Planetary isotope ratios in general vary quite a bit. We use them when we determine, say, that a rock is originally from Mars.
The fractionation seems to be based on the different masses of the isotopes and how they are subject to migration in the early solar system. But, for example, Jupiter has MUCH less deuterium than Earth and many comets have more. That said, some asteroids seem to have quite a bit more than even the comets we have seen.
Deuterium - Wikipedia
"The abundance of deuterium in the atmosphere of
Jupiter has been directly measured by the
Galileo space probe as 26 atoms per million hydrogen atoms. ISO-SWS observations find 22 atoms per million hydrogen atoms in Jupiter.
[14] and this abundance is thought to represent close to the primordial solar system ratio.
[4] This is about 17% of the terrestrial deuterium-to-hydrogen ratio of 156 deuterium atoms per million hydrogen atoms.
Cometary bodies such as
Comet Hale-Bopp and
Halley's Comet have been measured to contain relatively more deuterium (about 200 atoms D per million hydrogens), ratios which are enriched with respect to the presumed protosolar nebula ratio, probably due to heating, and which are similar to the ratios found in Earth seawater. The recent measurement of deuterium amounts of 161 atoms D per million hydrogen in Comet
103P/Hartley (a former
Kuiper belt object), a ratio almost exactly that in Earth's oceans, emphasizes the theory that Earth's surface water may be largely comet-derived.
[3][4] Most recently the deuterium/protium (D/H) ratio of
67P/Churyumov–Gerasimenko as measured by
Rosetta is about three times that of Earth water, a figure that is high.
[5] This has caused renewed interest in suggestions that Earth's water may be partly of asteroidal origin.
Deuterium has also observed to be concentrated over the mean solar abundance in other terrestrial planets, in particular Mars and Venus.
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