The Ultimate Field Trip (Part 6 of 8)

An Astronaut's View of Earth

by Kathryn D. Sullivan, Ph.D.
NASA Astronaut

Soil Erosion [STS029-84-040]
Deforestation exposes land to soil erosion. Heavy rains pick up the topsoil and carry it downstream to deposit it in the estuary. Here the Betsiboka River deposits sediment from deforested areas of northwestern Madagascar into the Bay of Bombetoka. We in already developed parts of the world may decry the environmental damage caused by this primitive form of development. But, as Kathy Sullivan suggests, North America might have looked much the same during its 19th-century development if one could have seen it from the same vantage point, 150 miles up.

Many people imagine that Earth would appear an idyllic place from this vantage point, that all signs of strife and conflict would vanish, and that the true unity of our planet and species would be evident. Sadly, this is not so. The world contains an abundant population of human beings, and our planet bears many signs of people's actions that are visible from orbit. I find the sight of national boundaries we've drawn between ourselves especially striking. Some of these lines reflect wars and continuing disputes (the Arab-Israeli treaty boundary of 1979, the Angola-Namibia border). Others are visible simply because adjacent countries divide their agricultural lands differently, creating subtly different patterns that the human eye and brain are quite adept at distinguishing. Examples of this are the borders of the United States with Canada and with Mexico or the border between Brazil and Paraguay.

Other signs of human population and activity are more worrisome, thrusting upon us daunting, intertwined questions of national sovereignty, natural resource utilization, and social development, even as we race by at 5 miles per second. Most of the once-lush Madagascan rain forest is now gone, and the resulting soil erosion chokes the rivers with immense loads of sediment.

Kuwaiti Oil Field Fires [STS039-72-060]
In this photo, taken by the crew of STS-39 in April of 1991, we can see that firefighters have had some success in extinguishing oil well fires ignited during the Persian Gulf War. In this view looking south from the delta of the combined Tigris and Euphrates Rivers, only a few of the fires in the patches at the top of the picture are still burning. The picture also indicates the pollution problems that will be left even after all the fires are put out: ponds of unburned oil, soot deposits on the sand, and air pollution. This acute pollution incident is a dramatic illustration of the chronic pollution of the Earth's atmosphere by our automobiles, power plants, and forest burning.

Malaspina Glacier [STS028-97-082]
Malaspina Glacier, on the southeastern coastof Alaska, shows the difference between alpine and piedmont glaciers in graphic fashion: Alpine glaciers, confined in mountain valleys, are linear rivers of ice. Piedmont glaciers spread out onto plains as sheets of ice. Here we see a confined river of ice emerging onto the coastal flats and widening dramatically. The black material is rocky moraine ripped by the ice from the valley walls and floor. In the confining valleys, these moraines appear as straight black stripes. As the ice spreads out on the unconfined flats, these black stripes are pulled sideways into zigzags. In the present warm, "interglacial" times, most glaciers have retreated way back up their host valleys to nestle near the mountain peaks, where the snow supply is still abundant. During the ice ages, many glaciers grew so large they flowed down the entire length of the valleys, becoming vast sheets of ice on the continental plains below.

What will happen to the people there? What will be the fate of the island's unique populations of rare birds, other animals, and plants? In South America, large regional developments expand into the Amazon Basin rain forest. Will this be the end of the Earth's great rain forests? Will their loss harm our global environment in permanent ways? How do we find better solutions to the very real social and economic issues propelling the developments in these countries? And, finally, wouldn't North America have looked very much like this, if I could have orbited overhead in the 19th century? What did my home continent look like way back then? What were the effects of North American development? The hallmark of a good educational experience: I'm left with far more questions than answers!

I suspect it will be many years before Earth-observing rides in space are generally available. In the meantime, what sorts of people will continue to explore this vast frontier?

Paraguay-Brazil Border [STS61A-32-087]
A difference in land use policy between Paraguay and Brazil is apparent in this Shuttle view of their boundary. The extensive forest clearing and agricultural development on the Brazil side of the river contrast sharply with the forested area and clumps of fields on the Paraguay side. You can see silt brightening the headwaters of at least two of the tributaries from Brazil but no similar signs of soil erosion from Paraguay.