'Goldilocks Zone' may go colder than previously thought

'Goldilocks Zone' may go colder than previously thought
Wallemia sebi fungi making spores. Image credit: Mycology blog/Cornell University.

(PhysOrg.com) -- The survival of life on Earth is possible only within a relatively narrow temperature range known as the "Goldilocks Zone," which ranges from around 0 to 100°C. In many ecosystems life is limited by cold temperatures rather than hot because of the reliance on liquid water for survival. Now new research has shown that in the presence of a certain type of solution, large populations of microbes can survive at the incredibly low temperature of -80°C, which is far below the accepted Goldilocks Zone. Since similar solutions exist on cold planets and moons such as Mars and Europa, this increases the likelihood that life may be found there.

Microbes called “extremophiles” are known to thrive in extreme conditions such as near hot water vents on the , where the temperature can rise to 120°C, but until now scientists thought were more limiting because at low temperatures cell membranes become increasingly rigid.

A team of microbiologists led by Dr John Hallsworth, Lecturer in Environmental at Queen’s University Belfast in Ireland, thought a special type of solute might prevent the water in cells from freezing, and could also reverse the rigidity of cold membranes. The solutes are called chaotropic after their property of disordering cellular macromolecules.

The research team first confirmed that , a solute often used to preserve cells at low temperatures in the laboratory, becomes chaotropic when present in high concentrations. They then grew extremophiles on a medium supplemented with either chaotropic or kosmotropic solutes (which stabilize macromolecules rather than destabilize them).

Starting with four types of xerophilic (aerobic extremophiles that thrive in environments with little water), the scientists found that at 30°C the fungi grew well in the presence of both chaotropic and kosmotropic solutes, but at 1.7°C the fungi on media supplemented with chaotropes grew better than those on kosmotropes, with some of the latter showing zero growth.

Hallsworth and his team then harvested spores from the xerophilic fungi and exposed them to temperatures as low as -80°C. Of the fungi from media supplemented with kosmotrope solutes, 60% died in the harsh conditions, while only 5% of the chaotrope group died. Hallsworth said the findings mean the so-called Goldilocks Zone may be much more extensive than previously envisaged because many cold planets and moons contain all the necessary ingredients for making chaotropic solutes.

The findings are published in the Proceedings of the National Academy of Sciences (PNAS).

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More information: Solutes determine the temperature windows for microbial survival and growth, PNAS, Published online before print April 19, 2010, doi:10.1073/pnas.1000557107

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Apr 20, 2010
Ummm hello... the Goldilocks Zone is as outdated as those who didn't believe planets orbited other star systems... can't that concept just die in old text books somewhere!!

Apr 20, 2010
Earth is Beyond the goldilocks zone , only the green house effects and tectonic activity makes the presence of liquid water posible in our blue planet. Local caracteristics are way more important than location relative to the star. Europe (the moon) for example gets way much more energy by tidal dissipation than from solar radiation.
Anyway , that experiment only proves that pre-existing live can endure extreme conditions , do not prove anything about the boundaries where live could emerge.

Apr 21, 2010
1st off, did this experiment not contain a control group? Next, this is great and all, but what are the possibilities of life arising using this chaotropic substance as iced primordial soup? The effect of this on the Goldilocks Zone is akin to our understanding of silicon based life forms, or hydrocarbon slurries on gas giant moons supporting life. There's no way to tell I think. Good thing to know though, hope is always good.

Apr 21, 2010
This work shows, indisputably that an earth type membrane is affected by these solvents. It says nothing about life which has originated and evolved on other planets and life which is not carbon based. The Goldilocks zone is the zone where life as we know it thrives -- but not necessarily where the three bears like to live.

Apr 21, 2010
LuckyBrandon, the number of miles depends on the star type and temperature. The Goldilocks zone is much closer to a dwarf red star than it is to a star like our sun.

Notice also that the Goldilocks zone only considers radiant energy sources. Since several of the outer moons in our solar system seem to have internal liquid water oceans driven by tidal forces, we must consider the possibility of other types of energy sources as well. For example, we have found extremophile cells living inside rock that use radioactive breakdown energy to grow right here on earth. So the Goldilocks zone has lost much of its predictive power where life might be found.

Apr 21, 2010
Indeed it says something about where life can endure rather than emerge, one can hardly imagine life emerging at -80 C, but it does extends the case for planets that have ie elliptic orbit and periodically dip in and out of the goldilocks zone, also for planets/moons who's distance to the host star or the host stars stage of evolution has changed to render the planet slightly outside the goldilocks zone, might have had life emerge in the past and clinging on to it when conditions came more harsh.

Apr 21, 2010
The effect of this on the Goldilocks Zone is akin to our understanding of silicon based life forms, or hydrocarbon slurries on gas giant moons supporting life. There's no way to tell I think. Good thing to know though, hope is always good.

Actually you're ignoring probability principle.

If it can happen, it MUST happen over an infinite timescale.

Apr 25, 2010
the universe is like an enormous amount of dice times an enormous amount of throws, no matter how small the changes of throwing that odd number, with this many throws life will allmost inevitably show up in the statistics, that's what i believe.

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