There have been a number of claims in recent years that there are small dark volcanic ash deposits on Mars, suggesting very recent volcanic eruptions. However, most of these claims have not stood up to scrutiny by HiRISE.
Dark wind blown sand, not volcanic ash, explains most examples of diffuse dark patches on Mars. This area is especially intriguing because the wind blown material in the region has a light, not dark, tone. Furthermore, there are fresh looking lava flows adjacent to the possible vent, lending additional weight to the idea of recent volcanism here.
The difference in the way small craters resist erosion within this dark deposit is also suggestive of coarser fallout from a lava fountain. Overall, this is a top contender for a recent volcanic vent on Mars.
Photo credit: NASA/JPL/University of Arizona