The Web Interface for Telescience (WITS) is an Internet-based tool that enables members of geographically distributed science teams to participate in daily planetary lander and rover mission planning. WITS enables the viewing of downlinked images and results in various ways, terrain-feature measurement and annotation, and the planning of daily mission activities. WITS is written in the Java language and is accessible by mission scientists and the general public via a Web browser. The public can use WITS to plan and simulate their own rover missions. WITS was used during the 1997 Mars Pathfinder mission primarily for public outreach and was evaluated as a science operations tool at the Jet Propulsion Laboratory (JPL). WITS will be used as an operations tool in the 1998 lander mission, which will land on Mars in December 1999, and in the 2001 and 2003 lander-rover missions to Mars.