In his 1984 novel The Flight Of The
Dragonf ly, physicist and science-
fiction writer Robert Forward
suggested a solar-sail starship, to be
built at and launched from Mercury:
“a Solar-System-wide machine that
would toss [the crew] to the stars on
a beam of light”. At the core of
Forward’s propulsion system is a set
of 1,000 laser stations, each 30km
wide, in orbit around Mercury.
These together capture solar energy
into laser beams with a combined
total power of 1300TW, equivalent
to about 1 per cent of all the sunlight
intercepted by Earth, and blasted at a
sail a thousand kilometres across.
But Mercury’s future may hold
greater miracles yet. Could we turn
it into a second Earth?
Terraforming, the art of turning
an uninhabitable world into a
habitable copy of Ear th, is usual ly
considered in the context of Mars.
Mars has a similar orbit to Earth’s, a
similar length of day, and at least
some of the necessities for life in
water and carbon. But Mercury does
have some natural advantages, even
over Mars. That relatively strong
gravity would enable it to hold on to
at least some of an impor ted
atmosphere. And Mercury has a
comparatively strong magnetic field- less than Earth’s, but stronger than
that of Mars or Venus, perhaps a
product of its huge iron core. Just as
on Earth, such a field would help
def lect harmful solar radiation from
the planet’s surface.
Otherwise, though, the challenge
of turning Mercury’s liquid-lead,
hard-vacuum surface into a
shirtsleeve environment seems
enormous. To emulate a sunny day
on Earth, the incident sunlight
would have to be reduced by some
84 per cent. Perhaps this could be
achieved with a huge def lecting
mirror – a sunscreen the size of
Mercury itself. Mercury lacks water
and other volatiles; even the polar
deposits would be a minor scrape in
this context. The dismantling of a
small moon of Saturn, perhaps
300km across, could supply this
need. Even then, imported terrestrial
life would suffer from Mercury’s
enormously long day-night cycle.
Perhaps this could be jury-rigged
using orbiting shields and mirrors.IN A SPIN
A more permanent but trickier
solution might be to spin up the planet,
so that it rotates more quickly. And in
the same spirit, the sunlight issue could
be solved simply by dragg ing the
planet further from the Sun. Such
schemes have been considered in sci-fi
literature, by shooting massive objects- the fragments of moons perhaps –
past the planet to use their gravitational
fields to spin or drag it. A much more
advanced culture than ours may have
better ideas in the future.
Mercury, a Moon-like world
spinning close to the Sun, seems a
dismal candidate for terraforming.
But such is Mercury’s potential
wealth in minerals and energy, and
such is the pivotal role it may one day
play in the development of an
interplanetary, or even interstellar
civilisation, that perhaps such a
project will be considered by a future
society inconceivably richer and
more powerful than our own. ß
STAGE 3
SCIENCE