Could life exist on Mars? There’s plenty of compelling evidence that it could, and also plenty of compelling evidence that it could not. As a result, we’re left with a big, fat maybe. Perhaps the biggest, most frustrating maybe in all of modern science.
After last month’s announcement that the Curiosity rover had found large, complicated organic chemicals on Mars, I was initially tempted to add another point to the “yes, life could exist on Mars” column. But then I read the actual research (which is excellent, by the way). At this point, I think the only thing we can say for certain is that the big maybe about Mars is even bigger and even more maybe-like.
The Curiosity rover dug up some samples from Martian mudstone, samples that apparently contained organic macromolecules. What are macromolecules? For now let’s just say they’re very big molecules. We can dive into the technical details of what defines a macromolecule in Friday’s episode of Sciency Words.
The problem, as I understand it from that research paper, is that these macromolecules were too big for Curiosity’s instruments to analyze. So Curiosity destroyed the molecules through a process called pyrolysis (also coming soon to Sciency Words) and analyzed the bits and pieces as they broke apart. Even those bits and pieces were difficult for Curiosity to study because there were so many of them, but for the most part they seemed to be aromatic compounds made of carbon, hydrogen, and sulfur.
These are the kinds of organic materials that could be deposited on a planet by meteor impacts. They could also have formed through rather ordinary geological processes. Or they could be the residue left behind by some kind of biological activity. And there doesn’t seem to be any way to know for sure where these organics came from based solely on the data Curiosity was able to collect.
So we’re still left with a big maybe. However, it was once thought by some that the Martian environment was too harsh to preserve these sorts of molecules at all. Thanks to Curiosity, we now know Mars can and does preserve its organic macromolecules.
And that means that if Mars has had any sort of biological activity, either in the past or present, the chemical record of that activity should be there for us to find. A definitive yes or no to our question is possible! We just have to keep digging.