What is this strange feature on Mars in Valles Marineris
Looking at the 2nd image in your question, namely of the vertical profile, the feature inhabits what appears to be an erosion channel to the valley floor (a very rough estimate of the erosion channel is shown below).  



(Please excuse the rough-MS Paint style arrow)

The feature has the appearance of being an example of a small slope failure, a similar, but much smaller example of other much larger landslides have been observed in the Valles Marineris according to the article Long-runout landslides and the long-lasting effects of early water activity on Mars (Watkins et al. 2014).

According to research based on observations of similar larger scale features, the article Mechanisms of slope failure in Valles Marineris, Mars (Neuffer and Schultz, 2006) slope failures on Mars have been found to occur due to gravitational, fluid or seismic (i.e. 'marsquakes') influences.  

The other influence as to why these landslides occur in the area is explained by Watkins et al. (2014) from observations and models based on spectral imaging and satellite image analyses, a significant amount of hydrated silicate clays contained within the stratigraphy of the Valles Marineris facilitate geomorphic processes, including landslides - the process is aptly used as the title of the Red Planet Report web-article Clays greased long landslides in Valles Marineris.