Geological analysis of the dome field in western Utopia Planitia, on Mars

Hundreds of domes are scattered over a plain composed of different geological units in the western margin of Utopia Planitia, near the northern martian dichotomy. These structures have traditionally been considered of igneous origin. In this work, we utilized recent data to study the geomorphological and compositional properties of this dome field. We found that the domes originated from an intrusive-to-extrusive system, since they range from cryptodomes to volcanic domes. Each dome appears to represent a single magmatic event, indicating they formed in a monogenetic regime. Two main groups of domes were identified according to their shapes and stratigraphic relationships with the floor units, which represent two different stages of igneous activity. It was established from a linear analysis that the domes are preferentially aligned following a NW-SE trend, which is consistent with the regional faults and fractures. The domes field in Utopia Planitia was likely created by two monogenetic magmatic events at different ages, which took advantage of the tectonic configuration of the area to be emplaced. Some magmas were able to reach the surface creating extrusive structures, while the majority crystalized near the surface creating intrusive ones. Of the last group, the majority were uncovered by tectonic or erosive processes, while a small number of them remained trapped underground as cryptodomes. This sequence of events would explain the large distribution of the domes, as well as the wide variety of morphologies that we observe today.