6 Reasons Astrobiologists Are Holding Out Hope for Life on Mars

On Earth, carbon and hydrogen are everywhere. In fact, 75% of your body (excluding water) is composed of these two elements.They make up everything from our DNA to our cell walls. We call these chemicals "organic" — and life as we know it on Earth wouldn't exist without them. 

So in 1984, when scientists found a Martian meteorite in Antarctica crawling with organic chemicals, their discovery raised an interesting question: Did the organic chemicals come from life? 

At first, scientists speculated that these chemicals could have been introduced to the meteorite after impact. However, the chemical signatures of the organic material weren't concentrated on the surface of the rock, as you would expect if it had picked them up later. Instead, the organic compounds grew denser and denser toward the center of the meteorite. 

Still, scientists were skeptical that they would ever find organic chemicals on Mars. The surface of the atmosphere-less planet is just too harsh to even sustain organic chemical structures, they speculated. However, more recently, Mars rovers like Curiosity have discovered clear traces of organic compounds on the planet's surface. In 2012, Curiosity found chemicals similar to kerogen, a component of fossil fuel. 

Life is an important source of organic compounds — but not the only one. Geological processes can also result in the creation of organic compounds, Boston said. For example, volcanoes sometimes spew organic compounds into the atmosphere. So while it's possible that the chemicals are a sign of past life, it's still not certain. 

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