Interested in more? Here are a couple resources that inspired me for this activity or offer a different approach to introducing astrobiology:

• Science learning activities for Afterschool – Astrobiology (NASA): nasa-astrobiology-activity.pdf
• Lesson Plan for Science in UK Secondary Schools (UK Centre for Astrobiology, University of Edinburgh): astrobiology-in-the-classroom.pdf
• Variety of classroom materials brought together on the NASA Astrobiology Website: http://astrobiology.nasa.gov/classroom-materials/

Have fun!