March 23, 2014 | David F. Coppedge

Carbon Cycle Keeps Earth from Fate of Venus, Mars

Another delicate balance making Earth habitable has been identified: the carbon cycle.

It’s the “Goldilocks principle” again.  Too much or too little would not be just right, but deadly.  According to Science Daily, USC scientists found Earth sits in another sweet spot:

Scientists have shown how geologic process regulates the amount of carbon dioxide in the atmosphere. Researchers have documented evidence suggesting that part of the reason that Earth has become neither sweltering like Venus nor frigid like Mars lies with a built-in atmospheric carbon dioxide regulator — the geologic cycles that churn up the planet’s rocky surface.

Geologic processes like plate tectonics are oblivious to concerns about balance in the atmosphere or habitable temperatures.  This means that independent factors conspire to keep the Earth in the Goldilocks zone.

Scientists have long known that “fresh” rock pushed to the surface via mountain formation effectively acts as a kind of sponge, soaking up the greenhouse gas CO2. Left unchecked, however, that process would simply deplete atmospheric CO2 levels to a point that would plunge Earth into an eternal winter within a few million years during the formation of large mountain ranges like the Himalayas — which has clearly not happened.

And while volcanoes have long been pointed to as a source of carbon dioxide, alone they cannot balance out the excess uptake of carbon dioxide by large mountain ranges. Instead, it turns out that “fresh” rock exposed by uplift also emits carbon through a chemical weathering process, which replenishes the atmospheric carbon dioxide at a comparable rate.

Mark Torres of USC realizes that our presence on Earth is dependent on this finely-balanced carbon cycle.  “The Earth is a bit like a big, natural recycler,” his co-author said.  In addition to the carbon cycle, Earth enjoys a nitrogen cycle, oxygen cycle, and water cycle.  Atmospheric winds and ocean currents also cycle about with some predictability as Earth cycles through its rotation and orbit.

You don’t need the millions of years to recognize the present balance in the carbon cycle.  It’s just one of at least 20 factors listed in the documentary The Privileged Planet that point to intelligent design of our home, where we can live, breathe, and conduct scientific research.  For more on habitable zones and Goldilocks parameters, see 9/19/13 and list in the 9/08/12 commentary.



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