"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."
Spacecraft
"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."