While looking for the full article by Clark which Barry keeps misusing by posting only the abstract I did a search on Benton Clark and Mars and came across an impressive body of work. A more complete biography than Barry has pasted can be found at this Genisis Mission page Clark is an astrobiologist AND has worked on missions to Mars both robotic AND manned. As such he is more likely to have a balanced view than Robert Zubrin with regard to back contamination issues and their potential impact on manned missions. Funny thing is in accepting this expertise Barry must admit manned misison are not scifi or be guilty of yet another double standard (Believe Clark on this but ignore him on that) like his contradictory use of panspermia evidence. While I haven't had time to read all of these or do more than skim the links on the first three pages, Benton seems supportive of manned missions to Mars and is working on the prerequisites.

A full report on this topic from a group Clark was a member of can be found at Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface

A summary is at Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface – Summary

Please note this information is from 2002 not 1960 like the info Barry tried to pawn off earlier.

Regards,
Mark