I was recently bemused to learn that Mt. Everest is not in the same place it was last year. Using precise satellite measurements, scientists have determined the mountain peak is creeping northward. Its steps are small ones — each year, its journey takes it about the width of your fingernail further to the north. Little bits add up, though. In the last millennium, the peak of Mt. Everest has moved further than a pitcher throws a fastball, over 60 feet. In the new millennium Mt. Everest and the rest of India will continue its slow inexorable migration into Asia.
Everest’s journey got me to thinking: What other matters might be on the move into this new century? Is there anything profoundly important happening now in science that a century hence a columnist will look back and see it as a turning point?
I have come up with two candidates, two current science stories — both about ice — that I suspect will resonate through the coming century. Each is a small story today, a pebble in a landslide of news. But I would bet my dog’s favorite bone that these two stories will grow in importance as the years pass. Here they are:
The Arctic Ocean is losing its ice. For several years scientists have noted that the sea ice floating at the top of the world is slowing shrinking in area, about 3% per decade by most estimates. They were not particularly excited by this shrinkage; at such a slow rate it would take 350 years for the Arctic Ocean to be ice free in summer. Now it appears there is more cause for alarm. The arctic ice pack is not only shrinking, but rapidly thinning as well.
Polar oceanographers have compared two sets of measurements of ice thickness taken by U.S. Navy nuclear submarines thirty years apart. Using upward-looking acoustic sounders, the submarines were able to measure ice thickness quite accurately. Comparing 26 sites, the deep-water Arctic Ocean ice has thinned from an average thickness of about 3.1 meters to about 1.8 meters. That’s a loss of about 15% per decade. Overall, the arctic ice has lost 40% of its volume in less than 30 years!
At this rate, the ice thickness will reach zero in a few decades. This would convert the Arctic Ocean from a white surface reflecting 80% of solar energy back to space into a dark surface absorbing 80% of incident sunlight — a massive heat collector that would produce profound changes in the world’s climate. If the thinning of the arctic ice reflects some sort of natural cycle, it may never reach zero thickness. But if it is being caused by increased levels of greenhouse gases in the atmosphere — global warming — then we are in for a warm century indeed.
Are we alone in the solar system? Having explored the planets with reconnaissance satellites, we can now say with some certainty that much of our solar system is made of barren rock or white-hot gases. Life as we know it could not exist there. There is, however, one glaring exception.
Europa is one of the large moons of Jupiter, about the size of earth’s moon. Spectroscopic studies carried out with powerful telescopes in the 60s revealed that Europa, like many outer satellites, has an icy shell of frozen water. With a surface temperature of minus 260 degrees Fahrenheit, the ice would be expected to be a rock-hard skin. Thus it came as a surprise when Voyager spacecraft in 1979 revealed a complex pattern of ridges and crevices on Europa’s surface, features resembling liquid-filled openings between floating plates of sea ice on earth.
Scientists now suspect that Europa’s skin is no more than 10 kilometers thick, covering a liquid ocean about 100 kilometers deep — a volume exceeding all the oceans of Earth combined. Why isn’t the liquid frozen solid? The gravitational push and pull of Jupiter’s four large satellites on Europa produces heat, much as does bending a paper clip back and forth rapidly. NASA calculates that the heat generated by this tidal flexing would keep Europa’s interior warm enough to melt ice below a depth of 10 kilometers.
If life on earth generated spontaneously in our warm oceans some 4 billion years ago, then it might be expected to have arisen in the warm oceans of Europa too. If on the other hand God rather than chemistry placed life here on earth, there is no reason to expect it on Europa. Is there in fact life in the warm oceans of Europa? It is difficult to imagine a more exciting, or profound, question.
The Europa Orbiter mission, scheduled for 2003, should be able to directly confirm the presence of liquid oceans. Then, in this new century we are entering, we are going to have to go look at that ocean. Whatever we find, it will be a heck of a story.
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