THERE ARE FOUR NORMALLY AIRLESS BODIES IN THE SOLAR SYSTEM THAT COULD SUSTAIN A TRANSIENT COLLISIONAL ATMOSPHERE AFTER BEING STRUCK BY AN ICY COMET: MERCURY THE MOON AND CERES/VESTA. OTHER AIRLESS BODIES ARE EITHER TOO SMALL TO GRAVITATIONALLY BIND WATER AND SIMILARLY VOLATILE VAPORS FOR LONG OR SO COLD THAT SUCH VOLATILES WOULD RAPIDLY FREEZE OUT. THE FOUR ARE THUS SINGULAR AND RELATED BY THIS SPECIAL FEATURE. ALTHOUGH MMCV CURRENTLY HAVE SURFACE BOUNDARY EXOSPHERES AT MOST THEY HAVE ICY DEPOSITS SUGGESTIVE OF ATMOSPHERIC/ EXOSPHERIC FLOW TO COLD TRAPS AND WERE CERTAINLY IMPACTED BY COMETS IN THE PAST. THESE BODIES ALSO EXPERIENCE SYSTEMATIC TRENDS IN PROPERTIES THAT WOULD INFLUENCE IMPACT-ATMOSPHERES: SURFACE GRAVITY ILLUMINATION INTENSITY PEAK SURFACE TEMPERATURE SPIN RATE AND MEAN COMET IMPACT SPEED. WE HAVE DEVELOPED THE ABILITY TO MODEL POST-IMPACT TRANSIENT ATMOSPHERES ON THE MOON (STEWART ET AL. 2011 PREM ET AL. 2015 2016). OUR DIRECT SIMULATION MONTE CARLO MODELS INCLUDE COLLISIONAL MOLECULAR GAS DYNAMICS PHOTO-CHEMISTRY COLLISIONAL CHEMISTRY LINE BY LINE RADIATIVE TRANSPORT THE ABILITY TO INCLUDE REFRACTORY OR ICY PARTICULATES WITH THE VAPOR LIGHT SCATTERING AND THERMAL EXCHANGE BETWEEN THE PARTICLES AND GAS AND POINT-WISE SURFACE TEMPERATURES BASED ON LOCAL SURFACE ROUGHNESS ON A ROTATING 3D BODY.