The success of no mission can be predicted ahead of time with any degree of confidence.

But a catastrophic failure now, at this historical point in time, in an arena which we mastered a half-century ago, cannot fail but be a totally demoralizing event. One of the reasons I’ve always felt we should pursue Mars rather than a Lunar return is that a failure there will be perceived, both domestically and in the world, as an inflection point, a cusp, in the arc of American progress. It will be seen as a sign of American decline. It will be much more damaging for American prestige to have a Lunar mission fail than a Martian one.