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© 2006 by Donald F. Robertson.

E-MAIL: DonaldFR@DonaldFRobertson.com.

This article originally appeared in Meme Therapy

A Web site asked me to answer the following question.  I did, and my answer amounts to a scientific justification for human lunar exploration.


If you had the power to resurrect a space program that was canceled or never got off the ground which one would you choose?

My answer now is probably significantly different than it would have been in even a few years ago, but my answer today is Apollo. After spending vast sums creating the transportation infrastructure required to send scientists to Earth’s moon, we let it go long before it could realize its potential. As Lyndon Johnson put it before it actually happened, we would “piss it all away.”

If Apollo had continued, we would have learned far more science on Earth’s moon than any set of automated missions could have achieved. Maybe we would not have had quite as extensive a scientific survey of the Solar System as we have today, but we would have gained truly detailed knowledge of the kind of regolith-dominated surface that most extraterrestrial bodies have. (A regolith is a “soil” without biology – essentially, mechanically processed rocks and fines.) We would also have gained crucial experience in survival on the types of world that dominates the inner Solar System. Moreover, the Saturn-V transportation infrastructure would have been steadily improved, rather than attempting the Shuttle project’s premature and generally unsuccessful leap to reusable launch vehicles. For the money we’ve spent in Earth orbit failing to reduce the cost of orbital flight, we could now have extensive operations on the easiest to reach nearby destinations: Earth’s moon, Earth-approaching asteroids, and the Martian moons. This ongoing activity may have provided the markets needed for private investment in better transportation.

When the last three approved Apollo flights were canceled, we were already on a steep learning curve. Compare the one day visit of Apollo-11 to the detailed geology and exploration done on Apollo-17, only six successful missions later. The Saturn infrastructure was also on steep cost decline as production lessons were being absorbed and implemented.

Everyone interested in these issues should read Exploring the Moon: the Apollo expeditions by David M. Hartland, especially the section on Apollo-16. This excellent book covers the geology that was attempted by the last three Apollo missions and reads like a novel of exploration. Even I was surprised at the extent and detail of the field geology undertaken, and by the capabilities of the astronauts to quickly travel and sample across entire “alpine” valleys, even under the severe operational constraints of these first-generation human missions. The key lesson of Apollo-16 is that expectations from both remote observation and automated probes turned out to be dead wrong, and a whole new theory of geological processes no longer extant on Earth was developed because of the Apollo-16 crew's discoveries (semi-fluid brecciating flow from an impact creating a fill that from a distance looks like remarkably like lava fill).

The geology of regolith and breccia's is the geology that most likely dominates the inner Solar System (and, indeed, the inner regions of most star systems). As such, it deserves great study. Mr. Hartland demonstrates that the commonly accepted view that the geology and surface of the moon are boring, is simply wrong. I think this view results partly because the geologic traverses done during the Apollo missions were largely ignored at the time. People were more interested in the success of actually getting there, and scientists wanted to hare off to Mars. This wide-spread ignorance of what Apollo actually accomplished and what the moon is really like resulted in a great distortion in our perception of the relative value of human exploration versus robotics. That, in turn, has damaged our space program ever since as we continue to convince ourselves that science can be automated. At the risk of over-stating my case, I'll argue that, today, here and now, sending geologists to the extraordinarily accessible moon is probably the best way to teach us about the processes creating the surfaces of most worlds throughout much of the galaxy.

The science that continuing Apollo would have achieved includes, but is not limited to, the following.

• The stratigraphy of lunar cratering can be used to date the basin-forming impacts, and thus more tightly constrain the largely unknown history of the early bombardment of the inner Solar System. This occurred as the asteroidal building blocks of the Solar System were swept up by the growing planets. Since life formed on Earth during or immediately after this bombardment, understanding and dating it is important to understanding the early Earth, but these records are long-since destroyed here. The cratering record can only be understood on-site through combining many cores over long traverses with absolute dating at each location. While this could in theory be done with robots, Apollo astronauts did it quickly and efficiently at most of their landing sites. The costs of sending the large numbers of robots required to duplicate that feat, and operating them for months or years to achieve what a single astronaut could do in hours, would quickly climb far higher than continuing Apollo would have cost.

• The moon's surface is a very common type of surface in the Solar System, while Earth, Venus, and to a lesser degree Mars, are all special cases. In many ways, it is more important to understand the moon's surface than the special cases; and once you do, the special cases will make more sense. Regoliths and impact breccias are virtually unknown on today’s Earth, and the early breccias on Mars will be heavily weathered, yet their behavior probably determine the surface properties of the vast majority of bodies in the universe, including the early Earth. As such, understanding them and their behavior over time is probably more important to understanding the universe than is even understanding the (special case) Earth, and certainly Mars.

• Detailed exploration of the lunar surface is the best way to map exploitable resources on this most accessible of worlds. Likewise, the asteroids that we may be able to exploit in the relatively near future also will have breccia-dominated surfaces. Understanding regolith is important both for understanding asteroids, and understanding how to separate usable resources, especially early on when the latter will of necessity be on a small scale.  There are bound to be surprises (e.g., Apollo-16) which are totally unexpected from what we believe today.

• The moon probably contains preserved materials from the earliest terrestrial continents, splashed up during the bombardment, which has long since been destroyed by weathering on Earth. These materials may preserve records of the earliest formation of life and its precursors. Finding such material would be of immeasurable value to geology, biology, palaeontology, and other sciences. However, these samples will be rare, scattered, and probably deep: they could never be directly sampled by robotic missions, and it would take an extensive geologic infrastructure to find them with human expeditions. The latter must be capable of traveling great distances and drilling great depths at many locations. Such an infrastructure could not be placed anywhere but on the moon in the near future -- but it can be there. Similar preserved remains may survive from the earliest periods from the other planets, particularly Mars and Mercury and the asteroids. The same may be true of interstellar materials and even the outer planets. Earth's moon has been a static trap for most of the history of the Solar System, and its accessibility makes it far more valuable (to us) than the other such traps.
  
  On the other hand, it is just possible that heavily modified but easier to find terrestrial samples may be located near the lunar surface. Explorers should look for areas where modern craters have excavated the original crust and lower layers of early impact debris. Material from the deepest layers will be on the rims and central peaks of the craters, so the ability to climb steep slopes covered with lose regolith and talus will be required. Astronauts can do that with relative ease. (Even Apollo astronauts handled more than twenty-degree slopes, and new-generation spacesuits will have greater mobility.)

• The bombardment must have struck both Earth and our moon at the same time. Both bodies, as well as Venus and Mercury, probably had impact-generated lava oceans with a "scum" rising to the surface that became the first crust. This may have happened repeatedly, although, even on the moon, the record of this has largely been destroyed by later impacts and covered by debris from the last basin-forming impacts. Apollo had great difficulty locating samples of this first deeply-buried crust, although they are believed to have succeeded. Finding such material tells us much about the Solar System in which the Earth was created.

• Mars’ relatively weathered surface may contain a poorer record of early breccias and processes in the early Solar System than does Earth's moon, but otherwise the surface of Mars probably is dominated by modified breccias and thus has much more in common with the moon than with Earth (or Venus). As such, understanding the lunar surface will teach us more about Mars than understanding Mars will about Earth. If we are ever going to go to Mars, Earth's moon probably provides a good analog for gaining experience.

Combine all this with its accessibility, and I think there is an excellent case for returning to Earth's moon and conducting detailed exploration before we get ahead of ourselves haring across the Solar System with robots. Doing the latter has given us great information about the easy stuff and the surfaces -- reconnaissance -- but in the long-term, our successes have probably done us a disservice. The history of science is replete with the wrong conclusions being drawn because you took a quick-and-dirty look at broad areas while failing to take a detailed look at the sites you can reach.

With Apollo, we could reach the moon. We could do detailed geology of a type that we cannot do anywhere else for decades to come. That's what we should have been doing, and it is what we should be doing now. It would be most valuable done with continued automated reconnaissance of the rest of the Solar System, but if you have to choose, you should do the former before you do the latter.

What technology exists right now that you think has the most underrated potential?

Without question, solar sails. Like on Earth, sailing is virtually free transportation. Why everyone insists on ignoring this obvious technique is beyond me.

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