Top Ten Reasons

for a

Mission to the Interstellar Medium

10) To explore the structure of the heliosphere

• Termination shock
• Heliopause
• Bow-shock?

9) To investigate the most distant matter in the solar system

• Kuiper Belt
• Interplanetary & interstellar dust
• Oort Cloud?

8) To investigate the interaction of the heliosphere with the interstellar medium

• 3 KHz radiation
• Plasma and dust deflection

7) To investigate fundamental astrophysical processes in the heliosphere and the interstellar medium

• Particle acceleration
• Ionization of neutrals/pickup ion production
• Charge exchange at the nose of the heliosphere

6) To determine the Sun's influence on its local neighborhood

• Ionization
• Energetic neutrals
• Seed material for cosmic rays?

5) To explore the nature of the interstellar medium

• Temperature, density, ionization state
• Magnetic field
• Low energy cosmic ray spectrum
• Plasma turbulence

4) To investigate the origin and evolution of matter in the nearby Galaxy

• Elemental composition of interstellar medium
• Interstellar dust composition
• Isotopic composition, e.g., ¹³C/¹²C
• Nucleosynthesis and galactic evolution
• Interstellar ²H and ³He from the Big Bang

3) To provide a platform for unique astronomical observations

• Using the Sun as a gravitaional lens at 550 AU and beyond
• Astrometric studies with a >100 AU baseline
• Gamma-ray bursts

2) To chart the Sun's journey through the local solar neighborhood

• Local interstellar cloud
• Interstellar clumps?

1) Exploration is what NASA does best!

• Heritage of Explorer-1, Mariner-2, Apollo, Pioneer, Voyager, Pathfinder