Motivated by recent spectroscopic observations suggesting that atmospheres of some extrasolar giant-planets are carbon-rich , i.e .
carbon/oxygen ratio ( C/O ) \geq 1 , we find that the whole set of compositional data for Jupiter is consistent with the hypothesis that it be a carbon-rich giant planet .
We show that the formation of Jupiter in the cold outer part of an oxygen-depleted disk ( C/O \sim 1 ) reproduces the measured Jovian elemental abundances at least as well as the hitherto canonical model of Jupiter formed in a disk of solar composition ( C/O = 0.54 ) .
The resulting O abundance in Jupiter ’ s envelope is then moderately enriched by a factor of \sim 2 \times solar ( instead of \sim 7 \times solar ) and is found to be consistent with values predicted by thermochemical models of the atmosphere .
That Jupiter formed in a disk with C/O \sim 1 implies that water ice was heterogeneously distributed over several AU beyond the snow line in the primordial nebula and that the fraction of water contained in icy planetesimals was a strong function of their formation location and time .
The Jovian oxygen abundance to be measured by NASA ’ s Juno mission en route to Jupiter will provide a direct and strict test of our predictions .