Astronomers looking back 13.8 billion years found ripples in the fabric of space-time that support a theory offered by physicists like Alan Guth: that of a universe being wrenched apart around its inception.
The ability of the human body to adapt to the extremes of terrestrial environments was largely irrelevant for Earth orbit and the Moon. Mars, however, presents a challenge of a different scale and character. Life on Earth has evolved over the past three and a half billion years in an unchanging gravitational field. Take gravity away, and our bodies become virtual strangers to us.