So just what does this picture show us?

An interferogram is a pattern of light and dark produced when light waves interfere with each other. Waves in phase (peaks coincide) reinforce each other to form bright spots. Waves out of phase (the peak of one coincides with the valley of another) cancel each other to form dark spots.

The bands you see in the two images here represent differences in the indices of refraction of the two fluid cells in Chuck. Those differences were caused by heating one fluid and not the other, so in effect the bands depict changes in density.

The Earth-based test shows turbulence which one would expect with gravity causing convection. The space-based test shows a single region of warm (lower density) fluid expanding outward as heat is transferred by diffusion and conduction.

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