  A fundamental puzzle of our solar system's formation is understanding why the
terrestrial bodies including the planets,comets,and asteroids are depleted in
$^{16}$O compared to the Sun. The most favored mechanism,the selective
photodissociation of CO gas to produce $^{16}$O depleted water,requires finely
tuned mixing timescales to transport $^{16}$O depleted water from the cold
outer solar system to exchange isotopically with dust grains to produce the
$^{16}$O depleted planetary bodies observed today. Here we show that energetic
particle irradiation of SiO$_2$ (and Al$_2$O$_3$) makes them susceptible to
anomalous isotope exchange with H$_2$O ice at temperatures as low as 10 K. The
observed magnitude of the anomalous isotope exchange (D$^{17}$O) is sufficient
to generate the $^{16}$O depletion characteristic of the terrestrial bodies in
the solar system. We calculated the cosmic-ray exposure times needed to produce
the observed $^{16}$O depletions in silicate (SiO2) dust in the interstellar
medium and early solar system and find that radiation damage induced oxygen
isotope exchange could have rapidly (~10-100 yrs) depleted dust grains of
$^{16}$O during the Sun's T-Tauri phase. Our model explains whythe oldest and
most refractory minerals found in the solar system, the anhydrous Calcium with
Aluminum Inclusions (CAIs),are generally $^{16}$O enriched compared to
chondrules and the bulk terrestrial solids and provides a mechanism for
producing $^{16}$O depleted grains very early in the solar system's history.
Our findings have broad implications for the distribution of oxygen isotopes in
the solar system, the interstellar medium, the formation of the planets and its
building blocks as well as the nature of mass-independent isotope effects.
