And the outstanding question which this type of experiment can address is how important they are in trench environments, in particular in the Japan Trench, and whether these are contributing a significant amount of the slip on the plate.
Let me briefly turn to the last research frontier - the deep biosphere - you'll hear more about that from an expert later today. I do not claim to be one on this topic. But let me just make a few general comments.
The first is that I have been impressed with the discoveries of the last few years of the incredible diversity of life and the ability of life forms, notably microbial life forms, to form habitats in environments that previously were thought to be too extreme for life, including deep in rock (fig.45) and, of course, the deep hydrothermal vents (fig.46). But at these deep hydro-thermal events, which have diversity of fauna , the bottom of the food chain has some pretty unusual microbial life forms. Shown here (fig.47) in a well-known scientific journal, "The Washington Post", is an illustration of - a now famous one - of a deep-sea microbe named after the late Holger Jannas, who was instrumental in discovering many of these species, because two years ago the genome, the sequence of DNA in this microbe, was completely worked out - one of the first microbial animals for which this was accomplished.
Shown on the left (fig.48) is a scanning electron micrograph of some mats of what is thought to be biogenic material, recovered from the Juan de Fuca Ridge shortly after eruption by a collector in the water column, suggesting to many that there is a bacterial community not only sitting on the deep-sea hydrothermal vents but somehow distributed at depth beneath the surface of the sea floor.
One of the reasons this may be exciting is the suggestion (certainly not proven) that deep sea hydrothermal vents could be an attractive site for the origin of life. Now this is controversial, but it's based on several arguments, and is capable of eventually being tested.
One of the lines of argument is shown here on the night (fig.49), which is a diagram that owes its origin to a man named Carl Woese at the University of Illinois, who worked out how different all members of the animal kingdom were, on the basis of nucleotide sequences in small snippets of a kind of RNA found in the ribosomes of all of these animals. And in particular he proposed, and this has since been confirmed by other techniques, that there is a class of objects that are neither bacteria nor the multi-celled organisms, the Eukarya, but is distinct, and he called it Archaea. The object I just showed you from The Washington Post is one representative of this class. And he named the Archaea the Third Kingdom of the animal world.
Now what is interesting about the Archaea is that many of them those shown in purple) live in high temperature environments. They're what the biologists call hyperthermophiles - they love high temperatures. And the fact that the Archaea have this niche, and that they diverge in this family tree (which represents how many cousins and generations you have to go back before you share a common ancestor with other branches of the tree) at the oldest part of this tree has strengthened, at least constrained, the suggestion that life began in hypothermal events.
A second line of argument, completely independent, comes from the study of the planets. At the time that life began, at least slightly before the oldest known life on the Earth, the surface of the Earth was a hellish place (fig.50). It was subjected to bombardments by large objects that have been recorded on other planets as big impact structures. And these large impacts would have melted the surface, at least in large regions, would have modified climate in drastic ways, and would have made it difficult for life to find a niche and maintain itself at the surface.
So did life begin at hydrothermal events ? We don't know. But it's at least entertaining to explore that question because if life does not depend on photosynthesis to begin or to evolve, then there are other objects in the solar system that could also haven been places where life began.
