Rock-dominated Uranus and Neptune?

The D/H ratio in the atmospheres of Uranus and Neptune from Herschel PACS observations
http://arxiv.org/abs/1301.5781

Quote :

... Conversely, adopting a cometary D/H for the protoplanetary ices between (15-30)$\times10^{-5}$, we constrain the interior models of both planets to have an ice mass fraction of 14-32%, i.e. that the two planets are rock-dominated.

Quote :

A possible solution to this unexpected result is that the interiors of Uranus and Neptune are actually dominated by rock. For icy material in the form of H2O and rocky material in the form of SiO2, an ice mass fraction of only 14-32 % is found. Still, a complete interpretation of the now accurate values of Uranus and Neptune D/H would greatly be aided by a more definite picture of their internal structures. The latter would benefit from improved gravity, shape and rotation data, that could be obtained from planetary orbiters.

We know rather less about these two planets than is good, particularly when considering models of extrasolar super-Earths.

As I said before, it is high time we sent another spacecraft to Uranus and/or Neptune.

VSTAR Modelling of the Infrared Spectrum of Uranus
http://arxiv.org/abs/1303.3330

Study of data from AAT obtains a D/H ratio of 7.5×10^-5, which is higher than the Herschel value. If I'm understanding it correctly, a higher D/H value suggests a higher ice fraction?