[jcarreiro]

  > as I understand, if you could cool it down to an
  > acceptable temperature, you could walk on the surface
  > with just a breathing apparatus, right?

Sadly, probably not. Cooling it down is already a very tall order, and even then, you would need to find a way to remove most of the atmosphere in order to reduce the pressure (~90 atm at the surface).

Mars is a much better bet for human habitation in the short term. Chemically, it has all the ingredients we need to support human life. And it is much easier to build structures that can withstand the thin atmosphere (0.6 kPa) and relatively tame temperature range (-87 C to 63 C, all figures according to Wikipedia) than to build something that can survive the 9 MPa and 450 C on the surface on Venus.

[jlgreco]

I always kind of thought that Venus would be a neat place to preform "grey goo" experiments. Lots of matter and energy, and really the only thing you are going to do is make it a nicer place. Worse case is that it remains Venus.

[ekianjo]

Yeah, I remember Venus was sometimes called as the "other blue planet" but it was an actual Hell of a place to live in. Looking like Earth but nothing close to it that would make it inhabitable.

[yread]

> survive the 9 MPa and 450 C on the surface on Venus

not even mentioning the sulfur acid rains, lead sulfide snow and lack of magnetic field (cosmic rays penetrating atmosphere if it would be weakened)

[lerouxb]

Doesn't mars also lack a magnetic field?

[jcarreiro]

  > Doesn't mars also lack a magnetic field?

Yes, that's correct. There is no global dipole magnetic field on Mars [1]. However there are weak fields "frozen" into some of the oldest rocks on Mars [2], which indicates that the planet did have a global magnetic field at some point in its early history. Scientists think that the lack of a global magnetic field was part of the reason that Mars lost its atmosphere. [3]

For humans to settle on Mars and stay for any length of time, we will need to find a way to shield ourselves from the ionizing radiation that reaches the surface. [4] On Earth, most of this radiation is either deflected by the global magnetic field, or absorbed by the atmosphere.

[1] http://www-ssc.igpp.ucla.edu/personnel/russell/papers/mars_m...

[2] http://cmex.ihmc.us/data/catalog/TectonismonMars/Paleomagnet...

[3] http://science.nasa.gov/science-news/science-at-nasa/2001/as...

[4] http://en.wikipedia.org/wiki/Colonization_of_Mars#Radiation

[Xcelerate]

Although what about from a human health perspective? Can humans survive in a gravity that weak for a long time? What about animals?

[njharman]

What's long? a year? twenty?

And to answer that question and others is why we(humans) have bothered with Space Lab, Mir, IST. You can Google answer.

[Xcelerate]

No, I mean if humans were to colonize Mars -- would gravity make that process difficult?

[wang2bo2]

Definitely, with little gravity it could even be impossible for women to bear and give birth to a child

[freehunter]

I'm unfamiliar with how gravity factors into pregnancy and birthing. Do you have any further details on that?

[saraid216]

I found this: http://curious.astro.cornell.edu/question.php?number=702