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Model of the distribution of ice at the lunar south pole

The question, “Is there water on the Moon?” is still with us. Although water is not stable on the lunar surface in vacuum, the poles of the Moon contain deep craters whose floors are in permanent shadow. These dark areas are extremely cold – only about 50º above absolute zero. If a water molecule gets into one, no known physical process can remove it.

Where would such water come from? The Moon is constantly pelted by meteorites and comets, many containing water, either as ice or bound into mineral structures. This water is mostly lost to space during an impact, but some molecules may hop around on the surface for an extended time (minutes to hours). If by chance a water molecule fell into a polar dark area, it would be trapped there forever. Of course, this would be an extremely slow process, but the Moon is old (over 4,500 million years) and has plenty of time.

We will soon be obtaining new information on the poles of the Moon from the ongoing Chandrayaan-1 orbital mission. On that spacecraft, the Mini-RF SAR experiment will use radar to map the poles, including all of the dark regions. Unlike neutron spectroscopy, radar probes a couple of meters below the surface and is sensitive to the presence of ice, not hydrogen.

The first hint that there may be ice in these polar cold traps came from a radio experiment on the Clementine mission in 1994. Four years later, a small satellite called Lunar Prospector (LP) carried an instrument designed to measure the amount of neutrons given off the Moon’s surface. Hydrogen absorbs neutrons, so when the LP investigators saw a decrease in neutron flux near the lunar poles, they concluded that excess amounts of hydrogen are present there.

A problem with the Lunar Prospector data is that its maps of hydrogen concentration are low in spatial resolution; we cannot identify any structure in the data smaller than about 40 km. Thus, in the LP neutron data, we see a large, smeared out area of enhanced hydrogen. We cannot tell if this excess is confined to the dark floors of permanently shadowed craters (consistent with the presence of water ice) or just an overall enrichment of hydrogen near the poles (consistent with implanted solar wind protons.)

Last week, new models of the distribution of water ice near the lunar poles were published. These maps indicate that if the polar hydrogen is present as water ice, ice concentrations may exceed 1 weight percent in some areas. This sounds like a small amount, but when added over a large area, it could constitute hundreds of millions of tons of water ice on the Moon. Moreover, because the neutron instrument only senses the outer 30 cm of the surface, total concentrations could be up to ten times greater than these results.

Of course, a model is not new data, but merely an attempt to envision how hydrogen might be distributed over the lunar poles. In concert, both neutron and radar data sets will provide an abundance of information that may allow us to finally resolve this vexing question: Is there water on the Moon?

The view from the Apollo 8 CSM, Christmas 1968

Tomorrow marks the 40th anniversary of the launch of the Apollo 8 mission, America’s first human mission to the Moon and by any measure, still a remarkable achievement. It’s difficult from our position so many years later to appreciate what a bold, giant leap this mission was, in some ways even greater than the subsequent lunar landing of Apollo 11. Before Apollo 8, no one had ever ventured more than a few hundred kilometers above the Earth. No one had ever seen, with their own eyes, the glowing disk of a full Earth nor the cratered dusty surface of the Moon up close. And no one had ever experienced the isolation of being on the far side of the Moon, cut off from all contact with the Earth and everything the human race has ever known.

It is not an exaggeration to say that Apollo 8 changed everything. It won the race to the Moon for the United States, although most didn’t realize it at the time. Apollo 8 was supposed to test the lunar module (LM) in Earth orbit, but technical problems meant that delivery of the LM was going to be late. Planned originally as a repeat of the Apollo 7 mission (the Command Module in Earth orbit), the lunar orbital mission was substituted instead because NASA had intelligence that the Soviets were planning a human lunar flyby before the end of the year. The successful flight of Apollo 8, coupled with the catastrophic explosions of their N-1 lunar rocket, convinced the Soviets that they had lost the Moon race.

The Apollo 8 mission was a positive, uplifting development for both the lunar program and the nation as a whole. The program had been resurrected from the ashes of the Apollo 1 fire by the successful flight of Apollo 7 in October, 1968, but serious questions remained about the reliability and space worthiness of the system. Apollo 8 demonstrated that the hardware and architecture devised for lunar flight would work well, boosting confidence in continuing forward with the goal of a man on the Moon before the end of the decade. Moreover, after a 1968 full of nothing but bad news, the Apollo 8 mission, coming at Christmastime, charmed even the famously cynical American press corps, enough so that Time magazine changed their choice of “Man of the Year” (from “The Protester”) to the crew of Apollo 8.

Although it took some time to develop, Apollo 8’s most lasting legacy was a permanently changed human perspective. Much had been written about how the various scientific revolutions (Copernican, Darwinian) removed man from the center of the universe. This is true enough, but so often, the most lasting changes come from images. The famous Apollo 8 picture of Earthrise over the lunar horizon was a stunningly beautiful image. Even though it had been photographed earlier by the first robotic Lunar Orbiter mission, both the magnificent color of the Apollo 8 picture and the fact that a human had taken it changed our view of the Earth and ourselves. Earth became “a grand oasis in the big vastness of space” to use Jim Lovell’s memorable phrase. This single image did more to raise a “global consciousness” — for good and ill — than did the tons of books, protest marches and pamphlets produced by the environmental movement.

The flight of Apollo 8 changed the way we perceive our world and the cosmos. For the first time in human history, people had traveled beyond the gravitational sphere of Earth and looked back upon it. That event changed history in many ways, some of which we are still trying to comprehend. What similar change in perspective and history awaits when people actually live on the Moon, and routinely look into the black sky to watch a constantly changing Earth?

There’s a huge hubbub in the press revolving around alleged “obstructionism” at NASA toward the Presidential Transition team. As this rather overwrought piece at the Orlando Sentinel has been posted and commented upon endlessly at several web sites, I do not propose to rehash it. Instead, I want to comment on a theme that I see running through many of the reader comments, viz., that the Vision for Space Exploration (VSE) is dead, that it was a stupid idea to begin with, and the Constellation project (NASA’s Shuttle-replacement spacecraft system) will be and should be terminated.

As I have discussed previously, the VSE was an attempt to give a long-term strategic direction to our national space program after the tragic loss of Space Shuttle Columbia in 2003. It called for the return of Shuttle to flight, completion of the International Space Station, retirement of the Shuttle, development of a new manned spacecraft, a return to the Moon and finally, human missions to Mars and other destinations. Unlike President Kennedy’s Apollo challenge to reach the Moon “before this decade is out”, the motivation for the VSE was to create a long-term, continuing commitment to human spaceflight. Toward that end, it specified what we were to do beyond low Earth orbit – to understand and use the resources of space to create new spacefaring capability. Such an expansion of capability was the purpose for making the use of local resources a principal activity of lunar return in the original Presidential speech.

Many people have conflated the Vision with NASA’s implementation of it, but they are two very different things. Project Constellation is the architecture that NASA has chosen to implement the VSE. In its essentials, Constellation is a launch system, a spacecraft, and a mission design. NASA chose to develop a new series of launch vehicles, the Ares I and V rockets, the Orion crew “capsule” (formerly called the CEV), and a craft designed to land on the Moon, the Altair lunar lander. The mission design is to launch the crew in the Orion capsule on an Ares I into low Earth orbit, launch the Altair lander and rocket departure stage separately on the Ares V, rendezvous and dock with the lander and depart from Earth orbit to the Moon. The crew would land and explore the Moon from the Altair spacecraft, return to the Orion in lunar orbit, and return to Earth in that vehicle.

Much of the criticism of NASA in recent years is actually criticism of this architectural plan, not necessarily of the goals of the Vision (although some have questioned it). But this architecture is an implementation of the VSE; it is not the VSE itself. The Vision specified long-range goals and objectives, not the means to attain them. To briefly review, we are going to the Moon to learn the skills and develop the technologies needed to live and work productively on other worlds. And there are many ways to skin that cat.

NASA spent many months and thousands of man-hours developing the architecture to implement the Vision. From the start, it was controversial, particularly the decision to develop a new launch vehicle (Ares I) using a single Shuttle solid rocket booster, whose sole purpose is to transport the crew vehicle to low Earth orbit. Note well: this vehicle cannot send people to the Moon. Ares I can only transport the crew in Orion to low Earth orbit. To go to the Moon, a second launch of a much larger rocket (Ares V) is required, carrying the lunar lander and an Earth departure stage. Critics allege that by developing Ares I, we are not moving towards the Moon, but rather creating an Earth to LEO system that is less capable than the existing Shuttle. The true objective of the Ares I program is not to build such a vehicle but rather to develop the pieces needed for the big rocket, the Ares V. These pieces include the 5-segment solid rocket motor, cryogenic upper departure stage, and flight avionics, all of which are needed to build the Ares V, which is capable of launching a lunar spacecraft.

One can criticize this architecture on a number of grounds, ranging from the technical to the programmatic, but it is important to distinguish the Constellation program from the Vision for Space Exploration. They are two separate and unequal things. Regardless of what happens to this architecture in the coming months of uncertainty, the VSE remains a logical and forward-looking set of strategic space goals for the nation.

The Space Shuttle Endeavour safely landed at Edwards yesterday, completing a highly successful 16-day mission to the International Space Station (ISS), which celebrated a decade of continuous operation last week. It’s common in my business of planetary science to complain about the ISS, how it sucks up money that should be used for scientific exploration, and numerous other sins. Today, I write of its benefits and how it is relevant to our expansion into the Solar System.

The idea of a space station is very old; Wernher von Braun made it one of the first pieces of a broadly based transport system in space in his original Collier’s articles. In its original incarnation, a manned space station would do many jobs – Earth observation, including weather forecasting, communications relay, astronomy, a servicing port for trips beyond low Earth orbit. In fact, almost all of these tasks came to pass, but not at ISS. We watch and monitor the Earth with robotic spacecraft. An unmanned communications satellite (comsat) network 22,000 miles above the Earth acts as a relay network that ties the entire Earth together. The Hubble Space Telescope observes the heavens with crystal clarity. Many of the jobs von Braun envisioned for a space station are done today, but by robotic satellites, not humans at ISS.

What about the station’s role as a jumping off point for voyages beyond Earth? There hangs an interesting tale. When NASA first began thinking about lunar bases in the early 1980s, Space Station Freedom (as it was then called) served exactly that role. Station would be a transportation hub between the Moon and other destinations in cislunar space, such as geosynchronous orbit (where comsats reside). The Shuttle would deliver people and goods to the station in low Earth orbit and from there, they would journey to the Moon and beyond.

But Space Station changed. To maintain political support for the program, it morphed from Space Station Freedom into the International Space Station, with significant participation by Russia. For the Russians to be able to access station from their launch facilities in Kazakhstan, the inclination from the equator of the plane of its orbit changed from 28 degrees to 52 degrees. This new inclination enabled station to fly over 80% of the globe (good for Earth studies) but made it more difficult for Shuttle to reach (lowering the total mass Shuttle could bring up) and making the station much less attractive as a staging node for voyages beyond LEO.

These consequences were known at the time and as no future human missions were planned beyond LEO for the foreseeable future, made operational sense of a sort. Now we find ourselves with a space station, but apparently one not optimally placed to support our movement into the solar system. This is one of the many criticisms of station – that it is essentially a dead end and cannot be used as a “jumping off point” for future missions.

But I contend that ISS is useful for future lunar and planetary exploration. For one thing, building and operating a million-pound spacecraft for over a decade has surely taught us something about spacefaring. One of the most remarkable facts about ISS is that it went from drawing board (more accurately, from computer-aided design bits) to working hardware in space, without numerous prototypes and precursors, and it worked the first time it was turned on. By any standard, that is a remarkable achievement. We have learned how to assemble and operate complex spacecraft in orbit, in many cases solving deployment problems and coaxing balky equipment into operation, as exemplified by the recent experience of Don Pettit and Mike Fincke with the renowned urine conversion machine. Assembling complex machines and making them work in space is a key skill of any spacefaring society. Building and operating ISS over the last decade has taught us much about that skill.

The station could be made even more important and relevant to future operations in space. A key requirement of routine operations in cislunar space is the ability to manage, handle and transfer rocket fuel, particularly the difficult to manage cryogenic liquid oxygen and hydrogen. We could begin to acquire real experience working with these materials at ISS – transfer a quantity of water, crack it into its component hydrogen and oxygen using solar-generated electricity on orbit, and experiment with different methods of handling, conversion and storage of these materials. None of this requires a new module, but some specialized equipment could allow us to experiment with cryogenic fuel in microgravity, mastering a skill of vital importance to future operations in space and on the Moon.

A decade of building the ISS has taught us much about real spaceflight and the experience gained will be vital to future, long duration human missions. We should take advantage of this asset to explore further the technologies and techniques we will need to create a true spacefaring infrastructure, one of von Braun’s original goals of an orbiting space station.