Timing of chaotic terrain formation in Argadnel Regio, Europa, and implications for geological history

I would like to share with you my new and first contribution about Europa, the satellite of Jupiter. This work has been made together with Dr. Javier Ruiz and Dr. Robert Pappalardo, and summarizes my final project of my masters degree. It is a joy for me to have published this research, and contribute in the study of the geology of Europe and, in particular, in the study and determination of chaos units and in the interpretation of the geological history of this icy moon of Jupiter.

Parro, L. M., Ruiz, J., Pappalardo, R. T., 2016. Timing of chaotic terrain formation in Argadnel Regio, Europa, and implications for geological history. Planetary and Space Science, doi:10.1016/j.pss.2016.02.002.

Abstract

Chaos terrains are among the most prominent landforms of Europa, and are generally among the youngest features recorded on the surface. Chaos units were formed by to endogenic activity, maybe related to solid-state convection and thermal diapirism in the ice shell, perhaps aided by melting of salt-rich ice bodies below the surface. In this work, we analyze the different units of chaotic terrain in a portion of Argadnel Regio, a region located on the anti-Jovian hemisphere of Europa, and their possible timing in the general stratigraphic framework of this satellite. Two different chaos units can be differentiated, based on surface texture, morphology, and cross-cutting relationships with other units, and from interpretations based on pre-existing surface restoration through elimination of a low albedo band. The existence of two stratigraphically different chaos units implies that conditions for chaos formation occurred during more than a single discreet time on Europa, at least in Argadnel Regio, and perhaps in other places. The existence of older chaos units on Europa might be related to convective episodes possibly favored by local conditions in the icy shell, such as variations in grain size, abundance of non-water ice-components, or regional thickness of the brittle lithosphere or the entire ice shell.

Figure1

Mosaic of Argadnel Regio (Galileo observation 14ESWEDGES01), the “wedges” area of the anti-jovian region of Europa, obtained during the 14th Galileo orbit. The white box indicates the study area (20°S to 24°S, and 184°W to 175°W).

Figure3

Example of relations among geological units and other principal structural elements in our study area. (a) Original mosaic image 14ESWEDGES01, with a resolution of 230 m/pixel and orthographic projection centered on 22°S, 180°W. The illumination is from the left side of the image. (b) Geological map showing different classes of bands and ridges, chaotic terrains, lenticulae and micro-chaos. The ridged plains represent the oldest “background” unit, which was subsequently modified by the other types of surface features.