The first American spacecraft that safely reached the surface of the Red Planet was Viking 1, happily landing Mars 40 years ago.
The device soon sent images back to Earth and performed a series of life-detection experiments that helped NASA to adjust their space program.
After the Viking-1 success, a second identical spacecraft reached the surface of Mars only six weeks later. The two devices had been created in partnership with Martin Marietta, who was the principal industrial contractor of the project. The landers were built by the company, while NASA built the orbiters.
The greatest challenges were to keep the size as small as possible and to make fit inside the spacecraft all the instruments that had to be used on the surface would have been reached.
At that moment, the density of the planet was not known. The descent engines had to be redesigned in order to fit all possible scenarios. Moreover, the lander had not been designed for a rocky surface, and the researchers were happy to observe that the device managed to land safely with all the solid blocks from Mars.
The participants on the project now consider that the successful landing was due to mere luck. Even if they had a hazard map and tried to avoid any piece of surface that might have brought them troubles while reaching the surface, it was impossible to determine in great detail the characteristics of the planet.
The first photo from Mars had been sent at an incredibly low rate, line by line. It showed a landscape of rocks, dust and pebbles, making everyone excited about the prospects of being able to catch the first up-close glimpse of the Red Planet.
The scientists filled up Viking with everything it was known of life biology and microbes, and after the landing, the device tested the air and the soil against that data. The results were contradictory, and the scientists were not able to infer a definite conclusion from the information collected from Mars.
However, a 2011 study that revisited the ‘70s information captured by the Viking revealed that the soil might contain organic substances, but the nature of the molecules is still to be determined.
An expected detail was that the liquid water on Mars exists in the form of salt-rich brines. This became one of the most relevant discoveries made by the Viking, involving the fact that the soil was entirely different from what we can find on Earth. The information changed the way the scientists defined life on alien planets.
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