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This is the second of a series about research for NASA in Brazil's Amazon basin.

In last week's column my student partner, Damian Kilday, and I were flying to Cuiaba in far western Brazil. Soon after dark, we spotted the lights of Cuiaba through the smoky haze. We had no idea of the adventures that awaited us there.

Cuiaba is the capital of Matto Grosso. The city is impressive in size, and its people are as friendly as Texans. Most of our time there was spent at the nearby government research laboratory, where we met our NASA contacts and set up my instruments.

We spent long days making endless measurements of the smoky sky. Occasionally we took breaks to find quartz crystals and watch monkeys in the trees. Some days the smoke was so thick we could barely see the skyline of Cuiaba.

Every day at noon, the NASA scientists joined their Brazilian counterparts for long meals of huge fish at a nearby restaurant. While they were gone, I compared my solar noon measurements of the ozone layer and the Sun's ultraviolet with those made by their Brewer spectrometer. I had learned how to use one of the $125,000 Brewers in 1995 when the Environmental Protection Administration and the University of Georgia placed one at my site on Geronimo Creek for two months.

Damian and I never had fish for lunch. I had to use most of our meager NASA budget to pay for expensive taxi rides between our hotel and the observatory. So we usually had peanuts, crackers and an orange for lunch. After two weeks of this diet, I lost so much weight it was necessary to punch new holes in my belt.

Cuiaba is famous for being located at the geographic center of South America. I had brought along a global positioning system (GPS) receiver to provide our exact location for the instruments. So one evening Damian and I decided to take the GPS over to the monument that commemorates Cuiaba's claim to fame.

Surveying methods at the turn of the 20th century did not match the precision of a GPS receiver, and the coordinates engraved on the monument didn't match those on the display of the GPS. Damian and I soon discovered that the real center of South America is around two blocks away atop a small wooded hill. Our discovery warranted an appropriate ceremony, so we found a rusty nail and pounded it into the red soil with a big rock. Someday a Brazilian geographer with a GPS will find our unofficial marker and realize we were there first.

One day a satellite and a research aircraft were slated to fly over the edge of the Pantanal, the world's largest swamp. I accompanied two NASA scientists and a several trunks of instruments to the overpass site.

A fisheye lens view of NASA scientists Brent Holben (left) and Tom Eck looking for a research aircraft in the smoky sky over the Pantanal while the robotic Cimel Sun photometer in the foreground measures the aerosol optical depth of the smoke. Photograph by Forrest M. Mims III. Click image to enlarge.

While waiting for the plane, we watched tropical birds and hundreds of caimans lounging around the edges of pools filled with piranhas. The NASA scientists were also treated to the spectacle of a terrified colleague fleeing a huge sow whose piglets he stumbled upon while placing an ultraviolet data logger on a post. That's the first time I've had to drop delicate instruments and run for my life.

After 10 days at Cuiaba, we and three sleepy NASA scientists boarded a midnight flight to remote Porto Velho. When we arrived, the plane circled low over the runway to check for stray animals. When we landed, the NASA scientists were so soundly asleep I couldn't wake them. A persistent flight attendant finally convinced them we were on the ground. They stumbled off the plane and promptly collapsed on the concrete floor of the terminal.

Damian and I continued on to Manaus, where we planned several days of measurements from a tree-house hotel on the Rio Negro a few hours away by river boat. We arrived in Manaus around 4:00 am and stayed at the airport until sunrise to make some measurements. We then found a hotel and slept until late afternoon.

The room was warm, so Damian took his shirt off to sleep. Fearing mosquitoes, I kept my shirt on. When we awoke, Damian's back was covered with welts from mosquito bites.

We had collected a large amount of data in Cuiaba, including measurements of how thick smoke greatly increases haze and reduces the blue and red photosynthetic wavelengths of sunlight. We also made numerous measurements of the ozone layer. We found that the total ozone in a column through the atmosphere increased significantly each day. This resulted from the synthesis of ozone by sunlight within the smoke layer.

The most significant scientific finding was that the thick smoke blocked most of the Sun's ultraviolet radiation on many days. At the time I didn't realize the interest this finding would generate among ultraviolet specialists back home after I published a paper on this finding in a scientific journal (F. M. Mims III, Significant Reduction in UV-B Caused by Smoke from Biomass Burning in Brazil, Photochemistry and Photobiology, 64, 123-125, 1996).

Over a supper of funny tasting pizza during our first meal at Manaus, I wondered what the instruments would reveal during the boat trip to our rain forest hotel just below the Equator. Farther south in Cuiaba, smoke from thousands of acres of burning forest shrouded the land of parrots and quartz. Would the mighty Amazon also be smoky? (To be continued.)

Forrest M. Mims III and his science are featured online at http://www.forrestmims.org/.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.