Martian settlers on a weekend excursion. Painting by Pat Rawlings, courtesy NASA.
At the National Space Society International Space Development Conference in Anaheim, California, on April 20, 1990, Robert Zubrin brought down the house with the first public presentation of the “Mars Direct” scenario developed by Zubrin and his colleague David Baker of the Martin Marietta company. The audience had not heard such an innovative proposal in many years. The Mars Direct scenario held new potential of lowering costs and of bringing the human exploration and settlement of the Red Planet into the realm of feasibility.
The Mars Direct scenario lowered cost in two key ways: (1) by extensively relying whenever possible on in situ (on site) resource utilization (ISRU), such as the automated manufacture of return fuel from the Martian atmosphere before the first humans even leave for Mars; and (2) by launching directly from Earth, making it unnecessary to first develop an infrastructure in Earth orbit or on the Moon (the hardware developed for Mars Direct could also be used on the Moon, however).
Zubrin describes his ideas quite effectively in the following three articles he wrote for the NSS magazine, Ad Astra:
1996: The Case for Mars: the Plan to Settle the Red Planet and Why We Must, by Robert Zubrin with Richard Wagner. The Free Press. Carl Sagan wrote: “Bob Zubrin really, nearly alone, changed our thinking on this issue.” [Buy from Amazon]
2003: A Traveler’s Guide to Mars: The Mysterious Landscapes of the Red Planet, by William K. Hartmann. Workman Publishing. Kim Stanley Robinson called this book “a masterpiece of scientific writing for the general reader.” We agree. Profusely illustrated. [Buy from Amazon]
NASA is actively pursuing a robotic Mars exploration program, but is not yet actively pursuing a human mission to Mars. Although there is no officially selected reference human mission, NASA has conducted a number of studies of such missions. Here are some reference materials:
1997: Human Exploration of Mars: The Reference Mission of the NASA Mars Exploration Team. NASA Special Publication 6107. 237 pages. [PDF 2.3 MB]
1998: Resource Utilization and Site Selection for a Self-Sufficient Martian Outpost. NASA/TM-98-206538. 54 pages. [PDF 6.4 MB]
2001: Humans to Mars: Fifty Years of Mission Planning, 1950-2000, by David S. F. Portree. NASA SP-2001-4521. 151 pages. [PDF 2.4 MB]
2002: Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface. National Academy of Sciences. 64 pages. [HTML]