> 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" in

> 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_mag/ http://www-ssc.igpp.ucla.edu/personnel/russell/papers/mars_m... [2] http://cmex.ihmc.us/data/catalog/TectonismonMars/Paleomagnetism.html http://cmex.ihmc.us/data/catalog/TectonismonMars/Paleomagnet... [3] http://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/ http://science.nasa.gov/science-news/science-at-nasa/2001/as... [4] http://en.wikipedia.org/wiki/Colonization_of_Mars#Radiation http://en.wikipedia.org/wiki/Colonization_of_Mars#Radiation