  It has previously been argued that 1. spicules do not provide enough
pre-heated plasma to fill the corona, and 2. even if they did, additional
heating would be required to keep the plasma hot as it expands upward. We here
address the question of whether spicules play an important role by injecting
plasma at cooler temperatures ($< 2$ MK), which then gets heated to coronal
values at higher altitudes. We measure red-blue asymmetries in line profiles
formed over a wide range of temperatures in the bright moss areas of two active
regions. We derive emission measure distributions from the excess wing
emission. We find that the asymmetries and emission measures are small and
conclude that spicules do not inject an important (dominant) mass flux into the
cores of active regions at temperatures $> 0.6$ MK ($\log T > 5.8$). These
conclusions apply not only to spicules, but to any process that suddenly heats
and accelerates chromospheric plasma (e.g., a chromospheric nanoflare). The
traditional picture of coronal heating and chromospheric evaporation appears to
remain the most likely explanation of the active region corona.
