1. Extreme Navigation NASA’s Discovery Missions: Stardust-NExT and EPOXI Missions NASA’s Discovery Missions: Stardust-NExT http://stardustnext.jpl.nasa.gov EPOXI http://epoxi.umd.edu

2. NASA Comet Explorations: Two Spacecraft, Three Comets, Four Missions, Oh My! Stardust Spacecraft First visited comet Wild 2 (“vilt 2”) now heading to comet Tempel 1 Deep Impact Spacecraft First journeyed to Tempel 1, now heading to comet Hartley 2

3. What are Comets? They contain a high percentage of rocky organic materials and ices –Ices include water, CO 2, methane ices Solid nuclei are generally smaller than asteroids –on average a few km in diameter They are left over “bits” or remnants from the formation of the Solar System –Believed to originate in either the Oort Cloud (long period) Kuiper Belt (short period) Comet McNaught in 2007 over Australia by Akira Fujii

4. Comet Anatomy  Nucleus: “dirty ice ball” (ice, dust, and rocky debris) usually only 1-10km across, but as big as 10 km in diameter and the only substantial part of the comet.  Coma: a cloud of water vapor, carbon dioxide, and other gases which sublimed off the nucleus and contain very little mass.  FACT: The coma and tail can be as large as Jupiter (about 10x’s the diameter of Earth). Together forming the head of the comet.  Tail: o Dust tail: composed of small (smoke-sized) dust particles driven off the nucleus by escaping gases, making it the easiest to see. o Ion Tail: composed of plasma (ionized gases) and created by interaction with solar winds. FACT: The ion tail can be as much as 1-2 AU (150-300 million km) when the comet is near the Sun. o Sodium Tail: composed of sodium ions, yellowish, challenge to perceive and many questions

5. Nucleus Dust Tail Coma Ion Tail

6. Comet Action

7. The orbital paths of the comets EPOXI and SD-NExT are visiting in 2010 and 2011

8. EPOXI’s trajectory to comet Hartley 2

9. Discover More! Stardust-NExT http://stardustnext.jpl.nasa.gov EPOXI http://epoxi.umd.edu NASA’s Discovery and New Frontiers http://discoverynewfrontiers.nasa.gov