following the water' in the search for life in the universe. Despite this, our deeper understanding of exactly what it is that makes water so very, very special is still surprisingly limited.
An intriguing new study by Rao, Garrett-Roe & Hamm in the Journal of Physical Chemistry (B), appears to offer a clue or two. By applying modeling techniques usually reserved for the study of complex and dynamic systems, they investigated what might be going on in liquid water on a moment-by-moment basis. The dipolar nature of water molecules means that weak electrostatic bonds (hydrogen bonds) are readily made and broken between structures. So in a crowd of water molecules all manner of temporary arrangements can be made as they jostle around. This new study indicates that there may be two main flavors of these arrangements - one a rather 'blobby' mass of several molecules, and the other a more regular, crystalline arrangement. These structures are exceedingly fleeting - breaking up and re-assembling many times a second at room temperature. The result is, and this is a very crude phrasing, a bit like a 3D piece of velcro that is constantly morphing into different shapes.
So, all jolly nice, but why do we care? Imagine throwing some other molecules into this sticky nest. Perhaps some carbonates, some amino acids, even some proteins. The shape-shifting water structures can provide the perfect chemical incubator - from catalyzing reactions to determining structural forms of complex organic molecules. This cuts to the heart of one of the long running discussions that crops up in the search for life. Why couldn't you have biology that uses something other than water? Why not methane, or hydrogen peroxide, or ammonia?
The answer may now be clearer - as far as anyone knows these other solvent-like molecules do not exhibit this same type of behavior - so it may be that they offer far fewer, if any, pathways for complex chemistry. Water may be far more intertwined in the processes of life than we had suspected.