[ { "id": "authors:bv16z-0rv79", "collection": "authors", "collection_id": "bv16z-0rv79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100412-091242476", "type": "article", "title": "Subsurface heat transfer on Enceladus: Conditions under which melting occurs", "author": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Pankine", "given_name": "Alexey A.", "clpid": "Pankine-A-A" } ], "abstract": "Given the heat that is reaching the surface from the interior of Enceladus, we ask whether liquid water is likely and at what depth it might occur. The heat may be carried by thermal conduction through the solid ice, by the vapor as it diffuses through a porous matrix, or by the vapor flowing upward through open cracks. The vapor carries latent heat, which it acquires when ice or liquid evaporates. As the vapor nears the surface it may condense onto the cold ice, or it may exit the vent without condensing, carrying its latent heat with it. The ice at the surface loses its heat by infrared radiation. An important physical principle, which has been overlooked so far, is that the partial pressure of the vapor in the pores and in the open cracks is nearly equal to the saturation vapor pressure of the ice around it. This severely limits the ability of ice to deliver the observed heat to the surface without melting at depth. Another principle is that viscosity limits the speed of the flow, both the diffusive flow in the matrix and the hydrodynamic flow in open cracks. We present hydrodynamic models that take these effects into account. We find that there is no simple answer to the question of whether the ice melts or not. Vapor diffusion in a porous matrix can deliver the heat to the surface without melting if the particle size is greater than ~1 cm and the porosity is greater than ~0.1, in other words, if the matrix is a rubble pile. Whether such an open matrix can exist under its own hydrostatic load is unclear. Flow in open cracks can deliver the heat without melting if the width of the crack is greater than ~10 cm, but the heat source must be in contact with the crack. Frictional heating on the walls due to tidal stresses is one such possibility. The lifetime of the crack is a puzzle, since condensation on the walls in the upper few meters could seal the crack off in a year, and it takes many years for the heat source to warm the walls if the crack extends down to km depths. The 10:1 ratio of radiated heat to latent heat carried with the vapor is another puzzle. The models tend to give a lower ratio. The resolution might be that each tiger stripe has multiple cracks that share the heat, which tends to lower the ratio. The main conclusion is that melting depends on the size of the pores and the width of the cracks, and these are unknown at present.", "doi": "10.1016/j.icarus.2009.09.015", "issn": "0019-1035", "publisher": "Elsevier", "publication": "Icarus", "publication_date": "2010-04", "series_number": "2", "volume": "206", "issue": "2", "pages": "594-607" }, { "id": "authors:09a24-mr984", "collection": "authors", "collection_id": "09a24-mr984", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130219-103653585", "type": "article", "title": "Interannual variability of Mars global dust storms: an example of self-organized criticality?", "author": [ { "family_name": "Pankine", "given_name": "Alexey A.", "clpid": "Pankine-A-A" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" } ], "abstract": "Previous simulations of martian global dust storms with a simple low-order model showed the desired interannual variability of storms if one of the model parameters\u2014the threshold wind speed for starting saltation and lifting dust from the surface\u2014was finely tuned. In this paper we show that the fine-tuning of this parameter could be the result of negative feedback in which processes associated with global dust storms raise the threshold and small-scale processes like dust devils, which are active in years between the storms, lower the threshold.", "doi": "10.1016/j.icarus.2004.04.006", "issn": "0019-1035", "publisher": "Elsevier", "publication": "Icarus", "publication_date": "2004-08", "series_number": "2", "volume": "170", "issue": "2", "pages": "514-518" }, { "id": "authors:c0wj2-mn234", "collection": "authors", "collection_id": "c0wj2-mn234", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151223-140035251", "type": "article", "title": "Directed aerial robot explorers for planetary exploration", "author": [ { "family_name": "Pankine", "given_name": "A. A.", "clpid": "Pankine-A-A" }, { "family_name": "Aaron", "given_name": "K. M.", "clpid": "Aaron-K-M" }, { "family_name": "Heun", "given_name": "M. K.", "clpid": "Heun-M-K" }, { "family_name": "Nock", "given_name": "K. T.", "clpid": "Nock-K-T" }, { "family_name": "Schlaifer", "given_name": "R. S.", "clpid": "Schlaifer-R-S" }, { "family_name": "Wyszkowski", "given_name": "C. J.", "clpid": "Wyszkowski-C-J" }, { "family_name": "Ingersoll", "given_name": "A. P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Lorenz", "given_name": "R. D.", "orcid": "0000-0001-8528-4644", "clpid": "Lorenz-R-D" } ], "abstract": "Global Aerospace Corporation (GAC) is developing a revolutionary system architecture for exploration of planetary atmospheres and surfaces from atmospheric altitudes. The work is supported by the NASA Institute for Advanced Concepts (NIAC). The innovative system architecture relies upon the use of Directed Aerial Robot Explorers (DAREs), which essentially are long-duration-flight autonomous balloons with trajectory control capabilities that can deploy swarms of miniature probes over multiple target areas. The balloons will serve a dual purpose as independent explorers and as microprobe delivery systems for targeted observations. Trajectory control capabilities will offer unprecedented opportunities in high-resolution, targeted observations of both atmospheric and surface phenomena. Multifunctional microprobes will be deployed from the balloons once over the target areas, and perform a multitude of functions, such as atmospheric profiling or surface exploration, relaying data back to the balloons or an orbiter. This architecture will enable low-cost, low-energy, long-term global exploration of planetary atmospheres and surfaces. We report here results of the preliminary analysis of the trajectory control capabilities and potential applications for DARE platforms at Venus, Mars, Titan and Jupiter.", "doi": "10.1016/j.asr.2003.07.049", "issn": "0273-1177", "publisher": "Elsevier", "publication": "Advances in Space Research", "publication_date": "2004", "series_number": "10", "volume": "33", "issue": "10", "pages": "1825-1830" }, { "id": "authors:psfgy-h3997", "collection": "authors", "collection_id": "psfgy-h3997", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121212-085654370", "type": "article", "title": "Interannual Variability of Martian Global Dust Storms - \n Simulations with a Low-Order Model of the General Circulation", "author": [ { "family_name": "Pankine", "given_name": "A. A.", "clpid": "Pankine-A-A" }, { "family_name": "Ingersoll", "given_name": "A. P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" } ], "abstract": "We present simulations of the interannual variability of martian global dust storms (GDSs) with a simplified low-order model (LOM) of the general circulation. The simplified model allows one to conduct computationally fast long-term simulations of the martian climate system. The LOM is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting LOM consists of 12 coupled nonlinear ordinary differential equations describing atmospheric dynamics and dust transport within the Hadley cell. The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit the output of the NASA AMES GCM and the fit is generally very good.\nInterannual variability of GDSs is possible in the LOM, but only when stochastic forcing is added to the model. The stochastic forcing could be provided by transient weather systems or some surface process such as redistribution of the sand particles in storm generating zones on the surface. The results are sensitive to the value of the saltation threshold, which hints at a possible feedback between saltation threshold and dust storm activity. According to this hypothesis, erodable material builds up as a result of a local process, whose effect is to lower the saltation threshold until a GDS occurs. The saltation threshold adjusts its value so that dust storms are barely able to occur.", "doi": "10.1006/icar.2001.6757", "issn": "0019-1035", "publisher": "Elsevier", "publication": "Icarus", "publication_date": "2002-02", "series_number": "2", "volume": "155", "issue": "2", "pages": "299-323" }, { "id": "authors:x98jj-0rc72", "collection": "authors", "collection_id": "x98jj-0rc72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121212-135114442", "type": "article", "title": "Ejecta Pattern of the Impact of Comet Shoemaker\u2013Levy 9", "author": [ { "family_name": "Pankine", "given_name": "Alexey A.", "clpid": "Pankine-A-A" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" } ], "abstract": "The collision of Comet Shoemaker\u2013Levy 9 (SL 9) with Jupiter created crescent-shaped ejecta patterns around impact sites. Although the observed impact plumes rose through a similar height of \u223c3000 km, the radii of the created ejecta patterns differ from impact to impact and generally are larger for larger impacts. The azimuthal angle of the symmetry axis of the ejecta pattern is larger than that predicted by the models of oblique impacts, due to the action of the Coriolis force that rotates ejecta patterns counterclockwise from the south. We study the formation of ejecta patterns using a simple model of ballistic plume above a rotating plane. The ejected particles follow ballistic trajectories and slide horizontally for about an hour after reentry into the jovian atmosphere. The lateral expansion of the plume is stopped by the friction force, which is assumed to be proportional to the square of the horizontal velocity. Two different mass\u2013velocity distributions used in the simulations produce qualitatively similar results. The simulated ejecta patterns fit very well the \"crescents\" observed at the impact sites. The sizes and azimuthal angles of symmetry axis of ejecta patterns depend on a parameterL, which has dimension of length and is related to the mass of the fragment. Thus more massive impacts produce larger ejecta patterns that are rotated through a wider angle.", "doi": "10.1006/icar.1998.6070", "issn": "0019-1035", "publisher": "Elsevier", "publication": "Icarus", "publication_date": "1999-04-01", "series_number": "2", "volume": "138", "issue": "2", "pages": "157-163" } ]