It might seem odd, but Mercury may
be a good site to m ine. If we move
off the Earth, a growing
interplanetary civilisation is going to
need resources, in terms of materials
and energy – and Mercury has
energy aplenty in the form of that
concentrated sunlight. To capture as
much energy as a square metre of
solar-energy cells on Mercury would
require six square metres on the
Earth – and 60 square metres at
Ceres, a dwarf planet that’s often
touted as a good candidate for
resource extraction.
RICH RESOURCES
As for the resources, there is strong
concern about the impact of mining
on Ear th, in ter ms of environmental
cost; plus, resources extracted from
Earth would be expensive to lift into
space. So it would be far better to
mine out there. That prospect may
be coming closer, with the
emergence of the Alliance for Space
Development, led by the US’s
National Space Society, to press for
legislation and initiatives to allow
development of space resources.
But where to mine? A first obvious
choice is the Moon. While the Moon
is deficient in volatiles like water, its
sur face is ful l of useful components
such as oxygen, calcium, magnesium,
potassium, even heavy metals like
titanium and aluminium. Mercury’s
mantle has pretty much the same
composition, and so techniques
developed on the Moon could easily
be transferred there. In addition, the
huge amount of solar energy received
by Mercury could be used to drive the
mining operations themselves, and for
firing packets of resources to sites
across the Solar System – perhaps using
‘mass drivers’. These electromagnetic
slingshots were first suggested by
Arthur C Clarke. It might be more
acceptable to mine remote Mercury
than to scar Earth’s Moon, plus
Mercury’s huge core – mostly iron, but
rich in other metals – is only 600km
down in some places, whereas the
Moon’s smaller core may be up to
1,400km down.
There are still more imaginative
schemes. All that sunlight could beused as a free propulsion system.
Imagine a solar sail, strong but thin,
perhaps built out of Mercury’s
alum inium. W hen sun light hits a
ref lecting surface, it exerts a pressure- as if the particles of light are
rebounding from the surface and
pushing it away. The effect is small,
but it’s useful, continuous and free. At
the distance of Earth, a sail measuring
800m across would receive a light-
pressure of about five newtons, which
is similar to the thrust of the low-drive
ion-propulsion engines used on
NASA’s Dawn spacecraft. And the
closer you get to the Sun, the greater
the thrust – at Mercury you would get
the same thrust with a sail measuring
less than half that diameter. If you
wished to r ide a solar sail to Neptune,
the most distant planet, it would be
better to pay a visit to Mercury first to
pick up the greater acceleration, and
then sail outwards.
Mercury may some day become
the shipyard and principal port of the
Solar System. And looking even
further into the future, there are
still bolder suggestions.
STAGE 2