Every mission has life-or-death moments.

At the time of Apollo 11, I was a grade-schooler, and I remember every time an Apollo mission would take place that, like a lot of little boys, I'd gather in front of the TV for hours and hours and hours with my little brother.

The first mission to Mars did not expect to find craters and river valleys, and yet they did. The first mission to Jupiter didn't expect to find ocean worlds and volcano worlds, but they did.

When I started working with NASA in 1989 as part of a mission to send spacecraft to Pluto, I knew it would take at least 10-15 years to see results of my efforts.

New Horizons is a very high-tech, small, roughly 1,000-pound spacecraft with the most powerful battery of scientific instrumentation ever brought to bear on a first reconnaissance mission.

There was a time when Pluto - which NASA's New Horizons spacecraft at last explored in 2015, a mission I led - was considered the last planet. We now know there are thousands of other - possibly inhabited - planets.