= Solution
<Helium> becoming partially immiscible in dense <hydrogen> can form helium-rich droplets that settle inward. <Gravitational energy> release and associated thermal evolution can supply extra <luminosity>, while the upper <hydrogen> envelope becomes <helium> depleted. Different interior temperature-pressure histories can make separation stronger in Saturn than in Jupiter.
\b[The source's ratio is reversed for this intended explanation.] Depleting <helium> lowers He/H and raises H/He. For a concrete example, keeping ten <hydrogen> units while reducing one <helium> unit to one half changes H/He from ten to twenty, not to a lower value. Thus the literal statement that Saturn has \i[lower H/He] cannot simultaneously be used as evidence for the stated upper-envelope helium-depletion mechanism. If the intended comparison is lower He/H, the observations and extra <heat> are mutually consistent with <helium> rain. Composition measurements and interior modeling are still needed; excess <heat> alone does not uniquely prove that process.<Cassini mission press kit by NASA>[Background on Saturn: helium-to-molecular-hydrogen ratio and helium migration as a heat source]{ref}
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