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.
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