Newsademic British English edition 260

18th February 2016 
N ew sadem ic.com
™
 - British English edition 
page 
14
A
n tar c tic
 
m eteorites
Many meteorites have been found 
either in dry deserts or in Antarcti­
ca. This is because they are easier to 
spot in these places. Meteorites ei­
ther contain a small amount o f iron 
(rocky) or are mainly made o f iron 
(iron-rich). Researchers have been 
puzzled why nearly all meteorites 
found in Antarctica are rocky. Sci­
entists working at a UK university 
now think that they know why.
Searching fo r m eteorites in Antarctica (R Score)
Meteors are pieces o f space rock. 
They can be many different sizes. 
Meteors become very hot and burn 
up as they fall through the Earth’s 
atmosphere. If this happens after the 
Sun has gone down, a bright trail of 
light can be seen in the night sky. 
This is known as a ‘shooting star’. 
If a meteor falls to the surface o f the 
Earth before it has completely burnt 
up, it’s called a meteorite.
M ost meteorites originally came 
from the asteroid belt. This is be­
tween Mars and Jupiter. The aster­
oid belt is a region o f space where 
there are many bits o f rock, or rub­
ble. These were ‘leftover’ when the 
planets in our Solar System formed 
billions o f years ago. This ring, or 
belt, o f bits o f rock stretches all the 
way around the Sun. Pieces o f rock 
in the asteroid belt range from a 
few kilometres wide to the size o f a 
piece o f dust.
In the past large asteroids or space 
rocks hit the other rocky planets:
Mercury, Venus, and Mars. They 
also crashed into the Moon. The 
force o f these impacts threw rocks 
high up beyond the planet’s gravita­
tional field. M ost meteorites found 
on the Earth travelled from the aster­
oid belt. Yet some came from M er­
cury, Venus, Mars, and the Moon.
Meteorites that come from the 
asteroid belt are usually about four 
billion years old. This is because 
they cooled and turned into rock 
soon after the formation o f the Solar 
System. Mercury, Venus, Mars, and 
the Moon were volcanically active 
for far longer. So, meteorites from 
these places are much younger.
Large ice sheets cover Antarctica. 
Ice streams form part o f the ice sheets. 
They move towards the sea very slow­
ly. Meteorites that fall on Antarctica 
become buried in ice. They are carried 
towards the sea by the ice streams. 
This can take thousands o f years. 
Many meteorites that land in Antarc­
tica are therefore lost in the sea.
However, there are a few places 
where meteorites are gathered to­
gether by the ice streams. W hat’s 
more, they appear on top o f the ice. 
These places are known as ‘strand­
ing zones’. Antarctica is divided into 
East Antarctica and West Antarc­
tica. They are separated by a moun­
tain range called the Transantarctic 
Mountains. Some ice streams in 
East Antarctica meet this mountain 
range. Here, strong winds strip away 
the top layer o f ice. This exposes the 
meteorites. Thus, over thousands of 
years, hundreds o f meteorites can 
collect at the stranding zones.
The scientists think that there 
are many iron-rich meteorites at 
these stranding zones, but they are 
under the ice. They set up an experi­
ment. The scientists froze a rocky 
and an iron-rich meteorite inside a 
big block o f ice. Both were about
the same size. A lamp above the 
ice block acted like the Sun. The 
iron-rich meteorite absorbed more 
heat than the rocky one. It therefore 
slowly sank deeper into the ice.
The scientists believe that the 
ice streams take many iron-rich 
meteorites to the stranding zones. 
Yet as the wind strips away the ice, 
these meteorites are warmed by the 
Sun. Then, they sink back into the 
ice. If the scientists are right, there 
could be a layer o f iron-rich me­
teorites about 75 centimetres (30 
inches) below the ice at the strand­
ing zones. The scientists now plan 
to use metal detectors to look for 
them. □
W