Part 2 of 8

The Ultimate Field Trip

An Astronaut's View of Earth

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

Strait of Gibraltar [STS41G-40-050] Highlighted by the sunglint, internal waves called "solitons" can be seen arching through the Strait of Gibraltar into the Mediterranean Sea. Once a day the high tide produces sufficient energy to propagate solitons atop the strong density boundary between the heavier, more saline bottom water flowing west and the lighter, fresher Atlantic water flowing east. The Strait is shallow enough to allow the internal waves (up to 60 meters in amplitude) to manifest themselves as crests (no more than 10 centimeters high) on the sea surface. During World War II, German U-boats were able to silence their motors and ride these internal waves undetected into the Mediterranean.

Regardless of their preflight level of interest or Earth training, all astronauts are entranced by the views out the window, and whenever possible they scavenge free moments from the busy flight plan for window gazing. Both the sweep of the view and the detail you can see are quite remarkable. On my second flight, at the relatively high altitude (for Space Shuttles) of 334 nautical miles, we could see the Great Lakes quite clearly from over the Gulf of Mexico; the Atlantic coastline of Brazil at Rio de Janeiro from above the Andes in Ecuador; Lake Eyre, Australia, from over Papua New Guinea.

If you're more interested in detail than grand views, you can detect cities, airports, rivers, and the like. Over ocean areas, catching the sun at just the right angle will let you see amazing spiral eddies, major current boundaries, and internal waves. In even a brief period at the window, you can get quite an introduction to all the diverse, interrelated Earth science disciplines - geography, geology, oceanography, ecology, meteorology - as this great planet slides before your eyes, revealing an ever-changing array of forms, patterns, and colors.

When several crewmembers meet at the windows to watch the world go by, the running commentary is a delightful mixture of science, history, personal anecdote, and childlike wonder: "Look at that! Florida really looks like the maps!" "Wow! No wonder this was called the Skeleton Coast - look at those dunes" "Look at those arcs in the sunglint . . . those must be pulses of Atlantic water flowing through the Strait on top of the Med water." We all try to find hometowns or other places we've been to or read about. At night, you can use the lights of major highways and towns in the United States to locate your hometown pretty accurately (if you know your geography!). Some of my most memorable sights include favorite cities (Oslo, Halifax, London), places where I've done field work or hiked (Death Valley; the Sierra Nevada; the Wind River Range; the Chugach Mountains and Kenai Peninsula), and places I've only dreamt of going to (the East African Rift Valley, the Tibetan Plateau, the Himalayas, the Galápagos).

The Kalahari Desert [AS17-148-22636] The Kalahari Desert is enlarged as the drought-resistant ground cover of the surrounding savanna is burned off by range fires. Two such fires are seen burning in this photo taken in 1972 from Apollo 17. The scars of many generations of such fires give the Kalahari its patchwork colors.

Experienced Earth observers in orbit take great pride in their ability to instantly identify any one of the world's deserts by its distinctive coloring and surface patterns. The Sonoran and Chihuahuan Deserts of North America are a medium tan, broken by the dark grays and browns of the cordilleran mountain ranges, whereas the North African deserts are a bright orangish-red and marked by huge wind streaks. The Kalahari is an odd patchwork of chalky grays and black-browns; scars from immense range fires are the cause of the distinctive patchwork pattern. Finally, the Tibetan Plateau (the world's highest and coldest desert) contains every imaginable shade of brown, tan, and earthy red, along with striking blue, green, and turquoise glacial lakes.

Spiral Eddies off the East Coast [STS41G-41-046] Spiral eddies spun off the inner edge of the Gulf Stream are revealed by sunlight reflecting off a slick formed by a very thin oily film, produced by marine organisms. Thicker oil slicks produced by petroleum products do not spread evenly across the sea surface but clump up in patches. Here the thin biological film has damped down the small waves on the surface and formed a slick that manifests the fine kinematic detail of the spiral eddies. Such ocean surface structure can also be seen by radar, but that technology is much more expensive than sunglint.

Part 2

This local copy was downloaded from http://eol.jsc.nasa.gov/newsletter/uft/uft1.html on 18 Jan 2000.