The Volcano Explorer In 2003, video producer John Catto captured footage of geologist Ken Sims climbing into Masaya. After arriving on the floor of volcano, he set up his instrument, a radon detector, near the edge of the smoking crater. While in this hot, noxious place, Sims gathered gas, communicated with scientist Pierre Gauthier on the surface, and kept an eye on rising magma in the crater.  (Video by John Catto, Alpenglow Pictures/Video editing by Tim Silva, WHOI)