I still say it's a cavern.
The big depression/crater on the lower part of the nucleus
has a much broader shadow than that of the nearly-as-large
depression/crater just above it. To me that implies the
one nearer the middle of the nucleus may indeed be a 'pure'
impact crater, but the one further down has walls so deeply shadowed
that it implies great depth...a cavern.
JPL needs to take another look.
Jacob