# GeekDad Puzzle of the Week: Quickly Now, the Clock is Ticking.

Spirit Illustration from JPL/NASA

This week, Pedro Vex must help navigate the Mars Exploration Rover, Spirit to safety before winter sets in. Solutions may be given as mathematics with explanation or as a diagram with explanation. Feel free to download, mark up, and attach the image in your solution, which must be e-mailed by Thursday 10:00 pm EST to be randomly chosen from the correct answers for a chance to win a \$50 gift code to ThinkGeek! Check the solution on Friday.

Puzzle after the jump.

Super-spy Pedro Vex often has to take odd jobs to maintain his anonymity. A year or so ago, Pedro was tracking Super-villan Jack Smith who had infiltrated the Jet Propulsion Laboratory in Pasadena, California and was stealing ITAR sensitive materials. Pedro took a job as a rover route planner at JPL to keep an eye on Jack, who had been hired on to the Mars Science Laboratory team responsible for choosing a safe landing site for the next rover.

Pedro’s first task as a route planner was to get the rover Spirit to a safe place to spend the winter. With winter coming on fast, Spirit was in danger of not receiving enough solar power to charge its battery sufficiently to survive the long, cold winter on the southern Hemisphere of Mars. A safe, north-facing spot had been picked out; all that was needed was to tell the drivers how to get there.

How should Pedro design the route to get Spirit to its winter camping spot in as short a time as possible, giving Pedro time to spy on Jack and Spirit time to charge its battery? Use the given diagram where Spirit starts in the southwest corner and has to travel to the camping spot in the northeast corner. Spirit can move twice as fast over hard ground as it can over soft, sandy ground. Find the best route within the given diagram (do not think outside this box). Assume there are no major obstructions on either the rocky or the sandy ground.