Here is a link inside of the article that you posted:
http://www.space.com/news/spacehistory/viking_life_010728-1.html The link above is for an article about the Viking I/II mission.
Here is a quote from the article:
""To my surprise, in their LR experiment, they seemed to have clear periodic oscillations in the release of gas from a Martian soil sample injected with a nutrient solution. The oscillations in gas release had a period of what appeared to be one Martian day. Being a circadian biologist, I became very excited," Miller told SPACE.com.
On Earth, Miller said, circadian rhythms -- oscillations with a period of nearly 24 hours -- are present in every species examined down to blue-green algae. Was it possible, he asked, that the LR experiment was recording the circadian rhythm of a Martian soil-dwelling microbe?
NASA worked with Miller, providing him the 1976 LR data sets, as well as converting the information to an electronic format. That allowed the circadian biologist to study the data using modern computer-based analytical tools.
"I found that the gas release was indeed rhythmic, with a period of precisely 24.66 hours, a Martian day," Miller said. This finding, along with other painstaking assessments about LR operations, the scientist feels that a Martian circadian rhythm in the experiment may constitute a biosignature - a sign of life."
How constant was the temperature? If it was allowed to deviate with day-night temperatures then, of course, the "chemical reactions" would be a function of temperature . . .