Why would I make that assumption? To fit your model? Are you now stating our knowledge of the mass of the Earth and Moon could both wrong by 25% , but in opposite directions?

You might as well say "Assume all planets are made of Brie"

The bulk density of Titan has been calculated via radio science of flybys. We now have a LOT of flybys, which have been used to shape the orbit of Cassini over nearly 4 years. If the bulk density of Titan as we understand is significantly wrong ( as you are now suggesting ) Cassini's mission wouldn't have worked. No debate. Accurate repeated flybys have changed the inclination of the orbit. Now - if you're going to argue that the flawed science of measuring the mass of Titan is the same flawed science used to then use that figure - feel free. But what of the composition of the surface known to be Icy via observations from Cassini. Guess what - we get a density for Titan, and low and behind it appears to be made of the right sort of stuff for that density from observations. Quelle Suprise.

How about an overview, from you, of all the major bodies in the Solar System ( Mercury, Venus, Earth, Moon, Mars, Phobos, Deimos, Ceres, Vesta, Jupiter, The Galileans, Saturn, Titan, Iap, Dione, Enceladus, Uranus, Neptune, Pluto ). How and why do these values : http://en.wikipedia.org/wiki/List_of...bjects_by_mass or other sites citing the known masses of the bodies in the solar system - vary from what YOU think they are. Give us your estimates for values on all those major bodies, citing why you believe their bulk composition to be different to that understood given the variations of density your values will incur.