10 / 56
SECOND LARGEST METEORITE
DISCOVERED IN ARGENTINA
The second largest meteorite ever found was
finally unearthed this September in Argentina.
The El Gancedo fragment of the Campo del
Cielo (Field of the Skies) meteorite has lain
undiscovered over 2m deep under the edge
of its 60m wide crater for over 5000 years.
Weighing in at over 30 tons, it is second only
to the giant Hoba meteorite in Namibia which
tips the scales at more than 66 tons.
El Gancedo, composed of 93% iron and 7%
nickel, was formed at the metallic centre of a
large asteroid between the orbits of Mars and
Jupiter from left over material when the other
planets formed about 4,500 million years ago.
Random collisions between asteroids
occasionally knock one out of its stable
orbit and send it on a collision course with
the Earth. We then run into these fragments
that are travelling at speeds up to 30km per
second. While most of the more than 300
tons of this dust or sandy material arriving
every day just burns up harmlessly in our
atmosphere, a few larger pieces such as
El Gancedo do occasionally make it to the
ground. It is only a small part of the estimated
100t of asteroid landing on that fateful day
5,000 years ago at Campo del Cielo.
CHELYABINSK METEORITE 2013
Some readers may remember the 2013 arrival
of a 20m asteroid fragment that streaked
over the city of Chelyabinsk in Russia at a
shallow angle. Many images were captured
at the time on dashcams and cellphones (see
right). Had it come straight down it would
have destroyed that city of 1 million people.
So even small bodies can be extremely
dangerous to us and nobody saw this
particular one coming!
CAN WE PROTECT OURSELVES?
The answer is yes… we live in amazing times.
For the first time in the Earth’s 4500 million
year history, a species is finally nearing the
time when it may be able to protect itself from
the kind of event that wiped out the dinosaurs.
In September NASA launched the Osiris-Rex
spacecraft on a 9 year mission to orbit and
carefully map the 250m asteroid Bennu. It will
arrive in 2018, eventually returning a small
sample to Earth for study in 2023.
Far left:
The El Gancedo meteorite fell to
Earth 5,000 years ago.
The 2013 Chelyabinsky asteroid captured at
left, streaked across the sky before crashing
through the ice (below). The surviving core
was recovered by divers.
The probe will closely monitor Bennu’s
gravitational field and, more importantly,
the effect the spacecraft’s own minute
gravity has on the asteroid. This is the first
test of the idea of the innovative ‘gravity
tractor’ method of deflecting an asteroid. If
we can detect these potentially dangerous
bodies many years or decades before they
are due to impact Earth the minute gravity
of a massive spacecraft parked alongside
the asteroid could move it just enough to
make it eventually miss us. There would
be no need to land on it or blow it up with
nuclear weapons Hollywood-style, as this
would just produce lots of smaller but still
extremely dangerous meteorite fragments.
Thanks to this new technology, the events
from the movie ‘Day After Tomorrow’ may
never come!
NOTE:
For those keen to actually see some
of the historic Campo del Cielo asteroid, a
1.5kg fragment of this metal now rests at
Kuaotunu and can be handled by guests at
Stargazers Astronomy Tours ... as can a tiny
piece of the 2013 Chelyabinsk meteorite.
10
COROMANDEL LIFE
SPRING/HOLIDAY 2016
We’re looking to the skies this season with Alastair Brickell,
astronomy buff and owner of Stargazers B&B and
Astronomy Tours in Kuaotunu.
THE SKY IS FALLING…
BOTH ON THE EARTH AND COMET 67P!
STARGAZERS