  The spectra of the planetary nebula M1-42 is reanalysed using spectral
measurements made in the mid-infrared with the Spitzer Space Telescope. The aim
is to determine the chemical composition of this object. We also make use of
ISO, IUE and ground based spectra. Abundances determined from the mid- and
far-infrared lines, which are insensitive to electron temperature, are used as
the basis for the determination of the composition, which are found to
substantially differ from earlier results. High values of neon, argon and
sulfur are found. They are higher than in other PN, with the exception of
NGC6153, a nebula of very similar abundances. The high values of helium and
nitrogen found indicate that the second dredge-up and hot bottom burning has
occurred in the course of evolution and that the central star was originally
more massive than 4Msun. The present temperature and luminosity of the central
star is determined and at first sight may be inconsistent with such a high
mass.
