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A handful of planetary scientists, aeronautical engineers and space
fanatics have a dream. A gargantuan vision. The concept is terraforming
– creating an environment like Earth on another world. The most likely candidate
for this daring engineering feat is Mars because it is close to Earth and
probably has the raw materials needed to carry out a task over 100 000 years
or so. However, some consider the very idea of a Martian metamorphosis a
dastardly environmental crime.

Once a popular science fiction theme, terraforming is now attracting
serious attention. Following calls for better funding and interest from
nearly one hundred scientists, at a recent conference on Mars exploration
in Boulder, Colorado, NASA plans to hold a conference devoted to terraforming
later this year.

¿ìè¶ÌÊÓƵs and science fiction writers alike have speculated about exploring
Mars, but any human visitor would find the environment hostile. Temperatures
plummet to below -100 °C, causing carbon dioxide to freeze and form
a white hoarfrost over the ochre deserts. A constant layer of dust colours
the sky pink. Violent storms sometimes cover the whole planet and the airborne
dust erodes the surface in winds of up to 200 kilometres per hour. The atmosphere,
at less than one hundredth of the atmospheric pressure on Earth, is so thin
that blood would boil without pressurised suits.

Changing atmosphere

Making Mars fit for humans is a mammoth task that terraformers have
divided into two phases. Chris McKay of the NASA Ames Research Center, whose
job is to investigate past, present and future life on Mars says the first
phase would raise the average surface temperature of Mars from the current
-60 °C to about 0 °C, allowing water to exist as liquid on parts
of the surface. The Martian atmosphere is around 95 per cent carbon dioxide,
3 per cent nitrogen and 2 per cent argon compared to Earth’s atmosphere
which is made up of 78 per cent nitrogen, 21 per cent oxygen and a 1 per
cent mixture of other gases such as argon. After between one and two hundred
years, this warmer and wetter Mars would be blanketed in a thicker atmosphere
at, perhaps, one-eighth of the atmospheric pressure on Earth.

In the second phase, estimated to take 100 000 years, organisms living
on water and trace elements, would use sunlight to remove CO₂
from the atmosphere. Over the same period, they would boost the oxygen
content to a level humans could breathe – a process that occurred on Earth
several billion years ago.

During the first phase, factories built on the surface of Mars would
play a large part in warming the planet by churning out greenhouse gases.
McKay says these gases would trap heat in the Martian atmosphere that would
otherwise escape into space. Terraformers would design the factories to
produce chlorofluorocarbons (CFCs), the same gases that contribute to the
destruction of the ozone layer on Earth, and their chemical cousins, perfluorides,
because they are composed of the elements carbon, fluorine and chlorine
which are known to exist as salts in Martian soil.

The factories would produce CFCs and other gases at a rate of 900 tonnes
per hour, using electrolytic and chemical methods used on Earth for decades.
The 4500 megawatts of electricity this process is expected to consume –
enough to power Boston – would be generated from solar or nuclear sources.
‘That’s a big operation, but it is not science fiction big,’ says Robert
Zubrin, a terraform specialist based in Denver at Martin Marietta, the US
aerospace company.

It might be possible to achieve extra warming by spreading soil from
the Martian surface over the polar caps to reduce the amount of solar energy
reflected into space, and by positioning giant mirrors in orbit around Mars
to direct sunlight towards the poles. The Martian polar caps are made of
frozen water and frozen CO₂ which would be released as the poles
melt.

The critical ingredient in the Martian terraforming recipe is another
greenhouse gas, CO₂. For the scheme to work, CO₂ must
be released from reserves trapped in the poles and the Martian soil as the
planet heats up. Unlike Earth, Mars is not expected to have any fossil fuel
reserves and, in any case, these could not be burnt easily to create CO₂
because of the lack of oxygen in the Martian atmosphere.

Thriving in the greenhouse

As a greenhouse gas, CO₂ accelerates the warming process,
liberating still more CO₂ in a positive feedback cycle. According
to calculations using models similar to those for the Earth’s climate, the
initial temperature increase would trigger a runaway greenhouse effect.
Zubrin and McKay, calculate that an artificial temperature rise of 4 °C
would eventually produce a 55 °C increase so that the average surface
temperature would be -5 °C – enough to allow water to flow across parts
of the surface. Human efforts would set the ball rolling, but nature would
perform 99.5 per cent of the work.

Plants might be able to grow on this world, but humans could not breathe
the oxygen-poor air. The increase in atmospheric pressure to around one-eighth
of Earth’s atmospheric pressure, however, would allow humans to travel on
the surface without pressurised suits. At this pressure it would be possible
to build inflatable, domed cities in which a breathable atmosphere could
be maintained. At lower pressures humans would have to live in pressurised,
air-tight buildings.

Natural resources on Mars are the chief stumbling block to the scheme.
According to McKay, terraforming becomes a dubious venture if Mars lacks
sufficient reserves of CO₂, water and nitrogen – molecules that
contain the elements considered most essential for life. The Mars Observer
satellite, which disappeared mysteriously last August, was supposed to have
provided some answers about water and CO₂ sup-plies. These answers
might come later this decade when other Observer missions are planned.

Nitrogen hunt

Neither the original Observer nor its successors have been designed
to take a thorough inventory of the Martian nitrogen reserves over which
hang the biggest question mark. The planet may have already lost most of
its nitrogen as molecules at the top of the atmosphere fly off into space.
Direct measurements of the concentration of nitrogen isotopes by the 1976
Viking spacecraft showed a significant amount of nitrogen had been lost
this way. Nitrogen may be hidden in the soil in the form of nitrates, as
is the case on Earth, but a Mars mission that can dig into the planet’s
surface will be needed before this mystery can be solved.

Hijacking ammonia-rich asteroids from the outer Solar System and then
smashing them into the Red Planet was proposed earlier this year by McKay
and Zubrin at a conference sponsored by the American Institute of Aeronatics
and Astronautics. The imp-act of an asteroid 2.6 kilometres in diameter,
guided towards Mars with nuclear-powered rocket engines, would produce the
same amount of energy as 70 000 megatonnes of explosives. Ammonia, which
would be released into the atmosphere is a potent greenhouse gas and could
raise the temperature by some 3 °C.

McKay is optimistic that terraforming could work on Mars. Three billion
years ago the planet was a more hospitable place with conditions similar
to those that gave rise to life on Earth. Pictures of the Martian surface
taken by the Viking spacecraft reveal dry riverbeds and an extensive network
of valleys and drainage patterns. These features, according to McKay, could
have been carved only by flowing water, which implies that temperatures
were once above freezing point. The atmosphere must also have been thicker
as water cannot exist in liquid form at very low pressures.

As McKay sees it, terraforming would help Mars revert to a previous
state rather than building a new atmosphere from scratch. ‘The important
point,’ he says, ‘is that we know how to warm a planet with greenhouse gases.
We’re doing it here at an alarming rate.’ He contends that greenhouse gases,
primarily water vapour and CO₂ with extra contributions from
methane, nitrous oxide and CFCs, keep our planet 30 °C warmer than
it would be otherwise.

James Kasting, a planetary scientist at Pennsylvania State University,
believes it might be possible to warm the surface of Mars, but he points
to many pitfalls. For one thing, CFCs survive for only about a hundred years
in the Earth’s atmosphere and would break down even faster on Mars because
of increased exposure to ultraviolet radiation. ‘To keep high enough concentrations
in the atmosphere, you’d have to manufacture this stuff at an extraordinary
rate and keep at it,’ he says. ‘Furthermore, it would be hard to figure
out how much you need. You can’t go from our experience here and scale it
up by a factor of a thousand or a million, because it’s not a linear extrapolation.
If you double the amount of gas in the atmosphere, you don’t double the
greenhouse warming. Unfortunately it’s a lot more complicated than that.’

Natural approach

In the long run, McKay admits that running factories for thousands of
years may not be ideal. Instead, he recommends using nature. ‘The only practical
tool for making Mars habitable is self-reproducing machines designed for
a specific job,’ he says. ‘These machines are called living microorganisms.’
McKay has in mind tiny creatures genetically engineered to produce greenhouse
gases. The notion is not as far-fetched as it seems since some forms of
oceanic plankton do produce methyl chloride, a greenhouse gas.

But doing this on a scale one million times bigger creates problems,
says Kasting. Methyl chloride survives only for a matter of months in the
Earth’s atmosphere and traps infrared radiation only at specific wavelengths.
The creatures would have to be engineered to produce a host of gases that
would absorb the entire spectrum of infrared radiation.

Technical uncertainties aside, there is also the question of funding.
A recent editorial in Space News, an international weekly newspaper covering
the space industry, argued that terraforming had languished in obscurity
for too long. ‘Terraforming ought to be more than a good subject for space
fanatics to debate over drinks,’ the paper maintained. ‘The idea is at least
as valuable as some of the other research NASA does (and is) worth spending
a modest amount of money on . . . perhaps a few million dollars.’

A Mars a day

Why is it worth investing in a futuristic concept like terraforming?
What advantages could we reap? One popular idea is that humans should start
preparing another home, a kind of Noah’s Ark, in case Earth becomes uninhabitable.
But McKay is cautious. ‘Even if Mars becomes the perfect paradise,’ he says,
‘we’ll never be able to move people there fast enough.’

The very existence of a Martian frontier could have a powerful impact
on society, according to Zubrin. ‘America created a new standard for the
treatment of humans,’ he says. ‘The same could be true with Mars, even
if just a handful of Earthlings go there.’

Zubrin contends that a couple of million dollars is peanuts for NASA.
With just a tiny fraction of the money it costs to launch a space shuttle,
he says, important studies and experimental research could be carried out.
¿ìè¶ÌÊÓƵs might design and test potent, new, artificial greenhouse gases,
for example – an activity that is not encouraged because these gases are
normally considered a nuisance. ‘Society could get five hundred times more
benefit from terraforming studies than from a shuttle flight costing five
hundred times more,’ Zubrin says.

Ultimately, knowledge may be the most important gain. Knowing how to
alter the climate of a planet is valuable, regardless of what we do on Mars,
says John Rummel, a scientist at NASA’s Washington headquarters. ‘Our studies
of Mars can give us clues about how planets work. That will help us figure
out what to do with Earth and keep us from doing the wrong things.’ This,
he says, was one of the main reasons for the space programme in the first
place. ‘Exploring the Solar System and investigating other planets gives
us some perspective in thinking about our own home.’

Realistically, could such a project ever reach fruition? If the experts
are right, the first stage of the terraforming agenda – creating a warmer
planet with some semblance of an atmosphere – might be accomplished within
two hundred years. Zubrin is optimistic. Although the challenge remains
fixed, he says, our ability to carry it out can only improve.

Steve Nadis is a science journalist.

* * *

The terrifying morality of terraforming

Assuming we can make Mars a more hospitable place, is it morally right
to change the climate of another planet? McKay believes that it depends
on whether life exists on Mars. If so, he says, we should do nothing to
harm the creatures there, though we might try to create a more comfortable
home for them.

But if Martian creatures still cling to life, argues Zubrin, they must
be primitive, such as bacteria. ‘Let’s get real,’ he says, ‘bacteria don’t
have rights. Would anyone hesitate to take antibiotics because of a fear
of killing billions of bacteria?’

Eugene Hargrove, editor of the US journal Environmental Ethics, disagrees.
‘If other life forms were found there, perhaps based on a different kind
of DNA, they would be considered so scientifically interesting it would
be unconscionable to destroy them.’ Besides, he says, our efforts to help
or manipulate ecosystems usually have unforeseen results. ‘The idea of trying
to manipulate another planet, without first demonstrating that we can reverse
the damage already inflicted on Earth, would have to be regarded as the
height of arrogance,’ he says.

McKay agrees to some extent. Given the dismal record of environmental
management on our planet, humans cannot be trusted to reshape Mars, he says.
‘Humans are almost certain to screw things up. The best engineer is the
biosphere itself. Life will develop in a way that enhances habitability.’

But leaving things alone seems to go against human nature. Hargrove
recalls a conference he sponsored a few years ago. One of the speakers,
a NASA official, stepped onto the podium, and said: ‘Mars is OK the way
it is, but Venus – now that place could use a lot of improvement.’