the large uncertainties involved in this problem. For example, most recently Mezzacappa et al.[@mezz00] claimed that they can successfully simulate a 13$M_\odot$ supernova explosion with the exact Boltzmann neutrino transport, without invoking convection. Thus the question whether strange stars are “obliged” to be formed during the supernova explosions remains open. The aim of this paper is to explore the possible consequences of the assumption that strange stars are the final products, and such consequences could be tested by the observations and in turn, shed light on the plausibility of the scenario itself.

Newborn strange stars: crusts or not?
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There are two kinds of strange stars discussed in the literatures, i.e., the strange stars with crusts composed of normal matter and the bare strange stars (strange stars with bare quark surfaces). Normal matter crusts above the bare quark surfaces of the strange stars were raised by Alcock et al.[@afo86] in their pioneering paper. However, they did not discuss the formation of such crusts, but simply addressed that the universe is a “dirty” environment. Glendenning & Weber[@gw92] discussed the maximum crust mass, $\Delta M\sim 10^{-5}M_\odot$ (later corrected to $\Delta M\sim
3\times 10^{-6}M_\odot$ by Huang & Lu[@hl97]), a strange star can sustain, 