Free_Astronomy_-_SeptemberOctober_2019

SMALL BODIES

be associated with the asteroid

have ever been found. Even if a sin-

gle crater unequivocally attributa-

ble to the ground impact of an

asteroid is never identified, studies

from a decade ago propose Lake

Cheko, located 8 km north of the

epicenter, as a probable site of fall

of a secondary fragment. This lake,

half a kilometer long and about

300 meters wide, does not seem to

have existed before 1908.

The very approximate knowledge

of the physical parameters of the

asteroid has never allowed for an

accurate description of the dynam-

ics of the Tunguska event; conse-

quently, all the forecasts made in

the past on the possible repetition

of such an occurrence were suspect

S

atellite views

of the vast

area affected by

the transit and

final explosion of

the Tunguska as-

teroid. Vanavara,

North-Northwest

of Lake Baikal,

was in 1908 the

nearest town to

the epicenter.

[Google Maps]

has undergone some significant updates.

The object that exploded in flight had to

be a small rocky asteroid (although the

cometary nucleus hypothesis has not been

entirely ruled out), with an initial diameter

between 30 and 60 meters, which traveled

at least 15 km/s and which produced an en-

ergy of 5 - 20 megatons, exploding at a

height between 5 and 10 km above the

ground. The explosion devastated a sur-

face are of over 2000 km^2 , destroying up-

to 80 million trees. No fragments that could

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