Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 27, 2026 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels the small scattered knobs in this picture as “potential rootless cones.” My vague understanding of this kind of geological feature is that it forms when a thin layer of hot lava flows and covers material containing ice, which once heated into steam bursts upward through the lava, almost like a suddenly formed pimple.

These tear-drop knobs as well as that large 3000-to-4,800 foot high mesa were also shaped by the prevailing winds at this location, blowing to the north. That fact, combined with the location, throws a bit of doubt into this rootless cone theory.

The white dot on the overview map to the right marks the location, on the edge of the Medusae Fossae Formation, the largest volcanic ash field on Mars and about the size of India. That edge is only about nine miles to the west, but it also includes the higher features seen in the inset. Over eons the wind has not only shaped these knobs, it has blown away the ash that once covered this location, leaving behind the knobs, mesas, and ridges.

That this location is in lava country is strong evidence that these are rootless cones. Almost all of landscape in the equatorial tropics between the giant volcanoes here is a vast field of flood lava. In fact, the base level in the picture above appears to be frozen flood lava. When that lava flowed such cones could have erupted.

At the same time, these cones could instead be just volcanic ash. During eruptions the ash piled up into thick layers on top of the flood lava, forming the Medusae ash field. Then over eons the thin Martian wind scoured it away, leaving behind mesas and cones of ash.

Without more data, it is impossible to determine one way or the other.