  We study the morphologies of core collapse supernova remnants (CCSNRs) and
find that about third of CCSNRs in our sample have two opposite `ears'
protruding from their main shell. We assume that the ears are formed by jets,
and argue that these properties are compatible with the expectation from the
explosion jet feedback mechanism (JFM). Based on previous studies of ears in
CCSNRs and the similarity of some ears to those found in planetary nebulae, we
assume that the ears are inflated by jets that are launched during the
explosion, or a short time after it. Under simple geometrical assumptions we
find that the extra kinetic energy of the ears is in the range of 1 to 10
percents of the explosion energy. As not all of the kinetic energy of the jets
ends in the ears, we estimate that the typical kinetic energy in the jets that
inflated the ears, under our assumptions, is about 5 to 15 percents of the
explosion energy. This study supports a serious consideration of jet-driven
core-collapse supernova mechanisms.
