So a couple years back I took a online System Engineering course taught by NASA and others (SSE101: Survey of Systems Engineering) and the topic of the end of course project was a robotic Mars Sample Return (MSR) mission. Here is a concept we used derived from SpaceX. I will see if I can find the project research files and final paper for download, if you are interested in more details than just the graphic just post a reply on my WordPress blog and let me know.
AJB's Blog 