Pluto would appear to have glaciers of nitrogen ice, the latest pictures from the New Horizons probe suggest.
Scientists believe they see evidence of surface material having flowed around mountains and even ponding in craters.
The activity is certainly recent, they say, and may even be current.
But the mission team cautions that it has received only 4-5% of the data gathered during 14 July's historic flyby of the dwarf planet, and any interpretations must carry caveats.
"Pluto has a very complicated story to tell; Pluto has a very interesting history, and there is a lot of work we need to do to understand this very complicated place," said Alan Stern, the New Horizons principal investigator.
In a briefing at the US space agency's HQ in Washington DC, he and colleagues then outlined a number of new analyses based on the limited data-set in their possession.