  The luminous unstable star (star system) eta Carinae is surrounded by an
optically bright bipolar nebula, the Homunculus and a fainter but much larger
nebula, the so-called outer ejecta. As images from the EINSTEIN and ROSAT
satellites have shown, the outer ejecta is also visible in soft X-rays, while
the central source is present in the harder X-ray bands. With our CHANDRA
observations we show that the morphology and properties of the X-ray nebula are
the result of shocks from fast clumps in the outer ejecta moving into a
pre-existing denser circumstellar medium. An additional contribution to the
soft X-ray flux results from mutual interactions of clumps within the ejecta.
Spectra extracted from the CHANDRA data yield gas temperatures kT of 0.6-0.76
keV. The implied pre-shock velocities of 670-760 km/s are within the scatter of
the velocities we measure for the majority of the clumps in the corresponding
regions. Significant nitrogen enhancements over solar abundances are needed for
acceptable fits in all parts of the outer ejecta, consistent with CNO processed
material and non-uniform enhancement. The presence of a diffuse spot of hard
X-ray emission at the S condensation shows some contribution of the highest
velocity clumps and further underlines the multicomponent, non-equilibrium
nature of the X-ray nebula. The detection of an X-ray ``bridge'' between the
northern and southern part of the X-ray nebula and an X-ray shadow at the
position of the NN bow can be attributed to a large expanding disk, which would
appear as an extension of the equatorial disk. No soft emission is seen from
the Homunculus, or from the NN bow or the ``strings''.
