scienceillustrated.com.au | 33test methods for bending or destroying the
threats, before they strike.
In the early 2020s, NASA hopes to send a
spacecraft to an asteroid to collect a
fragment of it. The Asteroid Redirect Mission
will, moreover, try to bend the asteroid’s path
by entering into an orbit beside it for months,
using its gravitational pull to push it. This will
be one of the first experiments with moving
an asteroid or comet away from its path.
ASTEROID WEAPONS ON STANDBY
If NASA learned about an asteroid heading
directly towards Earth today, it would take up
to five years to prepare and launch a craft to
try to prevent the collision. In many cases,
that would be too long, and so, NASA
recommends that the preparation time be
limited by always having the necessary
weapons on standby.
In some cases, asteroids and comets
however strike so suddenly that we cannot
prevent it. If the authorities only have a few
days or weeks, it is a question of calculating
the impact site so accurately that all affected
people can be evacuated in time. Hundreds of
thousands or millions of wounded and
displaced people reSquire emergency hospitals
and temporary living quarters of an unknown
scale, and infrastructure such as electricity
grids and roads must be reconstructed as
quickly as possible. Such major operations
require different national and global emergency
management than what we have today.
“It is highly unlikely that we will see an
impact of the kind which destroys civilizations
in the next couple of centuries, but the risk of
smaller, but still disastrous impacts is a real
one, and we do not have a complete strategy
for handling such an event at this point,” NASA
says in its strategy plan.
The introduction of the seven stages is
hence only the first step on the way towards
avoiding the feared scenario. Although Earth
has been spared in recent history, events
elsewhere in the universe demonstrate that
the risk is still a real one.
As recently as in 1994, fragments of the
Shoemaker-Levy 9 comet measuring up to 2
km hit Jupiter, causing an energy discharge
corresponding to about 400 million Hiroshima
bombs. Perhaps Earth is the next one to come
under attack.
6
IMPROVE GLOBAL
COOPERATION 7EXPECT THE
UNEXPECTEDNASA will share
research results
concerning asteroids
and comets with
other space agencies to improve
detection, and divert threats
against Earth. The nations of the
world must prepare international
standard procedures for handling
asteroid impacts causing
considerable damage in more
than one country/continent.An asteroid or a
comet could appear
with only a few days’
warning or without
warning. The authorities must test
simulated asteroid impacts to be
prepared to handle the situation
when it occurs. All countries must
have standard procedures for
national and international crisis
communication, so people get
the best possible information.Size
Potential
damageActual
event Frequency20 m None or slight
damage to structures
and people.The asteroid, which
struck the Russian city
of Chelyabinsk in 2013.Once every
50 years.50 m Could destroy
a city completely.The Tunguska River
impact, Siberia, 1908.
The 50,000-year-old
US Barringer Crater.Once every
100-1,000 years.140 m Could destroy
an entire region.Once every
5,000 years.1 km Could destroy
an entire continent.Once every
1 million years.10 km Releases enough
energy to destroy
Earth's civilisation and
many animal species.The Chicxulub event,
when a 10 km
asteroid or comet
struck Earth 65 million
years ago.Once every
100 million years.A History of
Hammerblows
Asteroids and comets 20m to 10km have
struck Earth several times, creating neat
craters or wiping out 95% of all life.An asteroid explodes above CHELYABINSK ASTEROID
the city of Chelyabinsk, leaving
SPLa "tail" of vapour in the sky.