Under a cloudless blue Colorado sky, I accompanied seven scientists, a graduate student, and an ed ucation specialist as they toiled up the shifting sands of the tallest dunes in North America. At 8,200 feet above sea level, the intense sunlight scorched our skin even though it was October, and in the thin air, the exertion left us panting. The incessant wind quickly smoothed away our footprints. We were in the Great Sand Dunes National Park and Preserve, but it felt as though we were alone on Mars.
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