NASA announced last month that
Mars has complex organic molecules, which could point to current or past life on the planet. There’s a lot of work to be done before we can understand the significance of this discovery, but some researchers have also started wondering why the discovery took so long. It turns out that NASA might have discovered and accidentally destroyed organic molecules on Mars back in the 1970s.
Scientists long expected organic molecules to be present on Mars if for no other reason than carbon-rich meteorites frequently hit the planet. However, the Viking landers which touched down on the red planet in 1976 found no trace of organics in their soil sample instruments. This was surprising at the time, and we now know the findings were inaccurate. So, what happened?
A new analysis of the Viking data focuses on other compounds that may have affected the results. In 2008, the Phoenix lander confirmed the presence of perchlorate on Mars. This chlorine-oxygen salt is used in the production of fireworks and propellants because it’s a powerful oxidizing agent that can be explosive under the right conditions.
The presence of perchlorate is important because the Viking landers used a gas chromatograph-mass spectrometer to analyze soil samples. That instrument heats material in order to determine the chemical composition, but heating perchlorate in the presence of organic molecules will destroy the organics. So, it’s possible NASA was on the verge of making this momentous discovery decades ago, but the lander burned up all the evidence.
So, that was the hypothesis, but a lack of organic molecules in the Viking data isn’t a smoking gun. The researchers turned to more recent findings from Curiosity, which indicated Mars has chlorobenzene in its soil as well. This compound appears when organics are oxidized by perchlorate. The team suspected that Viking might have also produced chlorobenzene from burning up organic molecules in its sample collector. They looked back at the original Viking data and confirmed that, yes, it also detected chlorobenzene.
This is not definitive proof, but it has many researchers convinced that NASA was tantalizingly close to discovering organics on Mars 40 years ago. That could have changed our approach to studying the planet over the intervening years, but it’s hard to account for all eventualities when your scientific instruments are millions of miles away.