5 December 2007

Between The Sheets

by Kate Melville

Life on Earth may have begun as an organic mash in the protected spaces inside of layers of the mineral mica, according to a new hypothesis developed by Helen Hansma, a research scientist with the University of California, Santa Barbara.

Hansma proposes that the narrow confined spaces between the thin layers of mica could have provided exactly the right conditions - effectively creating cells without membranes - for the rise of the first biomolecules. The separation of the layers would have also provided the isolation needed for Darwinian evolution. "Some think that the first biomolecules were simple proteins, some think they were RNA, or ribonucleic acid. Both proteins and RNA could have formed in between the mica sheets," contends Hansma.

RNA is composed of nitrogenous bases, sugar, and phosphates. Hansma says that RNA and many proteins and lipids in our cells have negative charges like mica. RNA's phosphate groups are spaced one half nanometer apart, just like the negative charges on mica. Interestingly, mica layers are held together by potassium and the concentration of potassium inside the mica is very similar to the concentration of potassium in our cells. Additionally, the seawater that bathed the mica is rich in sodium, just like our blood.

The heating and cooling of the day to night cycle would have caused the mica sheets to move up and down, and waves would have provided a mechanical energy source as well, according to the new model. Both forms of movement would have caused the forming and breaking of chemical bonds necessary for the earliest biochemistry.

Thus the mica layers could have provided the support, shelter, and an energy source for the development of precellular life, while leaving artifacts in the structure of living things today. Besides providing a more plausible hypothesis than the prebiotic oceanic "soup" model, Hansma said her new hypothesis also explains more than the so-called "pizza" hypothesis. That model proposes that biomolecules originated on the surfaces of minerals from the Earth's crust. The "pizza" hypothesis cannot explain how the earliest biomolecules obtained the right amount of water to form stable biopolymers.

She summed up her hypothesis of the origin of life by saying, "I picture all the molecules of early life evolving and rearranging among mica sheets in a communal fashion for eons before budding off with cell membranes and spreading out to populate the world."

New Rationale For Biological Complexity Proposed
Primordial Soup-In-A-Cup
Volcanic Clay May Have Served As Womb For Emergent Life

Source: University of California - Santa Barbara