Hmm … well … the distribution of D/H ratios can vary by an order of magnitude (or up to almost two orders) throughout a fairly narrow radial distance. Jupiter is about 2.3 x 10^5, Venus is about 1 x 10^4, Earth 10^2 (or 10^3, depending on what paper ya read
), so there's quite a variance.
I'm not saying the initial formation of the universe resulted in the variance .. but what happened after that, certainly has resulted in considerable differences.
David Grinspoon (the seeming Godfather of exo-planet atmospheric physics), has also written papers
questioning the beliefs about Venus having been wet. Admittedly, they're pretty old, but the recent spectroscopic investigations into protoplanetary disks has also shown quite a lot of variances with line of sight molecular column depths and densities. All this gives support to the cometary deposition theories ( … which I don't particularly swallow easily, either).
They've come up with quite a few chemical reactions which can bump up or destroy the deuterium levels in models, also.
The whole thing is very controversial, so some care is required in making definitive statements about the presence or absence of big water (when extrapolating into the past).
Most of these 'constants in physics' quoted in textbooks, can get outdated fairly rapidly during this 'Golden Age' of astrophysics, so gotta keep up with the trends ol' boy !!
Cheers