The present model provides estimates of the spectral radiance of Mars in the 0.4--5.7 &mgr;m domain. The model is based on several composite surface spectra that correspond to the main types of materials observed. Photometric effects are simulated with both a Minnaert model and a phase function derived from ISM spectra. Aerosols scattering is taken into account for small opacities (single scattering). Thermal emission is accounted for through an emissivity model previously used to derive reflectance from IRS data. Emission and scattering by molecules are also included. Temperature and pressure are allowed to vary with season, local time, and latitude; regional effects, including surface elevation, are averaged out in this version. Results are validated by comparisons with various data sets. One of the main discrepancies with observations is related to atmospheric absorptions deeper than observed, which is probably due to coupling between absorption and scattering. ¿ 2001 American Geophysical Union