O)K, I will accept that glaciers were on Mars if they will explain how the glaciers were formed.
On Earth, a glacier is made when there is more snow fall in the winter than snow melting in the summer. They do not just appear out of a rock.
Possibly, of course, is a comet striking Mars, importing water, causing snowfall until the water sublimes out of the atmosphere or is absorbed into the crust.
.....Bob
It’s more like crystal growing. What little water vapor that is present in the atmosphere might not fall as snow but condenses out directly onto an existing ice substrate.