It seems that the utter failure of the DS2 penetrator-probe mission to Mars
[1999] has dampened enthusiasm for what should be relatively cheap space hardware. Penetrator-probes can be comparatively cheap [millions, not tens
or hundreds of millions of dollars to design and build] and fairly small
and light [maybe a meter or so in length, less than 100 kg in mass].

The planned deepspace mission to the
asteroids "Vesta & Ceres" by a spacecraft named "Dawn", should also include a pair of penetrator probes.
It's one thing to orbit and image those asteroids close up, it would be a bonus,
icing on the cake, to land a functioning penetrator-probe on each of those worlds to obtainwhat scientists call "ground truth".

Jacob