Abstract Hyperactive comets have high water production rates, with inferred sublimation areas of order the surface area nucleus. Comets 46P/Wirtanen and 103P/Hartley 2 are two examples this cometary class. Based on observations comet Hartley by Deep Impact spacecraft, hyperactivity appears to be caused ejection water-ice grains and/or water-ice-rich chunks nucleus into coma. These materials inc...