Evidence is mounting that a significant fraction of the early-type galaxy population contains substantial reservoirs of cold interstellar gas and dust .
We investigate the gas and dust in NGC 5485 , an early-type galaxy with a prominent minor-axis dust lane .
Using new Herschel PACS and SPIRE imaging data , we detect 3.8 \times 10 ^ { 6 } ~ { } M _ { \odot } of cool interstellar dust in NGC 5485 , which is in stark contrast with the non-detection of the galaxy in sensitive H i and CO observations from the ATLAS ^ { \text { 3 D } } consortium .
The resulting gas-to-dust ratio upper limit is M _ { \text { gas } } / M _ { \text { d } } < 14.5 , almost an order of magnitude lower than the canonical value for the Milky Way .
We scrutinize the reliability of the dust , atomic gas and molecular gas mass estimates , but these do not show systematic uncertainties that can explain the extreme gas-to-dust ratio .
Also a warm or hot ionized gas medium does not offer an explanation .
A possible scenario could be that NGC 5485 merged with an SMC-type metal-poor galaxy with a substantial CO-dark molecular gas component and that the bulk of atomic gas was lost during the interaction , but it remains to be investigated whether such a scenario is possible .