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Tourists arrive at the new world (Library of Congress)

Yet again, the U.S. space program is in the slough of despond, whereby previous assumptions are questioned, the current path is discarded, the program is re-directed, and luminous enthusiasm heralds the new direction…

And then it all tapers off to nothing.

As long as we are navel-gazing during this policy hiatus, I want to examine a topic that many think is self-evident: what activities do we mean by the word “exploration?”  NASA describes itself as a space exploration agency; we had the Vision for Space Exploration.  The department within the agency developing the new Orion spacecraft and Ares launch vehicle is the Exploration Systems Mission Directorate.  So clearly, the term is tightly woven into the fabric of the space program.  But exactly what does exploration encompass?

Exploration can have very personal meanings, such as your own exploration of a new town, or a new and unknown field of knowledge.  Here, I speak of the collective, societal exploration exemplified by our national space program.  This exploration began in 1957, when the launch of Sputnik by the Soviet Union initiated a decade-long “space race” of geopolitical dimensions with the United States.  That race culminated with our first trips to the Moon.  Once its primary geopolitical rationale had been served, Moon exploration was terminated.  Since then, the “space program” has been astonishingly unfocused – drifting from a quest to develop a reusable spacecraft to building orbiting space stations – and despite numerous studies affirming needed direction, unfulfilled plans to send humans back to the Moon and eventually on to Mars.

When the race to the Moon began 50 years ago, space was considered just another field of exploration, similar to Earth-bound exploration of the oceans, Antarctica, and even more abstract fields such as medical research and technology development.  Moreover, many used the term “frontier” when speaking about space, touching a very familiar chord in our national psyche by drawing an analogy with the westward movement in American history.  What better way to motivate a nation shaped by the development of the western frontier than by enticing it with the prospect of a new (and boundless) frontier to explore?  After all, we are descended from immigrants and explorers.  Over time however, few recognized that there had been a shift in the definition and understanding of just what exploration represented.

Starting around the turn of the last century, while still retaining its geopolitical context, exploration became closely associated with science.  Although first detectable in the 19^th Century exploration of America and Africa, the tendency to use science as the rationale for geopolitical exploration reached its acme during the heroic age of polar exploration.  Amundsen, Nansen, Cook, Peary, Scott and Shackleton all had personal motivations to spend years of their lives in the polar regions, but all of them cloaked their ego-driven imperatives in the mantle of “scientific research.”  After all, the quest for new knowledge sounds much nobler than self-gratification, global power projection or land grabbing.

Science has been part of the space program from the beginning and has served as both an activity and a rationale.  The more scientists got, the more they wanted.  They realized that their access to space depended upon the appropriation of enormous amounts of public money and hence, supported the non-scientific aspects of the space program (although not without some resentment).  Because science occurs on the cutting edge of human knowledge, its conflation with exploration is understandable.  But originally, exploration was a much broader and richer term.  Which brings us back to the analogy with the westward movement in American history and the changed meaning of the word “exploration.”  A true frontier has explorers and scientists, but it also has miners, transportation builders, settlers and entrepreneurs.  Many are perfectly satisfied to limit space access to only the former.

“Exploration without science is tourism.” – Statement of the American Astronomical Society on the Vision for Space Exploration, July 11, 2005

This fatuous quote accurately reflects the elitist, constricted mindset of many in the scientific community.  In one fell swoop, the famous explorers of history – Marco Polo, Columbus, Balboa, Drake – are consigned to the category of  “tourist.”  Overcoming great difficulty and hardship, these men sought new lands for many varied reasons.  Exploration includes obtaining new knowledge but it does not end there; it begins there.  The quest for new lands has always been a search for new territories, resources, and riches.  Historically, survival and wealth creation are stronger drivers of exploration and settlement than curiosity.

What is missing from our current program of space exploration is a firm understanding that it must generate wealth, not just consume it.  Exploration is more than an experiment.  The idea of space as a sanctuary for science has trapped us in an endless loop of building expendable hardware to support science experiments.  Once the data are obtained, of what use is an empty booster or a used rover?  We’ve “been there” and a pipeline of new inquiry awaits, to be facilitated by new spacecraft and new sensors designed to reach new destinations of study.  Hugely expensive equipment must be developed to support science while the idea of creating transportation infrastructure or settlement is branded as “budget busting” (i.e., manned space exploration cuts into science’s budget).  So “exploration” lives to enable science, period.

This is our current model of space exploration.  I contend that it is not exploration as historically understood and practiced.  Traditionally, science (knowledge gathering) was a tool in the long process of exploration, which included surveys, mining, infrastructure creation and settlement (all advanced and protected with military assistance).  This was the model of national exploration prior to the 20^th Century and it is readily applicable today – if we change our business model for space.  What is needed is the incremental, cumulative build-up of space faring infrastructure that is both extensible and maintainable, a growing system whose aim is to transport us anywhere we want to go, for whatever reasons we can imagine, with whatever capabilities we may need.

These changes do not require that an ever-increasing amount of new money be spent on space.  Instead, true exploration requires only the understanding that it must contribute more to society than it consumes.  And the American people have every right to expect as much in return for their years of supporting NASA.

Teleoperated robots can emplace and build much of the lunar outpost infrastructure prior to human arrival (Astrobotic Technology Inc.)

In an interesting post at Vision Restoration, “Ray” tackles the desultory Flexible Path (FP) architecture of the Augustine committee, which calls for human missions to low gravity destinations and delays missions to the lunar and martian surface.  The problems he finds with FP are similar to points that I’ve discussed in a previous post.

The principal rationale for doing Flexible Path rather than the current program for return to the Moon is to avoid the cost of developing a new surface lander spacecraft for humans (either lunar or martian), which Augustine pronounced budget-busting for NASA.  By being “flexible” and avoiding deep gravity wells, the Augustine committee saw a low cost way to send people beyond LEO.  However, the Orion crew module and some type of heavy-lift booster still must be built.

Augustine committee member Jeff Greason discussed the FP architecture during a recent appearance on The Space Show.  Jeff pointed out that many people missed the principal rationale for the advancement of FP as an alternative to the existing program – that while we cannot afford the current ESAS architecture because of the requirement to do several developmental projects simultaneously (or nearly so), we might be able to afford to do it sequentially, so that development of the Altair lunar lander would only begin after we had developed and flown the Orion and its new heavy-lift launch vehicle.  In his conception of FP, Jeff sees increasing space faring capability over time as robots and people visit new and more distant destinations.  The FP destinations described in the Augustine report are the Lagrangian-points, near Earth asteroids, and martian moons Phobos and Deimos.

Ray points out that the two alternatives discussed in the Augustine report (Moon First and FP) assume a roughly $3 billion per year increase in the NASA budget.  He suggests that this is unlikely, especially on a continuing basis, a supposition made even more credible by recent stories in the space press.  The alternative he offers to Augustine’s FP takes a slightly different tack to the cost problem.  Ray’s solution, called Flexible Path to the Moon, shortens the destination horizon for FP and restricts it to cislunar space (GEO, the Earth-Moon L-points, and lunar orbit).

With Flexible Path to the Moon, we develop routine access to all cislunar space, which adds important national security and economic dimensions to the human spaceflight program.  Ray would defer not only the Altair lander but also (and this is critical) the new, proposed heavy lift vehicle called for by the Augustine report.  Instead, FP to the Moon uses existing and future commercial launch vehicles for LEO access and for the subsequent build up of transfer nodes, in-space re-fueling of vehicles, propellant depots and other features of the Augustine FP architecture.  Ray’s plan further calls for “a large number” of robotic missions to the Moon and other possible destinations prior to human arrival.

I like this architecture and have advocated a very similar approach that builds up space-faring capability incrementally and cumulatively—take small, affordable steps and make time and schedule the free variables.  We make progress as we can with a sustainable architecture and build an infrastructure that is cumulative, inevitable and inexorable.  One thing should be added to Ray’s architecture:  a statement of the “mission.”  The purpose of lunar return is to learn how to use the resources of the Moon and space to create new capabilities and a sustainable human presence in space.  This mission statement fits well with Ray’s mission architecture.  The significant level of robotic missions that he advocates in Phase 1 can be focused specifically on resource prospecting, characterization and demonstration.  We can begin to produce resources using robotic missions and machines teleoperated from Earth well before the arrival of the first humans, who will then have the assets of life-support consumables, propellant, and electrical energy to draw on when they arrive.

The Flexible Path to the Moon offers the build-up of new technologies and capabilities in space by using an incremental approach that falls within existing budgetary constraints.  It forgoes the building of a new heavy lift launch vehicle by creating a reusable, extensible space transportation system infrastructure using existing launch vehicles.  And it focuses efforts and builds infrastructure in cislunar space, where virtually all of our assets reside.  These are the stepping stones we need into the Solar System.

A robotic mission sends samples back to Earth: What can we learn from them?

Deciphering the cratering history of the Moon is an important scientific problem.  My previous post discussed early lunar cratering history, the apparent impact “cataclysm” 3.8 billion years ago, its significance to Earth’s early history and how remaining questions might be resolved by collecting and returning new samples from the Moon.  Here, I will describe the scientific difficulty and critical importance of planetary sample collection and analysis.  With so many demands on NASA’s budget, we need to approach this problem carefully, making every effort to maximize the prospect that we obtain not just samples but the right samples to answer the question of the Moon-Earth cataclysm.

NASA has announced that the proposed New Frontiers Moonrise robotic sample return mission is one of three selected for detailed concept study.  The objective of this mission is to sample, date and analyze the composition of the impact-generated rocks produced by the largest and oldest crater on the Moon, the South Pole-Aitken (SPA) basin.

The return of surface samples has the potential to answer many important scientific questions.  How do we reconstruct the history of a planet from rocks returned from its surface?  What are some of the difficulties in such a reconstruction?  How well do we really understand the history of the Moon from returned lunar samples?  Because context is vital to the correct interpretation of sample return data, these questions must be understood and considered, and underlie the mission strategy.

A great deal can be learned from remote surface measurements, but some properties can only be measured to very high degrees of precision by using returned samples.  One key piece of information that is difficult to measure remotely is a rock’s age (measured by its radiometric isotopes).  This determination requires a significant sample preparation, handling, and precision measurements; in some dating methods, we must literally take the rock apart, grain-by-grain.  The machinery needed to measure isotopic composition tends to be big, massive, and power hungry, all undesirable properties for lunar and planetary payloads.

Geologists collect samples because they cannot bring into the field all the complex and sophisticated equipment used to analyze and describe the physical, chemical and mineral properties of planetary crusts.  Samples allow them to conduct many different kinds of measurements in a controlled environment, eliminating external factors that can contaminate results.  In addition, samples have long-term value in that they can be stored, archived and examined in detail (sometimes by newly invented techniques) as concepts and understanding change.  It is for this reason that lunar sample studies continue to unravel new aspects of the complex history of the Moon 40 years after Apollo 11.

We are able to design a spacecraft to collect rocks and soil and return them to Earth.  After analysis, we have lots of data and numbers, but not necessarily any new understanding.  Context is important in translating sample data into knowledge.

The geologist in the field must collect samples carefully; field work is not just picking up rocks – it is the attempt to unravel and comprehend the spatial and temporal make-up of planetary crusts.  Samples must be representative of the larger, regional geological units they come from.  A sample must be of the appropriate size (coarse-grained rocks need larger samples than fine-grained rocks to be representative of their parent units).  If possible, we must collect rock samples from outcrop (in place bedrock); rocks obtained from loose pieces on the ground (called “float” by geologists) have uncertain or unknown context and hence, the conclusions we draw from such samples may not apply to regional units.  And when done on the Moon or another planetary body, all of this activity must conform to the constraints imposed by the flight system, such as total mass and volume limits for returned samples.

Recently, many countries have flown sensors that have yielded compositional information and globally mapped the Moon.  From these data, we can determine chemical and mineral compositions of the geological units of the Moon (which are delineated by extent, morphology and physical properties).  When this information is combined with data from returned samples, we can characterize the unit and its history even more fully than traditional field work, where intense, protracted ground study is possible.  This is the promise of the new approach – allowing us to combine the low fidelity but broadly distributed data of remote sensing with the highly detailed but narrowly restricted information provided from samples.

However, due to the very nature of the Moon, there are significant geological complications that must be taken into account.  Exposed bedrock is rare.  A thick cover of regolith is everywhere on the lunar surface.  In the highlands (the oldest geological units on the Moon), there may be no bedrock at all, the surface having been thoroughly pulverized into regolith by four billion years of impact bombardment.  Consequentially, the context of most Apollo highland samples remains poorly understood.  Exquisitely detailed measurements have been made on these rocks but we still cannot be certain about what they represent.  Was there a cataclysm at 3.8 billion years ago?  Currently, we are left wondering if we have sampled one, a couple, or a dozen basins.

During the Apollo missions, the astronauts did their best to sample and describe the context of representative rocks during collection, but the geological setting of most samples is still guesswork.  The location of the samples returned by a robotic spacecraft will be documented to within a fraction of a millimeter.  But as they are collected from regolith, their context will remain purely statistical.

By collecting hundreds of relatively small rocks (but still large enough for precision measurement) the argument is made that we will collect the desired SPA basin melt sheet through sheer statistical certainty.  I suspect that the mission might well do this.  But what about their context?  We need to know which of the pebbles collected are from the basin melt sheet.  In miniature, this situation duplicates and leaves us with exactly the same issue we currently have with the Apollo samples—which rocks represent the basins we intended to sample?  With few exceptions, despite having global remote sensing data to provide context, we still do not know which (if any) impact basins are represented in the collections, which keeps our scientific understanding hobbled by degrees of uncertainty.

A simple “grab” sample from a relatively young and unmodified geological unit on the Moon could solve a major problem.  A robotic spacecraft sent to the youngest lava flow on the Moon (dated relatively by crater density) could establish that flow’s absolute age to high precision with a fair degree of certainty.  As the age of the targeted geological unit increases, such certainty would decrease as younger events and deposits contaminate and disrupt the continuity of the older units.

The Moonrise mission proposes to sample the oldest preserved terrain on the Moon—the melt sheet floor of the SPA basin.  Younger units (craters, basins, and maria) are everywhere in this basin, superposed on top of the SPA melt sheet.  Although pieces of the original basin floor may be preserved in places, we will not know in advance what those pieces should look like, leaving us with uncertainty over what was collected from the mission.  In short, many samples will be collected, much data will be accumulated, and uncertainty will remain as to what it all means – the same knowledge gap we currently have with the Apollo samples.

The Imbrium basin immediately after formation, ~3.85 billion years ago. Artwork by Don Davis.

NASA recently announced that it has down-selected three New Frontiers mission concepts for additional study.  One of these missions, Moonrise, proposes to return rock and soil samples from the floor of the largest impact crater on the Moon, the South Pole-Aitken (SPA) basin, centered on the southern far side.  Not only is this the largest basin on the Moon, it is also the oldest, as evidenced by a high density of impact craters superposed on top of its deposits.  But knowing that it is the oldest basin does not tell us exactly when it formed.  Samples collected from its floor could potentially determine exactly when, during the early history of the Moon, it was created.

Why is the absolute age of this feature important?  When lunar samples are returned to Earth as they were by the Apollo missions forty years ago, they are subjected to virtually every conceivable chemical and mineral analysis we can imagine.  From those studies we have reconstructed a rough outline of lunar history and the processes that have shaped it.  From this work (which produced reams of detailed data on the elemental composition and make-up of the Moon) came the startling discovery that, not only is the heavily cratered crust of the Moon very old (older than 3.8 billion years), but that the largest impact features of that crust seemed to have formed at the very end of that early period.

The Moon’s molten crust solidified 4.3 billion years ago. Virtually all highland rocks assembled in large impact events date from around 3.8 billion years ago.  Because it was believed that many of these impact events had been sampled by the Apollo missions, it was inferred that the Moon underwent a massive bombardment of large body projectiles, all closely sequenced at that time.  This time period is referred to as the lunar “cataclysm” or the “late heavy bombardment.”  As both Earth and Moon orbit the Sun at the same distance, an impact cataclysm affecting the Moon also would have affected the early Earth.

A late, cataclysmic bombardment of the Earth-Moon system was not predicted by the then-existing models of lunar formation and growth.  In an unexpected turn, this time period (3.8 billion years ago) was significant in another respect, as it is the oldest epoch from which we have preserved fossil (bacterial) life in Earth’s rock record.  Does this mean there is a connection between the end of the early, heavy impact bombardment and the emergence of life on Earth?  It is very tempting to make this connection but when missions to the Moon ended, our ability to continue down this path of scientific inquiry also ended.  If we are ever able to draw such a paradigm-changing conclusion, we must first determine if the lunar cataclysm really happened.

Two things about the Apollo samples must be considered.  First, all were collected from six landing sites in the vicinity of the central, equatorial near side.   The large Imbrium basin is one of the youngest on the Moon—it subdivides lunar history and determining its absolute age was a top priority; at least two of the Apollo mission sites were chosen to address the composition and age of the Imbrium basin and two (and possibly the remaining four) additional sites are well within the possible influence of this large feature.  Thus, although we cannot be certain, many of the Apollo highland samples may contain the imprint of this single, watershed event, obscuring the record of earlier impacts.

Second, the nature of the Moon itself works against our understanding of the geological context of the returned samples. The Moon has had a complex history, whereby rocks were thrown hundreds of kilometers across its surface, mixed up with other deposits thrown out from other craters and basins, along with periodic lava flooding.  The continuous impact bombardment of the Moon for billions of years has “sandblasted” the crust into a crushed mixture of rock and fine powder (called regolith) that covers the surface.  True rock outcrop is hard to find and virtually none of the Apollo missions sampled it.

Although a lunar sample can be subjected to excruciatingly detailed measurements and age determinations, such data are valueless unless you are able to relate the sample to some larger, regional geological unit.  In the case of the impact cataclysm, how many and which basins did the Apollo missions sample?  Unless we can answer that question with some certainty, we cannot be sure that a “cataclysm” occurred – we may be looking at only the last (or last few) largest basin-forming impacts.

To resolve the issue of the cataclysm, we must collect samples from older, distinctly different impact basins, preferably far removed from the zones where Apollo explored.  Hence, we desire to collect samples from an area exactly opposite to the near side Apollo sites—the far side’s South Pole-Aitken, the largest and oldest basin on the Moon.  If we sample impact melt from this event, we could determine the age of SPA with a degree of confidence and understand whether all basins formed at nearly the same time (which would be the case if SPA is the same 3.85 billion year age as the near side Imbrium basin, sampled by Apollo) or if the formation of the basins was spread out over 400 million years, as would be the inference if SPA is 4.3 billion years old.

Obtaining this key sample would be monumentally important for lunar science.  Does this sound too good to be true?  Perhaps, but it is exciting to anticipate the possibilities of such a discovery.

In my next post, I will discuss some of the difficulties in deciphering the cratering history of the Moon from its rocks.