Synoptic presentation of measurements of the fractional Jovian deuterium abundance, as determined from HD/H₂ (bright green) and CH₃D/CH₄ (dark green). Values for Saturn, Uranus, and Neptune are shown for comparison. Deuterium fractions in various relevant environments are given as follows (from top to bottom): terrestial (dark-blue bar), represented by the Vienna standard mean ocean water (VSMOW, Gonfiantini et al. 1995); solar-wind derived (without and with corrections for protosolar ³He), orange-hatched area; high-z (violet bar); local ISM (gray-filled area). The latter comprises determinations by Linsky (1998) and, including interstellar dust, Linsky et al. (2006). For further references see main text.