A trough observed in the free-air gravity of Mars along the edge of Tempe Terra has been interpreted as a large channel that has been completely buried by sediments. Here, we show that this trough is likely real and not a product of ringing in a truncated harmonic expansion, but that it is poorly resolved. A detailed examination of the high-resolution topographic data displays no evidence for a buried channel, instead showing that the trough straddles the highlands-lowlands boundary. As an alternative, we propose this gravity trough in a large way arises from the surface topography, due to an effect that occurs when there exists a relatively sharp boundary on a long-wavelength, partially compensated feature.