New findings point to an Earth-like environment on ancient Mars

To infinity and beyond.

> But what puzzles me is why we have never followed up with any further experiments to try and detect life? After the Viking missions we never conducted any further experiments that could rule out any other possible chemical reactions to get closer to confirming the presence of microbial life.

According to Wikipedia, the radiation levels are too high:

https://en.wikipedia.org/wiki/Life_on_Mars#Cosmic_radiation

> Even the hardiest cells known could not possibly survive the cosmic radiation near the surface of Mars since Mars lost its protective magnetosphere and atmosphere.[63][64] After mapping cosmic radiation levels at various depths on Mars, researchers have concluded that over time, any life within the first several meters of the planet's surface would be killed by lethal doses of cosmic radiation.[63][65][66] The team calculated that the cumulative damage to DNA and RNA by cosmic radiation would limit retrieving viable dormant cells on Mars to depths greater than 7.5 meters below the planet's surface.[65] Even the most radiation-tolerant terrestrial bacteria would survive in dormant spore state only 18,000 years at the surface; at 2 meters—the greatest depth at which the ExoMars rover will be capable of reaching—survival time would be 90,000 to half a million years, depending on the type of rock.[67]

Given how long it took for Earth to develop multicellular life, Mars was probably pretty dead before it could take off(although it's very likely microbes still exist on Mars). But who knows, maybe Earth was late to the multicellular party, but I doubt it. If Mars did somehow evolve to multicellular life before Earth it's very likely that the multicellular would have been seeded to Earth via asteroids with something akin to a martian tardigrade

But then how did life get on mars?

Read the wikipedia link and it seems there are credible explanations for what is going on:

> "With unsterilized Terrestrial samples, though, the addition of more nutrients after the initial incubation would then produce still more radioactive gas as the dormant bacteria sprang into action to consume the new dose of food. This was not true of the Martian soil; on Mars, the second and third nutrient injections did not produce any further release of labeled gas."

> "Albet Yen of the Jet Propulsion Laboratory has shown that, under extremely cold and dry conditions and in a carbon dioxide atmosphere, ultraviolet light (remember: Mars lacks an ozone layer, so the surface is bathed in ultraviolet) can cause carbon dioxide to react with soils to produce various oxidizers, including highly reactive superoxides (salts containing O2−). When mixed with small organic molecules, superoxidizers readily oxidize them to carbon dioxide, which may account for the LR result. Superoxide chemistry can also account for the puzzling results seen when more nutrients were added to the soil in the LR experiment; because life multiplies, the amount of gas should have increased when a second or third batch of nutrients was added, but if the effect was due to a chemical being consumed in the first reaction, no new gas would be expected. Lastly, many superoxides are relatively unstable and are destroyed at elevated temperatures, also accounting for the "sterilization" seen in the LR experiment."