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Could we really terraform Mars?
By Paul Sutter about 12 hours ago

Don't hold your breath.

Illustration of the terraforming of Mars, to a world not unlike ours.
(Image credit: Daein Ballard, CC BY-SA)

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron
Institute, host of Ask a Spaceman and Space Radio, and author of How to
Die in Space.

Almost every sci-fi story begins (and sometimes ends) with the
terraforming of Mars to turn it into a more hospitable world.

But with its frigid temperatures, remoteness from the sun and general
dustiness, changing Mars to be more Earth-like is more challenging than
it seems (and it already seems pretty tough).

Incredible technology: How to use 'shells' to terraform a planet

(Video avaliable)

A dead world
The thing is, Mars used to be cool. And by cool, I mean warm. Billions
of years ago, Mars had a thick, carbon-rich atmosphere, lakes and oceans
of liquid water, and probably even white fluffy clouds. And this was at
a time when our sun was smaller and weaker, but occasionally much more
violent than it is today — in other words, our solar system is a much
more favorable place for life now than it was 3 billion years ago, and
yet Mars is red and dead.

Sadly, Mars was doomed from the start. It's smaller than Earth, which
means it cooled off much faster. The core of our planet is still molten,
and that spinning blob of iron-rich goo in the center of Earth powers
our strong magnetic field. The magnetic field is a literal force field,
capable of stopping and deflecting the solar wind, which is a
never-ending stream of high-energy particles blasting out of the sun.

When Mars cooled off, its core solidified and its magnetic force field
shut off, exposing its atmosphere to the ravages of the solar wind. Over
the course of 100 million years or so, the solar wind stripped away the
Martian atmosphere. When the air pressure dropped to near-vacuum, the
oceans on the surface boiled away and the planet dried up.

It's so tantalizing: Mars was once Earth-like, and so is there any way
to bring it back to its former glory?

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Polar opposites
Thankfully (or unfortunately, depending on your point of view), we
humans have plenty of experience in warming up planets. Inadvertently,
through our centuries of carbon emissions, we've raised the surface
temperature of Earth through a simple greenhouse mechanism. We pump out
a lot of carbon dioxide, which is really good at letting sunlight in and
preventing thermal radiation from escaping, so it acts like a giant
invisible blanket over Earth.

The increased heat encourages moisture to leave the oceans and play
around as a vapor in the atmosphere, which adds its own blanketing
layer, adding to the increase in temperature, which evaporates more
water, which warms the planet more, and before you know if prime
beachfront property is now better suited as an underwater submarine base.

But if it works on Earth, maybe it could work on Mars. We can't access
the OG Martian atmosphere, because it's completely lost to space, but
Mars does have enormous deposits of water ice and frozen carbon dioxide
in its polar caps, and some more laced just underneath the surface
across the planet.

If we could somehow warm the caps, that might release enough carbon into
the atmosphere to kick-start a greenhouse warming trend. All we would
need to do is kick back, watch and wait for a few centuries for physics
to do its thing and turn Mars into a much less nasty place.

Unfortunately, that simple idea probably isn't going to work.

Related: What would it be like to live on Mars?

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Radical ideas
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The first issue is developing the technology to warm the caps. Proposals
have ranged from sprinkling dust all across the poles (to make them
reflect less light and warm them up) to building a giant space mirror to
put some high-beam action on the poles. But any ideas require radical
leaps in technology, and a manufacturing presence in space far beyond
what we are currently capable of (in the case of the space mirror, we
would need to mine about 200,000 tons of aluminum in space, whereas we
are currently capable of mining … well, zero tons of aluminum in space).

And then there's the unfortunate realization that there isn't nearly
enough CO2 locked up in Mars to trigger a decent warming trend.
Currently Mars has less than 1% of the air pressure on Earth at sea
level. If you could evaporate every molecule of CO2 and H2O on Mars and
get it into the atmosphere, the Red Planet would have … 2% of the air
pressure on Earth. You would need twice as much atmosphere to prevent
the sweat and oils on your skin from boiling, and 10 times that much to
not need a pressure suit.

Let's not even talk about the lack of oxygen.

To counter this lack of easily accessible greenhouse gases, there are
some radical proposals. Maybe we could have factories devoted to pumping
out chlorofluorocarbons, which are a really nasty greenhouse gas. Or
maybe we could shove in some ammonia-rich comets from the outer solar
system. Ammonia itself is a great greenhouse blanket, and it eventually
dissociates into harmless nitrogen, which makes up the bulk of our own
atmosphere.

Assuming we could overcome the technological challenges associated with
those proposals, there's still one major hurdle: the lack of a magnetic
field. Unless we protect Mars, every molecule that we pump (or crash)
into the atmosphere is vulnerable to getting blasted away by the solar
wind. Like trying to build a pyramid from desert sand, it's not going to
be easy.

Creative solutions abound. Maybe we could build a giant electromagnet in
space to deflect away the solar wind. Maybe we could girdle Mars with a
superconductor, giving it an artificial magnetosphere.

Naturally, we don't have nearly the sophistication to realize either of
those solutions. Could we ever, possibly, terraform Mars and make it
more hospitable? Sure, it's possible — there's no fundamental law of
physics getting in our way.

But don't hold your breath.

Learn more by listening to the episode "Could we really terraform Mars?"
on the Ask A Spaceman podcast, available on iTunes and on the Web at
http://www.askaspaceman.com. Ask your own question on Twitter using
#AskASpaceman or by following Paul @PaulMattSutter and
facebook.com/PaulMattSutter.

Paul Sutter
Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron
Institute in New York City. Paul received his PhD in Physics from the
University of Illinois at Urbana-Champaign in 2011, and spent three
years at the Paris Institute of Astrophysics, followed by a research
fellowship in Trieste, Italy, His research focuses on many diverse
topics, from the emptiest regions of the universe, to the earliest
moments of the Big Bang, to the hunt for the first stars. As an "Agent
to the Stars," Paul has passionately engaged the public in science
outreach for several years. He is the host of the popular "Ask a
Spaceman!" podcast, author of "Your Place in the Universe" and "How to
Die in Space," and frequently appears on TV.

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