What feature of Jupiter might be discerned with slightly larger apertures if atmospheric conditions are steady?

Answer

Cloud bands and possibly the Great Red Spot.

While the four largest moons are visible even in small scopes, larger apertures allow for the possible discernment of the planet's cloud bands and, given stable air, the Great Red Spot.

What feature of Jupiter might be discerned with slightly larger apertures if atmospheric conditions are steady?
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