  We present results and an analysis of a ROSAT PSPC pointed observation of the
galaxy cluster CL0939+472. This very rich and very distant cluster is known to
contain an unusually high fraction of blue and E+A galaxies, and a lot of
merging of galaxies is going on. The X-ray properties we find are also quite
unusual. The luminosity in the ROSAT band (0.1-2.4 keV) is $L_X = (6.7\pm 0.3)
\times 10^{44}$erg/s, rather on the low side for such a rich cluster. We find a
temperature of 2.9$_{-0.8}^{+1.3}$ keV, which is also relatively low, but has
also a large uncertainty. The cluster shows indications of substructure, which
results in a high value for the core radius and a steep drop off outside the
core, if one fits a spherically symmetric $\beta$-model. The lower limit on the
mass inside a radius of $1.0 h_{50}^{-1}$Mpc is $2.6 \times 10^{14} \msol$, and
the upper limit on the gas mass fraction is 50\%. All the unusual properties of
this cluster can be explained if in fact we see the merging of two clusters of
roughly equal mass, which is also supported by recent optical observations.
