Pale Blue Dot - Carl Sagan [66]
Early Soviet landers were designed for an atmosphere somewhat like our own. They were crushed by the high pressures like a tin can in the grasp of a champion arm wrestler, or a World War II submarine in the Tonga Trench. Thereafter, Soviet Venus entry vehicles were heavily reinforced, like modern submarines, and successfully landed on the searing surface. When it became clear how deep the atmosphere is and how thick the clouds, Soviet designers became concerned that the surface might be pitch-black. Veneras 9 and 10 were equipped with floodlights. They proved unnecessary. A few percent of the sunlight that falls on the top of the clouds makes it through to the surface, and Venus is about as bright as on a cloudy day on Earth.
The resistance to the idea of a hot surface on Venus can, I suppose, be attributed to our reluctance to abandon the notion that the nearest planet is hospitable for life, for future exploration, and perhaps even, in the longer term, for human settlement. As it turns out there are no Carboniferous swamps, no global oil or seltzer oceans. Instead, Venus is a stifling, brooding inferno. There are some deserts, but it’s mainly a world of frozen lava seas. Our hopes are unfulfilled. The call of this world is now more muted than in the early days of spacecraft exploration, when almost anything was possible and our most romantic notions about Venus might, for all we then knew, be realized.
MANY SPACECRAFT CONTRIBUTED to our present understanding of Venus. But the pioneering mission was Mariner 2. Mariner 1 failed at launch and—as they say of a racehorse with a broken leg—had to be destroyed. Mariner 2 worked beautifully and provided the key early radio data on the climate of Venus. It made infrared observations of the properties of the clouds. On its way from Earth to Venus, it discovered and measured the solar wind—the stream of charged particles that flows outward from the Sun, filling the magnetospheres of any planets in its way, blowing back the tails of comets, and establishing the distant heliopause. Mariner 2 was the first successful planetary probe, the ship that ushered in the age of planetary exploration.
It’s still in orbit around the Sun, every few hundred days still approaching, more or less tangentially, the orbit of Venus. Each time that happens, Venus isn’t there. But if we wait long enough, Venus will one day be nearby and Mariner 2 will be accelerated by the planet’s gravity into some quite different orbit. Ultimately, Mariner 2, like some planetesimal from ages past, will be swept up by another planet, fall into the Sun, or be ejected from the Solar System.
Until then, this harbinger of the age of planetary exploration, this minuscule artificial planet, will continue silently orbiting the Sun. It’s a little as if Columbus’s flagship, the Santa María, were still making regular runs with a ghostly crew across the Atlantic between Cádiz and Hispaniola. In the vacuum of interplanetary space, Mariner 2 should be in mint condition for many generations.
My wish on the evening and morning star is this: that late in the twenty-first century some great ship, on its regular gravity-assisted transit to the outer Solar System, intercepts this ancient derelict and heaves it aboard, so it can be displayed in a museum of early space technology—on Mars, perhaps, or Europa, or Iapetus.
*For Titan, imaging revealed a succession of detached hazes above the main layer of aerosols. So Venus works out to be the only world in the Solar System for which spacecraft cameras working in ordinary visible light haven’t discovered something