The latest find from the many observations is what appears to be a lake of frozen liquid nitrogen nestled in Pluto's mountains.

"In addition to this possible former lake, we also see evidence of channels that may also have carried liquids in Pluto's past," said Alan Stern, principal investigator of the New Horizons mission.

The imaging system on New Horizons' Long Range Reconnaissance Imager (LORRI) can capture details as small as around 430 feet (130 meters), leading NASA to estimate that the lake is about 20 miles (30 km) across at its widest point.

Scientists speculate that liquids may have flowed and pooled on Pluto's surface billions of years ago when atmospheric pressure and temperatures on the surface of the distant world were both higher than they are today.