Thousands of images of Mars are available from the University of Arizona’s High Resolution Imaging Science Experiment (HiRISE), see here. This catalogue contains 16,784 images. When you click on the image, you also get an explanation for the photo.
You can also view photos by Themes where the photos are grouped by process such as volcanic action, aeolian (wind), and fluvial (water) forms.
HiRISE is aboard the Mars Reconnaissance Orbiter that was launched in 2005. According to NASA,
“After a seven-month cruise to Mars and six months of aerobraking to reach its science orbit, Mars Reconnaissance Orbiter began seeking out the history of water on Mars with its science instruments. The instruments zoom in for extreme close-up photography of the martian surface, analyze minerals, look for subsurface water, trace how much dust and water are distributed in the atmosphere, and monitor daily global weather.
These studies are identifying deposits of minerals that may have formed in water over long periods of time, looking for evidence of shorelines of ancient seas and lakes, and analyzing deposits placed in layers over time by flowing water. The mission is examining whether underground martian ice discovered by the Mars Odyssey orbiter is the top layer of a deep ice deposit or a shallow layer in equilibrium with the atmosphere and its seasonal cycle of water vapor.”