Goldilocks searched for the perfect porridge to eat, one that was not too cold or too hot. Scientists have been on a similar quest for the ideal environment for the origins of life - and according to a new theory, mica might be it.
Helen Hansma, a researcher at the University of California, Santa Barbara, developed the "life between the sheets" hypothesis.
The idea explains how the compartments between layers of mica - a class of minerals that cleaves into smooth, flat planes - provides a favorable chemical and physical environment for the development of biological molecules, such as RNA.
Hidden nooks and crannies between mica sheets can trap water and nutrients, and may have acted as refuges where the first replicating molecules could evolve and multiply in safety. As they grew larger and more complex, they could migrate to the spaces along the sheets, like tiny cave-dwellers (as shown in the image above).
It is possible that the compartmentalized structure of mica provided the basis for the tidy architecture of life forms as cells, Hansma told Discovery News.
It also could have served to regulate water for the building blocks of life. Only a limited amount of water can seep in between the sheets, preventing water from flooding the structure and washing away fragile biological building blocks.
Accounting for water regulation is one of the issues in the "pizza" origins of life model. This alternate models predicts all the components for life pooled together on the Earth's surface, but cannot explain how the first creatures overcame flooding or drought events.
Micas are also full of potassium.
"I calculated that if you pull mica sheets apart about 1 sheet width, you get the potassium concentration seen in our cells. All cells, going down to the bacteria level, have nearly this same amount of potassium," Hansma said.
But even if mica provided a perfect house for the first molecules to live in , there still needed to be a spark, or energy spurt, that set things into motion.
This is a big problem another model for the start of life, called the "soup" model, which predicts life was born out of a broth of chemicals, but provides no mechanism for how the soup mixed together.
In the "between the sheets" model, Hansma hypothesizes that energy from early ocean waves and the sun moved micas up and down like a spring, constantly deforming the structure so that previously isolated molecules were then pressed together. Eventually they formed bonds and created complex molecules, setting the stage for early life.
Hansma's model brings together aspects of the "soup" and "pizza" models, into a neat sandwich model that seems not too hot, and not too cold, but just right.