  We revisit the XMM-Newton observation of M87 focusing our attention on the
temperature structure. We find that spectra for most regions of M87 can be
adequately fit by single temperature models. Only in a few regions, which are
cospatial with the E and SW radio arms, we find evidence of a second
temperature. The cooler component (kT ~ 0.8-1 keV) fills a small volume
compared to the hotter component (kT ~ 1.6-2.5 keV), it is confined to the
radio arms rather than being associated with the potential well of the central
cD and is probably structured in blobs with typical sizes smaller than a few
100 pc. Thermal conduction must be suppressed for the cool blobs to survive in
the hotter ambient gas. Since the cool gas is observed only in those regions of
M87 where we have evidence of radio halos our results favor models in which
magnetic fields play a role in suppressing heat conduction. The entropy of the
cool blobs is in general smaller than that of the hot phase gas thus cool blobs
cannot originate from adiabatic evolution of hot phase gas entrained by buoyant
radio bubbles, as suggested by Churazov et al. (2001). An exploration of
alternative origins for the cool gas leads to unsatisfactory results.
