Cosmic ray synthesis of organic molecules in Titan's atmosphere

We have studied the possible synthesis of organic molecules by the absorption of galactic cosmic rays in an N ₂CH ₄H ₂ Titan model atmosphere. The cosmic-ray-induced ionization results in peak electron densities of 2 × 10 ³ cm ^-3, with NH ₄⁺, C ₃H ₉⁺, and C ₄H ₉⁺ being among the important positive ions. Details of the ion and neutral chemistry relevant to the production of organic molecules are discussed. The potential importance of N( ²D) reactions with CH ₄ and H ₂ is also demonstrated. Although the integrated production rate of organic matter due to the absorption of the cosmic ray cascade is much less than that by solar ultraviolet radiation, the production of nitrogen-bearing organic molecules by cosmic rays may be greater.