Using observations of Earth's bow shock by the Magnetospheric Multiscale
mission, we show for the first time that active magnetic reconnection is
occurring at current sheets embedded within the quasi-parallel shock's
transition layer. We observe an electron jet and heating but no ion response,
suggesting we have observed an electron-only mode. The lack of ion response is
consistent with simulations showing reconnection onset on sub-ion timescales.
We also discuss the impact of electron heating in shocks via reconnection.