Life on Mars?

Is there life on Mars? That’s the question NASA wanted its first Mars mission to answer – in 1976. They designed their remarkable Viking rover -- well before modern computers -- to collect and test soil samples, 140 million miles from Earth. First, Viking added a nutrient solution to the soil, looking for carbon dioxide that microbes would produce if they consumed it. And the test showed a small amount! Next, Viking incubated the sample to see if microbes, if present, could produce organic matter. A tiny amount was detected! But the third test would be conclusive. The rover incinerated the soil to gasify its compounds, then used a spectrometer to evaluate them. If there were organic matter, it would surely show up. But it didn’t. At the time, the answer was: no life on Mars. Several decades later, subsequent missions, using different tests, did find signs of microbial activity. So NASA went back to review the Viking data. With 50 years of new understanding, many scientists now believe that salt compounds in the Martian soil, when heated, would have destroyed any organic matter. Meaning Viking’s gas test may not have been designed or understood correctly. Today, there’s still no solid proof that Mars has microbial life. But new -- and half-century old -- tests haven’t ruled it out either!