Modelling and simulations of particle resuspension and transport for the assessment of terrestrial-borne biological contamination of the samples on the mars 2020 mission

The Mars 2020 mission aims to answer key questions about the potential for life on Mars, in part, by searching for signs of past microbial life. Soon after landing, a rover similar to Curiosity will acquire scientifically selected samples of martian material for possible return to Earth by a future mission. Naturally then, each sample must be kept clean of viable organisms with a terrestrial origin according to the stringent biological contamination requirements imposed on the mission. All known vectors that can lead to the contamination of the samples by terrestrial-borne particles must, therefore, first be evaluated before engineering solutions are devised to meet these requirements. One of the significant contributors to the biological contamination is associated with the dislodgment and transport of particles from the rover to the surrounding soil. It is also one of the most complex vectors since its assessment requires multi-disciplinary analyses involving, at minimum, fluid mechanics and the physics of particle adhesion and resuspension, from a multifarious rover geometry. Here we provide an overview of the models developed to capture these particle processes, followed by representative estimates of the concentrations of terrestrial viable organisms in the vicinity of the rover.