Abstract
Triton is one of the few satellites in the Solar System which shows an
ongoing geological activity, with plumes and geysers whose origin is
still controversial [1]. Its surface is relatively young, as shown
by the paucity of craters detected on its surface [2]. Our knowledge
of this moon comes from the Voyager 2 mission, which obtained several
images, covering about 40% of Triton’s surface [3]. However, few
studies were focused principally on surficial geomorphology, and those
are mostly limited to the cantaloupe region and surrounding areas.
Triton’s crust is composed predominantly by solid nitrogen (N2) but
several other ices have been detected [3]. Crater counting has
revealed that the surface is very young and likely it went through a
resurfacing process in the past. In fact, a very small number of craters
has been detected, and these usually exhibit a typical bowl-like shape
[2]. Geological features on Triton include regions, called terrains,
such as cantaloupe terrains or plains, which show different textures.
Usually, plains are categorized within smooth, walled and terraced
plains [3]. The latter are the flattest areas on Triton, a
characteristic which has been explained by evoking a lava-like or other
viscous liquid infill. Their central depressions also present a cluster
of irregular pits, which have been interpreted as drainage pits or
eruptive vents [3]. These peculiar morphologies seem to indicate the
presence of a viscous fluid on the surface in a remote epoch, which may
imply potential climatic and atmospheric changes during Triton’s
geological history. In this work we analyse an area located at NW of
Tuonela Planitia, which shows several depressions rimmed by sharp
margins. Two of these depressions are named Kulilu Cavus and Mah Cavus
[4]. Cavi are elliptical-shaped depressions, distributed in an
ordered trend, which constitute the cantaloupe terrain [3].
Diapirism is the main candidate process to explain these collapsed
depressions [3] but other hypotheses, such as cryovolcanism or
impact cratering [5], have also been proposed. Methodology A new
geological map has been realized. We used Voyager 2 imagery named
c1139533 [6] (600 m/px), properly calibrated, filtered and
georeferenced using the Integrated Software for Imagers and
Spectrometers (ISIS4) [7]. We mapped the different geological units
and main features according to differences in surface morphology
(fig.1). We also produced a DEM of the study area, using the open-source
suite of tools NASA Ames Stereo Pipeline (ASP) [8]. We applied the
photoclinometry-based “shape-from-shading” (SfS) tool to produce the
DEM. Since SfS needs an input DEM generated preferably with stereo
images, and we do not have such data for Triton, we used the methodology
proposed by Lesage et al. 2021[9]. We analysed four different cross
sections to measure the relative height of Kulilu Cavus, Mah Cavus and
two other depressions, as well as their associated terraces (fig.2).
Discussion Geologic