The increasing robotic exploration of Mars and eventual human exploration and settlement of that planet threatens to have a significant environmental impact on scientifically important sites and sites of natural beauty in the form of contamination with micro-organisms and spacecraft parts. By definition, the sites that we might wish to preserve are likely to be those to which robots and humans will be sent. An interventionist step to protect pristine regions of Mars with the formation of a Planetary Park system is proposed. Possible locations for the first seven Planetary Parks are suggested. Landing of unmanned craft in these parks would be forbidden. Although global dust storms can carry microorganisms across the planetary surface, the regulations suggested for these parks will allow for the maximum level of preservation. We also suggest that the Planetary Park system could be applied to the Moon. (C) 2004 Elsevier Ltd. All rights reserved.