Forty years ago, space engineers launched a probe that would play a pivotal role in changing our understanding of our place in the cosmos. On May 30, 1971, Mariner 9 was dispatched to Mars on an Atlas Centaur rocket and in November that year slipped into orbit around the Red Planet.
In doing so, the US robot spaceship became the first manmade object to be placed in orbit around another planet. Humans had added an artificial satellite to another world. A few days later, two other spacecraft, Mars 2 and Mars 3, both built by the Soviet Union, followed suit and achieved Martian orbit. In three weeks, the Red Planet had become a scientific hotspot.
Thus began a revolution in our understanding of the solar system, a family of planets that space probes have shown to be far stranger and more exotic than expected, with Mars producing the largest number of surprises. Mariner 9 showed it possesses the solar system’s largest mountain and its biggest canyon, while ancient riverbeds and streams were discovered at several sites, findings that have been confirmed and explored in far greater detail by subsequent probes and which continue to maintain hopes that we will one day find signs of life on another world.
Forty years on, Mars is still a place of fascination for humanity, though its investigation has been a rocky business.
“The story of Mars exploration has been a real rollercoaster,” says Fred Taylor, Oxford astronomer and professor, who has worked closely with NASA on a number of missions to the planet.
“Once, it seemed destined to support life. Then we thought it was utterly dead and featureless. Then we discovered — thanks to Mariner 9 — that it had a landscape through which water had poured. After that, craft found its soil contained no signs of biological material. Since then, we have bounced back and are hopeful life may exist deep underground,” he says.
As a result, a swath of missions to Mars is being planned for the next few years with the US, Russia, China and Europe all preparing spacecraft. These will include automated rovers, with one, called ExoMars, that is being built in the UK; craft that drill deep below the planet’s surface; another that will land on Mars’s moon, Phobos, and survey the planet from there; and, ultimately, a robot spaceship that will fire samples of Martian soil and rocks back to Earth for analysis.
“Once we get our hands on that, we will have a real chance of finding out if there is life underneath the Martian surface,” says David Parker, director of space science at the British National Space Centre.
If this flotilla of interplanetary craft succeeds in finding life, the study of Mars will have come full circle. In the years leading up to the space age, it was still hoped that the most closely studied planet in the solar system possessed life. Changes in surface features, which could be seen through ground-based telescopes, were assumed to be caused by seasonal changes in vegetation that were fed by meltwater pouring from the planet’s icecaps. In the 19th and 20th centuries, astronomers, such as Percival Lowell, had even argued that these melt-waters were being channeled through canals built by intelligent beings.
By the mid-20th century, however, few scientists clung to such notions. As telescopes got more and more powerful, Mars seemed less and less hospitable. Nevertheless, those color changes on the surface kept alive some hopes of finding primitive life.