  We combined deep Chandra, ROSAT HRI, and XMM-Newton observations of M87 to
study the impact of AGN outbursts on its gaseous atmosphere. Many X-ray
features appear to be a direct result of repetitive AGN outbursts. In
particular, the X-ray cavities around the jet and counter jet are likely due to
the expansion of radio plasma, while rings of enhanced emission at 14 and 17
kpc are probably shock fronts associated with outbursts that began
1-2\times10^7 years ago. The effects of these shocks are also seen in
brightenings within the prominent X-ray arms. On larger scales, ~50 kpc from
the nucleus, depressions in the surface brightness may be remnants of earlier
outbursts. As suggested for the Perseus cluster (Fabian et al.), our analysis
of the energetics of the M87 outbursts argues that shocks may be the most
significant channel for AGN energy input into the cooling flow atmospheres of
galaxies, groups, and clusters. For M87, the mean power driving the shock
outburst, 2.4\times 10^{43} ergs/sec, is three times greater than the radiative
losses from the entire ``cooling flow''. Thus, even in the absence of other
energy inputs, outbursts every 3\times10^7 years are sufficient to quench the
flow.
