233 research outputs found
Micrometeoroid infall onto Saturnâs rings constrains their age to no more than a few hundred million years
There is ongoing debate as to whether Saturnâs main rings are relatively young or ancientâ having been formed shortly after Saturn or during the Late Heavy Bombardment. The rings are mostly water-ice but are polluted by non-icy material with a volume fraction ranging from âŒ0.1 to 2%. Continuous bombardment by micrometeoroids exogenic to the Saturnian system is a source of this non-icy material. Knowledge of the incoming mass flux of these pollutants allows estimation of the ringsâ exposure time, providing a limit on their age. Here we report the final measurements by Cassiniâs Cosmic Dust Analyzer of the micrometeoroid flux into the Saturnian system. Several populations are present, but the flux is dominated by low-relative velocity objects such as from the Kuiper belt. We find a mass flux between 6.9 · 10â17 and 2.7 · 10â16 kg mâ2sâ1 from which we infer a ring exposure time âČ100 to 400 million years in support of recent ring formation scenarios
Charge Separation and Isolation in Water and Ice Particles on Strong Impacts
TarrasĂł, Olga;Fuente Fuente, Carlos;ReventĂłs, Manue
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
Modelling CDA mass spectra
We present the initial results from a simulation of ion behaviour within Cassini's cosmic dust analyser (CDA) instrument, using an in-house ion dynamics code. This work is to enable and enhance the detailed interpretation of dust impact ionisation mass spectra returned from the Saturnian system. Early work has already provided insights into the properties of the impact plasma in both low- and high-velocity impacts. We find that the isotropic emission of ions from the impact plasma successfully reproduces features seen in flight spectra and that the emitted ions have a higher range of energies (tens to hundreds of eV) than previously reported in some studies. Using these new ion characteristics, we have successfully modelled CDA flight mass spectra
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
- âŠ