The year 2025 marks 50 years since the two spacecraft launched, three weeks apart.
(Article is written by an atmospheric scientist who worked on the Viking missions in the 70s)
https://theconversation.com/50-years-ago-nasa-sent-2-spacecraft-to-search-for-life-on-mars-the-viking-missions-findings-are-still-discussed-today-262186
2 Comments
Here’s the thing with biosignatures. If the data from an observation can be produced either biologically or abiologically, you should assume it’s abiological. It’s too big of a discovery to say it’s biological unless you can absolutely rule out an abiological process.
And *especially* with potential biosignatures on exoplanets, just because we don’t know an abiological way to obtain that biosignature doesn’t mean there isn’t one. Geology is hard. Atmospheric science is hard. Chemistry is hard. Astronomy is hard. We don’t know all the different kinds of funky planet/atmospheric concentrations and geological processes and chemistry that can happen to say that a specific claimed “biosignature” can’t be produced abiologically.
Just because an observation is consistent with life doesn’t mean life produced it.
Post facto, the detection of perchlorates in Martian soil increases the odds that Viking did detect life on Mars.
The perchlorates decompose into chlorine when heated. So it is very possible that the process of conducting the Viking experiments that involved heating the soil samples released enough chlorine to sterilize those experiments, producing the null results especially in the gas chromatograph experiment.
The presence of perchlorates was not known at the time and wasn’t confirmed until 2008.