"We will remember him fondly as the great explorer who reached out to embrace the universe," NASA Administrator Jim Bridenstine said.
Ireland's Prime Minister described the result as the culmination of a "quiet revolution" in what was once one of Europe's most socially conservative countries.
The two leaders met at the demilitarized zone on the Korean border.
Bans on plastic straws are starting to catch on. But a similar fight against plastic bags shows just how hard it is to regulate plastics.
The man's release comes a little over a week after he posted two short videos on his Facebook page in which he said a prison riot was endangering his life.