Final answer:
The statement is true; Mars's red color is due to iron oxides, and its weak magnetic field suggests the absence of a molten core capable of generating a global magnetic field.
Step-by-step explanation:
The statement that the red color of the Martian surface testifies to the presence of lots of iron, and that the weak magnetic field suggests it may not have a molten core anymore, is true. Mars is indeed known for its red hue caused by iron oxides in the soil. Moreover, the lack of a global magnetic field on Mars, despite there being areas of strong surface magnetization, indicates that there used to be a magnetic field billions of years ago, likely generated by a molten metallic core similar to what the Earth currently has.
However, the planet's current lack of a global magnetic field implies that it no longer has a molten core capable of creating such a field. As metals such as iron are magnetic and can sustain a magnetic field, the absence of such a field suggests that any metallic core present is not in a liquid state.