|
|
|||||||||||||||
Journal of Cosmology, 2011, Vol , In Press. JournalofCosmology.com, 2011 Katarina Miljković, Ph.D. The Open University, Planetary and Space Sciences Research Institute, Walton Hall, MK7 6AA, Milton Keynes, United Kingdom
Europa, like Earth, is unique and may have the three necessary conditions for existence of life as we know it: carbon, water and energy; hence Europa is of major interest for future space missions. However, costs and technological issues present obstacles to placing a robotic analyzer on Europa. Micrometeoroid bombardment of the bodies in the solar system is a constant process. Europa has low gravity and a tenuous atmosphere which allows for this bombardment to cause ejection of the fresh surface material into the surrounding space with little atmospheric ablation. If there were a dust analyser in orbit around Europa, it could sample the surface material via the collection and analysis of the ejected surface fragments. No landing probes would be required.
1. Introduction In 1610, Galileo Galilei reported in The Starry Messenger the discovery of four “planets”, revolving around Jupiter which he named The Medicean stars. It was not until the mid-20th century that the physical and chemical environment of Io, Europa, Ganymede and Callisto could be studied in detail. These investigations led to discoveries which some interpreted as supporting the possibility that Europa could harbor life.
 Groundbased observations by Moroz (1966) suggested that Europa's surface is mostly covered with water ice. In 1979, the Voyager 1 and Voyager 2 spacecraft recorded the first closeup images of Europa. Even though the resolution was only ~2 4 km pixel1, the images revealed Europa's bright surface and a network of long bright and dark bands that looked like 'a ball of string' (Smith et al., 1979a; Smith et al.. 1979b). The next spacecraft to visit Europa was Galileo in the period 1994 2000. The imaging resolution obtained by Galileo was as high as 6 m pixel1 (Greenley et al., 2004) which allowed the detection of many more interesting features on Europa's surface (Greenley et al., 2000; Figueredo and Greenley, 2000), some of which suggested the probable existence of subsurface liquid water (as speculated by Ojakangas and Stevenson, 1989), a salty ocean (Zimmer and Khurana, 2000), an icy crust and a rocky core (Anderson et al., 1997).
 The three ingredients necessary for the origin, evolution and existence of life, as we know it, are an energy source, liquid water and organics. It is possible that all these ingredients could exist on Europa (Cooper et al., 2001; Chyba and Phillips, 2002; Chela-Flores 2010; Tyler, 2010), and this supports the possibility of life. Many theories have been developed in the past 30 years about how and where on Europa some form of primitive life could exist (e.g. Consolmagno and Lewis, 1978; Reynolds et al., 1983; Gaidos et al., 1999; Kargel et al., 2000; Chyba and Phillips, 2002; Raulin, 2005; Lipps and Rieboldt, 2005; Greenberg, 2005). 2. A Mission to Europa Jupiter and its moons have been chosen as one of the primary exploration targets in the Solar system by both ESA and NASA in a joint proposal for EuropaJupiter System Mission (EJSM). EJSM would be composed on two orbiters, JupiterEuropa Orbiter (JEO) and Jupiter Ganymede Orbiter (JGO), whose primary goals would be investigation of Europa and Ganymede from 100200 km and 200600 km orbital altitudes, respectively (Blanc et al., 2009). Even though it was proposed in the initial stages of the EJSM planning, unfortunately according to the latest EJSM reports a dust detector is unlikely to be a part of the JEO payload. Still, a study proposed here shows that if there were a dust detector onboard JEO or any other future Europa orbiter, it could be possible to sample the surface without making a landing. 3. Europa's Interior and Surface Properties For geologically inactive, atmosphereless bodies in the Solar system, the surface age can be calculated from the frequency of large craters on their surface. However, on Europa's surface there is a paucity of large impact craters. Hence, Europa's surface seems to be younger than 100 million years (Moore et al. 1998). This is unlikely because Europa should have evolved at a similar time as the rest of the Jupiter system. Instead, it appear that the scarcity of surface craters is due to the likelihood that this moon has an active surface (Greenberg, 2005), showing only the last ~1 % of its total history (Greenley et al., 2004).
 During Europa's rotation and revolution, its diurnal, radial and librational deformations cause stressing of its icy shell (similar to tectonic processes) and tidal heating of the interior. The stressing of the icy shell generates different kinds of surface cracks such as lineaments (Geissler et al., 1998) or cycloidal features (Hoppa et al., 1999). The localized melting induced by the tidal heating creates other features in the icy shell, such as lenticulae and larger chaos regions (Sotin et al., 2002; Greenberg et al., 1998) or folds, assumed to be created by localised large temperature gradients (Prockter and Pappalardo, 2000). The ice shell thickness is estimated to be at least 3 to 4 km thick (Turtle and Pierazzo, 2001) and up to 20 to 40 km (Spohn and Schubert, 2003).
 Europa's geological activity suggests that some sort of cryovolcanism could also exist on Europa (e.g. Crawford and Stevenson, 1988; Kargel, 1995). The nonsynchronous stresses are much higher than diurnal, and are potentially sufficiently strong to open deep cracks (such as those km long linear features observed) in the icy shell, potentially exposing Europa's interior material (Greenberg et al., 1998). Once a crack opens, it could be possible for the subsurface material to be exposed and then frozen near the surface (Greenberg et al., 1998). Dissipation of gravitationally induced strains warms the interior in a form of tidal heating (Jeffreys, 1961), indicating the likely existence of a global subsurface ocean. Subsurface ocean is assumed to be cold, reduced, alkaline, Na, Clrich but not saline, depleted in Mg, sulphides and sulphates, with possibilities of forming complex organic molecules (Zolotov and Shock, 2004; Zolotov et al., 2006).
 On a micro scale and shallow surface depths which are affected by micrometeoroid bombardment and ionizing radiation, Europa's surface could be described as a dirtyice regolith (Pappalardo et al., 2004). Almost Europa's entire surface is covered with porous amorphous water frost (Morrison and Burns, 1976; Pollack et al., 1978), or a combination of ice and snow low in density and mechanical strength (Ostro, 1982; Hansen and McCord, 2004).
 2.1. Chemical properties of Europa's top surface. Globally, Europa's trailing side is generally darker than the leading side, probably due to higher irradiation flux at that side, whereas the leading side is almost entirely composed of water ice (Pollack et al., 1978). However, some darker, reddish, regions are distributed in a patchy pattern on both hemispheres (McCord et al., 1998a,b). In these regions the surface water ice contains a higher percentage of impurities. By analysing the spectra recorded by Galileo Near Infrared Mapping Spectrometer (NIMS), these impurities have been identified as hydrated minerals, sulphates and possibly hydrocarbons, such are NaCO3. 10H2O, MgSO4.nH2O and/or NaSO4.nH2O, n=6, 7 (McCord et al., 1998a,b; Spencer et al., 2006). The patchy distribution indicates an endogenous rather than an exogenous origin, since if the origin was purely exogenous the distribution of salts would be expected to be more uniform. This argues in favour of the active moon scenario, in which the interior material circulates inside the moon, allowing warmer material to uplift towards the surface, melt the ice and embed there as the surface refreezes (Orlando et al., 2005; PrietoBallesteros et al., 2005; ChelaFlores, 2006) allowing from any material from the warm ocean to refreeze close to the surface.
 3. Micrometeoroid Dust in the Solar and Jupiter's system Solid micron-sized dust particles, called micrometeoroids, are a common constituent in the Solar system. Their trajectory and velocity are mostly governed by gravity of the bodies in the Solar system. Once they reach the surface of those bodies, usually at tens of km s1, they cause ejection of surface material into the surrounding space. Micrometeoroids that originate from within the Solar system are called interplanetary dust particles (IDPs). At Jupiter's distance from the Sun, the most common are IDPs originating from the asteroidal belt and Oort cloud (Divine, 1994; Colwell and Horányi, 1996; Grün et al., 2001). As the Solar system moves through the Galaxy, it passes through the dust that originates from beyond the Solar system; therefore those interstellar dust (ISD) particles can also reach inside the Solar system (Landgraf et al., 1999). Jupiter and its system of many orbiting lunar bodies resemble a miniature Solar system. The immense mass of Jupiter and its corresponding strong gravitational field allow Jupiter's system to act not only as a sink for large bodies such as asteroids and comets (proof of which are recorded comet impacts into Jupiter in 1994 and 2010) but also for the smaller, much more numerous dust particles, both those originating externally (trapped by Jupiter's gravity) or generated within the Jupiter system. Dust fragments that originate from the Jupiter system are referred to as Jupiter system dust (JSD). 3.1. Jupiter's system dust. Since Jupiter's system is too distant for ground based observations of dust in its system, we can only rely on spacecraft missions. Even by spacecraft, the amount of gathered data is sparse. The Pioneer 10 and Pioneer 11 missions revealed dust in the Jupiter system (Humes et al., 1974), the nature of which was investigated in greater details by later missions, Galileo and Ulysses, in the 1990s and most recently by the Cassini flyby in 2000. The analysis of dust in the outer Solar system, in particularly complex systems such as Jovian system, is not simple. The most important data for the study of the dust in the Jupiter's system were collected by the Dust Detector System (DDS) onboard the Galileo spacecraft. DDS measurements allowed a distinction between at least three different groups of dust particles within 60 RJ from Jupiter (Grün et al., 1997; Krüger and Grün, 2002): (a) dust surrounding the Galilean satellites (Krüger et al., 1999); (b) streams of dust particles spreading out to more than 1 AU from Jupiter (Grün et al., 1993) and (c) dust rings in Jupiter's equatorial plane (Thiessenhusen et al., 2000). 3.1.1. Dust around Europa. Between December 1995 and January 2002, the Galileo spacecraft flew by the Galilean satellites a total of 31 times at no closer than 600 km away from the moon's surface (Krüger and Grün, 2002). During many of these flybys (lasting ~2 h each (Krüger et al., 2003)), the impact rates peaked during the 30 minutes of closest approach and the number density decreased with distance away from the surface of the satellites, indicating that the surface of the satellites could be a possible origin of the dust (Grün et al., 1997). However, only a handful of dust from this cloud has been detected by DDS (Krüger and Grün, 2002). Mostly IDPs and to a lesser extent ISD and JSD are responsible for the creation of the dust population around Europa, (Miljković, 2009). Europa's low gravity allows the ejected fragments to reach higher altitudes than at more massive bodies and a very tenuous atmosphere (Hall et al., 1995; 1998) cause very little ablation of the incoming micrometeoroids and ejected surface fragments. Since the micrometeoroid bombardment is a constant process, there is a constant production of freshly ejected dust from Europa's surface, such that the dust cloud around it seems permanent (Krüger and Grün, 2002). Those ejecta dust fragments are of micron size and therefore gravity is the dominant force (Krüger and Grün, 2002). Depending on their kinetic energy, the ejecta fragments could fall back to the surface or leave Europa's gravitational influence. Detailed spatial and mass densities calculations of the dust population around Europa are reported in Miljković (2009), Krüger et al. (2003), Krivov et al. (2003), Sremčević et al. (2003; 2005).
 No chemical analysis of the dust in Jupiter's system has been made yet, apart from the Cassini's Cosmic Dust Analyser (CDA) measurements of the Io stream dust at more than 1 AU away from Jupiter (Postberg et al., 2006). The main constituent of the detected Io stream dust was NaCl, with Na2SO4 and K2SO4 as minor constituents. Because these grains were detected far out in the Jupiter's system, it can be assumed that any outer, probably, icy layers were stripped by a long exposure to Jupiter's ionizing radiation. However, in the case of freshly generated dust detected at low orbital altitudes (soon after its creation), there is not enough time for the ionizing radiation to alter its composition significantly (Miljković, 2009; Miljković et al., 2010).
 Since Europa's top surface material is composed of pure water ice, sulphates and possibly hydrocarbons, it can be expected that the dust fragments ejected from the Europa's surface by micrometeroid bombardment contain the chemical signature of these compounds and their decomposition products. Many theoretical calculations and high velocity impact experiments were made in the past related to pure ice (e.g. Burchell et al., 2001; Burchell and Johnson, 2005; Miljković, 2009; Iijima et al., 1995; Koschy et al., 2001), various rocks (e.g. Ahrens, 1993), homogeneous (e.g. Arakawa et al., 2000; Hiraoka et al., 2008) and inhomogeneous (e.g. Sharp and de Carli, 2006) mixtures that provided a great knowledge of the impact response of materials that could also be used as surface analogues to Europa and other Solar system bodies. The cratering mechanisms (e.g. Melosh, 1980) and rescaling of impacts to planetary scales (e.g. Housen et al., 1983) have been studied in details over the years. Going up a level in material complexity, a number of impact experiments made into complex organic and biological materials, including various bacteria showed that in some impacts these compounds survived and in some were destroyed (Horneck et al., 2001; Mastrapa et al., 2001; Burchell et al., 2003; Willis et al., 2006; Bowden et al., 2009). Therefore, even if there were any complex biologically related material contained in the top surface on Europa, there is a possibility for it to survive the micrometeoroid ejection process. Although, more investigation of impact survivability in complex materials is needed before any detailed conclusions could be made. 4. Using a Dust Analyser to Sample the (Sub)Surface Material on Europa A combined dust detector instrument composed of a dust capture device and a mass spectrometer should be able to provide a satisfying chemical analysis of the dust fragments ejected from the surface (Taylor et al., 2007). The dust analyser should be capable of detecting icy and sulphate compounds as well as organics (e.g. Schonfeld, 1982; Carlson and Hand, 2006) and other biomarkers (Miljković and Taylor, 2007), ideally sulphur and other stable isotopic fractionations (Kaplan, 1975; Bhattacherjee and ChelaFlores, 2004; Seckbach and ChelaFlores, 2007). Relative impact speeds from these dust ejecta fragments to an inorbit detector, would typically be no more than a couple of km/s. This impact speed is generally low for complete vaporisation of the impactor (incoming dust into the detector), therefore the initial conditions for dust capture should preserve genuine surface chemistry. Intensive research on the creation of the dust cloud around Europa, including a comparison with previous models (Krivov et al., 2003; Krüger et al., 2003) is presented in Miljković, 2009; Miljković et al., 2009. This research was composed of high velocity impact modelling and experiments done at the Open University's Hypervelocity impact laboratory (Patel et al., 2010; Taylor et al., 2006; McDonnel, 2006). Our results show that the total dust density should be ~0.8 m-3 at 200 km altitude above Europa's surface. After taking into account the ejecta velocities, the flux of ejected surface dust fragments should be ~2000 m-2s-1 into a sweeping dust detector. However, the dust density and flux are strongly dependant on the surface strength, which could vary locally and bring even up to a magnitude change in dust density (Miljković, 2009). The expected mass range of the ejected surface fragments included in the calculations was 10-15 g to 10-8 g. A long term orbital mission could then collect a large amount of dust data, sufficient to represent the Europa's surface chemical composition. 5. Conclusions Detection and analysis of the dust around Europa could provide information about its surface, as the surface composition should be “written” in the detected dust. Assuming that the internal material circulates inside the moon and could reach very close to the surface in that process, it could be assumed that it is possible to have both surface and subsurface material ejected from Europa's surface by micrometeoroid bombardment. The composition of the ejected dust fragments should be very similar to the actual surface material of the regions from which they were ejected. After taking into account the exposure to a shock during a micrometeoroid impact and a relatively gentle capture process by the dust detector, the surface chemistry could be mostly preserved or retraced by using the current shock physics knowledge. Due to Europa's active and icy surface, there are large uncertainties and risks associated with landing a probe on the Europa's surface. Hence, this is not just safer, but much cheaper and technically less demanding that landing way to sample the surface of Europa.
Ahrens, T.J. (1993) Equations of state, in HighPressure shock compression of solids, (Eds.) J.R. Assay and M. Shahinpoor, XIII, 412, 751113, SpringerVerlag, New York, USA. Ai, H.A., Ahrens, T.J. (2004) Dynamic tensile strength of terrestrial rocks and application to impact cratering, Meteoritics & Planetary Science 39, 2, 233–246. Anderson, J.D., Lau, E.L., Sjogren, W.L., Schubert, G., Moore, W.B. (1997) Europa's differentiated internal structure: Influences from two Galileo encounters, Science, 276, 1236 – 1239. Arakawa, M., Higab, M., LeliwaKopysty'ski, J., Maeno, N. (2000) Impact cratering of granular mixture targets made of H2O ice–CO2 ice–pyrophylite, Planet. Space Res. 48, 14371446. Blanc, M., Pappalardo, R., Greenley, R., Clark, K., Lebreton, J.P., Stankov, A., Grunthaner, P., Falkner, P., Fujimoto, M., Zelenyi, L. (2009) The EuropaJupiter system mission: study results and prospects, International workshop on Europa lander: Science goals and experiments, 9 – 13 February, 2009, Space Research Institute (IKI), Moskow, Russia. Bhattacherjee, A.B. and ChelaFlores, J. Search for bacterial waste as a possible signature of life on Europa, in Life in the Universe: From the Miller Experiment to the Search for Life on Other Worlds. Edited by J. Seckbach, J. ChelaFlores, Tobias Owen, and François Raulin. 387. (ebook). Published by Springer, Berlin, 2005, p.257. Bowden, S.A., Parnell, J., Burchell, M.J. (2009) Survival of organic compounds in ejecta from hypervelocity impacts on ice, Int. J. Astrobiology 8 (1) 19–25. Burchell, M.J., Grey, I.D.S., Shrine, N.R.G (2001) Laboratory investigations of hypervelocity impact cratering in ice, A&J.Space Rex 28, 10, 15211526. Burchell, M.J., Galloway, J.A., Bunch, A.W., Brandăo, P.F.B. (2003) Survivability of bacteria ejected from icy surfaces after hypervelocity impact, in Origins of Life and Evolution of the Biosphere 33: 53–74, 2003. Burchell, M.J. and E. Johnson, E. (2005) Impact craters on small icy bodies such as icy satellites and comet nuclei, Mon. Not. R. Astron. Soc. 360, 769–781. Carlson, R.W., Anderson, M.S., Johnson, R.E., Schuman, M.B., Yavrouian, A.H. (2002) Sulfuric acid production on Europa: The radiolysis of sulfur in water ice, Icarus 157, 456–463. Carlson, R.W. and Hand, K.P. (2006) Biomarkers on Europa: Unique signatures produced by radiolysis?, EPSC, Berlin, Germany, September 2006., p.472. Carlson, R.W., Johnson, R.E., Anderson, M.S. (1999) Sulfuric acid on Europa and the radiolytic sulfur cycle, Science, 286, 9799. ChelaFlores, J. (2006) The sulphur dilemma: are there biosignatures on Europa's icy and patchy surface?, Int. J. Astrobiol., 5, 17 – 22. Chela-Flores, J. (2010). From the Moon to the Moons: Encedalus and Europa. The Search for Life and Reliable Biomarkers. Journal of Cosmology, 5, 971-981. Chyba, C. and Phillips, C.S. (2002) Europa as an abode of life, in Origins Life Evol. B., 32, 47 – 68, Kluwer Academic Publishers, Springer, Netherlands. Colwell, J.E. and Horányi, M. (1996) Magnetospheric effects on micrometeoroid fluxes, J. Geophys. Res. 101 (E1), 2169 – 2175. Consolmagno, G.J. and Lewis, J.S. (1978) The evolution of icy satellite interiors and surfaces, Icarus, 34, 280 – 293. Cooper, J.F., Johnson, R.E., Mauk, B.H., Garrett, H.B., Gehrels, N. (2001) Energetic ion and electron irradiation of the icy Galilean satellites, Icarus, 149, 133 – 159. Crawford, G.D. and Stevenson, D.J. (1988) Gasdriven water volcanism and the resurfacing of Europa, Icarus, 73, 66 – 79. Delitsky, M.L. and Lane, A.L. (1998) Ice Chemistry on the Galilean Satellites, JGR 103(E13), 3139131403. Divine, N. (1993), Five populations of Interplanetary Meteoroids, J. Geophys. Res., 98 (E9), 17029 17048. Figueredo, P.H. and Greenley, R. (2000) Geological mapping of the northern leading hemisphere of Europa and Galileo solidstate imaging data, J. Geophys. Res., 105 (E9), 22629 – 22646. Gaidos, E.J., Nealson, K.H., Kirschvink, J.L. (1999) Life in icecovered oceans, Science, 284, 1631 – 1633. Galilei, Galileo (1610) The starry messenger, Venice. Geissler, P.E., Greenberg, R., Hoppa, G., McEwen, A., Tufts, R., Phillips, C., Clark, B., OckertBell, M., Helfenstein, P., Bums, J., Veverka, J., Sullivan R., Greenley, R., Pappalardo, R.T., Head III, J.W., Belton, M.J.S., Denk, T. (1998) Evolution of lineaments on Europa: clues from Galileo multispectral imaging observations, Icarus, 135, 107 – 126. Greenberg, R., Geissler, P., Hoppa, G., Tufts, B.R., Durda, D.D., Pappalardo, R., Head, J.W., Greenley, R., Sullivan, J., Carr, M.H. (1998) Tectonic processes on Europa: tidal stresses, mechanical response, and visible features, Icarus, 135, 64 – 78. Greenberg, R. (2005) Europa: The Ocean Moon: Search for an Alien Biosphere, Springer–Praxis, Chichester, UK. Greenley, R., Figueredo, P.H., Williams, D.A., Chuang, F.C., Klemaszewski, J.E., Kadel, S.D., Prockter, L.M., Pappalardo, R.T., Head III, J.W., Collins, G.C., Spaun, N.A., Sullivan, R.J., Moore, J.M., Senske, D.A., Tufts, B.R., Johnson, T.V., Belton, M.J.S., Tanaka, K.L. (2000) Geologic mapping of Europa, J. Geophys. Res., 105 (E9), 22559 –22578. Greenley, R., Chyba, C.F., Head III, J.W., McCord, T.B., McKinnon, W.B., Pappalardo, R.T., Figueredo, P. (2004) Geology of Europa in Jupiter. The Planet, Satellites and Magnetosphere, T. Bagenal, T. Dowling and W. KcKinnon, (eds.), Cambridge University Press, Cambridge, United Kingdom, 329 – 347. Grün, E., Zook, H.A., Baguhl, M., Balogh, A., Bame, S.J., Fechtig, H., Forsyth, R., Manner, M.S., Horányi, M., Kissel, J., Lindblad, B.A., Linkert, D., Linkert, G., Mann, I., McDonnell, J.A.M., Morfill, G.E., Phillips, J.L., Polanskey, C., Schwehm, G., Siddique, N., Staubach, P., Svestka, J., Taylor, A. (1993) Discovery of Jovian dust streams and interstellar grains by the Ulysses spacecraft, Nature, 362, 428 – 430. Grün, E., Krüger, H. and Dermott, S. et al. (1997) Dust measurements in the Jovian magnetosphere, Geophys. Res. Lett., 24, 2171. Grün, E., Baguhl, M., Svedhem, H., Zook, H.A. (2001) In situ measurements of cosmic dust, in Interplanetary Dust, E. Grün, B.A.S. Gustafson, S.F. Dermott, H. Fechtig (eds.), SpringerVerlag Berlin Heidelberg, Germany, 295 342. Hall, D.T., Strobel, D.F., Feldman, P.D., McGrath, M.A. and Weaver, H.A. (1995) Detection of an oxygen atmosphere on Jupiter's moon Europa, Nature, 373, 677 – 679. Hall, D.T., Feldman, P.D., McGrath, M.A. and Strobel, D.F. (1998) The farultraviolet oxygen airglow of Europa and Ganymede, Astrophys. J., 449, 475 – 481. Hand, K.P., Chyba, C.F., Carlson, R.W., Cooper, J.F. (2006) Clathrate hydrates of oxidants in the ice shell of Europa, Astrobiology, 6, 463 – 482. Hansen, G.B. and McCord, T.B. (2004) Amorphous and crystalline ice on the Galilean satellites: A balance between thermal and radiolytic processes, J. Geophys. Res.,109, E01012. Hiraoka, K., Arakawa, M., Setoh, M., Nakamura, A.M. (2008) Measurements of target compressive and tensile strength for application to impact cratering on icesilicate mixtures, J. Geophys. Res. 113, E02013. Hoppa, G.V., Tufts, B.R., Greenberg, R., Geissler, P.E. (1999) Formation of cycloidal features on Europa, Science, 285, 1899 – 1902. Horneck, G., Stöffler, D., Eschweiler, U., Hornemann, U. (2001) Bacterial Spores Survive Simulated Meteorite Impact, Icarus 149, 285–290. Housen, K.R., Schmidt, R.M., Holsapple, K.A. (1983) Crater ejecta scaling laws: Fundamental forms based on dimensional analysis, J. Geophys. Res. 88 (B3), 24852499. Humes, D. H., Alvarez, J. M., O'Neal, R.L., Kinard, W. H. (1974) The interplanetary and nearJupiter meteoroid environment, J. Geophys. Res., 79, 3677 – 3684. Iijima, Y., Lkato, M., Arakawa, M., Maeno, N., Fujimura, A., Mizutani, H. (1995) Cratering experiments on ice: Dependence of crater formation on projectile materials and scaling parameter, Geophys. Res. Lett., 22, 15, 20052008. Jeffreyes, H. (1961) The effect of tidal friction on eccentricity and inclination, Mon. Not. Roy. Astron. Soc., 122, 339 343. Johnson, R.E., Quickenden, T.I., Cooper, P.D., McKinley, A.J. and Freeman, C.G. (2003) The production of oxidants in Europa's surface, Astrobiology, 3, 4, 823 – 850. Kargel, J.S. (1995) Cryovolcanism on the icy satellites, Earth Moon Planets, 67, 101 – 113. Kargel, J.S., Kaye, J.Z., Head III, J.W., Marion, G.M., Sassen, R., Crowley, J.K., Ballesteros, O.P., Grant, S.A., Hogenboom, D.L. (2000), Europa's crust and ocean: origin, composition, and the prospects for life, Icarus, 148, 226 – 265. Kaplan, I.R. (1975) Stable isotopes as a guide to biogeochemical processes, Proc. R. Soc. Lond. B. 189, 183221. Koschny, D., Kargl., G., Rott, M. (2001) Experimental studies of the cratering process in porous ice targets, Adv. Space Res. 28, 10, 15331537. Krivov, A.V., Sremčević, M., Spahn, F., Dikarev, V.V., Kholshevnikov, K.V. (2003) Impactgenerated dust clouds around planetary satellites: spherically symmetric case, Planet. Space Sci. 51, 251 – 269. Krüger, H., Krivov, A.V., Hamilton, D.P., Grün, E. (1999) Detection of an impact generated dust cloud around Ganymede, Nature, 399, 558 560. Krüger, H. and Grün, E. (2002) Dust enroute to Jupiter and the Galilean satellites, in COSPAR colloquia series, 15, Dust in the Solar System and Other Planetary Systems, Proceedings of the IAU Colloquium 181, S.F. Green, I.P. Williams, J.A.M. McDonnell and N. McBride (eds.), University of Kent, Canterbury, UK, April 2000, Oxford: Pergamon, 144 – 159. Krüger, H., Krivov, A.V. and Sremčević, M. (2003) Impactgenerated dust clouds surrounding the Galilean moons, Icarus, 164, 170 – 187. Landgraf, M., Baggaley, W. J., Grün, E., Krüger, H., Linkert, G. (1999) Aspects of the mass distribution of interstellar dust grains in the Solar system from insitu measurements, J. Geophys. Res., 105 (A5), 10343 – 10352. Lipps, J.H. and Reiboldt, S. (2005) Habitats and taphonomy of Europa, Icarus, 177, 515 – 527. Mastrapa, R.M.E., Glanzberg, H., Head, J.N., Melosh, H.J., Nicholson, W.L. (2001) Survival of bacteria exposed to extreme acceleration: implications for panspermia, Earth Planet. Sci. Lett. 189, McCord, T. B., Hansen, G. B., Clark, R. N., Martin, P. D., Hibbitts, C. A., Fanale, F.P., Granahan, J. C., Segura, M., Matson, D. L., Johnson, T.V., Carlson, R. W., Smythe, W. D., Danielson, G. E. (1998a) Nonwaterice constituents in the surface material of the icy Galilean satellites from the Galileo nearinfrared mapping spectrometer investigation, J. Geophys. Res., 103 (E4), 8603 – 8626. McCord, T.B., Hansen, G.B., Fanale, F.P., Carlson, R.W., Matson, D.L., Johnson, T.V., Smythe, W.D., Crowley, J.K., Martin, P.D., Ocampo, A., Hibbitts, C.A., Granahan, J.C. (1998b) Salts on Europa's surface detected by Galileo's near infrared mapping spectrometer, Science, 280, 1242 – 1245. McDonnell, J.A.M (2006) The Open University planetary impact facility: A compact twostage light gas gun for all impact angles, Int. J. Impact Engng. 33, 410 – 418. Melosh, H.J. (1980) Cratering mechanics – observational, experimental, and theoretical, Annu. Rev. Earth Planet. Sci. 8, 6593. Miljković, K. and Taylor, E.A. (2007) Investigations of Europa biosignatures with hypervelocity impact physics, 7th EANA workshop, 2224th October, Turku, Finland, poster. Miljković, K. (2009) Investigation of the dust around Europa by impact experiments and modelling, PhD thesis, The Open University, UK. Miljković, K., Mason, N.J., Zarnecki, J.C. (2009) Research on Europa's dust cloud at The Open University's Hypervelocity Impact (HVI) Laboratory, Trans. JSASS Space Tech. Japan 7, ists26, Tr_2_37Tr_ 2_39. Miljković, K., Mason, N.J., Zarnecki, J.C. (2010) Environmental effects on dust around Europa, 42st, LPSC, March, The Woodlands, Texas, USA. Moore, J.M., Asphaug, E., Sullivan, R.J., Klemaszewski, J.E., Bender, K.C., Greeley, R., Geissler, P.E., McEwen, A.S., Turtle, E.R., Phillips, C.B., Tufts, B.R., Head III, J.W., Pappalardo, R.T., Jones, K.B., Chapman, C.R., Belton, M.J.S., Kirk, R.L., Morrison, D. (1998) Large impact features on Europa: results of the Galileo nominal mission, Icarus, 135, 127 – 145. Moroz, V.I. (1966) Infrared spectrophotometry of the moon and the Galilean satellites of Jupiter, Soviet Astronomy–AJ, 9, 6, 999 – 1006. Morrison, D and Burns, J.A. (1976) The Jovian satellites, in Jupiter. Studies of theinterior, atmosphere, magnetosphere and satellites, Gehrels, T. (ed.), The University of Arizona Press, Tucson, Arizona, USA, 991 – 1034. Ojakangas, G.W. and Stevenson, D.J. (1989) Thermal state of an ice shell on Europa, Icarus, 81, 220 – 241. Orlando, T.M., McCord, T. B., Grieves, G.A. (2005) The chemical nature of Europa surface material and the relation to a subsurface ocean, Icarus 177, 528533. Ostro, S.J. (1982) Radar properties of Europa, Ganymede and Callisto, in Satellites of Jupiter, Morrison, D. (ed.), The University of Arizona Press, Tucson, Arizona, USA, 213 – 236. Pappalardo, R.T., Collins, G.C., Head III, J.W., Helfenstein, P., McCord, T.B., Moore, J.M., Prockter, L.M., Schenk, P.M., Spencer, J.R. (2004) Geology of Ganymede, in Jupiter. The Planet, Satellites and Magnetosphere, T. Bagenal, T. Dowling and W.KcKinnon (eds.), Cambridge University Press, Cambridge, UK, 363 396. Pollack, J.B., Witteborn, F.C., Erickson, E.F., Strecker, D.W., Baldwin, B.J. and Bunch, T.E. (1978) Nearinfrared spectra of the Galilean satellites: observations and compositional implications, Icarus, 35, 271 – 303. Postberg, F., Kempf, S., Srama, R., Green, S. F., Hillier, J. K., McBride, N., Grün, E. (2006) Composition of jovian dust stream particles, Icarus, 183, 1, 122 – 134. PrietoBallesteros, O., Kargel, J.S., FernándezSampedro, M., Selsis, F., Sebastián Martínez, E., Hogenboom, D.L. (2005), Evaluation of the possible presence of clathrate hydrates in Europa's icy shell or seafloor, Icarus 177, 491–505. Prockter, L.M. and Pappalardo, R.T. (2000) Folds on Europa: implications for crustal cycling and accommodation of extension, Science, 289, 5481, 941 – 943. Raulin, F. (2005) Exoastrobiological aspects of Europa and Titan: from observations to speculations, Space Sci. Rev., 116, 471 – 487. Reynolds, R.T., Squyres, S.W., Colburn, D.S., McKay, C.P. (1983) On the habitability of Europa, Icarus, 56, 246 – 254. Schonfeld, E. (1982) Organic chemistry on Europa?, LPSC XIII, 691. Seckbach, J. and ChelaFlores, J. (2007) Extremophiles and Chemotrophs as Contributors to Astrobiological Signatures on Europa: A Review of Biomarkers of SulfateReducers and Other Microorganisms, in Instruments, Methods, and Missions for Astrobiology X, (Eds.) Richard B. Hoover, Gilbert V. Levin, Alexei Y. Rozanov, Paul C. W. Davies, Proc. of SPIE Vol. 6694, 66940W1. Sharp, T.G. and de Carli, P.S. (2006) Shock effects in meteorites, in Meteorites and the early Solar system II, (Eds.) D.S. Lauretta and H.Y. McSween Jr., University of Arizona Press, Tucson, 943, 653667 Smith, B.A., Soderblom, L.A., Beebe, R., Boyce, J., Briggs, G., Carr, M., Collins, S.A., Cook II, A.F., Danielson, E.G., Davies, M.E., Hunt, G.E., Ingersoll, A., Johnson, T.V., Masursky, H., McCauley, J., Morrison, D., Owen, T., Sagan, C., Shoemaker, E.M., Strom, R., Suomi, V.E., Veverka, J. (1979a) The Galilean satellites and Jupiter: Voyager 2 imaging science results, Science, 206, 4421, 927 – 950. Smith, B.A., Soderblom, L.A., Johnson, T.V., G.E., Ingersoll, Collins, S.A., Shoemaker, E.M., Hunt, G.E., Masursky, H., Carr, M., Davies, M.E., Cook II, A.F., Boyce, J., Danielson, E.G., Owen, T., Sagan, C., Beebe, R., Veverka, J., Strom, R., McCauley, J., Morrison, D., Briggs, G., Suomi, V.E. (1979b) Jupiter system through the eyes of Voyager 1, Science, 204, 4396, 951 – 972. Sotin, C., Head III, J.W., Tobie, G. (2002) Europa: Tidal heating of upwelling thermal plumes and the origin of lenticulae and chaos melting, Geophys. Res. Lett., 29, 8, 1233. Spohn, T. and Schubert, G. (2003) Oceans in the icy Galilean satellites of Jupiter?, Icarus, 161, 456 – 467. Spencer, J.R., Grundy, W.M., C. Dumas, Carlson, R.W (2006) The nature of Europa's dark nonice surface material: Spatiallyresolved high spectral resolution spectroscopy from the Keck telescope, Icarus 182, 202210. Sremčević, M., Krivov, A.V., Spahn, F. (2003) Impactgenerated dust clouds around planetary satellites: asymmetry effects, Planet. Space Sci. 51, 455 – 471. Sremčević, M., Krivov, A.V., Krüger, H., Spahn, F. (2005) Impactgenerated dust clouds around planetary satellites: model versus Galileo data, Planet. Space Sci., 53, 6, 625– 641. Strazzulla, G., Baratta, G.A., Palumbo, M.E., Satorre, M.A. (2000) Ion implantation in ices, Nuclear Instruments and Methods in Physics Research B, 166167. Taylor, E.A., Batham, M.G., Gilmour, M. A., Green, S. F., Hall, C., McBride, N. M., McDonnell, J. A. M., Miljkovic, K., Towner, M.C., Watson, K.V. and Zarnecki, J. C. (2006) The Open University Hypervelocity Impact Laboratory, , in 57th ARA meeting proc., 1822 September, 2006, Venice, Italy. Taylor, E. A., Miljkovic, K., Ball, A. J., Barber, S. J., Cockell, C. S., Hillier, J. K., McBride, N., Morse, A. D., Rothery, D. A., Sheridan, S., Wright, I. P. and Zarnecki, J. C. (2007) A combined dust impact detector and ion trap mass spectrometer for a Europa orbiter, Poster presented at the EGU General Assembly, Vienna, 1520 April 2007. Geophys. Res. Abstracts 9, 10928. Thiessenhusen, KU, Krüger, H., Spahn, F., Grun, E. (2000) Dust grains around Jupiter – The observations of the Galileo dust detector, Icarus, 144, 89 – 98. Tyler, R. (2010). Water Worlds and Oceans May be Common in the Universe. Journal of Cosmology, 5, 959-970. Turtle, E.P. and Pierazzo, E. (2001) Thickness of a Europan ice shell from impact crater simulations, Science, 294, 1326 – 1328. Willis, M.J., Ahrens, T.J., Bertani, L.E., Nash, C.Z. (2006) Bugbuster—survivability of living bacteria upon shock compression, Earth Planet. Sci. Lett. 247, 185 – 196. Zimmer, C. and Khurana, K.K. (2000), Subsurface oceans on Europa and Callisto: constraints from Galileo magnetometer observations, Icarus, 147, 329 – 347. Zolotov, M.Y., Krieg, M.L., Shock, E.L., McKinnon, W.B. (2006), Chemistry of a primordial ocean on Europa, 37th LPSC, March 1317, 2006, League City, Texas, 1435. Zolotov, M.Y. and Shock E.L. (2004) A model for lowtemperature biogeochemistry of sulfur, carbon, and iron on Europa, JGR, 109, E06003.
|
|
|
|
|
|
|
|
 Colonizing the Red Planet ISBN: 9780982955239 |
 Sir Roger Penrose & Stuart Hameroff ISBN: 9780982955208 |
 The Origins of LIfe ISBN: 9780982955215 |
 Came From Other Planets ISBN: 9780974975597 |
 Panspermia, Life ISBN: 9780982955222 |
 Explaining the Origins of Life ISBN 9780982955291 |