Papers by gianfranco magni
<p><strong>Introduction. </strong>Oxia Planum is the se... more <p><strong>Introduction. </strong>Oxia Planum is the selected landing site of the ExoMars mission [1]. A drilling system is installed on the ExoMars rover, able to analyze down two meters in the subsurface of Mars. Among the scientific objectives of the ExoMars mission, the searching of the organics or volatiles species plays an important role. The Ma_Miss spectrometer (Mars Multispectral Imager for Subsurface) [2] will investigate the borehole generated by the drill and it will be able to characterize and map the presence of possible ices. In this work we developed a numerical model to predict the subsurface temperatures after the heat released by the drilling operations. The increase in temperature due to the drilling operations, in fact, could affect the survivor of the volatile species [3]. Here we report the results about subsurface temperature of Oxia Planum.</p> <p><strong>Numerical modeling</strong></p> <p>We developed a numerical modeling to predict the subsurface temperature of Oxia Planum. In the subsurface we solve the classical heat equation [3]:</p> <p><img src="" alt="" /></p> <p>where ρ is the density, c p the specific heat, K the thermal conductivity and T the temperature. Heat transfer occurs only by conduction since convection is negligible due to the small temperature gradients involved as well as the characteristic size of the sample. At the top we imposed a radiation boundary condition. In order to take into account the heat released by the drilling operations we imposed a frictional heating flux on the sides “in contact” with the drill (the lateral sides of the borehole of Fig.1). This flux is defined by the equation [3]:</p> <p><img src="" alt="" /></p> <p>where η is the coefficient of friction, Fn the thrust, ω the rotational velocity, r the radius of the hole and h the height of the domain of integration (in our case 50 cm).</p> <p>The parameters adopted in this work are F n = 300 N, rpm = 30 or 60, η = 0.3 or 0.9, tip density = 3500 kg m-3, tip thermal conductivity = 540 W m-1K-1, tip specific heat = 790 J kg-1K-1 and a drilling window of 90 min, characterized by 30 min in “on mode”, followed by 30 min in "off mode” and finally 30 min in “on mode”. The surface and subsurface of Oxia Planum is characterized by a thermal inertia of 650 TIU, with an initial temperature fixed to 200 K. Some assumptions are made: I) instantaneous drilling<br />(drill excavation is not modeled); 2) constant thrust; 3) constant rotational velocity.</p> <p><img src="" alt="" /></p> <p><em>Fig.1: Geometry adopted in this work. The borehole of the drilling system is represented by the cylinder embedded in this domain of integration, with a radius of 13 mm (the thickness of the drill tip).</em></p> <p>In Fig.2 we report an example of 1-D temperature profile at z=50 cm (the maximum depth of the borehole). In the x-axis we report the distance from the hole, where shadowed red rectangle identifies the drill (or equivalently the borehole). Top panel of Fig.2 is characterized by rpm=30 and η=0.3 while the bottom panel by rpm=30 and η = 0.9. From these plots we note a difference, in the maximum value after 90 minutes, of about 40 K in favour of the case with η=0.9. The increase in temperature due to the drilling operations, in case of η=0.9, respect the initial assumed value (200 K) is about 80 K. The initial value of 200 K is chosen since is close to the surface equilibrium temperature value for Mars. As in [4] we can calculate the lifetime of an ice spherical deposit of mass m0, with a radius equal to the radius of the drill tip. The relative loss of ice mass at time (t) after the deposit is raised the temperature T is:</p> <p><img src="" alt="" width="269" height="91" /></p> <p>where t is the time expressed in seconds. In this equation, Г represent the water rate emission, rp the radius of the tip and рice the density of the ice. By using the maximum sublimation rate, we obtain in case of rpm = 30 and η=0.3 a loss of about 60% of the initial mass, while in case η=0.9 of the loss is complete.</p> <p><img src="" alt="" /></p> <p>In Fig.2 we report an example of temperature internal profile after the heat released by the drilling operations. Both panels refer to rpm=30: top panel is characterized by η=0.3 while bottom panel by η=0.9.</p> <p><strong>Summary and Conclusions. </strong>We simulated the heat released by the drilling operations in different case of friction (η) and rotatonal speed (rpm) of the drill. We observed that in case of…
EGS - AGU - EUG Joint Assembly, Apr 1, 2003
<p><strong>1 – Introduction&amp... more <p><strong>1 – Introduction</strong></p> <p>The early dynamical evolution of the Solar System is nowadays clear to be likely occurred in an non isolated context, like many studies of Sun evolution inside an Open Cluster suggest (see Pfalzner, 2015 for istance). Such a framework indicates us that even protoplanetary matter around young stars may evolve in complex environments, which is further proved by some recent observations of protoplanetary disks around stars in Open Clusters (<span lang="en-GB">Mann </span><span lang="en-GB">et</span><span lang="en-GB"> al., 2015</span>).</p> <p>An important role in the evolution of a disk in a non isolated system may be played by secular perturbations due to the far field stars, and, on the other hand, by the strong perturbations induced, on a shorter time-scale, by the close fly-bys. Occasional encounters with passing-by stars may considerably affect the dynamical evolution of the gas and change the balance of distribution of matter around each star.</p> <p>We aim to investigate such a framework by means of 3D numerical hydrodynamical simulations, schematizing a solar-like star+disk system perturbed by close encountering stars.</p> <p>By means of a Lagrangian Smoothed Particles Hydrodynamics (SPH) scheme, we calculate the evolution of the gas by including also the thermal effects induced by both the propagation of the radiation through the optically thick disk and the effects of the radiation coming from the stars. The temperature profile of a disk, which is substantially dependent on the thermal scheme assumed, may determine the turbulent viscous evolution of the disk itself and its susceptibility to the strong macroscopical perturbations induced by fly-by events.</p> <p><strong>2 – gas mixing and gas migration</strong></p> <p>It is worth to consider some recent formation models according which the time scale of giant planet formation inside the disks may be less than 10<sup>5</sup> yr (Magni & Coradini, 2004; Brennecka et al., 2020), far shorter than the previous classical results which amount of the order of 10<sup>6</sup> yr . Such a framework changes considerably the action of the cluster in altering the disk evolution.  As a matter of fact, on one hand, the role of far field star becames less prominent in influencing the destiny of a gaseous disk since the secular perturbations has a small interval of time to act. On the other hand, the early stages of an Open Cluster are typically characterized by a chaotic non-relaxed state, in which the close interactions have a substantially high probability to occur. Thus, if the key processes inside the disk happen in a relatively short time, the disks itself have good chances to undergo strong perturbations by close approaching stars during its crucial evolutionary phases close to the planet formation stage.</p> <p>We are interested to investigate two peculiar phenomena connected to the transport of matter induced by fly-by perturbation. One is represented by the macroscopical transport of matter from the inner to the outer layers of the disk, which may explain a still opened question about the Solar System consisting in unexpected observation of crystalline sylicates in comets (Brownlee et al. 2006). Despite sylicate compounds in comets are expected to be amorphous, they present a crystalline structure which need to be generated in the hot inner regions, hence incompatible with the current cometary distances from the sun.</p> <p>On the other hand, we focus our attention to gas swapping among stars consisting in substantial capture and migration of matter towards another star during a close encounter. The simplest case that may happen is characterized by a star, previously lacking of any gas distribution around, that acquires a new disk. But a rather more complex situation occurs when gas migrates towards another disk during its phases of gaseous planet formation, altering the planetary cores feeding process.</p> <p>The figure 1 shows an interesting example of gas migrated and captured by an approaching star, the sequence illustrates the main phases of truncation of a protoplanetary revolving around a single solar-like star, and further formation of a secondary tiny disk around the second star.</p> <p><img src="data:image/png;base64,…
M. Ciarniello (1), M. C. De Sanctis (1), E. Ammannito (1,2), F. Capaccioni (1), M. T. Capria (1),... more M. Ciarniello (1), M. C. De Sanctis (1), E. Ammannito (1,2), F. Capaccioni (1), M. T. Capria (1), F. G. Carrozzo (1), S. Fonte (1), A. Frigeri (1), M. Giardino (1), A. Longobardo (1), G. Magni (1), E. Palomba (1), A. Raponi (1), F. Tosi (1), F. Zambon (1), C. A. Raymond (3), C. T. Russell (2) , J.-Y. Li (4) and the Dawn Science Team, (1) Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale de Astrofisica, Rome, Italy, ([email protected] ), (2) University of California Los Angeles, Earth Planetary and Space Sciences, Los Angeles, CA-90095, USA, (3) Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA-91109, USA (4) Planetary Science Institute, USA
Japan Geoscience Union, 2017
<p><strong>Abstract</strong></p> <p><br />We performed thermo... more <p><strong>Abstract</strong></p> <p><br />We performed thermophysical simulations of Oxia Planum, the landing site of the ExoMars 2022 mission [5]. The numerical simulations concern: I) the influence of the thermal inertia on the subsurface temperature at the latitude of Oxia Planum; II) the heat released in the subsurface by the drill installed on the ExoMars rover. The numerical simulations are performed using a 3-D model using the discretization technique of the finite element method (FEM).</p> <p><strong>1. Introduction</strong></p> <p>Numerical simulations are required to characterize, from a thermophysical point of view, Oxia Planum, the landing site of the mission ExoMars 2022. A drilling system is installed on the ExoMars rover and it will be able to analyze up 2 meters in the subsurface of Mars. The spectrometer Ma_Miss (Mars Multispectral Imager for Subsurface) [1] will investigate the lateral wall of the borehole generated by the drill, providing hyperspectral images. Among the scientific objectives of Ma_Miss there are the&#160;&#160; characterization and the mapping of possible volatiles. In this regard, numerical simulations are useful to understand if the temperatures in the subsurface are such as to preserve volatiles, especially after the heating provided during the drilling operations.</p> <p><strong>2. Numerical Method</strong></p> <p>We performed our simulations by using a 3-D finite element model [2, 3], which solves the classical heat equation in a parallelepipedal domain representing a portion of Oxia Planum, the landing site of the ExoMars mission. The top of this domain is modeled with a Gaussian random surface in order to simulate the roughness of the surface. The dimensions of the domain are 1cm x 1cm x 5cm. The depth (5 cm) has been chosen since it is compatible with the likely skin depth. At the top we imposed a radiation<br />boundary condition, while on the other sides zero heat flux is imposed. The initial temperature is set at 200 K, which is compatible with the surface equilibrium temperature. Self-heating between the facets of our domain is taken into account. We investigate: I) the dependence of the subsurface thermal response to different thermal inertia; II) the<br />heat released by the drill in the subsurface of Mars. In particular, for the point II, we assume: a) the drilling is instantaneous in a well-defined &#8220;drilling temporal window&#8221;; b) thrust and rotational velocity are constant. The contribution of the drill is taken into account by applying an heat flux (depending in particular on the thrust, angular velocity and frictional heating) on the wall of the rock matrix in contact with the drill.</p> <p><strong>3. Summary and conclusions</strong></p> <p>In Fig.1 we report an example of the results we obtained by applying our numerical model. Fig.1 shows the temperature profile vs time at different depths for two cases: case</p> <p><img src="data:image/png;base64,…
Science, 2011
c GM d ⋅ v0 ⋅ sin a′ cos b , where a′ = 172.18°is the direction to Earth projected into the flyby... more c GM d ⋅ v0 ⋅ sin a′ cos b , where a′ = 172.18°is the direction to Earth projected into the flyby plane and b = 3°is the direction angle to Earth above the flyby plane. Using the fit solution for Lutetia of GM = (11.34 T 0.11) × 10 −2 km 3 /s 2 , the analytical result of the relation above is 36.4 T 0.4 mHz. 4. H. Sierks et al., Science 334, 487 (2011). 5. Similar high bulk densities are known for the asteroids 4 Vesta, 16 Psyche, 20 Massalia, and 22 Kalliope, all
Journal of Geophysical Research, 2010
In this paper we describe the measurements obtained by the M channel of the Visual and Infrared T... more In this paper we describe the measurements obtained by the M channel of the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS-M) and the first scientific results derived from their analysis. The broad spectral coverage of the VIRTIS-M in the IR permitted the study of various phenomena occurring in the Martian atmosphere; observations were further exploited to achieve accurate absolute radiometric calibration. Nighttime data from the VIRTIS-M constrain the air temperature profile in the lower atmosphere (5-30 km), using variations in CO 2 opacity at 4.3 mm. A comparison of this data with the global circulation model (GCM) by Forget et al. (1999) shows a trend of slightly higher air temperature in the VIRTIS-M retrievals; this is accompanied by the presence of moderate decreases (∼5 K) in large sections of the equatorial region. This is potentially related to the occurrence of water ice clouds. Daytime data from the VIRTIS-M reveal CO 2 non-local thermodynamic equilibrium emission in the high atmosphere. A mapping of emission intensity confirms its strict dependence on solar zenith angle. Additionally, devoted limb observations allowed the retrieval of vertical emission intensity profiles, indicating a peak around 105 km in southern tropical regions. Ozone content can be effectively monitored by the emission of O 2 (a 1 D g) at 1.27 mm. Retrieved emission intensity shows that polar regions are particularly rich in ozone. Aerosol scattering was observed in the 1-2.5 mm region above the night region above the night disk, suggesting the occurrence of very high noctilucent clouds.
Astrobiology, 2008
The Jovian InfraRed Auroral Mapper (JIRAM) has been accepted by NASA for inclusion in the New Fro... more The Jovian InfraRed Auroral Mapper (JIRAM) has been accepted by NASA for inclusion in the New Frontiers mission "Juno," which will launch in August 2011. JIRAM will explore the dynamics and the chemistry of Jupiter's auroral regions by high-contrast imaging and spectroscopy. It will also analyze jovian hot spots to determine their vertical structure and infer possible mechanisms for their formation. JIRAM will sound the jovian meteorological layer to map moist convection and determine water abundance and other constituents at depths that correspond to several bars pressure. JIRAM is equipped with a single telescope that accommodates both an infrared camera and a spectrometer to facilitate a large observational flexibility in obtaining simultaneous images in the L and M bands with the spectral radiance over the central zone of the images. Moreover, JIRAM will be able to perform spectral imaging of the planet in the 2.0-5.0 m interval of wavelengths with a spectral resolution better than 10 nm. Instrument design, modes, and observation strategy will be optimized for operations onboard a spinning satellite in polar orbit around Jupiter. The JIRAM heritage comes from Italian-made, visual-infrared imaging spectrometers dedicated to planetary exploration, such as VIMS-V on Cassini, VIRTIS on Rosetta and Venus Express, and VIR-MS on the Dawn mission.
By 7-October-2011, the Dawn mission will have completed Survey orbit and commenced high altitude ... more By 7-October-2011, the Dawn mission will have completed Survey orbit and commenced high altitude mapping of 4Vesta. We present a preliminary analysis of data acquired by Dawn's Framing Camera
Advances in Space Research, 2001
IPSE is a micro-laboratory for Mars soil and environment analysis. It provides the capability to ... more IPSE is a micro-laboratory for Mars soil and environment analysis. It provides the capability to serve and handle scientific miniaturised instruments accommodated inside its envelope. The instruments have the goal to perform in situ study of the collected martian samples, thus quantitatively characterizing the mineralogy, the composition, the mierophysical structure of the materials of the Martian soils down to the depth available to the sampling mechanism. Given the complex structure of the surface material it will be essential to perform in-situ science, both at the surface and at different depths. This is done in order to validate remote sensing observations through specific measurements, identify local characteristics of the selected landing areas, document sample collection both for in situ and sample return. IPSE is an example of a small and flexible lab, that can be integrated on different Landers and Megarovers. IPSE contains: • Scientific instruments • A small robotic arm-with five degrees of freedom-to provide samples to the IPSE instruments. • Power conditioning. • Electronics for system and thermal control, communications and instrument data handling. The Phase A report for all the IPSE instruments has been already provided to the Italian Space Agency. The experiments MAGO, IRMA, MA_FLUX are inherited from previous space qualified instruments and breadboards of them already exist. DOSE is a new experiment, however, a breadboard of the detector and of the photomultiplier is under development.
Advances in Space Research, 2001
Recently agreements have been signed between the Italian Space Agency (ASI) and ESA and NASA for ... more Recently agreements have been signed between the Italian Space Agency (ASI) and ESA and NASA for the exploration of Mars. These agreements initiate the participation of the Italian scientific community as well as the Italian industrial community in the international program to explore Mars. ASI and NASA have agreed to cooperate in a long-term systematic program of robotic exploration of Mars sustained by a series of missions to Mars in support of their respective strategic goals. The Mars Surveyor Program is a sustained series of missions to Mars, each of which will provide important focused scientific results. ASI is expecting to participate in the future missions with the provision of two subsystems: a subsurface drill and a scientific package. The drill will be capable of drilling and collecting several samples and delivering them to instruments located within a scientific package fixed on a landed platform. ASI is also providing scientific instruments placed on a scientific package (IPSE) fixed with on the lander platform. The goals of the investigations are to study physical and mineralogical properties of bulk soil and dust (atmospheric and surface) as well as geochemical, structural, radiation and geophysical properties of subsurface materials to a depth of 0.5 meters.
Advances in Space Research, 1990
... 13. A. Coradimi, P. Cerroni, C. Federico and G. Magni, Formation of the satellites of the out... more ... 13. A. Coradimi, P. Cerroni, C. Federico and G. Magni, Formation of the satellites of the outer Solar System: sources of their atmospheres, in: Origin and evolution of ... W. Cabot, VH Canuto, 0. Hubickyj, and JB Pollack, The role of turbulent convection in the primitive solar nebula. ...
ABSTRACT The relation between the formation of the regular satellite system around giant planets,... more ABSTRACT The relation between the formation of the regular satellite system around giant planets, and the formation of the central planet is discussed. Some characteristics of regular satellites systems are quite similar, and suggest a common origin in an accretion disk present around the central body. The origin of this disk is described with attention being given to the so called &#39;disk phase&#39;, the disk phase links the formation of the primary body to that of satellites. The subsequent stages of the disk evolution can lead first to the formation of intermediate size bodies, and further, through the collisional evolution of these bodies, to the birth of satellite &#39;embryos&#39; capable of gravitationally capturing smaller bodies. The predictivity of this scheme in explaining the characteristics of different satellite systems is reviewed.
Uploads
Papers by gianfranco magni