  To constrain the conditions for very early nucleosynthesis in the Universe we
compare the chemical enrichment pattern of an extremely metal-poor damped Lyman
alpha (DLA) absorber with predictions from recent explosive nucleosynthesis
model calculations. For this, we have analyzed chemical abundances in the DLA
system at z_abs=2.6183 toward the quasar Q0913+072 (z_em=2.785) using public
UVES/VLT high spectral resolution data. The total neutral hydrogen column
density in this absorber is logN(HI)=20.36. Accurate column densities are
derived for CII, NI, OI, AlII, SiII, and FeII. Upper limits are given for FeIII
and NiII. With [C/H]=-2.83, [N/H]=-3.84, and [O/H]=-2.47, this system
represents one of the most metal-poor DLA systems investigated so far. It
offers the unique opportunity to measure accurate CNO abundances in a
protogalactic structure at high redshift. Given the very low overall abundance
level and the observed abundance pattern, the data suggest that the chemical
evolution of this DLA system is dominated by one or at most a few stellar
generations. With reference to numerical model calculations, the chemical
abundances in the DLA system are consistent with an enrichment from a single
starburst of a zero-metallicity population of massive stars (10-50 M_sun)
exploding as core-collapse Supernovae (SNe), i.e., the classical Type II
Supernovae (SNeII), and possibly as hyper-energetic (E>10^51erg) core-collapse
Supernovae, so-called Hypernovae (HNe), as well. In contrast, models using
non-zero metallicity progenitors or other explosion mechanisms, such as
pair-instability Supernovae (PISNe) or Type Ia Supernovae (SNeIa), do not match
the observed abundance pattern.
