Forty years of missions to Mars

“Getting to Mars was really hard to do,” Nasa’s chief historian Dr Bill Barry said, in a major feat of understatement, as the US space agency celebrated the 40th anniversary of the Viking 1 landing on Mars.

On 20 July 1976 – seven years to the day after Apollo 11 landed on the moon – Nasa managed to take the “big, difficult step” of landing on the red planet. Technically they were not the first to do so: in 1971 the USSR’s Mars 3 mission’s lander reached the surface. However, it operated for just 20 seconds before losing contact.

The USSR entered the Mars race first, having launched six unsuccessful flyby attempts between 1960 and 1964. But it was the Americans who conducted the first successful flyby when the Mariner 4 successfully captured 21 black-and-white photos of of the planet in 1965. More frustratingly for the USSR, they were the first to launch two successful orbiters in May 1971 – only for the US Mariner 9 to overtake them both. It achieved orbit two weeks before the first USSR orbiter, Mars 2, reached its destination.

Between them, the two Soviet orbiters returned 60 images. The US mission did somewhat better: as well as becoming the first spacecraft to orbit another planet, Mariner 9 returned 7,329 images, photo-mapping the surface of the planet and analysing the atmosphere with infrared and ultraviolet instruments.

On the back of this success, the US launched the two-part Viking programme in August 1975. Viking 1’s orbiter reached its position on 19 June 1976, and a month later the lander was deployed, successfully reaching the western slope of Chryse Planitia on 20 July. The orbiter operated until 17 August 1980, while the lander operated for over six years. Viking 2 achieved orbit on 7 August 1976, and its lander was deployed on 3 September, reaching Utopia Planitia, on the opposite side of the planet to the Viking 1 lander’s position. The Viking orbiters mapped 97% of the planet’s surface, and its landers and orbiters returned more than 50,000 images.

Getting to Mars still isn’t easy. In the 40 years since the successful Nasa mission, there have been 18 attempts to reach the planet (excluding a joint European Space Agency (ESA)/Russian mission, which is currently en route).

Of those 18 missions, just half were fully successful. All but one of them were launched by the US, the exception being India’s successful Mars Orbiter mission, which arrived in September 2014 and continues to operate.

Two other missions achieved partial success. The USSR’s Phobos 2 mission, launched in 1988, successfully achieved orbit, although its lander and hopper failed to reach Phobos, one of the planet’s two moons.

The ESA’s Mars Express, which achieved orbit in 2003, has imaged 95% of the surface of the planet and taken various measurements, hugely expanding our knowledge. The mission successfully carried and released the UK-built Beagle 2, but nothing was heard from the lander after it touched down. The ESA declared the lander lost in 2004. However, in 2015, it was spotted in images taken by a NASA orbiter.