Ralph Aeschliman Planetary Cartography and Graphics | home
From Sky & Telescope, June 2003
Ralph Aeschliman describes himself as a frustrated amateur astronomer from the Pacific Northwest. Fresh out of college with an art degree, he took his 6-inch refractor to Flagstaff, Arizona, in 1989 to look for a job and clear skies. His timing was perfect. He was hired by the astrogeology group of the U.S. Geological Survey and began work as an airbrush cartographer. During his 11 years at the USGS, he moved from using a Paasche AB airbrush and electric eraser to a computer. Aeschliman now lives in Ventura, California, where he has set up his own computer environment to perform serious planetary cartography and has begun work on an atlas of Mars.
The maps in this article combine two images. The first is a global color mosaic by Alfred McEwen and Laurence Soderblom (1993) that Aeschliman worked on while at the USGS. Recently he modified this digital image model to make it conform exactly to the second image, one based on elevation data from the Mars Orbiter Laser Altimeter (MOLA) instrument on NASA's Mars Global Surveyor. The combination portrays albedo markings as they were at the time of the Viking missions, together with consistent relief topography. Of course, the coloration and shapes of dark areas are subject to unpredictable changes, and particular regions might be obscured by atmospheric haze, clouds, or dust storms at any given time. So as not to hide known land features, the maps show both polar caps at minimum extent; depending on the season, at least one cap will be more extensive than shown in these images.
"When I started at the Survey in 1989," says Aeschliman, "we had a computer room with system administrators and techs, a photo lab with cartographic cameras the size of a garage, a team of programmers, airbrush/touch-up experts, etc. Now I do it at the dinette table on my sailboat. Blows me away!"