  The Sun exhibits a depletion in $^{17,18}$O relative to $^{16}$O by 6 %
compared to the Earth and Moon$^{1}$. The origin of such a non-mass-dependent
isotope fractionation has been extensively debated since the
three-isotope-analysis$^{2}$ became available in 1970's. Self-shielding$^{3,4}$
of CO molecules against UV photons in the solar system's parent molecular cloud
has been suggested as a source of the non-mass-dependent effect, in which a
$^{17,18}$O-enriched oxygen was trapped by ice and selectively incorporated as
water into planet-forming materials$^{5}$. The truth is that the Earth-Moon and
other planetary objects deviate positively from the Sun by ~6 % in their
isotopic compositions. A stunning exception is the magnetite/sulfide
symplectite found in Acfer 094 meteorite, which shows 24 % enrichment in
$^{17,18}$O relative to the Sun$^{6}$. Water does not explain the enrichment
this high. Here we show that the SO and SO$_2$ molecules in the molecular
cloud, ~106 % enriched in $^{17,18}$O relative to the Sun, evolved through the
protoplanetary disk and planetesimal stages to become a sulfuric acid, 24 %
enriched in $^{17,18}$O. The sulfuric acid provided a cryofluid environment in
the planetesimal and by itself reacted with ferric iron to form an amorphous
ferric-hydroxysulfate-hydrate, which eventually decomposed into the symplectite
by shock. We indicate that the Acfer-094 symplectite and its progenitor,
sulfuric acid, is strongly coupled with the material evolution in the solar
system since the days of our molecular cloud.
