20 July 2016: 40 years ago the Viking 1 lander touched down on Mars
On 20 July of 40 years ago, the Viking 1 lander touched down on Mars and made history as the first NASA space mission to perform a successful landing on the fourth planet of the solar system (all international missions to Mars: NASA Mars Exploration).
The Viking mission to study the planet Mars, declared concluded on 21 May 1983, consisted of two twin probes, Viking 1 and Viking 2, each of which consisting of an orbiter and a lander. The primary objectives of the mission were to obtain high-resolution images of Mars, characterise the structure and composition of both the planet’s atmosphere as well as its surface and search for traces of alien life.
Viking 1 was launched on 20 August 1975, Viking 2 on 9 September 1975, both from Cape Canaveral (Florida, USA); the first reaching the orbit of Mars on 19 June 1976, the second on 7 August 1976. Viking 1 remained in orbit for about a month before the landing procedure was launched, taking numerous images of the Martian surface in search of the place most suitable in order to make a soft landing on the planet’s surface. Finally, on 20 July 1976 (40 years ago), the Viking 1 lander broke away from the orbiter and touched down on the Martian surface, in the Chryse Planitia (Plains of Gold) site, a plain nearby that originally planned as the destination (judged not suitable after studying the images). On 3 September 1976 it was instead the turn of Viking 2 to land in the Utopia Planitia site.
The expected duration of the mission was 90 days from the moment of landing, but both the landers and the orbiters continued to operate well after the planned deadline. The Viking 1 orbiter remained operational until 7 August 1980, that of Viking 2 until 25 July 1978, until the fuel needed to keep the solar panels oriented towards the Sun ran out. The two orbiters, which had made 1,489 orbits around Mars, sent thousands of images of the Red Planet to NASA, with a resolution of between 300 and 150 metres per pixel and, in certain particular regions, even 8 metres per pixel (high resolution images at the time). Transmissions with the landers, however, ceased on 11 November 1982 (Viking 1) and 11 April 1980 (Viking 2). The mission was declared finally concluded on 21 May 1983, more than 6 and a half years after the date initially envisaged by the project engineers.
The Viking probes carried a large amount of scientific instrumentation with them. Thanks to this mission we obtained not only the first colour photos of the Martian surface and the famous image of the Face on Mars (the case of pareidolia is renowned), but also such a huge amount of detailed scientific data as to still today arouse discussions and reviews.
Arctic temperatures were measured by the landers in the landing sites (between 150 and 250°K, i.e. between -123 and -23°C); seasonal dust storms, changes in atmospheric pressure and movements of atmospheric gases between the polar ice caps were observed; only one event of probable seismic origin was detected by the seismometer during the duration of the mission. Moreover, the Viking probes carried out three biological research experiments to try to find out if there was life on the red planet: the GEX (Gas EXchange) experiment, the PR (Pyrolytic Release) experiment and the LR (Labeled Release) experiment. Although the data collected on the composition of the Martian surface and atmosphere did not at the time provide any traces of chemical reactions of an organic nature and of the existence of microorganisms in the ground, a review in 2012 suggested that the probes had discovered the existence of microbial forms of life on the red planet (to learn more: International Journal of Aeronautical and Space Sciences).
by Enzo Scasciamacchia