[math-fun] Size of the Cherbakul Lake Meteorite Fragment

From a National Post (newspaper) article today: "Viktor Grokhovsky, who led the expedition from Urals Federal University, said Monday the meteorites plucked from the ice-covered Chebarkul Lake so far are less than a centimeter and had an iron content of about 10 percent. Locals saw a big meteorite fall into the lake on Friday, leaving a six-meter-wide hole in the ice. Grokhovsky said a meteorite up to 50-60 centimeters could eventually be found in the lake." When the initial reports of the 6 m hole surfaced, I thought (looking at a picture of the hole in the ice): That must be a 4 m (or more) chunk of rock. But .5 m? An impact in a surface ice layer surely is not like an impact on ground where a wider hole might be expected.