For the little girl in the three bears’ cottage, the parameters for a healthy life stretched from a bowl of lukewarm porridge to a medium-hard bed. But living organisms on earth reveal to scientists a constantly growing range of extremes that can be survived

Do you remember when Goldilocks took a walk in the woods and came to a little cottage? She knocked at the door and when no one answered she pushed the door and went inside. There was no one there. She saw three bowls of porridge on the table. She tasted the porridge in the very big bowl. It was too hot. She tasted the porridge in the medium sized bowl; it was too cold. Then she tasted the porridge in the tiny little bowl. It was just right and soon she had eaten it all up. Scientists tell this story differently, says a talk on NASA Science website, and use the term “Goldilocks Zone” to represent cosmic imagery.

“For many years they (scientists) looked around the solar system. Mercury and Venus were too hot. Mars and the outer planets were too cold. Only Earth was just right for life, they thought. Our planet has liquid water, a breathable atmosphere, a suitable amount of sunshine. Perfect. It didn’t have to be that way. If Earth were a little closer to the sun it might be like hot choking Venus; a little farther, like cold arid Mars. Somehow, though, we ended up in just the right place with just the right ingredients for life to flourish. Researchers of the 1970s scratched their heads and said we were in ‘the Goldilocks Zone’,” says the talk.

The points of similarity range from being just the perfect temperature to being the smallest space as compared to the space that was inhabitable. “Goldilocks Zone seemed a remarkably small region of space. It didn’t even include the whole Earth. All life known in those days was confined to certain limits: no colder than Antarctica (penguins), no hotter than scalding water (desert lizards), no higher than the clouds (eagles), no lower than a few mines (deep mine microbes),” says the talk sketching a comfortable periphery of existence.

And then it goes on to tell the charming story of modern science which has stretched the borders far beyond our imagination. “In the past 30 years, however, our knowledge of life in extreme environments has exploded. Scientists have found microbes in nuclear reactors, microbes that love acid, microbes that swim in boiling-hot water. Whole ecosystems have been discovered around deep sea vents where sunlight never reaches and the emerging vent-water is hot enough to melt lead. The Goldilocks Zone is bigger than we thought.”

One of the species scientists have found which has expanded the Goldilocks Zone is called Tindallia californiensis. It was found in Mono Lake in California.

Says the talk, “Mono Lake is an extremely salty and alkaline body of water, almost three times saltier than seawater.” It goes on to say it registers a pH value of 10, which is almost the same as that of a household glass cleaner. “Surprisingly, though, Mono Lake supports a wide array of life, from microbes, to plankton, to small shrimp. T. californiensis is right at home there. It thrives in highly alkaline conditions (pH 8-10.5) and at salt concentrations near 20 per cent.”

Earlier this year scientists who are searching for new species which stretch the Goldilocks Zone announced another strange microbe: Spirochaeta americana. “They found it living with T. californiensis and perhaps hundreds of other microbial species in Mono Lake mud samples. Finding new species in this abundant collection of microbial life is a detective story worthy of Perry Mason or Hercule Poirot.”

The talk reveals how difficult it is to take samples from the muddy bottom of lakes, since these species are killed by the presence of oxygen and therefore must be carefully protected. “For an organism to be identified and then recognised as a new species, it must be completely understood. This includes identifying its growth requirements and metabolism, colonial habit, cellular characteristics, DNA and genome properties, and sensitivity to antibiotics for detailed comparison with other known life forms,” the talk explains.

At another level does this go to show that we must admit diversity, for what was “just right” for Goldilocks need not necessarily be so for all.

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