Cutting edge: David Meldrum

I grew up in cold-war Scotland, where regular reports of missile and bomb tests imbued our daily lives with a distinct sense of unease. Then, in parallel to the arms race, came the space race. President Kennedy's commitment to put a man on the Moon within ten years assured Nasa of limitless funds for space exploration. But it was the Voyager missions, the exploration of the outer reaches of the solar system by small smart probes, that really caught my imagination.

In a way, the explorers of space had it easy. The missile programme had solved the launcher problems, so escaping the Earth's gravity was eminently feasible, if expensive. Once in space, the rest was straightforward - limitless supplies of energy from solar panels (or your personal chunk of plutonium as in the Voyager craft), no motion resistance and no corrosion. But the greatest boon of space was its transparency to the electromagnetic spectrum, allowing unfettered optical and radar imaging of planetary surfaces and, more significantly, ease of radio-communication with the spacecraft.

However, my university education in physics, coupled with several summers exploring in Greenland, led not to space science but to the Scott Polar Research Institute. There I joined a team using airborne radars to map the Antarctic continent, hidden under several kilometres of ice. Unfortunately, ice is not as transparent as space: powers that could bounce signals off the Moon are needed to generate detectable echoes through 5km of polar ice. But at least radio waves do penetrate ice. And we did find the unexpected - Lake Vostok, deep in the heart of the continent, under more than 4km of ice.

When this programme wound down I moved back to Dunstaffnage in Scotland to study a natural medium that is, for all practical purposes, totally opaque to radio waves - the sea. Because of this, the bottoms of the oceans are much less well mapped than, say, the far side of the moon, or the surface of Mars. Satellite-borne instruments, which have done so much to advance our knowledge of the Earth's surface and atmosphere, are powerless to see beyond the surface of the ocean. Sea-bed mappers have to rely on acoustic instruments to build images of the ocean floor, and these instruments have to be within the water. Unlike space, water resists the motion of objects through it: building the oceanographic equivalent of a satellite - an autonomous underwater vehicle (AUV) - presents the immediate problem of supplying the vehicle with enough energy to navigate. And, unlike the days of Voyager, small nuclear reactors are no longer popular.

Water friction can, however, be turned to advantage. The oceans move, and it is possible to hitch a free, if largely unpredictable, ride on the back of ocean currents. At Dunstaffnage I have become closely involved in exploiting this free ride, and in recycling new technologies such as global positioning system for the detailed study of ocean currents. We have deployed drifting instruments in many areas, including the polar ice packs, where they have yielded new data for the climate change debate. Elsewhere, the profiling floats of the international Argo programme drift for days on deep currents, surfacing periodically to download thermal data that will help us understand the interplay between the oceanic heat reservoir and climate change.

This still leaves the ocean floor largely unmapped as speculative reconnaissance - exploration in the true sense - is largely ruled out. However, change is afoot, spurred by events such as the chance discovery of the biological communities thriving around hydrothermal vents. Plans are well advanced in many countries for the establishment of ocean observatories linked by sea-floor cables - an internet of the deep ocean, open to primary schools as well as universities. Instrument pods, connected to the network via sea-floor junction boxes, will deliver data and receive commands and energy. AUVs will be able to dock routinely to report their findings and recharge their batteries. The spirit of exploration that has led to such amazing discoveries as the volcanic activity on Jupiter's moon Io, and Lake Vostok in the Antarctic, is about to be fostered once more in the oceans. And, connected to the internet, what new wonders will our last frontier reveal - and to whom?

David Meldrum leads the Scottish Association for Marine Science's technology development team at the Dunstaffnage Marine Laboratory.