Papers by Lorenza Giacomini
Tumuli and pingos are important distinctive features for inflated flows and unconsolidated water-... more Tumuli and pingos are important distinctive features for inflated flows and unconsolidated water-rich periglacial terrains respectively. Therefore distinguishing these two classes is useful to understand the origin of the terrain where such features occur; this however could be complex since their morphologies are very similar. We focused our study on the dome-like forms detected on Daedalia Planum and Elysium Planitia regions taking into account a morphological analysis coupled with a density distribution study of mounds and age determinations of the surfaces where they were observed. Such comparative study revealed that Elysium Planitia features are more compatible with a pingo nature whereas the Daedalia Planum morphologies are more likely associable with tumuli. This would confirm the presence of inflated flows on Daedalia Planum lava field.
We performed a comparative study between the Daedalia Planum and Elysium Planitia mounds consider... more We performed a comparative study between the Daedalia Planum and Elysium Planitia mounds considering the morphology, density distribution and the age. The analysis revealed that Elysium features could be pingos while the Daedalia ones can be tumuli.
Daedalia Planum is a large lava plain, consisting of more than 1500 km lava flows emplaced over a... more Daedalia Planum is a large lava plain, consisting of more than 1500 km lava flows emplaced over an almost flat terrain in the south-east area of Arsia Mons. The morphology of this region has been studied by Giacomini et al. (Planet.SpaceSci., 2009) and revealed the presence of various features indicative of inflation mechanisms. Thirteen morphologic units have been delineated and
Our study has been focused on the Daedalia Planum geological mapping. THEMIS, MOC, HiRISE images ... more Our study has been focused on the Daedalia Planum geological mapping. THEMIS, MOC, HiRISE images were analyzed to perform a stratigraphic and morphological analysis. OMEGA data revealed spectral differences that permitted to improve our mapping.
Daedalia Planum is one of the Tharsis volcanic plains and is located southwest of the Arsia Mons.... more Daedalia Planum is one of the Tharsis volcanic plains and is located southwest of the Arsia Mons. According to MOLA data, the flanks of Arsia have an average slope < 5°, while the surrounding regions, including Daedalia Planum, have slopes < 0.5° and commonly < 0.1°. MOC and THEMIS images show a plain covered by a huge number of lava
... 3) INAF - Osservatorio Astronomico di Padova, Italy, (4) Open University, Milton Keynes, Unit... more ... 3) INAF - Osservatorio Astronomico di Padova, Italy, (4) Open University, Milton Keynes, United Kingdom, (5) Johns Hopkins University Applied Physics Laboratory, Laurel, Mariland, USA, (6) Dipartimento di Astronomia, Università di Padova, Italy ([email protected] ...
Geological Society, London, Special Publications, 2014
ABSTRACT At a global scale, Mercury is dominated by contractional features manifested as lobate s... more ABSTRACT At a global scale, Mercury is dominated by contractional features manifested as lobate scarps, wrinkle ridges and high-relief ridges. Here, we show that some of these features are associ- ated with strike-slip kinematic indicators, which we identified using flyby and orbital Mercury Dual Imaging System (MDIS) data and digital terrain models. We recognize oblique-shear kinematics along lobate scarps and high-relief ridges by means of (1) map geometries of fault patterns (frontal thrusts bordered by lateral ramps, strike-slip duplexes, restraining bends); (2) structural morphologies indicating lateral shearing (en echelon folding, pop-ups, pull-aparts); and (3) esti- mates of offsets based on displaced crater rims and differences in elevation between pop-up struc- tures and pull-apart basins and their surroundings. Transpressional faults, documented across a wide range of latitudes, are found associated with reactivated rims of ancient buried basins and, in most cases, linked to frontal thrusts as lateral ramps hundreds of kilometres long. This latter observation suggests stable directions of tectonic transport over wide regions of Mercury’s surface. In contrast, global cooling would imply an overall isotropic contraction with limited pro- cesses of lateral shearing induced by pre-existent lithospheric heterogeneities. Mantle convection therefore may have played an important role during the tectonic evolution of Mercury.
Planetary and Space Science, 2011
In this paper we present a crater age determination of several terrains associated with the Radit... more In this paper we present a crater age determination of several terrains associated with the Raditladi and Rachmaninoff basins. These basins were discovered during the first and third MES-SENGER flybys of Mercury, respectively. One of the most interesting features of both basins is their relatively fresh appearance. The young age of both basins is confirmed by our analysis on the basis of age determination via crater chronology. The derived Rachmaninoff and Raditladi basin model ages are about 3.6 Ga and 1.1 Ga, respectively. Moreover, we also constrain the age of the smooth plains within the basins' floors. This analysis shows that Mercury had volcanic activity until recent time, possibly to about 1 Ga or less. We find that some of the crater sizefrequency distributions investigated suggest the presence of a layered target. Therefore, within this work we address the importance of considering terrain parameters, as geo-mechanical properties and layering, into the process of age determination. We also comment on the likelihood of the availability of impactors able to form basins with the sizes of Rachmaninoff and Raditladi in relatively recent times.
Mercury has remained an "enigmatic body" among the terrestrial planets for more than th... more Mercury has remained an "enigmatic body" among the terrestrial planets for more than three decades, caused by the paucity of data collected by the NASA Mariner 10 spacecraft in the Seventies. The recent flybys of the Discovery mission MESSENGER with Mercury updated our knowledge about this planet, in particular new areas of Mercury have been imaged, revealing structures never observed before. One new feature, a double-ring impact basin named Raditladi, soon appeared very interesting for the small number of craters detected either on its floor and its ejecta, suggesting a very young age. The peculiarity to have a very young age estimate in the case of such a large impact crater is the starting point for a deepen analysis on this structure. In this work we will show the result of the hydrocode simulations of the basin to be used to investigate the layering, at the basis of the age determination, and the impactor size.
Mercury surface appears to be interested by several tectonic structures, the most interesting one... more Mercury surface appears to be interested by several tectonic structures, the most interesting ones being numerous lobate scarps formed mainly thanks to planet cooling and contraction. The Messenger cameras (MDIS WAC and NAC) allowed us to map several structures not previously detected. Among these a 250 km-long thrust has been detected crossing a peak ring basin. The region encircled within the inner ring of the basin is covered by a smooth plain with evidence of a sin-deformational emplacement. Dating this smooth plain with crater counting technique allowed us to give an age constrain of the tectonic structure.
ABSTRACT Mercury hosts the largest population of peak-ring basins among all the rocky planets and... more ABSTRACT Mercury hosts the largest population of peak-ring basins among all the rocky planets and satellites of the Solar System. Among the database of such structures, we take into analysis two recently imaged peak-ring basins, Raditladi and Rachmaninoff, both located in the northern hemisphere and about 300 km in diameter. In this work, we present the state of art on these basins. In particular, we focus on their differences, and the possible mechanisms or surface properties that could have led to such a diversification between two similar structures. This work wants to be a review of the present knowledge on Raditladi and Rachmaninoff in the view of a subsequent deep investigation on the impact process that led to the formation of these basins.
ABSTRACT The Scientific Imaging System for Rosetta, OSIRIS, acquired an imaging sequence of Lutet... more ABSTRACT The Scientific Imaging System for Rosetta, OSIRIS, acquired an imaging sequence of Lutetia allowed the detection of a huge number of lineaments distributed over most of the asteroid surface Thomas et al., 2012, Planet. Space Sci., 66, 96-124; Massironi et al., 2012, Planet. Space Sci., 66, 125-136) . Several categories of features has been observed, like troughs, scarps, faults, and ridges. These lineaments are generally more than 50 km long and 1.2 km in width in places and seem to form systems. Moreover, in the different geomorphological regions of the asteroid, the lineaments show a preferred orientation but in all regions there are lineaments which cross or do not follow the local preferred orientation. Lineaments radial to impact craters as seen on other asteroidal bodies are mostly absent (Thomas et al., 2012, Planet. Space Sci., 66, 96-124). However, on a non-spherical body it is not obvious to determine the relationship occurring between the different lineaments. Indeed, lineations that appear to be similarly oriented on different asteroid facets could have no correlation at all (Buczkowski et al., 2007, Icarus, 193, 39-52). In this context, the mapping of the lineation on Lutetia shape model allow us to obtain a three-dimensional view of these structures that have been interpolated to define planes cutting through the asteroid. This can give us new clues to understand how these structures formed and if surface lineations are representative of internal asteroid structure, yielding information about the nature and history of Lutetia.
ABSTRACT A 3-D mapping of Lutetia lineaments has been performed. This has allowed us to gain new ... more ABSTRACT A 3-D mapping of Lutetia lineaments has been performed. This has allowed us to gain new clues about the internal structure and origin of the asteroid.
Mapping tectonic features using MESSENGER data mainly acquired at high Sun incidence angle (>50°)... more Mapping tectonic features using MESSENGER data mainly acquired at high Sun incidence angle (>50°) reveals previously undetected structures. The analysis of the latter features determines an upward revision of measurements of density and spatial distribution of tectonism and thus of estimates of average contractional strain and planetary radius decrease. We calculated an average surface contraction of $0.23-0.30% ($0.28% for fault dip angle h = 30°) within an area corresponding to 21% of the planet. This strain, extrapolated to the entire surface, corresponds to a decrease in radius of about 2.4-3.6 km ($3.0 km for h = 30°). These values are three-four times higher with respect to previous estimates and are compatible with results from thermomechanical models.
Science, 2011
The Visible, InfraRed, and Thermal Imaging Spectrometer (VIRTIS) on Rosetta obtained hyperspectra... more The Visible, InfraRed, and Thermal Imaging Spectrometer (VIRTIS) on Rosetta obtained hyperspectral images, spectral reflectance maps, and temperature maps of the asteroid 21 Lutetia. No absorption features, of either silicates or hydrated minerals, have been detected across the observed area in the spectral range from 0.4 to 3.5 micrometers. The surface temperature reaches a maximum value of 245 kelvin and correlates well with topographic features. The thermal inertia is in the range from 20 to 30 joules meter(-2) kelvin(-1) second(-0.5), comparable to a lunarlike powdery regolith. Spectral signatures of surface alteration, resulting from space weathering, seem to be missing. Lutetia is likely a remnant of the primordial planetesimal population, unaltered by differentiation processes and composed of chondritic materials of enstatitic or carbonaceous origin, dominated by iron-poor minerals that have not suffered aqueous alteration.
Planetary and Space Science, 2009
Inflation is an emplacement process of lava flows, where a thin visco-elastic layer, produced at ... more Inflation is an emplacement process of lava flows, where a thin visco-elastic layer, produced at an early stage, is later inflated by an underlying fluid core. The core remains hot and fluid for extended period of time due to the thermal-shield effect of the surface visco-elastic crust. Plentiful and widespread morphological fingerprints of inflation like tumuli and lava rises are found on the Payen volcanic complex (Argentina), where pahoehoe lava flows extend over the relatively flat surface of the Pampean foreland and reach at least 180 km in length.
Journal of Geophysical Research: Planets, 2012
ABSTRACT The accurate definition of the lunar cratering chronology is important for deriving abso... more ABSTRACT The accurate definition of the lunar cratering chronology is important for deriving absolute model ages across the lunar surface and throughout the Solar System. Images from the Lunar Reconnaissance Orbiter Narrow Angle Cameras and Wide-Angle Camera and the SELENE/Kaguya Terrain Camera provide new opportunities to investigate crater size-frequency distributions (CSFDs) on individual geological units at lunar impact craters. We report new CSFD measurements for the Copernican-aged craters North Ray, Tycho, and Copernicus, which are crucial anchor points for the lunar cratering chronology. We also discuss possible reasons for an age discrepancy observed between the impact melt and ejecta units. Our CSFDs for North Ray and Tycho crater ejecta deposits are consistent with earlier measurements. However, for Copernicus crater and one of its rays, we find significantly lower cumulative crater frequencies than previous studies. Our new results for Copernicus crater fit the existing lunar absolute chronologies significantly better than the previous counts. Our derived model ages of the ejecta blankets of North Ray, Tycho, and Copernicus agree well with radiometric and exposure ages of the Apollo 16, 17, and 12 landing sites, respectively, and are generally consistent with a constant impact rate over the last 3 Ga. However, small variations of the impact rate cannot be resolved in our data and require further investigations.
... IUGG 2007, Perugia, Italy. Abstract 10028. Cerca con Google. Giacomini, L., Massironi, M., Ma... more ... IUGG 2007, Perugia, Italy. Abstract 10028. Cerca con Google. Giacomini, L., Massironi, M., Martellato, E., Pasquar??, G., Frigeri, A., Cremonese, G., 2009. Inflated flows on Daedalia Planum (Mars)? Clues from a comparative analysis with the Payen volcanic complex (Argentina). ...
Icarus, 2012
ABSTRACT The great variety of morphologies observed in the Daedalia Planum lava flows (Mars) enco... more ABSTRACT The great variety of morphologies observed in the Daedalia Planum lava flows (Mars) encouraged a detailed study of their spectral characteristics, in order to obtain information about lava composition and detect possible differences in the spectra of the flows. The OMEGA spectral data collected from the lava field appear rather similar, with absorptions between 0.8 and 1.4 μm and 1.8 and 2.5 μm, suggesting the presence of mafic minerals, which are typical primary mineral phases of volcanic rocks. Moreover, after the subtraction of the background absorption (continuum removal), we highlighted the presence of two classes of spectra both compatible with tholeiitic basalts but with different proportions of Ca in the pyroxene. Despite the similar absorption bands, Daedalia spectra show differences in albedo and spectral slope. By employing the average spectra of the different flow units as end-members, a SAM (Spectral Angle Mapper) classification was performed. The resulting spectral map reveals a relationship between spectral behavior and flow surface textures.
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Papers by Lorenza Giacomini