Bursts of triboluminescence (200 count s(-1) over ca. 1 s) were observed when 5 mt blocks of purified H2O ice (Th) at temperatures just below 0 degrees C were dropped into liquid nitrogen while viewed by a photon counter. The triboluminescence was neither quenched nor enhanced by oxygen. The spectrum contained a broad emission between 200 and 350 nm and another emission between 350 and 500 nm. We calculate that a photon counter in a space probe viewing the shadowed icy surface of an outer solar system body might be able to map mechanical stresses in the ice surface by measuring this triboluminescence.