QUESTION:
Is it possible to colonize mars to the extent that human beings could
live there?  If so, then how would you go about it?

ANSWER from R. Bourke on January 9, 1997:
It may be possible for people to live on Mars in the future, but they must
be protected from the environment.  Conditions on Mars are much more harsh
than any on Earth.  It is very cold--far below freezing--there is no water,
and the air is very thin and mostly carbon dioxide.  Thus people will not
be able to breath the air without space suits.  In fact, machinery must be
used to decompose the carbon dioxide to separate the oxygen to produce
breathable air.

ANSWER from Jack Farmer on January 30, 1997:
The colonization of Mars by humans is being thought of in terms of
"terraforming", which simply means modifying the Martian atmosphere and
climate to make the "red planet" habitable for life.

The Surface Environment of Mars: Cold, Dry and Full of Radiation
The present surface of Mars is an inhospitable place for any terrestrial
life form, whether microbe or person.  The atmospheric pressure averages
about 7.5 millibars (the avg. for Earth is 1000 mb).  This means that water
is unstable and can exist only as ice or vapor at the surface.  In
addition, the thin atmosphere of Mars is composed almost entirely of carbon
dioxide (95%) and it lacks the oxygen needed to support human colonists
without creating airtight shelters or spacesuits filled with our kind of
atmosphere.  The lack of oxygen also poses another risk. There is no
protective ozone shield and the surface gets a very heavy dose of
ultraviolet radiation (3-4X that at the Earth's surface).  We know that UV
is harmful to most life forms (that's why we have to use sunscreen!). As
far as we know, Mars lacks a magnetic field, and that means that lots of
other harmful radiation reaches the surface of Mars from the sun that, on
Earth, is deflected away from the surface by the magnetic field.  The
temperature of the Martian surface is below freezing most of the time over
most of the surface.  Lastly, Mars is very cold (mostly below freezing most
everywhere), but humans are able to live in cold climates on Earth, so that
is not an insurmountable problem.  However, combined with everything else,
it makes colonization a real challenge.

Building a Martian Atmosphere: An Oxygen-rich Greenhouse
Terraforming would involve increasing the atmospheric density of Mars by
liberating the water and carbon dioxide that lies frozen in the soils and
on the polar caps of Mars to create a "greenhouse" effect (carbon dioxide
and water both absorb heat energy from the sun and retain it causing the
atmosphere to warm up) that would raise the surface temperature to the
point where liquid water would be stable.  There are a number of ideas for
how to do that, but most involve installing large atmosphere-producing
plants on Mars that would pump out carbon dioxide and perhaps other
greenhouse gases like methane continuously until the atmiosphere was built
up to the right level.  Obviously, at some point we would also want to add
oxygen to make the atmosphere breathable.  On Earth, oxygen in our
atmosphere is almost entirely formed by photosynthesis of green plants.  So
during terraforming, sometime after water ahd been rendered stable by the
increased atmosphere, we would introduce photosynthesizing plants to
contribute oxygen.  What other benefit do you think oxygen would add, based
on the preceeding discussion? There are a number of people and approaches
that have been suggested for terraforming.

Additional Reading:
Some of these ideas were reviewed in a recent book by Robert Zubrin titled
"The Case for Mars: The Plan to Settle the Red Planet and Why We Must"
(1996, Free Press Publishing).

Jack D. Farmer, PhD.
NASA Ames Research Center

ANSWER from Mark Adler on June 20, 1997:
Yes.  But it won't be easy.  Mars is deathly cold (around minus 100 F), has
a very thin carbon dioxide atmosphere with almost no oxygen, and has no
ready supply of water.  You'd have to *really* want to live there.

A few people could be sustained on Mars with a steady line of supplies
coming from Earth.  In the long term, decades, we could find ways to provide
some of those supplies on Mars, allowing the small colony to become more and
more self-sufficient over time, and to possibly even grow.  It would be a
very long time, perhaps a century or more, before a colony on Mars could be
completely independent.  On even longer time scales, a few centuries, some
people believe that we could change Mars globally to make it more hospitable
for people by somehow making the atmosphere thicker and warmer.

ANSWER from Mark Adler on July 29, 1997:
There is certainly the possibility of humans exploring Mars.  It's simply a
matter of the rather high cost.

Mars' atmosphere is extremely thin (less than 1/100th as thick as our
atmosphere), is composed mostly of carbon dioxide, and is very cold. In
short, Mars' atmosphere cannot support humans or other Earth life.

However, that does not mean that we cannot inhabit the planet someday. We
would need special enclosures to contain a warm, Earth-like atmosphere to
live in.  Mars' atmosphere of carbon dioxide and some nitrogen can be used,
with some machinery and electrical power, to create and replenish an
oxygen/nitrogen atmosphere in the enclosures. Water is a bit more of a
problem, but there may be solutions there as well.

Some people talk about actually changing Mars' atmosphere on a global scale
to make it thicker and warmer in order to make habitation easier This is
inspired in part by human's inadvertent but noticeable effect on Earth's
atmosphere.  However, it will likely be a long time before we have the
technology and sheer presence to make global changes on Mars.

Mark Adler