[First published in: Astronomy & Geophysics, 39(6), pp. 14-17, (December 1998)]

Many scientists are sceptical about the scientific value of sending people into space. Here I argue that this scepticism is seriously misplaced, and that science has been, and will continue to be, a major beneficiary of human space flight

Introduction

Scientists have been arguing about the benefits of venturing into space since before the space age began. Indeed, the ambivalence, and to some extent the short-sightedness, of the astronomical establishment towards space exploration is well illustrated by its famous dismissal as "utter bilge" by the incoming Astronomer Royal, Richard Woolley, in January 1956 (Woolley 1956).

Although Woolley's off-the-cuff remark is often quoted out of context (it was actually aimed at speculations about interplanetary travel, rather than at the technical feasibility of launching objects into space), it is perhaps revealing of a widespread scepticism among astronomers about the value of space research that, four years later, the Astronomer Royal was still able to doubt the scientific usefulness of even artificial satellites (Woolley 1960). Fortunately for astronomy, the other side of this debate, championed most notably by Lyman Spitzer (e.g. Spitzer 1946, 1960), carried the day, and the enormous scientific benefits of space astronomy are now clear for all to see.

However, while the fundamental scientific contributions of unmanned space probes are now universally acknowledged, arguments continue about the scientific role of people in space. Primarily, these concern the scientific relevance of the International Space Station, and proposals for human missions to Mars. But before discussing these future issues, we should perhaps consider the scientific legacy of the most ambitious human space flight programme to date.

The legacy of Apollo

It is well known that the primary driving forces behind the Apollo project were geopolitical rather than scientific. Indeed, it is naive to believe that anything other than powerful political motives (which at the time were firmly rooted within the context of the Cold War) could have sustained a project which, at its peak, consumed over 4% of the US federal budget. The key question here, however, concerns the extent to which scientific knowledge was increased as a result of the Apollo project, regardless of the political forces behind it.

The fact that Apollo was expensive and not primarily science driven seems to have irritated many in the scientific community, and has even caused some to deny that it had any scientific relevance at all. For example, on the eve of the Apollo 11 landing, the Astronomer Royal, alluding to his remarks over a decade earlier, asserted that "from the point of view of astronomical discovery it [the Moon landing] is not only bilge but a waste of money" (Woolley 1969). Indeed, 25 years after Apollo I overheard a senior astronomer making exactly the same point at a dinner party.

The truth, of course, is that science was an enormous beneficiary of Apollo, primarily because of the 382 kg of lunar rock samples returned to Earth. The analysis of this material has had a huge impact on our understanding, not only of lunar history, but of the early evolution, and indeed the origin, of the solar system as a whole. By permitting an absolute calibration of the impact-cratering rate, the dating of these samples provided strong support for the theory of terrestrial planet formation by planetesimal accretion, as well as our only reliable method of estimating planetary surface ages throughout the solar system. Moreover, their geochemical analysis, which demonstrated the compositional similarity of the Moon to the Earth¹s mantle, provided one of the main arguments for the ³giant impact² theory of lunar origins (Hartmann and Davis 1975), which further supports models of the merger of planetesimals in the early solar system (Wetherill 1990). The composition of these samples is now being used to calibrate the excellent multispectral images of the Moon recently obtained by the Clementine spacecraft (e.g. Blewett et al. 1997). Nor should we forget the geophysical studies carried out during the Apollo project, most notably of the lunar interior by means of active seismology ­ the Moon is still the only planetary body, apart from the Earth, whose structure has been probed in this way (see Goins et al. 1981 for a review).

The opponents of human space flight will argue that all this could have been achieved much more cheaply with robotic missions. However, I think this is a mistake. While it is true that much of the Apollo science could, in principle, have been performed robotically, there must be considerable doubt as to how much would actually have happened had the manned landings not taken place. For example, although it is true that three unmanned Soviet space probes (Lunas 16, 20 and 24) successfully collected 321 g of lunar material in the 1970s, it is notable that this was less than 0.1% of the amount returned by the Apollo missions. Moreover, the Apollo material consisted of more than 2000 individual samples, intelligently collected from many locations around each landing site, while the Luna material consisted of a single core from each site. No practical, or (within a purely scientific budget) affordable, robotic programme could have returned anywhere near the quantity, or the diversity, of the Apollo lunar samples.

It is, of course, quite obvious why the Apollo missions were able to carry a large quantity of scientific equipment to the Moon, and to return with hundreds of kilograms of rock samples. As each flight had to transport three men and all their life-support equipment to the Moon anyway (in order to satisfy the political objectives of the programme), the marginal cost of carrying bulky scientific equipment (such as the seismic arrays and their explosive charges), and of bringing back the rock samples, was a negligible fraction of the total cost. This illustrates an important scientific advantage of human space flight: any space mission that has to transport people will, by its very nature, be able to carry a significant scientific payload, even if science is not the primary driver for the mission.

The Space Station

The International Space Station (ISS) is another major human space project which is not primarily science driven. Predictably, therefore, it has again raised the ire of those in the scientific community who confuse an absence of overriding scientific purpose with scientific worthlessness. The ISS, like Apollo before it, is being built primarily for political reasons (many of which, like the encouragement of international co-operation, are good reasons) but this does not mean that science will not be a beneficiary (see Lewis 1998 for a review). It may be true that the proposed scientific uses of the ISS, such as microgravity and life science research, could never justify the construction costs of the ISS on their own, but they are nevertheless important scientific disciplines which stand to benefit substantially from it. Even astronomy is likely to benefit, with the recent proposal to place an all-sky X-ray monitor on board (Matsuoka et al. 1997), and other astronomical applications are likely to follow.

The real significance of the ISS, however, is that it will help lay the foundations for future space programmes with vastly greater scientific potential. There are three aspects to this. Firstly, the ISS will provide considerable experience in space engineering; although many scientists are sceptical of the suggested scientific applications of the ISS itself, a moment¹s reflection will show that considerable scientific advantages are likely to follow from the ability to construct large structures (e.g. telescopes and interferometers) in space.

Secondly, studies of the physiological effects of weightlessness to be conducted on the ISS will be essential before human beings are able to undertake long journeys to other planets in the solar system. Notwithstanding the objections of the critics of human space flight, I shall argue below that the scientific returns of such missions are likely to be considerable.

The third point concerns the development of new institutional arrangements for the management of complex international space projects. Indeed, one space analyst has already expressed the view that "in effect, an international space agency has been created for the station" (Logsdon 1998). This may be overstating things at present, but there are strong reasons for believing that, if humanity is to have a significant future in space, something along these lines will be both necessary and desirable (Crawford 1992). If experience in building and operating the ISS helps to develop the institutional foundations for a future world space programme, that alone will be one of its most important legacies.

Let us now consider the scientific opportunities of human space flight in the post-ISS era.

A return to the Moon

There are broadly three scientifically important reasons for humans to return to the Moon:

Science on the Moon
The Moon is an important object of scientific study in its own right, and one that is likely to continue to provide major insights into the origin and evolution of the solar system. However, a moment¹s reflection will reveal that we have not yet achieved anything like a complete understanding of its structure, environment, or history. This is especially obvious when we consider that all our lunar samples and in situ measurements have come from low to mid latitudes on the nearside only. Thus the scientific case for renewed lunar exploration is extremely strong, and, as for Apollo, I suggest that more exploration will be carried out as part of a manned programme than if we rely exclusively on robotic means.

Science from the Moon
The potential advantages of the Moon as a platform for astronomical observations have been reviewed extensively elsewhere (e.g. Burns and Mendell 1988, Burns et al. 1990), and I will not repeat them all here. Briefly, they arise from the stability of the lunar surface (possibly an advantage for the construction of long-baseline optical/IR interferometers); the slow rotation period of the Moon (permitting very long integration times on a single object); the extreme cold (<100 K) in shadowed areas (a significant advantage for infrared instruments); and the extreme radio-quietness of the lunar farside (probably the best site for radio astronomy anywhere in the solar system). It may be that some of these applications could, in principle, be performed from unmanned space observatories. However, the point here is that a human return to the Moon, undertaken for whatever reason, is likely to provide astronomy with great opportunities which might not otherwise be practical or affordable.

Experience gained on the Moon
Finally, a human return to the Moon would provide experience in living and working on hostile planetary surfaces. This will be particularly important when it comes to constructing human outposts elsewhere in the solar system, and in particular on the surface of Mars.

Part 1

Part 2

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