Pluto

The papers seek to explain why Sputnik Planitia -- a 1,000 kilometer-wide, nitrogen-covered basin in Pluto's heart-shaped northern region -- is permanently aligned with the dwarf planet's moon Charon.

The first paper, from the University of Arizona,suggests that Sputnik Planitia filled with ice and altered tidal forces between Pluto and Charon.

The team responsible for the New Horizons flyby of Pluto last week released new pictures Friday of the previously unexplored world.

Scientists say layers of haze stretch 100 miles (160 kilometers) into the atmosphere, much higher than anticipated. All this haze is believed to account for Pluto's reddish color.

As for the incredible ice flows, they appear to be relatively recent: just a few tens of millions of years.