8 research outputs found
Understanding the Noachian-Hesperian transition in the area of Meridiani Planum, Mars: a stratigraphic, compositional and morphological study
No full textNumerous exploration missions over the last decades have gathered compelling evidence that early Mars experienced a warm climate with abundant liquid water at the surface. During this period, termed as Noachian, water carved out fluvial valleys, filled craters to create lakes, and transported sediments that formed deltas and alluvial fans, while the prolonged interaction of alkaline water with the Martian crust led to the formation of several types of clay minerals. This exceptional period came to an end about 3.7 billion years ago. The subsequent period, the Hesperian, saw a net decrease in fluvial erosion and the build up of sulfates in some regions of the planet, indicating enhanced water evaporation and increasingly acidic conditions. The Noachian-Hesperian climatic transition eventually led to the current cold, dry, and inhospitable surface. However, its exact characteristics remain largely unknown and subject of debate. This thesis focuses on the orbital morphological, mineralogical, and stratigraphic characterization of selected areas in Meridiani Planum, where a complex, regionally-extensive, sequence of layered sedimentary rocks rich in clays and sulfates are key evidence of the Noachian-Hesperian transition. High-resolution hyperspectral imaging data is combined with digital elevation models for a detailed characterization of the units. Spectral analysis is approached with a wide range of methods, from traditional spectral index analysis to advanced approaches based on unsupervised machine learning. Results indicate that the Noachian-Hesperian climatic transition was highly complex and dynamic, and that the shift from a warm and wet to a cold and dry environment was not linear, but likely underwent cyclical oscillations at different frequencies
Paleoenvironmental significance of Fe/Mg phyllosilicate and sulfate deposits in Mikumi crater, northern Meridiani Planum, Mars
Get PDFThe region of Meridiani Planum on Mars retains the evidence of multiple surface and near-surface aqueous processes that span from the Noachian to the Hesperian. This makes it an interesting spot for better understanding the characteristics and the evolution of Mars' aqueous environment between these two fundamental epochs. Here we investigate the mineralogy, stratigraphy, and morphology of the Noachian-Hesperian sedimentary materials that fill a 16-km-wide crater named Mikumi, located in the northern part of Meridiani Planum. The analysis was carried out combining observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), the High Resolution Imaging Science Experiment (HiRISE), and the Context Imager (CTX). About 20-30 meters, on average, of Fe/Mg phyllosilicate-rich rocks and a thick sequence (75 m) of both mono- and polyhydrated Mg sulfates are detected on the crater floor. Both layers postdate the impact event. Most of the hydrated terrains are extensively polygonally fractured, suggesting the possible action of water-related processes such as desiccation and hydro fracturing on the sediments. Stratigraphic analysis clearly shows that Fe/Mg phyllosilicates were deposited on top of the sulfate sequence, meaning that they are younger than sulfates. This can have interesting implications on paleoclimatic studies of Mars as it shows that a simple timeline going from a clay-rich Noachian to a sulfate-rich Hesperian oversimplifies the evolution of Mars' mineralogy and related aqueous environment at the Noachian-Hesperian boundary
Python Scripts for absorption band characterization
No full textThis database contains the Python scripts to calculate spectral indexes. For the visible-near infrared range, we measure the slope of the absorption band shoulders, while for the short-wave infrared range, we measure:
- band area
- band depth
- band centre
- full width half maximu
Mineralogical and Geomorphological Analysis of the Martian Delta in Dogana Crater
No full textopenIl cratere marziano Dogana, dal diametro di 41.2 km circa, si trova all’interno di
Aurorae Planum, una regione caratterizzata da strutture associate a processi di attività
idrologica e tettono-magmatica.
Il presente studio consiste nell’analisi della regione nord-est di tale cratere, che comprende
un delta situato alla base di una corta valle e un cratere di impatto secondario, con
l’obiettivo di caratterizzarne la composizione mineralogica e delineare le principali unità
morfologiche. L’indagine integra dati geomorfologici e spettrali, elaborati rispettivamente
con QGIS e ENVI.
L’analisi geomorfologica è condotta attraverso l’elaborazione di mosaici globali acquisiti
dallo strumento CTX a bordo di Mars Reconnaisance Orbiter (MRO). Mediante tecniche
di fotogrammetria applicate alle immagini CTX si ricavano i modelli di elevazione (DEM)
necessari alla costruzione di profili altimetrici.
Per ricavare le informazioni sulla composizione, è svolta una prima analisi qualitativa
dell’immagine HRL000080CB di CRISM, che permette di delineare aree di potenziale
interesse mineralogico, studiate successivamente in dettaglio attraverso l’estrapolazione
di spettri. Dall’elaborazione di questi si arriva al riconoscimento dei minerali presenti
nelle aree analizzate. I risultati evidenziano la presenza di fillosilicati come nontronite e
saponite nel delta, nella valle e nel cratere secondario, ossidi di ferro come goethite nella
valle e nel cratere secondario, e un’abbondanza di pirosseno concentrata principalmente
nel fronte del delta.
Queste osservazioni, combinate con l’assetto morfologico, suggeriscono una storia evolutiva
con processi fluviali che hanno scavato la valle e depositato sedimenti nel bacino craterico,
seguiti da eventi di impatto. L’intero studio contribuisce alla comprensione dell’evoluzione
geologica di Aurorae Planum e fornisce elementi utili per analisi comparative in aree
marziane simili
Geomorphological Evidence of Ice Activity on Mars Surface at Mid-Latitudes
No full textExtensive radar investigations, observed spectral signatures, geomorphological, and paleoclimate modeling support the presence of mid- to low-latitude ground ice on Mars. The presence of near-surface ice and glacial features has been proposed in Ismenius Lacus, but the ice composition and age remain unconstrained. Our high-resolution stereoscopic analysis reveals distinctive landforms, including sharp-edged polyhedra, chevron patterns, and en-echelon open fractures, indicative of plastic glacial deformation. Current climatic conditions may support year-round ice stability, while sharp-edged polyhedra, open fractures, and the absence of superposed craters suggest active glaciation. The Ariguani delta system lacks fluvial signatures but aligns with glacial erosional and depositional processes. Unlike terrestrial glaciers, ice accumulation here is likely driven by escarpment-fed melt from seasonal permafrost thawing under lithostatic pressure, generating neo-glacial flows that sustain the glacial tongue. This mechanism can also explain regional features, including U-shaped valley subsidence, gravitational slides, flow of low-viscosity material lobes, and ring-mold craters. Thus, we propose sharp-edged polyhedra as diagnostic markers for identifying ongoing ice dynamics on Mars, enabling future automated detection of active glacial environments
First results of Unsupervised Learning techniques applied to CRISM dataset on Mars
No full textSpectral and hyperspectral data from remote sensing instruments provide essential information on the composition of planetary surfaces. On Mars, high resolution hyperspectral data are provided by the CRISM instrument, onboard NASA’s MRO spacecraft. CRISM collects hyperspectral cubes in the 0.4-4 micron range, with a spectral sampling of 6.55 nm/channel and a spatial resolution up to 18.4 meter/pixel. A CRISM scene is traditionally explored through RGB maps of spectral parameters, such as band depth. To guide the user in this work, the CRISM team provided a set of 60 standard spectral parameters, identified based on the known spectral variability of the planet. After a first assessment with this method, extraction of single or mean spectra from selected ROIs (regions of interest) is usually performed. This is a solid approach, however, as it focuses on a few portions of the available spectral range at once, it does not fully exploit the potentials of a hyperspectral dataset. Machine Learning techniques can help us explore CRISM data more efficiently. Here we present the results from the development of a Python framework that allows the application of two different Unsupervised Learning techniques (k-Means and Gaussian Mixture Models, GMMs)
Development of an Open Source Tool to Perform Unsupervised Clustering of CRISM/MRO data on Mars: first results
Get PDFHere we present the results from the development of a Python framework that allows the application of two different unsupervised clustering techniques (k-Means and Gaussian Mixture Models) to the CRISM dataset. Results on specific CRISM data are shown and evaluated, discussing the impact of different processing steps and comparing the performance of the two algorithms used
Hydrothermal Alteration of Ultramafic Rocks in Ladon Basin, Mars—Insights From CaSSIS, HiRISE, CRISM, and CTX
Get PDFThe evolution of the Ladon basin has been marked by intense geological activity and the discharge of huge volumes of water from the Martian highlands to the lowlands in the late Noachian and Hesperian. We explore the potential of the ExoMars Trace Gas Orbiter/Color and Stereo Surface Imaging System color image data set for geological interpretation and show that it is particularly effective for geologic mapping in combination with other data sets such as HiRISE, Context, and Compact Reconnaissance Imaging Spectrometer for Mars. The study area displays dark lobate flows of upper Hesperian to early Amazonian age, which were likely extruded from a regional extensional fault network. Spectral analysis suggests that these flows and the underlying rocks are ultramafic. Two distinct altered levels are observed below the lobate flows. The upper, yellow-orange level shows hundreds of structurally controlled narrow ridges reminiscent of ridges of listwanite, a suite of silicified, fracture-controlled silica-carbonate rocks derived from an ultramafic source and from serpentine. In addition to serpentinite, the detected mineral assemblages may include chlorite, carbonates, and talc. Kaolin minerals are detected in the lower, white level, which could have formed by groundwater alteration of plagioclase in the volcanic pile. Volcanism, tectonics, hydrothermal activity, and kaolinization are interpreted to be coeval, with hydrothermal activity and kaolinization controlled by the interactions between the aquifer and the hot, ultramafic lobate flows. Following our interpretations, East Ladon may host the first listwanite ridges described on Mars, involving a hydrothermal system rooted in a Hesperian aquifer and affecting ultramafic rocks from a magmatic source yet to be identified
