Background: The study of airborne dust and water vapor properties at the Martian surface level is an important task for the achievement of some of the primary scientific goals of Mars exploration: to study the water cycle and present / past habitability, climate history and hazardous conditions. Method: The MEDUSA instrument has been designed for the direct in situ measurement of dust and water vapor properties, such as dust size distribution, number density, deposition rate and electrification, and water vapor abundance. Conclusion: The MEDUSA instrument reached a Technical Readiness Level > 5 within the ESA ExoMars mission development and it is well suited to be accommodated on landers and rovers for Mars exploration