Scientists long suspected the presence of organic molecules on Mars, as the planet is often bombarded with carbon-rich meteorites, and were surprised when neither Viking I nor Viking II found any on the Martian surface.
“It was just completely unexpected and inconsistent with what we knew,” noted NASA Ames Research Center planetary scientist Chris McKay.
In 2014, NASA’s Curiosity rover did find a variety of organic molecules on Mars. One of these is chlorobenzene, which is produced by the burning of carbon molecules with a salt known as perchlorate. First discovered on Mars by NASA’s Phoenix lander in 2008, perchlorate explodes at very high temperatures.
Now, in a new study published in the Journal of Geophysical Research: Planets, a team of researchers propose the Viking landers, both of which heated up Martian soil during their searches for organics with their gas chromatograph-mass spectrometers (GCMS), inadvertently destroyed the very molecules they sought to find by causing perchlorates in the soil to explode.
Heating the soil was necessary in order to find any organic present.
If the scenario described above occurred, the chlorobenzene discovered by Curiosity could have been created as a byproduct of the burning of Martian soil by the Vikings.
Reviewing data sent back by the Vikings, study leaders McKay, Melissa Guzman of the LATMOS research center in France and their colleagues discovered that both landers detected chlorobenzene in their Martian soil samples.
While the chlorobenzene could have been produced by the burning of organic material in the samples, they could also have come from Earth via the Vikings’ equipment.
Scientists, including those who conducted this latest study, remain divided as to whether the Viking landers brought the organics from Earth or accidentally destroyed them during their Mars operations.