22. Robotics and Space Exploration - Part 2
In the science fiction of the 1950s, the planet Venus was often described as a lush jungle world thriving in the warmth of a nearby sun. Probes sent from Earth discovered a very different world: a hellish landscape of crushing heat and overwhelming pressure, choked by thick, poisonous clouds. The robotic probes that explore this environment must be extremely hardy, and the engineers responsible for their designs must be creative in dealing with such an inhospitable world.
As the Soviets were completing their final Venera missions, the United States was also finding novel ways to explore Venus. In 1978, the Pioneer Venus Orbiter (Pioneer 12) settled into its orbit around Venus and began mapping the planet’s clouds and weather, as well as its ionosphere and the interaction between the planet and the solar wind. The probe also used radar to penetrate Venus’ thick cloud cover, revealing the planet’s topography as well. Arriving the same year, the Pioneer Venus Multiprobe (Pioneer 13) carried four components: a large probe and three smaller, simpler units. The large probe descended slowly, under a parachute, and carried seven science experiments. In an attempt to gather data in the harsh Venusian environment, the probe was equipped with nine windows: eight made of sapphire and one made of diamond. Specially designed openings on the probe’s spherical titanium body also allowed for direct atmospheric sampling. The smaller probes fell without parachutes, tumbling through the atmosphere for almost an hour. probe managed to send data from the surface for 67 minutes.
Following the success of Venera 13 and 14, the Soviet Union continued to explore Venus from orbit with Venera 15 and 16, two identical probes equipped with synthetic aperture radar (SAR) to penetrate the clouds that obscure the planet’s surface. In 1984, the Vega missions brought another pair of landers to the surface, as well as a new exploration approach, a pair of balloons designed to carry science experiments through the middle layer of Venus’ three-tiered clouds about 35 miles above the surface. The Vega missions also turned Soviet exploration in a new direction when the orbital components were redirected to photograph Comet Halley.
The arrival of the American Magellan probe in 1990 fi nally revealed the surface of Venus. Although earlier probes had used low-resolution radar to detect continent-sized features, the high-resolution radar aboard Magellan provided detailed images of geological features such as craters, hills and ridges, allowing scientists on Earth to analyze the structure and formation of Venus’ surface to a degree never thought possible.
During the 1990s, robotic probes continued to expand human understanding, exploring the solar system with increasing scientifi c abilities and constantly providing new directions for scientists on Earth. The Solar and Heliospheric Observatory (SOHO) was launched in 1995, and used its dozen instruments to examine our local star in unimaginable detail. SOHO has also discovered more than 1,300 comets. In 1997, the Mars Pathfinder mission created new interest in the exploration of Mars and set the stage for other missions that followed, by rekindling interest in Mars and space exploration in general. The next year, the autonomous spacecraft Deep Space 1 used an ion-drive to explore space, relying on new technologies to navigate, and returning stunning close-up pictures of asteroid Braille and Comet Borrelly. Other probes explored the moon, Mars and the asteroid belt, providing a steady stream of new data. The Galileo spacecraft arrived at Jupiter in 1995, fi nding new moons and surprising environments. In 2003, the probe was intentionally destroyed in the crushing atmosphere of Jupiter to prevent contamination of one of its discoveries, a subsurface ocean on the Jovian moon Europa.
In recent years, other probes have continued to revolutionize our understanding of the solar system. In 2004, the Mars Exploration Rovers (MER) “Spirit” and “Opportunity” arrived on Mars and, in their roles as geologists, made a rapid case for ancient water on the red planet, while also discovering tantalizing clues for more recent moisture. The same year, the Cassini-Huygens Spacecraft arrived at Saturn, returning new images of the planet and its stunning system of rings, and a wealth of new information about the planet’s moons. The Huygens probe, designed by the European Space Agency (ESA), was released from the larger Cassini spacecraft and descended into the mysterious orange clouds of Saturn’s largest moon, Titan. The probe’s cameras showed a landscape scarred by rivers and tributaries, leading to pools as large as Earth’s Lake Superior. The extreme cold of Titan prevents water from existing there; the Cassini probe had photographed channels carved by rivers of liquid methane.
In 2006, the Stardust probe returned the first directly collected samples of interstellar dust and comet debris. The probe used aerogel, an incredibly lightweight solid, to catch the particles as they streamed through space. After the samples were returned to Earth, scientists discovered that some of the collected materials suggested new classes of organic compounds and a more complex structure for comets than previously thought. Dr. Donald Brownlee, an astronomy professor at the University of Washington, served as the principal investigator for the Stardust mission.
The planet Mars remains an irresistible target for exploration, and to augment the capabilities of the two rovers currently working on the surface, NASA and other agencies have plans for other robotic systems. The Phoenix lander, currently traveling through space, will investigate the Martian polar ice, searching for signs of life. In 2009, NASA will launch its Mars Science Laboratory (MSL), an advanced six-wheeled rover almost twice the size of Spirit and Opportunity. The rover will carry an impressive suite of science tools and will eschew the solar panels of previous missions in favor of a radioisotope thermoelectric generator (RTG), a portable nuclear power source that will allow the rover to operate without relying on the feeble sunlight that reaches Mars.
Because of the extreme environments that explorers must contend with in space, human exploration will continue to rely on robotic systems for years to come. As robotic capabilities increase, so will the knowledge gained by their use. The role of humans in space will also increase, but the need for robots will never diminish, growing steadily as the needs of their relatively fragile creators continue to evolve.