Mars is our nearest neighbour in the solar system, with the exception of our own satellite Luna. It will be considerably easier to hit the moon of course, but what will we find when we get there? Plenty to interest the scientist, the mining engineer, and the cosmologist. But the Biologist will find only fossilised traces of Lunar life, if he finds anything at all.
On Mars the story will be vastly different. We know that there is vegetation there. We still argue about those enigmatic canals. Are they optical illusion or...? What if...? What if an intelligent civilisation cut those great water courses? What if that civilisation still exists? Is man the only intelligence in God's great Universe? How will earth's envoys react when they first encounter non-human intellect for the first time? Will the aliens be friendly, or...?