I worked on this exact same thing when I was in college at Arizona State (not to be confused with this team at the University of Arizona). We were developing a glider that could be dropped from 100-115k ft and soar for long distances at very high altitudes.
Earth’s atmosphere at 100k ft is awfully similar to the atmosphere near the surface of Mars. Pressure, density, and temperature can be roughly the same. Our team had a grant from NASA to develop a method to study the martian atmosphere, and we were using weather balloons with a deployable glider just like this article!