Program: GS-2007A-C-4

By studying the inner, planet-forming regions of circumstellar disks around low-mass pre-main sequence stars we can refine theories of giant planet formation and develop timescales for the evolution of disks and their planets. $Spitzer$ infrared observations of T Tauri stars in the Chamaeleon star-forming region have given us an unprecedented look at dust evolution in young objects. However, despite this ground breaking progress in studying the dust in young disks, the gas properties of the inner disk remain essentially unknown. Using the high-resolution of Phoenix, we propose to measure the 4.7 $\mu$m CO fundamental emission originating in the innermost disk regions of classical T Tauri stars in different stages of evolution with the objective of revealing the timescales of gas dissipation and its relationship to dust dissipation. With the combined results of $Spitzer$ and $Gemini$, our theoretical analysis will unveil the state of the dust and gas in disks in which planets may already be forming and starting to open gaps.