196 research outputs found
Charge Separation and Isolation in Water and Ice Particles on Strong Impacts
TarrasĂł, Olga;Fuente Fuente, Carlos;ReventĂłs, Manue
Impact ionization mass spectra of anorthite cosmic dust analogue particles
Anorthite, the Ca-rich end-member of plagioclase feldspar, is a dominant mineral component of the Lunar highlands. Plagioclase feldspar is also found in comets, meteorites and stony asteroids. It is therefore expected to contribute to the population of interplanetary (and circumplanetary) dust grains within the solar system. After coating micron- and submicron-sized grains of Anorthite with a conductive layer of Platinum, the mineral was successfully accelerated to hypervelocity speeds in the Max Planck Institut fĂŒr Kernphysikâs Van de Graaff accelerator. We present impact ionization mass spectra
generated following the impacts of anorthite grains with a prototype mass spectrometer (the Large Area Mass Analyser, LAMA) designed for use in space, and discuss the behavior of the spectra with increasing impact energy. Correlation analysis is used to identify the compositions and sources of cations present in the spectra, enabling the identification of several molecular cations (e.g., CaAlO2, CaSiO2, Ca2AlO3/CaAlSi2O2)
which identify anorthite as the progenitor bulk grain material
Probing IMF using nanodust measurements from inside Saturn's magnetosphere
We present a new concept of monitoring the interplanetary magnetic field (IMF) by using in situ measurements of nanodust stream particles in Saturn's magnetosphere. We show that the nanodust detection pattern obtained inside the magnetosphere resembles those observed in interplanetary space and is associated with the solar wind compression regions. Our dust dynamics model reproduces the observed nanodust dynamical properties as well as the detection pattern, suggesting that the ejected stream particles can reenter Saturn's magnetosphere at certain occasions due to the dynamical influence from the timeâvarying IMF. This method provides information on the IMF direction and a rough estimation on the solar wind compression arrival time at Saturn. Such information can be useful for studies related to the solar windâmagnetosphere interactions, especially when the solar wind parameters are not directly available. Key Points A new method to probe IMF with nanodust measurements inside the magnetosphere Under changing IMF, ejected nanoparticles can reâenter Saturnâs magnetosphere IMF direction and solar wind compression arrival time can be derivedPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99078/1/grl50604.pd
The production of platinum-coated silicate nanoparticle aggregates for use in hypervelocity impact experiments
We present a method for producing metal-coated low-density (?3) aggregate silicate dust particles for use in hypervelocity impact (HVI) experiments. Particles fabricated using the method are shown to have charged and electrostatically accelerated in the Max Planck Institut fĂŒr Kernphysik (MPI-K) 2 MV Van de Graaff accelerator, allowing the production of impact ionization mass spectra of silicate particles (impacting at velocities ranging from ?1 to >30 km s?1, corresponding to sizes of >1 ?m to <0.1 ?m) using the Large Area Mass Analyser (LAMA) instrument, designed for cosmic dust detection in space. Potential uses for the coated grains, such as in the calibration of aerogel targets similar to those used on the Stardust spacecraft, are also discussed
A New View on Interstellar Dust - High Fidelity Studies of Interstellar Dust Analogue Tracks in Stardust Flight Spare Aerogel
In 2000 and 2002 the Stardust Mission exposed aerogel collector panels for a total of about 200 days to the stream of interstellar grains sweeping through the solar system. The material was brought back to Earth in 2006. The goal of this work is the laboratory calibration of the collection process by shooting high speed [5 - 30km/s] interstellar dust (ISD) analogues onto Stardust aerogel flight spares. This enables an investigation into both the morphology of impact tracks as well as any structural and chemical modification of projectile and collector material. First results indicate a different ISD flux than previously assumed for the Stardust collection period
Partitioning of crystalline and amorphous phases during freezing of simulated Enceladus ocean fluids
This work was supported by The Leverhulme Trust (grant number RPGâ2016â153).Saturn's iceâcovered moon Enceladus may contain the requisite conditions for life. Its potentially habitable subsurface ocean is vented into space as large cryovolcanic plumes that can be sampled by spacecraft, acting as a window to the ocean below. However, little is known about how Enceladusâ ocean fluids evolve as they freeze. Using cryoâimaging techniques, we investigated solid phases produced by freezing simulated Enceladean ocean fluids at endmember cooling rates. Our results show that under flashâfreezing conditions (>10 K sâ1), Enceladusârelevant fluids undergo segregation, whereby the precipitation of ice templates the formation of brine vein networks. The high solute concentrations and confined nature of these brine veins means that salt crystallization is kinetically inhibited and glass formation (vitrification) can occur at lower cooling rates than typically required for vitrification of a bulk solution. Crystalline salts also form if flashâfrozen fluids are reâwarmed. The 10 ”mâscale distribution of salt phases produced by this mechanism differs markedly from that of gradually cooled (âŒ1 K minâ1) fluids, showing that they inherit a textural signature of their formation conditions. The mineralogy of cryogenic carbonates can be used as a probe for cooling rate and parent fluid pH. Our findings reveal possible endmember routes for solid phase production from Enceladusâ ocean fluids and mechanisms for generating compositional heterogeneity within ice particles on a subâ10 ”m scale. This has implications for understanding how Enceladus' ocean constituents are incorporated into icy particles and delivered to space.Publisher PDFPeer reviewe
Origin and Evolution of Saturn's Ring System
The origin and long-term evolution of Saturn's rings is still an unsolved
problem in modern planetary science. In this chapter we review the current
state of our knowledge on this long-standing question for the main rings (A,
Cassini Division, B, C), the F Ring, and the diffuse rings (E and G). During
the Voyager era, models of evolutionary processes affecting the rings on long
time scales (erosion, viscous spreading, accretion, ballistic transport, etc.)
had suggested that Saturn's rings are not older than 100 My. In addition,
Saturn's large system of diffuse rings has been thought to be the result of
material loss from one or more of Saturn's satellites. In the Cassini era, high
spatial and spectral resolution data have allowed progress to be made on some
of these questions. Discoveries such as the ''propellers'' in the A ring, the
shape of ring-embedded moonlets, the clumps in the F Ring, and Enceladus' plume
provide new constraints on evolutionary processes in Saturn's rings. At the
same time, advances in numerical simulations over the last 20 years have opened
the way to realistic models of the rings's fine scale structure, and progress
in our understanding of the formation of the Solar System provides a
better-defined historical context in which to understand ring formation. All
these elements have important implications for the origin and long-term
evolution of Saturn's rings. They strengthen the idea that Saturn's rings are
very dynamical and rapidly evolving, while new arguments suggest that the rings
could be older than previously believed, provided that they are regularly
renewed. Key evolutionary processes, timescales and possible scenarios for the
rings's origin are reviewed in the light of tComment: Chapter 17 of the book ''Saturn After Cassini-Huygens'' Saturn from
Cassini-Huygens, Dougherty, M.K.; Esposito, L.W.; Krimigis, S.M. (Ed.) (2009)
537-57
Charged nanograins in the Enceladus plume
There have been three Cassini encounters with the south-pole eruptive plume of
Enceladus for which the Cassini Plasma Spectrometer (CAPS) had viewing in the
spacecraft ram direction. In each case, CAPS detected a cold dense population of heavy
charged particles having mass-to-charge (m/q) ratios up to the maximum detectable by
CAPS ( 104 amu/e). These particles are interpreted as singly charged nanometer-sized
water-ice grains. Although they are detected with both negative and positive net charges,
the former greatly outnumber the latter, at least in the m/q range accessible to CAPS.
On the most distant available encounter (E3, March 2008) we derive a net (negative)
charge density of up to 2600 e/cm3 for nanograins, far exceeding the ambient plasma
number density, but less than the net (positive) charge density inferred from the RPWS
Langmuir probe data during the same plume encounter. Comparison of the CAPS data
from the three available encounters is consistent with the idea that the nanograins leave the
surface vents largely uncharged, but become increasingly negatively charged by plasma
electron impact as they move farther from the satellite. These nanograin
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