Why Explore the Moon?

Planetary scientist Ian Crawford presents the case for our return to the Moon.

After a long hiatus following the Apollo missions forty years ago, the scientific exploration of the Moon is undergoing something of a renaissance. In the last few years a flotilla of robotic spacecraft has been sent to orbit the Moon by the space agencies of China, Europe, India, Japan, and the United States. This international concentration of effort is unprecedented in the history of space exploration. In part it reflects a renewed scientific interest in the Moon in its own right, and in part the aspirations of new space-faring nations to demonstrate their growing technical capabilities.

The primary scientific importance of the Moon arises from the fact that it has an extremely ancient surface, mostly older than 3 billion (i.e. 3 thousand million) years, with some areas extending almost all the way back to the origin of the Moon 4.5 billion years ago. It therefore preserves a record of the early geological evolution of a terrestrial planet, which more geologically active bodies, such as Earth, Venus and Mars, have long lost. The ancient lunar surface also preserves a record of everything that has fallen on it throughout the history of the Solar System. This includes fragments of meteorites and comets, as well samples of the ancient solar wind and, possibly, samples of the Earth’s oldest crust, blasted into space by giant meteorite impacts on our planet and collected by the Moon. Taken together, this is potentially a very rich scientific record of Solar System history which, with the possible exception of the much less accessible surface of Mercury, is unlikely to be preserved anywhere else. And it lies only three days away with current spacecraft technology.

Harrison Schmitt

The first, and so far only, geologist to visit the Moon: Harrison Schmitt stands next to a large boulder in the Taurus-Littrow Valley, visited by Apollo 17 in December 1972.

The idea that samples of the Earth’s earliest crust might be preserved on the Moon is particularly intriguing. Although we have strong grounds for believing that the Earth, like the rest of the Solar System, is 4.5 billion years old, the oldest actual Earth rocks found to-date are only 3.5 to 3.8 billion years old. All older rocks have been destroyed or buried by Earth’s active geology and climate. The oldest Earth rocks already show tantalising evidence for life having been present on our planet by that early time, but as we don’t have access to any older rocks we cannot be sure exactly how or when life first appeared on our planet. However, as noted above, ancient Earth rocks, blasted into space by meteorite impacts, may be preserved on the Moon. Perversely, therefore, our natural satellite may preserve fragments of Earth’s earliest crust, along with a record of the origin and evolution of life on our planet, which the Earth itself has destroyed. Finding such samples could become a holy grail of future lunar exploration.

The airless surface of the Moon has other scientific advantages as well. It is a superb site for some types of astronomical observation. The lunar far-side, in particular, is probably the best site for radio astronomy anywhere in the inner Solar System, as it is permanently shielded from artificial radio transmissions from Earth, and also shielded from solar radio emissions during the 14-day lunar night. Optical astronomy may also benefit from the establishment of lunar observatories. As the Moon lacks any obscuring atmosphere, the lunar surface is a much better site for astronomical telescopes than the surface of the Earth.

Altair lunar lander

The proposed Altair lunar lander. Although NASA's plans to return people to the Moon in the near future are currently in a state of flux, significant scientific advantages would follow from a renewed period of human lunar exploration.

To fully exploit the scientific potential of the Moon, to access the geological record of early Solar System history it undoubtedly contains, and to establish astronomical observatories on its surface, will require us once again to land astronauts on the lunar surface – and this time to stay. This must be the next step in lunar exploration, hopefully in the context of a fully international exploration programme, and science will be a major beneficiary. The Apollo missions demonstrated that human beings are highly efficient as explorers of planetary surfaces, and it is difficult to see how we will ever learn all that the Moon has to teach us about the history of the Solar System, and of our own planet, until people are once again actively exploring its ancient battered surface. Looking to the longer term, the human exploration of the Moon will also help develop essential experience that will be required for the human exploration of other locations in the Solar System, not least the planet Mars which also has much to tell us about the evolution of the Solar System and our place within it.

By helping to identify scientifically interesting places on the Moon, which may be explored when people do eventually return its surface, Moon Zoo participants can make a significant contribution to these exciting future activities.

Ian Crawford is a planetary scientist in the Department of Earth and Planetary Sciences, Birkbeck College London, and a member of the Moon Zoo Science Team.


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8 responses to “Why Explore the Moon?”

  1. Thomas says :

    Thank you, Ian, for a great blog and an interesting read.

  2. Jules says :

    Excellent blog. Thanks Ian! 🙂

  3. weezerd says :

    Thanks for an enjoyable read, with exciting prospects.

  4. yoosungyeul says :

    Thanks about this

  5. brobof says :

    And the funding, the British funding for all this?
    Ian, a question. Which would you rather have: a minimal 10 person outpost with most of their efforts dedicated to keeping the outpost going. Along with a HUGE supply chain draining any other exploration. Or one hundred -possibly one thousand- Tele-operated Lunokhods; Spirit IIs; Curiosities roving at will across the Lunar surface. Remember the time lag is minimal and our virtualisation technology improving. Robonaut 2!

    A human outpost on the Moon may be good for Boots n’ Flags but is not cost effective if the only goal is science.

    The only need for a base on the moon is as a radiation shelter for human operations in LLO and the L-points. However there may well be better in-space mitigation techniques.
    My latest blog posting refers.

  6. Guest says :

    Most people don’t see this as a clear or important argument. I’d be more interested in how this research will help us to utilize the moon to better our lives on Earth and elsewhere. For instance what potential does the moon have for the mining of resources? Could mining operations on the moon allow us to preserve more sites on Earth from mining? Could the Moon hold valuable raw materials for fueling fusion reactors? Etc… Could the moon sustain a civilization? Could we grow food on the moon? Those are questions I’d find more inspiring.

  7. Ian Crawford says :

    Dear Brobof and Guest,

    Thanks for your comments.

    Brobof, in answer to your question, I don’t think human and robotic exploration should be seen as mutually exclusive. Both can play important roles in planetary exploration. However, in answer to your direct question: I would personally far rather see people back on the Moon than 100, or even 1000, teleoperated vehicles. I certainly think that a renewed human presence would deliver much more science, in part because humans are much more efficient explorers (by a factor of at least 100 if you compare Apollo astronauts with the MERs), and in part because humans can do some things that robots can’t do anyway (like think on their feet). Rather than reiterate all these arguments here, I’ll refer you instead to the White Paper that myself and colleagues submitted on this subject to the Plantary Science Decadal Survey, which can be found at:

    Click to access Crawford_decadal_white_paper.pdf

    Guest, the thrust of my blog article was the scientific benefits of returning to the Moon. However, I fully accept that there are other reasons for wanting to do so. I think it is too soon to tell whether the Moon offers anything of economic value to humanity. I rather doubt it in the short term, but until we complete the geological investigation of the Moon we will not know whether it has anything useful to offer or not. This is another reason for continuing the scientific investigation of the Moon. However, even if the Moon does not have economically viable raw materials that could help sustain the world economy, I do think it will still play a very important role in building a human civilisation in space. The Moon is a place where we can learn to live and work on planetary surfaces (while doing good science at the same time), and develop skills that can be transferred to Mars and beyond. In the long term, I agree with you that these reasons for exploring the Moon may prove even more important than the more purely scientific ones. However, these objectives are not mutually exclusive either — we will not be able to build up a civilisation on the Moon unless we have done the basic scientific exploration of its surface environment first!

    Best wishes,


  8. Clemantine says :

    I believe the future lies in increased robotical exploration, as opposed to manned missions. Whilst humans can obviously do great things that robots can’t, humans are in comparison a whole lot more fragile and vulnerable. If a strong gamma ray blast rolls over a space craft it could do tremendous damage to astranouts, whilst a robot might suffer a fried curcuit or two…

    Just a thought.

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