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NASA announced final 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 washed before we can empathize the significance of this discovery, only some researchers have besides started wondering why the discovery took so long. It turns out that NASA might accept 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 downwards on the crimson planet in 1976 establish no trace of organics in their soil sample instruments. This was surprising at the time, and nosotros now know the findings were inaccurate. And so, what happened?

A new assay of the Viking information 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 product of fireworks and propellants considering information technology'due south a powerful oxidizing agent that can be explosive nether 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 textile in order to determine the chemic composition, but heating perchlorate in the presence of organic molecules will destroy the organics. And so, it's possible NASA was on the verge of making this momentous discovery decades ago, but the lander burned upwards all the evidence.

The belatedly astronomer Carl Sagan stands next to a model of the Viking landers.

And then, 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 Marvel, which indicated Mars has chlorobenzene in its soil as well. This chemical compound appears when organics are oxidized by perchlorate. The team suspected that Viking might take likewise produced chlorobenzene from burning up organic molecules in its sample collector. They looked back at the original Viking data and confirmed that, aye, 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 agone. That could have changed our approach to studying the planet over the intervening years, merely it's hard to account for all eventualities when your scientific instruments are millions of miles abroad.