“We’ve got galaxies at home.” Reminiscent of distant galaxies amid clouds of interstellar dust, this image taken 20 years ago today by the Landsat 7 satellite shows chunks of sea ice drifting through graceful swirls of grease ice in the frigid waters of Foxe Basin near Baffin Island in the Canadian Arctic. Sea ice often begins as grease ice, a soupy slick of tiny ice crystals on the ocean's surface. As the temperature drops, grease ice thickens and coalesces into slabs of more solid ice. Throughout most of the year, the waters of this area are choked with sea ice, but by the end of summer open water typically returns to dominate this part of the Canadian Arctic. Observations such as this have been collected by the joint NASA and USGS Landsat program since 1972 and were made available to the public in 2008 at no charge. The data gathered by Landsat has allowed scientists worldwide to utilize these observations to study climate change and a host of other natural and human-caused chan...