Broca's Brain - Carl Sagan [115]
All these spacecraft have sensors that extend astonishingly the range of human perception. There are devices that can determine the distribution of radioactivity over another planet from orbit; that can feel from the surface the faint rumble of a distant planetquake deep below; that can obtain three-dimensional color or infrared images of a landscape like none ever seen on Earth. These machines are, at least to a limited degree, intelligent. They can make choices on the basis of information they themselves receive. They can remember with great accuracy a detailed set of instructions which, if written out in English, would fill a good-sized book. They are obedient and can be reinstructed by radio messages sent to them from human controllers on Earth. And they have returned, mostly by radio, a rich and varied harvest of information on the nature of the solar system we inhabit. There have been fly-bys, crash-landers, soft-landers, orbiters, automated roving vehicles, and unmanned returned sample missions from our nearest celestial neighbor, the Moon—as well as, of course, six successful and heroic manned expeditions in the Apollo series. There has been a fly-by of Mercury; orbiters, entry probes and landers on Venus; fly-bys, orbiters and landers to Mars; and fly-bys of Jupiter and Saturn. Phobos and Deimos, the two small moons of Mars, have been examined close up, and tantalizing images have been obtained of a few of the moons of Jupiter.
We have caught our first glimpses of the ammonia clouds and great storm systems of Jupiter; the cold, salt-covered surface of its moon, Io; the desolate, crater-pocked, ancient and broiling Mercurian wasteland; and the wild and eerie landscape of our nearest planetary neighbor, Venus, where the clouds are composed of an acid rain that falls continuously but never patters the surface because that hilly landscape, illuminated by sunlight diffusing through the perpetual cloud layer, is everywhere at 900°F. And Mars: What a puzzle, what a joy, enigma and delight is Mars, with ancient river bottoms; immense, sculpted polar terraces; a volcano almost 80,000 feet high; raging windstorms; balmy afternoons; and an apparent initial defeat of our first pioneering effort to answer the question of questions—whether the planet harbors, now or ever, a home-grown form of life.
There are on Earth only two spacefaring nations, only two powers so far able to send machines much beyond the Earth’s atmosphere—the United States and the Soviet Union. The United States has accomplished the only manned missions to another body, the only successful Mars landers and the only expeditions to Mercury, Jupiter and Saturn. The Soviet Union has pioneered the automated exploration of the Moon, including the only unmanned rovers and return sample missions on any celestial objects, and the first entry probes and landers on Venus. Since the end of the Apollo program, Venus and the Moon have become, to a certain degree, Russian turf, and the rest of the solar system visited only by American space vehicles. While there is a certain degree of scientific cooperation between the two spacefaring nations, this planetary territoriality has come about by default rather than by agreement. There have in recent years been a set of very ambitious but unsuccessful Soviet missions to Mars, and the United States launched a modest but successful set of Venus orbiters and entry probes in 1978. The solar system is very large and there is much to explore.