The Gizmodo article It Looks Like Pluto Has a Liquid Water Ocean shows a large image of Pluto with obliquely lit peaks near both the terminator and the edge of the disk where the topography is really striking.
Four questions, I can split the last one as a separate question if necessary, but it's quite possible a single source is going to contain contain answers to all of them, so let's wait an see.
- How tall are these things?
- Are they made of ice?
- Are they the tallest things on Pluto?
- Are these the tallest ice features in the Solar System?
below: Plutonian landscapes in twilight. Image: NASA/JHU APL/SwRI (cropped and half-sized versions, original is almost 3 MB.