We will demonstrate a spoken dialogue interface to a Geologist’s Field Assistant that is being developed as part of NASA’s Mobile Agents project. The assistant consists of a robot and an agent system which helps an astronaut wearing a planetary space suit while conducting a geological exploration. The primary technical challanges relating to spoken dialogue systems that arise in this project are speech recognition in noise, open-microphone, and recording voice annotations. This system is capable of discriminating between speech intended for the system and for other purposes.