Between the Mica Sheets

Helen Hansma, a research professor at UCSB, just published her theory on the origin of life in the Journal of Theoretical Biology. According to the so-called “life between sheets” hypothesis, mica, a common mineral that cleaves easily into smooth sheets, may have sheltered molecules that were the progenitors to cells.

In other words, life on the earth may have originated between the mica sheets.

Hansma’s exposure to mica, according to a recent press release from UCSB, started when she participated in the pioneering research for building an Atomic Force Microscope (AFM) – a high-resolution imaging technique that improves observation and manipulation on molecular and atomic levels. Since then she has conducted a variety of research using mica. Her hypothesis that life began between mica sheets was first introduced at the 2007 annual meeting of the American Society for Cell Biology. “Initially it encountered some criticism,” said Hansma, “but as time goes by there seems to be an increase of interest in the hypothesis.” Indeed, Hansma’s theory is now fully described in the September 7, 2010 issue of Theoretical Biology.

There are three main areas of evidence supporting the “life between the mica sheets” hypothesis. Firstly, the mica sheets’ compartmental structure: It acts as a sheltering space that maintains the proper humidity and warmth for life. There is also vast space between layers, providing sufficient isolation for the evolvement of individual cells.

Secondly, mica sheets are held together by potassium. The high level of potassium found in mica sheets could be the explanation of the high potassium level even in human cells. Hansma believes the mica sheets used in her laboratory come from salt water, and “after all,” she said, “the ocean is where all the life comes from.”

And this leads to the last set of key points supporting the hypothesis: Mica sheets embedded in rocks in the early oceans received abundant mechanical energy from currents and waves. For the molecules caught in between these sheets, this mechanical energy could have greatly enhanced the “making and breaking of chemical bonds” and the development of complex molecules.

Although Hansma’s hypothesis has involved some of the most forefront research technologies, the scientist’s pronounced fondness for mica seems to be rather personal. “Why do I like mica so much?” she responded. “Well, it is so shiny! Plus it’s fun to split – you can just stick some Scotch tape on mica and pull it off to get a nice clean layer.” This feature has made DNA observation much easier.

Because mica surfaces are hospitable to all the major classes of large biological molecules such as proteins, nucleic acids, carbohydrates and fats, Hansma’s hypothesis is consistent with various famous hypotheses on the origin of life, including the RNA world hypothesis.

However, Hansma is well aware of the remaining uncertainties in the between-the-sheets theory. “We are trying to recreate the origin of life in the lab, a process that took millions of years in nature,” said Hansma. “There’re a lot of uncertainties about what the chemical conditions were when life originated, so there’s a lot of ways to guess wrong about what to put in-between the mica sheets.” She sees the research in the origin of life as quite similar to the process itself – a lot of failed attempts in all directions have to occur before molecules successfully evolve into cells.

Hansma has always been interested in inter-disciplinary research projects. Analogous to the Big Bang theory, which offers an explanation as to the origin of our universe, the “life between the mica sheets” hypothesis strives to answer the age-old question: “Where did life on Earth start?” After all, it is our strong curiosity on such fundamental issues that has motivated scientific research in all the fields.