", Science, Vol. 258, 23 October 1992, pp.635-640 4 J.K. Harmon and M.A. Slade, "Radar Mapping of Mercury: Full-Disk Images and Polar Anomalies", Science, Vol. 258, 23 October 1992, pp.640-643 5 David A. Paige, Stephen E. Wood, Ashwin R. Vasavada, "The Thermal Stability of Water Ice at the Poles of Mercury", Science, Vol. 258, 23 October 1992, pp.643-646 6 Jonathan V. Post, "Future Spacecraft Sensors", concluding keynote address, in "Images from Space: Yesterday, Today and Tomorrow", AIAA 30th Aerospace Sciences Meeting & Exhibit, Reno, NV, 6 January 1992 [included 1st brief public presentation of manned Mercury polar mission proposal] 7 Jonathan V. Post, "Mars Polar Cap and Mercury Polar Cap Manned Science Missions", unscheduled talk at Mars Session, Session co-chairman Willy H. Sadeh, AIAA 30th Aerospace Sciences Meeting & Exhibit, Reno, NV, 7 January 1992 [1st detailed public presentation of manned Mercury polar mission proposal] 8 Jonathan V. Post, "Lunar Farside, Mars Polar Cap, and Mercury Polar Cap Neutrino Experiments", Proceedings of Space 92 (3rd International Conference on Engineering, Construction and Operations in Space), pp. 2252-2263, ed. Willy H. Sadeh, Stein Sture, Russell J. Miller, 31 May - 4 June 1992, Denver, CO, American Society of Civil Engineers, New York [1st published proposal for robotic & human missions to icy poles of Mercury] 9 MIRROR, A Discovery Mission Concept, Duane O. Muhleman, G. Edward Danielson,, 9 September 1992 10 Strom, Robert G., "Mercury: The Forgotten Planet", Sky & Telescope, September 1990, pp.256-260 11 Jonathan V. Post, "Loading Up for Liftoff", Ad Astra, March/April 1992 [NASA data suggests overweight, high blood pressure, aerobically unfit astronauts might be preferred for long- duration zero-gravity missions] 12 James B. Stephens, JPL, November 1991, personal communication 13 Davies, Atlas of Mercury, NASA SP-423 14 Chen-Wan L. Yen, Mercury Dual Orbiter Mission and Flight System Definition, 29 March 1990, JPL D-7443 15 David L. Kuck, Proceedings of Space 92, "In Situ Recovery of Water from Dormant Comet Cores & Carbonaceous Chondrites", pp.2367-2381 tells how to drill for water ice in "Space ... the driest of deserts" 16 Anthony Zuppero, Proceedings of Space 92, "Rocket Fuel to Earth Orbits from near-Earth Asteroids and Comets", pp.2271-2281, outlines an approach and economic analysis for bringing back 10,000 tons of cometary icewater per trip 17 Jonathan V. Post, "Unusual Spacecraft Materials", Proceedings of Vision-21 (Space Travel in the Next Millennium), NASA Lewis Research Center, 2-4 April 1990, NASA Conference Publication 10059, 1991, pp.391-403 [use of frozen hydrogen in advanced space missions] [see also my frontispiece poem in this volume] 18 Jonathan V. Post, "Unusual Spacecraft Materials", Proceedings of Space 90 (2nd International Conference on Engineering, Construction and Operations in Space), 23-26 April 1990, Albuquerque, NM, pp. 1055-1064 [more on hydrogen ice spacecraft] 19 Jonathan V. Post, "Hydrogen Ice Spacecraft", Proceedings of AIAA Space Programs and Technologies, Huntsville, AL, September 1990, with an exhaustive reference list on cryogenic ices for space 20 R. Spangenburg and D. Moser, "Ice Ships", in "Notes from the Radical Fringe", ed. T. Reichhardt, Final Frontier, Vol.3, No.3, May/June 1990, p.26 [1st popularized report of J. Post's hydrogen ice spacecraft concept] 21 Leonard David, "Hydrogen Iceships", in "Vision for the 21st Century", Ad Astra, Vol.2, No.6, June 1990, p.27, [2nd popularized report of J. Post's hydrogen ice spacecraft concept] 22 Jonathan V. Post, "Snowball in Hell to Catch Ghost Particles", in preparation for Analog magazine, 1993-94 23 Jonathan V. Post, "Snowball in Hell", fictional treatment of Mercury polar mission to appear in Deathworlds, ed. Harry Harrison, 1993-4 24 Daphna Zeilingold, John Hoey, John Irwin, Jonathan V. Post (ed.), Space Exploration Initiative Automation and Robotics Trade Study, Space Systems Division, Rockwell International, Downey, CA, 30 April 1990, with 300+ references 25 Dr. Robert Zubrin -- many articles in print, including "Missions to Mars and the Moons of Jupiter and Saturn Using Nuclear Thermal Rockets and Indiginous Propellants", AIAA 90-0002, 1990 26 Dr. Robert Zubrin, "Humans to Mars in 1999", Aerospace America, August 1990, pp.30-32, 41 27 Dr. Robert Zubrin and Benjamin Adelman, "The Direct Route to Mars", Ad Astra, July/August 1992, pp.10-15, 52-53, 55 28 Dr. Robert Zubrin and Jonathan V. Post, Life or Death on Mars, unpublished book manuscript 29 R.B. Leighton, and Bruce C. Murray, Science, Vol.153, p.136, 1966 -- the classic paper which hypothesized ice at the lunar poles and just missed predicting ice at the poles of Mercury 30 Jonathan V. Post and Ray Bradbury, "To Sail Beyond the Sun: A Luminous Collage", pp.33-39; in Project Solar Sail, ed. Arthur C. Clarke, David Brin, and Jonathan V. Post, New York: Roc (Penguin USA), April 1990 31 Jonathan V. Post and Chauncey Uphoff, "A Rebel Technology Comes Alive", pp.95-104; in Project Solar Sail, op.cit. 32 Robert M. Zubrin, "The Magnetic Sail", Analog, May 1992, pp.58-75 [Zubrin credits himself & Dana Andrews of Boeing with inventing the magnetic sail, based on work of Robert Bussard. Zubrin & Analog editor Dr. Stanley Schmidt now acknowledge that my qualitative analysis of large superconducting loops the solar wind and the magnetospheres of planets, while I worked with Andrews, constitutes an essential historical step prior to the Andrews/Zubrin collaboration] 33 Jonathan V. Post,, "Integrated Space Plan", Version 1.1, February 1989, Rockwell International, Downey, CA [unified vision of the next century in space, erroneously listing co-author as sole author] 34 Jonathan V. Post, "Star Power for Supersocieties", Omni, April 1980 -- on gravity waves for SETI 35 Arthur C. Clarke, personal correspondence, 25 January 1993