  We report the discovery of a double ring structure in the waist of the nebula
surrounding eta Carinae. The rings are detected in the mid-IR dust continuum at
wavelengths of 7.9, 11.9, 12.9 and 20 micronmeter. The dust in the rings has a
temperature of about 300 K. The orientation of the rings is inclined with
respect to the axis of the homunculus by either 37 or 58 degrees. The central
star is not in the projected centre of the structure defined by the two rings.
This geometry is reminiscent of that seen in SN1987A and some planetary
nebulae. We discuss several possible origins for this remarkable geometry and
its orientation.
