By Duncan Lunan

The asteroid Eros was the 433^rd to be discovered, by Witt, at Berlin in 1898  (H4701).  It immediately became important because it can approach to within 23 million km. of the Earth, and could be used to gain a more accurate value of the Astronomical Unit, the Earth’s mean distance from the Sun, which gives the scale of the whole Solar System.  In 1900 Von Oppolzer noticed big changes in magnitude as the asteroid rotated, indicating an elongated shape.  That featured in a US comic, which I read as a child;  many personnel from the USAF base at Prestwick were billeted in Troon, where I grew up, and their children had a never-ending supply of comics compared with ours.  The story-line concerned a landing on Eros with an experimental payload which caused the whole asteroid to inflate enormously in size, so that its imagined tiny life-forms became hugely dangerous.

Although the comic exaggerated the shape, making Eros a long thin spike, it was known to be about 37 km. long and 16 km. wide  (H4702).  With a rotation in only 5 hours 16 minutes, that would give it a gravity of about one-hundredth of Earth’s at the poles, but only one thousandth at the equator because of centrifugal force.  In their book Islands in Space, the challenge of the planetoids  (1966), Cole and Cox argued that the USA should abandon its target of a Moon landing before 1970 and go for a  mission to an Earth-grazing asteroid instead.  Some of them could be reached with less fuel expenditure than the Moon itself, but their mission plan would take weeks longer than a Moon landing, and put a severe demand on life-support.  They proposed landing their whole stretched Apollo tail-first on the target, and I discussed the difficulty of that using Eros as an example, in Man and the Planets  (1983).

Eros turned out to be a dumb-bell, but when the NEAR-Shoemaker probe went into orbit around it in 2000, the mystery deepened.  Eros has a huge saddle-shaped bite out of it, but it’s still a single object.  Another mystery is that its surface is dotted with small boulders, although its surface gravity is too low to pull impact debris back.  One possible explanation is that they’ve been left exposed as softer material was worn away by thermal and micrometeorite erosion.  At the end of its mission NEAR-Shoemaker touched down on Eros:  it wasn’t designed to do it and lost contact with Earth, but the landing proved much easier than expected.     

Eros crosses the orbit of Mars and that led to suggestions that astronauts could hitch a ride out to Mars on it.  The last of the stories in Men Into Space by Murray Leinster  (Berkley, 1960), based on the US TV series starring William Lundigan, turned on that.  But Eros ranges out much of the way to the inner edge of the main Asteroid Belt, so it would actually take more fuel to rendezvous with it than to reach Mars direct.  It might be a different story if it were a carbonaceous asteroid, on which rocket fuel could be manufactured, but Eros has a stony-iron composition, not much use except for radiation shielding.  There may well be ‘precious minerals’, but mining them and shipping to Earth would be a very costly undertaking unless it was part of a bigger programme to industrialise the inner Solar System.  

The mineral resources of the asteroids will be of great importance in the future.  The total mass of the asteroids amounts to 10% of the Earth’s mass at most, but all of it is accessible, in microgravity and vacuum, allowing large-scale extraction.  When we do come to industrial extraction from the asteroids, the conventional SF image is of loners, outliers of a ‘Belter’ civilisation centred on Ceres, who go to great lengths to shun the gravitational fields of planets.  But in a classic article ‘Those Pesky Belters and their Torchships’  (A Step Father Out, W.H. Allen, 1980),  Jerry Pournelle showed that orbital dynamics require the Belters’ capital to be Earth, and if they have enough power and reaction mass available to fly between asteroids, then transfers to and from the planets are easy by comparison.  

The mineral wealth of the asteroids could meet the entire needs of an industrial civilisation far more advanced than our present one.  But there is a catch about mining them for precious metals such as gold, silver or platinum.  In his contribution to the ASTRA Man and the Planets discussions, the late A.T. Lawton remarked that the iridium and platinum content of a typical asteroid could be worth as much as $50 billion.  “What would that do to the economy if you brought it to Earth?” he asked.   The late Chris Boyce replied, “The value would plummet,” and Robert Shaw added, “…especially at the point of impact!”  We hear a lot about the amount of gold, platinum etc in the asteroids, but many of those metals can be found on the Moon and the first need from the asteroids will be for compounds of carbon, nitrogen and hydrogen which the Moon lacks but are essential for life-support.  The first targets will be NEOs, ‘Near Earth Objects’, and making use of them will also develop the full technology which we need to protect Earth from collisions like the one which wiped out the dinosaurs 65 million years ago.

On April 25^th 2012 I had two calls from BBC Scotland, asking me to appear on radio discussing the new proposal to mine the asteroids.  Planetary Resources, a new consortium of entrepreneurs including the film producer and adventurer James Cameron  (lately returned from the Marianas Trench), intends to launch exploratory probes to Earth-grazing asteroids, with a view to moving at least one into orbit around the Moon and extracting its resources.

Asked for prompts by the BBC researcher, I mentioned three points  (two of which we got to cover in the programme).  The first concerned an assessment of the possibilities which I read online the previous night.  The essence was that even if the asteroid was 10% platinum, like something out of Jules Verne, it wouldn’t be economic to reach it, extract it and return it to Earth.  The most useful product at this stage of development would be water, which is difficult and expensive to launch from Earth – you can’t compress it and it’s heavy as well as bulky.  But up there, it can provide rocket fuel and radiation shielding as well as life-support, and has many other useful applications.   Fuelling and provisioning a space programme from the top, instead of from ground level on Earth, would make an enormous difference to the economics of exploration and development.

The second major point, which I have yet to see mentioned, is whether the consortium intends to honour the existing United Nations treaties concerning extraterrestrial resources.  Under the 1967 Treaty on the Peaceful Uses of Outer Space, all such resources are stated to be ‘the common heritage of mankind’, and if they are exploited it should be for the benefit of all nations.  Most UN members signed it, including Britain and the USA.  Neither signed the much stronger 1980 Moon Treaty, drafted under heavy Soviet influence, but France and Canada signed it and so did most of the developing world.  For years now, right-wing groups in the USA have been calling for the nation to withdraw unilaterally from the 1967 Treaty, supposedly because it’s a brake on private enterprise.

Their claim is that nobody can make money out of land unless they own it.  Historically this is nonsense:  technically, nobody in Scotland owned any land until the Scottish Government abolished the historical relic of ‘feu duty’.  Some years ago I organised a meeting between Scottish opponents of the Treaty and Professor Angus McAllister of Paisley University, an expert on the law of leases, who politely but firmly put them straight:  extracting minerals and using other resources under license is very common practise and mining leases, especially international mining leases, are a specialist area of law in themselves.  In The Moon:  Resources, Future Development and Colonization  (Wiley, 1999), my friend Bonnie Cooper and her co-authors make out a detailed case for a lunar administration analogous to port authorities on Earth.  If Planetary Resources intend to honour the Treaty, they will attract hostile criticism from the right wing in the USA;  if they don’t, they can expect massive hostility from much of the rest of the world – and under the Treaty, the US government will be held responsible for the consortium’s actions.

The third point is that if the technology to extract materials from Near-Earth Asteroids is developed, we then have the means to protect the Earth from incoming comets and asteroids.   In my book New Worlds for Old  (David & Charles, 1979), before the possible means of deflecting hazards had been thought of, our discussion group thought that industrialising the asteroids was perhaps the only answer.   Just send a task force to the threatening asteroid, use up its valuable resources and release the rest as dust!   Even if new methods of deflection proved effective, they’re only short-term answers:  it can be shown mathematically that any object whose orbit crosses the Earth’s must hit the Earth, Moon, Mars or Venus within a maximum of ten million years.   

To deflect an asteroid, the standard Hollywood answer of tossing an H-bomb at it isn’t going to work:  some studies indicate that it might work with a decade of warning and careful planning, but I’m not convinced.   My colleague Gordon Ross, of ASTRA and then of the Industrial Design Unit at Glasgow School of Art, came up with the design for Solaris, a ‘Comet-chaser’ which Sydney Jordan illustrated for our article ‘Keep Watching the Skies!’, Analog, October 1994, with extended versions in 1995 and 2002.   That year my friend Bill Ramsay proposed a discussion project to answer the question, ‘If we knew there was going to be an impact in ten years’ time, what could we do?’, followed significantly by ‘What would we do?’   The discussions ended with a seminar which I organised at Glasgow University in October 2012, and my book Incoming Asteroid!  What could we do about it?  was published by Springer International the following year.  Recently I gave a 2-part online lecture on it to the Clydesdale Astronomical Society, followed by a condensed one for the British Interplanetary Society, further condensed for their magazine Spaceflight in October.  

At the International Astronautical Federation Congress in London in 1951, L.R. Shepherd of the British Interplanetary Society advanced the concept of an asteroid hollowed out into an artificial world, for multi-generation interstellar travel.   He described it in a paper called ‘Interstellar Flight’, first published in 1952 and reprinted in Realities of Space Travel, ed. L.J. Carter, Putnam, 1957.   It was illustrated over several weeks of 1957 in the now-forgotten comic Rocket, begun by the News of the World in 1956, just to early for the excitement of Sputnik.   It  also ran a serial featuring one Gi-Gi Nash, who was kidnapped by Martians operating a fleet of hollowed-out asteroids – influenced in no small degree by the similar ones in ‘The World in Peril’, the third of the BBC’s Journey into Space serials written by Charles Chilton.

Frank Tinsley portrayed an alternative, wholly artificial sphere, ten miles in diameter, in his book The Answers to the Space Flight Challenge  (Whitestone, 1958).   Isaac Asimov subsequently demonstrated that an asteroid of that size, suitably hollowed out, could house the entire human race.   (‘The Universe and the Future’ in Is Anyone There?, Ace, 1957.)   If one of those were to arrive here now, it would be like adding an entire populated world to the Solar System – something no science fiction writer has ever attempted to portray, as far as I know.   In Fritz Leiber’s The Wanderer an actual earth-sized planet gets added, but only temporarily, and the novel is almost entirely concerned with the physical effects on Earth. 

See also: Beginner’s Astronomy: Asteroids and Impacts  2 and Beginners Astronomy: Asteroids and Impacts