The first life on Earth began in the protected spaces between sheets of mica. So says Helen Hansma, of the University of California, Santa Barbara.

Presenting her hypothesis at this week’s American Society for Cell Biology, Hansma says her ‘soup and sandwich’ is more plausible than the rival idea of life appearing in a prebiotic soup. Mica, she thinks, provides ideal conditions for molecules to organise into cells. She cites the chemical and physical similarities between a cell interior and the space between mica sheets – they are both being potassium-rich and negatively-charged. Movements of mica sheets could have helped shift molecules and triggered bond formation between them (press release one, press release two).

Nature’s Brendan Maher is blogging the conference at the In The Field blog:

While looking at a chunk of mica under a microscope one day, she noticed bits of organic gunk growing in between it’s flaky layers and thought, “Hey that would be a neat place for an organism to thrive.” Having spent years tuning atomic force microscopes to observe biomolecules on mica sheets, she knew how amenable the structure of mica is to interaction. Another clue had her hooked on the hypothesis. No one, she says, has ever adequately explained how cells first obtained potassium.

The story also appears on LiveScience/Fox News and Xinhua.

Image: sketch showing hypothesis for the evolution of different types of biological molecules in the spaces between mica sheets. Image width is ~50 nm. Courtesty Helen Greenwood Hansma, UC Santa Barbara