Sun is our need to find inner self-fulfillment, a comfortable sense of ourselves.
The sign it is in indicates what style of behavior enhances this inner wholeness, and the house Sun is in indicates where we look, in life, to enhance our inner wholeness.
How easy or difficult this is to accomplish, how well or poorly we take action towards self-fulfillment, THIS depends on how Sun "aspects" any of the other planets.
In fact, the FIRST thing we look at are the aspects (certain distances, which create an interaction between those two inner needs/planets) ... even before we consider the sign.
Because a planet which has mostly harmonious aspects with other planets will operate smoothly and effectively. And expressed the positive behaviors of whatever sign it is in.
And a planet which has mostly discordant, conflicting aspects with other planets operates dysfunctionally, as an automatic reaction to trying to blow off internal stress. Expressing the negative behaviors of its sign.
Note: since astrology is only an influence, and all it indicates is how we will be IF we do nothing to change, even the influence of a badly-aspected planet CAN be overcome, if the person develops self-awareness and a commitment to inner change.
Having said all this .. there is not much I CAN say about these two planetary placements. I would have to see the entire circular map, not just to see the aspects to your Sun and Moon, but to see how the entire set of dynamics push and pull as a whole.
Sun in Libra is something who expresses positive/negative Libra behaviors as a way to try to seek inner wholeness. In the 9th house, abstract concepts and philosophies/religion tend to be where they look for inner wholeness. Sometimes living abroad and learning about other cultures, since that increases our ability to see things in a broader perspective.
Moon is our automatic emotional responses, and how we try to work with our emotions. In Aries, they will be positive/negative Aries expressions for HOW we respond emotionally, as well as how we try to cope with our emotions.
The 3rd house is the house of concrete thinking (as opposed to the abstract thinking of the 9th house), so we are talking about people who gather information and facts, and try to use them ... in this case, this would be using them for increased emotional coping.
We have someone here who finds inner wholeness through abstract thinking, but emotional health through factual and concrete thinking.