The SBS 0335-052 system is a very peculiar object: it is comprised of two
extremely metal deficient starburst dwarfs, one, the blue compact dwarf SBS
0335-052 itself with Z~Z_sun/41 is the second most metal deficient object in the
universe, and the other at Z~Z_sun/31 is a more evolved dwarf irregular. Both
objects are embedded in a single huge HI cloud (64 kpc by 24 kpc) which is very
likely to be primordial: our GHRS/HST spectrum show no OI absorption implying an
oxygen abundance at least 3000 times lower than in Orion. This system is
probably our best and closest example of the earliest stages of galaxy
evolution.
We propose here to study the properties of its interstellar medium (dust and
gas) to gain insights into the physical processes involved in galaxy formation.
From the spectral energy distribution in the mid-infrared, we will determine (1)
what is the dust composition, (2) what is its excitation state and (3) are
energy exchanges between stars and dust significantly effected by the low
metallicity.  FIR photometry will reveal (4) what is the dust-to-gas ratio in
very metal-deficient environments and (5) Is the abundance of the dust large
enough to explain the lack of Ly alpha emission in SBS 0335--052?  Finally,
with the photodissociated [CII] line, we will assess (6) what is the amount of
molecular material present in SBS 0335-052 and constrain the minimum fraction
needed to start a significant starburst.