The extreme environments found outside Earth’s atmosphere represent a significant exploration challenge. The rewards, both philosophical and scientific, are difficult to ignore, but for the humans who live and work in space, extraordinary care must be taken to ensure their survival. As a result, our understanding of the solar system, and the improbably large cosmos of which it is one small part, has been dramatically augmented by robotic explorers: electromechanical devices custom-built to survive the rigors of space.
Although its scientific capabilities were limited, the launch of Sputnik in 1957 demonstrated the potential for machines in orbit. Alarming to some, Sputnik’s simple transmission carried significant political weight, and accelerated American efforts to produce a similar device. This was a period of incredible Soviet momentum, however, and even as the United States was perfecting simpler satellites, the Soviet probe Luna 1 flew past the moon in 1959. The probe returned information about the solar wind and discovered that the moon has no magnetic field.
In 1962, the United States sent Mariner 2 on its way to Venus, after the rocket carrying Mariner 1 went off course and was destroyed. The probe carried instruments to measure the solar wind, confirming the earlier data sent by Luna 1. From orbit, Mariner 2’s radiometers discovered cool clouds surrounding a surprisingly hot planet. The mission was the first completely successful flight to another planet by any nation, and marked the beginning of a series of increasingly capable probes.
At the same time, the Soviet Union was also trying to reach Venus. Although several early attempts were unsuccessful, the Soviet probe Venera 3 finally arrived on Venus in 1966. Communication with the probe was lost before the probe entered the Venusian atmosphere, and the landing was, in fact, more of a crash. However, the probe was the first human-made object to reach another planet, and would be followed by other, more capable designs. Venera 4 returned the first information from the atmosphere of another planet in 1967; Venera 5 sent similar data before the planet’s enormous atmospheric pressure crushed the probe miles above the surface. Venera 6 fared slightly better, but met a similar fate. On December 15, 1970, Venera 7 became the first spacecraft to land on another planet, and survived for 23 minutes before it was destroyed by heat and pressure. Venera 8 lasted for almost an hour.
The true capabilities of the Venera probes, and robotic spacecraft in general, were demonstrated by Venera 9, which returned the first pictures of the Venusian surface in 1975. Subsequent probes resisted the crushing pressure and intense heat with increasing success, adding to the data generated by earlier missions. The last of the Venera landers reached Venus in 1981, returning the first color images of the surface of Venus and discovering types of rock similar to that of Earth’s midocean ridges.
American capabilities had also continued to improve and, in 1976, the United States guided two landers, Viking 1 and 2, onto the surface of Mars. During their 10-month trip to Mars, the Viking probes were combined with an orbiter, separating from the larger vehicle and descending to the surface using a combination of parachutes and retrorockets. Due to fears of landing site contamination, the Viking mission relied on a complex, 18-nozzle rocket system designed to spread the propellant over a wide area, removing only a thin layer from the surface. Because the landers were immobile, the integrity of the Martian soil within reach was paramount. Twenty-five seconds after it landed, Viking 1 sent its first image, a panorama of Chryse Planitia, the first picture from the surface of Mars. Both landers used a robotic arm and onboard laboratories to test nearby soil for evidence of Martian life. The results were largely negative, optimistically described as “inconclusive.”
The reach of robotic spacecraft was extended dramatically in 1977 with the launch of Voyager 1 and 2. The mission was designed to take advantage of a rare planetary arrangement that would allow the spacecraft to use the gravity of Jupiter, Saturn, Uranus and Neptune to accelerate through space. The probes returned images and scientific data that gave scientists new insights into the gas giants. The discovery of active volcanoes on Jupiter’s moon Io showed the outer system to be surprisingly dynamic, as did the discovery that wind speeds on Saturn can exceed 1,100 miles per hour. During their visit to Uranus, the Voyager probes discovered new rings, and 10 new moons, as well as an unexpectedly large and oddly shaped magnetic field. In 1989, Voyager 2 became the first spacecraft to photograph Neptune.
Currently, the Voyager probes are traveling out of the solar system. Each probe is equipped with a gold record containing images and sounds meant to collectively represent the people of Earth. Although the chances that the records will ever be found are remote, the idea is compelling. The contents of the record, perhaps reflecting the spirit of the time, are surprisingly emotional, and offer alien listeners a gentle introduction to human civilization. Among many other sounds, the records include a mother’s first words to her baby and the sound of a human kiss. As of January 1, 2008, Voyager 1 will have been almost ten billion miles away from Earth, hurtling silently into interstellar space at almost 40,000 mph.
The robotic exploration of the solar system has continued to provide new information about our planetary neighbors and new ideas about the nature and origin of the universe. These amazing successes, however, were merely the beginning. The next chapter would be written closer to Earth, on Venus and Mars, hinting at a future when robots and humans would explore space together.
|21. Robotics and Space Exploration - Part 1 - November 20, 2007||1.6 MB|