Argument: Mars is more scientifically interesting than the Moon
Apollo astronaut Michael Collins, who circled the Moon alone while Mr Armstrong and Mr Aldrin walked on it, said Mars was more interesting than the Moon: "Sometimes I think I flew to the wrong place. Mars was always my favourite as a kid and it still is today."
"Why Go to Mars?" Imagineering on Mars: "Mars has a fascinating and more complex geology than our moon. There are clear signs that liquid water once flowed on the surface of Mars. Water is the elixir of life. To live on another planet you must have water. Most scientists believe that water still exists, just below the surface in the form of permafrost.
Mars also has some very tall mountains on Mars. The tallest volcanic mountain towers 15 miles above the plain. There may still be some geothermal activity going on. Geothermal activity would be a great source of heat that could be used to extract water from the frozen ground.
The sand and rocks on the surface of Mars appear to contain a lot of carbon compounds that are needed to sustain life. Some believe that Mars may have supported primitive life in its early history. Theoretically, life may still exist if Mars does, in fact, have underground oceans of water heated by geothermal action.
Scientists were surprised by the findings that complex ecosystems could flourish deep in the earth's oceans. The heat and minerals spilling out from deep thermal vents are the life-sustaining forces of these complex ecosystems."