00:00 The Viking I and Viking II landers carried out experiments to test for biology on Mars, and the results have sparked a long-standing debate among researchers about the existence of life on the planet.

01:33 The Viking 1 and Viking 2 landers were the first to safely land on Mars in 1976, and they conducted experiments specifically designed to search for signs of biology on the planet.

02:42 The Viking landers conducted four experiments to determine if there was biological life and organic matter in the soil samples, including a gas chromatograph mass spectrometer, a gas exchange experiment, and a pyrolytic release experiment.

03:51 The Viking landers conducted experiments to determine if there was organic matter in the soil samples, and the results showed a small but significant formation of organic matter, with the control test on sterilized soil not showing the same results.

04:59 In the years following the Viking missions, more evidence has accumulated suggesting the possibility of life on Mars, including the Curiosity rover's discovery of organic compounds and the presence of an excess of carbon-13 in the Martian atmosphere.

06:07 The Viking mass spectrometer wasn't sensitive enough to detect organic molecules on Mars, but a repeat mission with improved technology and a test for chirality could provide strong evidence for life on Mars if organic molecules show a preference for one type of chirality.

07:15 NASA currently has no chemistry or biology experiments planned like those from the Viking missions, leaving the question of whether the Viking landers detected life on Mars 45 years ago unanswered, but a potential future mission called the Biological Occident and Life Detection Mission (BOLD) could provide the first proof of life on Mars if evidence is found.