By Gail Gallessich

Life may have begun in ancient oceans within the protected spaces among layers of the mineral mica, according to a new hypothesis.

The hypothesis was developed by Helen Hansma, a research scientist with UC Santa Barbara and a program director at the National Science Foundation. Hansma presented her findings at the annual meeting last month of the American Society for Cell Biology in Washington, D.C.

The mica hypothesis proposes that the confined spaces between the nanometer-thin layers of mica could have provided exactly the right conditions for the rise of the first biomolecules––effectively creating cells without membranes. 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,” said Hansma. “Both proteins and RNA could have formed between the mica sheets.”

RNA plays an important part in translating the genetic code, and is composed of nitrogenous bases, sugar, and phosphates. RNA and many proteins and lipids in human cells have negative charges like mica. RNA’s phosphate groups are spaced one- half nanometer apart, just like the negative charges on mica.

Mica layers are held together by potassium, Hansma noted. The concentration of potassium inside the mica is very similar to the concentration of potassium in human cells. And the seawater that bathed the mica is rich in sodium, just like human 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.

In addition to providing a plausible hypothesis in opposition to 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.

A biophysicist, Hansma has worked with mica for decades. “We put our samples on mica, because it is so atomically flat, so flat that we can see even bare DNA molecules as little ridges on the mica surface,” she said.

Hansma came upon her idea last spring when she was splitting some mica under her dissecting microscope. She had collected the specimens in a mica mine in Connecticut. The mica was covered with organic material. “As I was looking at the organic crud on the mica, it occurred to me that this would be a good place for life to originate.”

Summing up her hypothesis on the origin of life, she said, “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.”