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Explained in
60 Seconds
Explained in 60 Seconds: Why Visit a Comet?
Emily Baldwin
EJR-Quartz for European Space Agency (ESA)
[email protected]
Space exploration, Solar System formation,
comets, Rosetta
Blazing across the night sky, comets have
captured people’s imaginations for centuries. Once considered harbingers of doom,
we now know them to be priceless treasure
troves of dust and ice with the secrets of
the early Solar System locked within.
The Solar System was a chaotic place
4.6 billion years ago, but from tiny dust and
ice particles to colliding boulders and swirling gas, the planets eventually took shape.
Comets, the leftover detritus in this planetary construction yard, were banished to
the cold outer reaches of the Solar System.
But, as the planets slowly settled into the
orbits we see today, huge gravitational perturbations sent showers of comets through
our cosmic neighbourhood, slamming into
planets and moons, and leaving impact
scars that are visible on their rocky surfaces even today.
As well as bringing destruction, comets
are thought to have ferried some of the
key ingredients that are needed for life as
we know it on Earth; perhaps even complex organic molecules and water.
As they approach the Sun, the increasing
heat slowly warms their surfaces, turning
ice into vapour and dragging out dust to
form the beautiful tails seen from Earth.
Occasionally, unpredictable and dramatic
outbursts reveal material from within the
comet’s interior, opening a window onto
the processes that drove the evolution of
the early Solar System.
While today our corner of the Universe is,
fortunately, a lot quieter, these frozen time
capsules are still occasionally jolted into
new orbits that slingshot them closer to the
Sun. Many meet a fiery death and ­others are
flung clear of the Solar System, but some
become trapped in elliptical orbits that see
them returning time and time again.
By investigating a comet up close — from
orbit and from its surface — and living
with it for two years, the Rosetta mission
is ­giving us an unprecedented opportunity to study the behaviour of these once
­mysterious worlds, and to better understand the role that they may have played
in our origin.
Figure 1. Comet 67P/Churyumov–Gerasimenko pictured by ESA’s navigation camera, NavCam, on 11 September 2015. Rosetta was 319 kilometres from the centre of the
comet at this time. Credit: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0
CAPjournal, No. 19, March 2016