32
SMALL BODIESIt will therefore be
essential to con-
tinue and intensify
the search for
smaller and smaller
asteroids, until a
complete census of
those whose orbits
can intersect the
Earth’s orbit will be
available.
Many telescopes are
already engaged in
this type of survey
and others are
about to start oper-
ations both on the
ground and in orbit.
Also, the knowl-
edge of the struc-
ture and composi-
tion of the small
bodies of the Solar System is important
for a correct modeling of Tunguska-likeevents, and in this context, automatic mis-
sions such as Hayabusa and Rosetta are
crucial. No effort will be superfluous in the
attempt to avoid the only foreseeable and
predictable natural disaster.!deduced that if the Tunguska asteroid was
larger than previously believed, events of
this type must neces-
sarily be less frequent
than expected, since
the number of exist-
ing asteroids de-
creases as the diame-
ter increases.And, in
fact, combining the
results obtained by
the Ames models with
the most recent esti-
mates of asteroid pop-
ulations, researchers
concluded that the av-
erage interval be-
tween Tunguska-like
impacts should be on
the order of millennia
and not centuries, as
hypothesized in the
past. This data is cer-
tainly reassuring, but
since human beings al-
ready inhabit around 10 % of the Earth’s
surface, the probability that the next Tun-
guska event will occur above a built-up
area, with obvious consequences, is far
from negligible.L
ake Cheko is
the only prob-
able trace left by
a fragment of the
Tunguska aster-
oid. On the left, a
three-dimensional
computer simula-
tion of the lake
immediately after
the impact, recon-
structed based on
topography and
bathymetry data.
The water level is
kept about 40
meters lower
than actuality for
a better view of
the bottom
shape. [Institute
of Marine Sci-
ences, CNR]
Below is how it
looks today.
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