The goal of this lesson is for students to understand how to plan a mission to another world in the solar system. They begin by discussing the path of a spacecraft traveling between planets, examining the journey from the Earth to Mars as an... (View More) example. In Activity 1, students determine the pros and cons for different ways we can explore another world, either by observing from the Earth or by sending a spacecraft to fly by, orbit, or land on the world. In Activity 2, the students plan a complete mission to explore another world in the Solar System. By the end of the lesson, the students come to understand that what scientists want to learn about an object determines how they plan the mission, but real-life constraints such as cost and time determine what actually can be accomplished. Note: The MESSENGER mission to Mercury that is mentioned in this lesson ended operations April 30, 2015. For the latest information about MESSENGER and NASA's solar system missions see the links under Related & Supplemental Resources (right side of this page). (View Less)