Recurring Slope Lineae (RSL) are dark, narrow features which form on steep Martian slopes during warm seasons, lengthening, fade in cold seasons and recurring annually. There are many hypotheses on the formation mechanism of RSL. A number of these hypotheses suggest that RSL are liquid brines flowing on the surface. Brine based hypotheses often state that sub-surface aquifers are necessary to supply the water needed to recharge RSL. One problem with this is that RSL are observed forming on isolated peaks and ridgelines where a sub-surface aquifer is unlikely. This study uses a thermal model called KRC to examine the correlation between RSL activity and surface temperature at several RSL sites in Valles Marineris. This correlation is compared to the freezing temperature of several brines. Results show an interesting relationship between RSL activity and the surface temperature of very steep (> 60º) slopes. This could indicate that RSL are caused by thermal stresses loosening material on the face of bedrock outcroppings instead of briny flows.