1976 Viking NASA search for life on Mars in 2 locations, they are the only major experiments to look for life- the results were so boring they didn't get more funding until 2008

The spaceship was very small and the experiments were close- this means that the one that heated the water also heated the rest of the experiments and meant that none of them were conducted at earth temperature.

Only searched for life very, very similar to Earthlife, and only would have found life if there was a lot of it/high density -> The results were largely positive

Why don't people know about this?

Positive results for any of the 3 experiments would be enough to announce life on mars
Two gave positive results, one gave weird results

Experiment 1
Mars soil mixed with CO2 and helium, with and without water, heated to earth temperatures, gave nutrients, tested gases emitted
gases emitted when water was added, more gases when nutrients were added. It was not the same as any gases by known life from earth
this COULD be explained by weird inorganic chemistry or it could be life

Experiment 2
Mars soil mixed with radioactive gas and no water to see if the soil would take up the gas.
this was supposed to happen at Mars temperature but it was actually hotter
This was a positive result- there is life on Mars?

Experiment 3
Radioactively tag earth nutrients, put it in soil and see if radioactive gas comes out
Positive result- life on Mars, or something else weird going on

Phoenix 2008 mission
Suggests strong oxidising chemicals on Mars that could be the explanation for experiment 1 results
There is water on Mars as ice