  We have studied the conditions of through passage of asteroids with diameters
200, 100 and 50 m, consisting of three types of materials -- iron, stone and
water ice across the Earth's atmosphere with the minimum trajectory altitude
10--15 km. The conditions of this passage with subsequent exit into outer space
with the preservation of a substantial fraction of the initial mass have been
found. The results obtained support our idea explaining one of the
long-standing problems of astronomy -- the Tunguska phenomenon which has not
received reasonable and comprehensive interpretations to date. We argue that
Tunguska event was caused by an iron asteroid body, which passed through the
Earth's atmosphere and continued to the near-solar orbit.
