One disadvantage to studying off-world planets is that we do not have an easy method for determining the interior of it. The explanations propounded by scientists today are based on facts and still some theory. Currently, they suggest that Mars is very much similar to Earth in respects to the presence of a thin crust, a mantle and a core.
To ascertain the size of the core in Mars, four figures need to be determined. Three of these parameters include the total mass, the size, and the moment of inertia. Based on information gathered by various methods, these facts have already been determined. However, the fourth parameter has not yet been acquired and so the size of the core in Mars has not yet been scientifically established.
Scientists speculate that if the inner core is composed primarily of sulfur and iron, the maximum radius will be no more than approximately 2000 kilometers across. Else, if the core is made of mainly iron, then the maximum radius would probably around 1300 kilometers.
In addition, scientists are now hoping to find evidence of life deeper in the crust of Mars. So far, all the missions to Mars has not yielded any truly conclusive evidence that life exists or had existed on the planet at one point or another. The Mars pathfinder mission viewed from this perspective has thus failed, but the search will continue...