Consider the lowly sinkhole.

There are those who will guffaw the way they do that a process occurring beneath the surface of a planet - oh, let's say Mars for example - could be responsible for large, even titanic formations at the surface of said planet. But there you are.

This is an illustration of one means of sinkhole formation on Earth:

Could sinkholes occur on another planet, most especially on Mars, and could such formations be mistaken for impact structures?

Could they occur on vast scales, such as that of the immense Hellas Basin? Or could Hellas be the result of multiple causes, among them impact, internal undermining and collapse, volatile storage and release, and possibly convection within the mantle?

Could water flow underground on Mars today, and has it been flowing underground for the past many eons? If water is flowing underground today, how would it be expressed on the surface? If water flowed underground in the past, how would that flow be expressed on the surface today?

Could other fluids, in addition to, or in place of, water flow or have once flowed beneath the surface of Mars and if they did, what would such flows look like at the surface today?

As some of you know, I have asked whether some - or possibly many - circular formations on the surface of Mars have been misidentified. Nearly all are, by convention, interpreted as impact formations. But what if they are not impact-generated but instead are the result of internal forces?

How would it affect understanding of Mars history and geology if many circular formations seen at the surface are not impact structures,though they mimic them nearly exactly? Is there any way to certain of the origin of all circular formations on the surface of Mars without inspecting and testing on site?

Our bias, of course, is toward the interpretation of surface formations as if they result from actions at the surface, such as impact. But in fact, Mars may have and may have had a much more active interior than previously believed. Once we integrate previously neglected internal forces with surface modification by impact and volatile release and flow, we may begin to have a deeper understanding of planetary dynamics.

Or at least come to a better understanding of Mars.

Cheers, BRFelix