The broken edge of Mars’ largest volcanic ash field
Click for original image.
Cool image time! The picture above, reduced and rotated to place north to the left, was taken on November 5, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
The science team labeled it “Stepped Features in Tartarus Skopulus”. The white dot on the overview map to the right marks the location, right at the equator on the northern edge of the Medusae Fossae Formation, the largest volcanic ash field on Mars, about the size of the subcontinent of India. As I wrote in a post in 2024:
It is believed that most of the planet’s dust comes from this ash field. It is also evident that the ash is a leftover from the time period more than a billion years ago when the giant volcanoes that surround this field were erupting regularly. The eruptions laid down vast flood lava plains that coat the surface for thousands of miles.
The ash either came from the eruptions themselves, or was created as the thin Martian wind eroded those flood lava plains, slowly stripping ash from the top. The ash then gathered within the black-outlined regions on the map.
In that 2024 post the cool image showed another location on the north edge of Medusae. In that case the prevailing wind had carved long parallel ridges as it pulled ash from the field.
Here, the wind appears to play no part, or if it did, it produced a very different terrain. At first glance it appears the stepped terraces formed as the ash field began to slide downhill to the north, spreading to crack along the curved lines. The inset especially suggests this explanation.
A closer look instead suggests these terraces each represent a different layer of ash placed down by a sequence of eruptions. Over time the prevailing winds, which here appear to generally blow to the south, stripped off the top of each layer, creating this stair-step landscape.
I however have no guess as to why the terraces are curved. Regardless, it is all strange, but quite beautiful in its own way.
