Probes to the Inner Planets: 1975 to 1990
In the fifth chapter of The Next Fifty Years in Space Patrick Moore looks ahead at the next fifteen years of unmanned missions to Mercury, Venus and Mars. By 1975 the Russians and the Americans had already dispatched a handful of probes to several of the inner planets with varying success, so it is not surprising that Moore’s predictions for this period are reasonably accurate:
... there is no reason to doubt that before the end of the century our automatic probes will have penetrated to the very boundary of the Sun’s main system. ―Moore 52
His timetable for the first visits to Saturn, Uranus and Neptune was only off by one year for each of these planets. The only serious discrepancy concerns Pluto. New Horizons only reached this diminutive icy world in 2015, more than a quarter of a century later than Moore’s estimate.
Venus
As usual, Moore precedes his predictions with a brief look back at the history of exploration. By 1975 the Russians had landed several Venera probes on the surface of Venus and the American probes Mariner 2 and Mariner 10 had flown by the planet. These revealed that the surface of Venus was a blisteringly hot desert:
The Mariner 10 pictures of Venus showed the belts of high cloud very clearly, but of course it was impossible to see through to the surface, and we have to admit that Venus guards its secrets well. There can be no hope of obtaining views from below the clouds ... ―Moore 60
This prediction did not age well. In 1975, when Moore made it, the Russians launched Venera 9 and Venera 10, both of which successfully transmitted images from the surface of Venus. Moore’s next prediction, however, was well founded:
In 1978, if all goes well, a space-craft weighing over 800 pounds will be used to drop four scientific probes on to the surface, after which the main vehicle will itself enter the planet’s atmosphere and continue to transmit data until it is destroyed ... There is considerable enthusiasm in NASA circles for further missions, both orbiters and landers, during the 1980s and 1990s, and undoubtedly the Russians will continue in the same vein. ―Moore 65–66
NASA’s Pioneer Venus Project successfully deployed an orbiter, which continued to transmit data from 1978 through 1992, and a multiprobe consisting of four small probes that sent back data from within the Venusian atmosphere. The Soviet Venera program continued to flourish with Venera 9–16, consisting of both landers and orbiters. The Venera program ended in 1984, but was immediately followed by the Vega program, comprising two Soviet-led multinational probes to Venus. The Americans followed up their successes with the Magellan orbiter, which remained operational around Venus between 1990 and 1994.
Mercury
Mariner 10 was the first probe to visit Mercury. Following its flyby of Venus, it went on to make three flybys of Mercury in 1974 and 1975. This initial success tempted Moore to make one of his more rash predictions:
[Mercury] is, on average, a mere 36,000,000 miles from the Sun, and during daylight it is exposed to the full fury of the solar radiation. An automatic transmitting station set up there would be highly informative, and there seems no reason to doubt that one will be set up there in the foreseeable future. I suggest that it will be operative by 1985 at the latest, and perhaps earlier―say 1983, though it will have to be very carefully designed and manufactured in order to cope with the amazingly hostile environment. Before then there may well have been a Mercury orbiter, and certainly another fly-by probe to complete the mapping begun so triumphantly by Mariner 10. ―Moore 70
None of this took place. The second visitor to Mercury was NASA’s MESSENGER, which did not reach the planet until 2008, following two flybys of Venus en route.
Mars
NASA and the Soviet Union had already sent several probes to Mars when Moore wrote The Next Fifty Years in Space in 1975―with decidedly mixed results. The Soviets led the way with seven Mars probes between 1962 and 1973, though none of these was a complete success. The Americans had considerably more luck with their Mariner program. Mariners 4, 6, and 7 made successful flybys in 1965 and 1969, and Mariner 9 went into orbit around the red planet in 1971.
Among Mariner 9’s many discoveries were what appeared to be river valleys:
There is also the highly significant point that many of the winding valleys look so like old riverbeds that in all probability they are old riverbeds. Were they really ancient, by our own geological standards, they would be largely eroded away and filled in, whereas they look remarkably fresh. This leads on to a strange paradox. As we have seen, liquid water cannot exist on Mars now; but if it existed in the fairly recent past (that is to say, a few tens of thousands of years ago) the planet must then have made much more atmosphere than it has at the present epoch. ―Moore 74
It is interesting to learn that in 1975 it was the opinion of mainstream scientists like Patrick Moore that the dried-up river beds of Mars were no more than tens of thousands of years old. Today we are assured that Mars has been a dry barren desert for at least a billion years. Something doesn’t quite add up.
By 1975 NASA’s ambitious Viking probes were in an advanced stage of preparation, so it was easy for Moore to predict their subsequent successful deployment, but he was on shakier ground when he tried to peer ahead at the post-Viking future of Mars exploration:
The subsequent exploration of Mars is bound to depend very largely upon the Viking results. If there is any hint of life, I believe that research will be financed and pressed forward as quickly as possible, because the discovery of any living organism beyond the Earth would be of the most tremendous significance. Even if not, a further Viking is scheduled for 1979, and there is no reason to doubt that others will follow. The next milestone will then be the recovery of samples from Mars, by means of a probe which goes there, lands, collects the required samples and brings them home, as the Russians have already done with regard to the Moon ... Later Vikings will carry “Martian rovers”, or wheeled vehicles which are able to move around in much the way that the Soviet Lunokhods have done on the Moon, and undoubtedly the Russian plans allow for robots of the same kind. . ―Moore 76–78
NASA’s planned Viking 3 mission was cancelled due to budgetary constraints and the Administration’s shifting priorities. Nevertheless, Mars was not forgotten and between 1976 and the present day the planet has been targeted by more than two dozen probes from six or seven different space agencies, many of which have been successful. To date, none of these missions has returned samples of Martian rocks to Earth, but the Americans have had great success with their Martian rovers.
Moore takes up the story of Martian exploration in Chapter 8, with more far-reaching predictions.
And that’s a good a place to stop before the next stage of our journey.
References
- Patrick Moore, The Next Fifty Years in Space, With Drawings by Andrew Farmer, William Luscombe Publisher Limited, The Mitchell Beazley Group, Artists House, London (1976)
Image Credits
- The Next Fifty Years in Space: William Luscombe publisher Limited, Andrew Farmer (illustrator), foyled-again (photographer), Fair Use
- The Surface of Venus (Venera 14): © Russian Academy of Sciences/Ted Stryk, Creative Commons License
- Mercury (Mariner 10): NASA/JPL/USGS, Public Domain
- Carl Sagan and a Full-Scale Model of a Viking Lander: NASA/JPL, Public Domain
- Patrick Moore: Anonymous Photograph, Fair Use
