July 20, 1969 Neil Armstrong descended the stairs of the lunar module Eagle and uttered the famous phrase "one small step for a man, one giant leap for mankind." At that moment the moon was still a reference in the sky to become a place; and certainly the time during the Cold War it became a collective catharsis regardless of the flag which ended planted on its surface. Definitely they stood before one of the most important milestones of mankind, to compare of the domain of fire.
But December 14, 1972 in Eugene Cernan and Harrison Schmitt left the Moon, we never return. In these 45 years there has been speculation about the cause of no return, including the possibility that it was all staged. This was the Apollo XVII was provided to 20, but US have won the race to the Russians, added the fact that people had also lost interest, and maxing coinciding with the oil crisis, ended the program. But were these the primary reason?
The moon is far, more far than most of us can imagine. Obviously in the 60s astronomers was well known how far was the moon, as the distance to stars light years with extraordinary precision; but there was an erroneous conception of space, which they thought empty but today we know that space is plenty of objects of very small and undetectable size which have a relative speeds of the order of kilometers per second (faster than a bullet from a gun) that they can cleanly through our ships fuselages aluminum with few millimeters. In other hand we always believed that the crossing would be a challenge comparable with Columbus's voyage to America; The new continent could be unknown but there was water, plants, animals, air necessary for survival, but on the Moon and other Solar System there is nothing about this; for practical purposes be wandering through space or trapped on the moon is the same. And our only island available, Earth, involves land, because to go out into space to rescue months of preparation that an accident does not have needed, and this requires that they are undamaged parts of the ship unless we want to end up in as the Columbia disaster in 1997.
We live in a comfortable world protected by an invisible shield that is Earth's magnetic field deflects the solar wind. Mars has no such protection, and Mars has no organic matter on its surface. Luckily the Apollo astronauts were only a few days of travel and agreed in peaceful by making solar flares period. The space station is 400 km high in the Earth's magnetic field and never venture out of this assignment.
Apollo XVII the last Moon mission
Apollo XIII the wake-up call
There is an official version because jumped by half air command module but it does not really have the slightest idea. A part of that annoying drawback, What caused the accident? We must add that only luck saved the crew. Depending on how events have evolved the fate of these would have been worse to explore the ship. None could deliver, no redundant parts or circuits, and worst screenplay exit the safety of the trip is almost lost in space. To get the notion an Apollo did not differ much as thought of traveling within a cannonball as narrated by Jules Verne.
Although in reality it had already this notice in the Apollo XI. Almost all spent fuel reserves (which was not much) seeking a landing site: the Moon was much more rugged than previously thought. Even worse was to leave, the ignition lever without air lost when opening the ship to go broke, they could just go with the dresses pressurized impossible to make complex mechanical hands because the gloves; luckily they found a pen (which was not to be at all there) with which to handle and able to operate the ignition, without the pen today would still be up there mummified.
We don’t turn because the 80% confidence that proclaimed as 50% for advertising purposes to give more emotion, but really it wasn’t reached the 20%; when truth and only the luck allowed that there wasn’t any victim in the eight Apollos who circled the moon. The more we increases our knowledge, more we know about our ignorance; and lots of drones and studies on Earth have given us a knowledge of our planetary system, unimaginable in distant 60s. Ironically at that time they saw walked by Mars in ours current dates but they didn’t imagine how much we know today about this planet. We end up traveling to the stars but before our robotic emissaries have flattened the way.