If we're going to send Humans to Mars it should be an international effort where cooperation with the Russia and other partners is essential. However relations with Russia have taken a decided cold turn of late including barring NASA from working with Russian colleagues unless it's directly related to the International Space Station.
Testifying before the U.S. Senate Committee on Commerce, Science, and Transportation's Subcommittee on Science and Space were the following expert witnesses who discussed NASA's exploration strategy, commercial space efforts and international cooperation;
Mr. William H. Gerstenmaier
Associate Administrator, Human Exploration and Operations
National Aeronautics and Space Administration (NASA)
Ms. Susan Eisenhower
Chairman Emeritus, the Eisenhower Institute
President, the Eisenhower Group, Inc.
Dr. Leroy Chiao
Former NASA NASA Astronaut; Commander, International Space Station Expedition 10
Special Advisor for Human Spaceflight, the Space Foundation; and Chairman, National Space Biomedical Research Institute User Panel
Mr. Jeffrey Manber
Unfortunately the hearing was poorly attended as Senator Bill Nelson presided over an empty dais as no other Senators were present during the beginning of the hearing and only Senator Marco Rubio appeared later filling in for Senator Ted Cruz.
In discussing commercial opportunities for Mars, Jeffrey Manber of NanoRacks offered the best quote of the day in saying "Mars in our hearts, but the Moon in our business plan."
The crux of the problem of sending humans to Mars was summed up nicely in the testimony of Dr. Leroy Chiao who stated "the first step to plan 'from here to Mars' is to ensure that the budget is sufficient to support the program. The realistic, sustainable funding level for B-LEO (Beyond Low Earth Orbit) should be determined, and then the program scoped accordingly. If we cannot adequately support a credible B-LEO program politically and financially, then we should not attempt it."
Listen to the Hearing