Detection, Analysis, and Mapping of Surface Material from Europa

2020 ◽  
Author(s):  
William Goode ◽  
Sascha Kempf ◽  
Juergen Schmidt
Keyword(s):  
Chemical Composition ◽  
Dust Particles ◽  
Surface Material ◽  
Detection Analysis ◽  
Spacecraft Trajectory ◽  
Exchange Processes ◽  
Subsurface Ocean ◽  
Chemical Measurements ◽  
Geological Features

<p>Europa Clipper, NASA’s next flagship mission launching in 2024, will closely study Jupiter’s icy ocean moon in order to determine if it has conditions favorable for life. Among the nine scientific instruments will be the Surface Dust Analyzer (SUDA), a state-of-the-art instrument for in situ chemical analysis of dust grains. During a series of close flybys of Europa (~25 to 100 km at closest approach), SUDA will collect and measure the chemical composition of thousands of ice and dust particles ranging from ~200 nm to 100 microns in radius, which will be direct samples from Europa’s surface. This is possible due to the flux of interplanetary micrometeoroids impacting the surface producing a cloud of ejecta particles, which SUDA detects and analyzes. Knowing the spacecraft trajectory, instrument pointing, and particle velocity through the instrument aperture, SUDA’s in situ chemical measurements will be linked to their site of origin on Europa’s surface near the spacecraft ground-track, thereby offering geological context for chemical composition. This method implements established models of impact ejecta dynamics and derives distributions for each measurement’s site of origin on the surface using Monte Carlo simulations. These studies are especially useful for evaluating the science return for particular tour designs since we can simulate SUDA’s effectiveness at mapping the composition of geologically interesting areas. With well targeted flybys by Europa Clipper, SUDA will be help constrain the chemical composition of surface material originating from various geological features, particularly those characterized by non-icy materials. This will enhance our understanding of the exchange processes between the icy surface and subsurface ocean as well as assess the habitability of Europa.</p>

Structural Studies on Mitotic Spindle Fibres

1978 ◽  
Vol 36 (3) ◽  
pp. 615-626
Author(s):  
J.R. Mcintosh
Keyword(s):  
Chemical Composition ◽  
Mitotic Spindle ◽  
Structural Studies ◽  
Mitotic Apparatus ◽  
Chemical Studies ◽  
Medical Interest ◽  
Spindle Fibres

The mitotic apparatus is a structure of obvious biological and medical interest, but it has proved to be a difficult cellular machine to understand. The chemical composition of the spindle is only slightly elucidated, largely because of the difficulties in preparing useful isolates of the structure. Chemical studies of the mitotic spindle have been reviewed elsewhere (Mcintosh, 1977), and will not be discussed further here. One would think that structural studies on the mitotic apparatus (MA) in situ would be straightforward, but even with this approach there is some disagreement in the results obtained with various methods and by different investigators. In this paper I will review briefly the approaches which have been used in structural studies of the MA, pointing out the strengths and problems of each approach. I will summarize the principal findings of the different methods, and identify what seem to be fruitful avenues for further work.

scholarly journals An Atmospheric Origin for HCN-Derived Polymers on Titan

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 965
Author(s):  
Zoé Perrin ◽  
Nathalie Carrasco ◽  
Audrey Chatain ◽  
Lora Jovanovic ◽  
Ludovic Vettier ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Formation Process ◽  
Upper Atmosphere ◽  
Gas Mixture ◽  
Space Probe ◽  
Atmospheric Haze ◽  
Formation And Evolution ◽  
Haze Formation

Titan’s haze is strongly suspected to be an HCN-derived polymer, but despite the first in situ measurements by the ESA-Huygens space probe, its chemical composition and formation process remain largely unknown. To investigate this question, we simulated the atmospheric haze formation process, experimentally. We synthesized analogues of Titan’s haze, named Titan tholins, in an irradiated N2–CH4 gas mixture, mimicking Titan’s upper atmosphere chemistry. HCN was monitored in situ in the gas phase simultaneously with the formation and evolution of the haze particles. We show that HCN is produced as long as the particles are absent, and is then progressively consumed when the particles appear and grow. This work highlights HCN as an effective precursor of Titan’s haze and confirms the HCN-derived polymer nature of the haze.

scholarly journals Spreading of warm ocean waters around Greenland as a possible cause for glacier acceleration

2012 ◽  
Vol 53 (60) ◽  
pp. 257-266 ◽  
Author(s):  
E. Rignot ◽  
I. Fenty ◽  
D. Menemenlis ◽  
Y. Xu
Keyword(s):  
Initial Conditions ◽  
Independent Study ◽  
Ocean Temperature ◽  
The North ◽  
Subsurface Ocean ◽  
Subsurface Waters ◽  
Glacier Flow ◽  
Horizontal Grid ◽  
Possible Cause

AbstractWe examine the pattern of spreading of warm subtropical-origin waters around Greenland for the years 1992–2009 using a high-resolution (4km horizontal grid) coupled ocean and sea-ice simulation. The simulation, provided by the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, qualitatively reproduces the observed warming of subsurface waters in the subpolar gyre associated with changes of the North Atlantic atmospheric state that occurred in the mid-1990s. The modeled subsurface ocean temperature warmed by 1.5˚C in southeast and southwest Greenland during 1994–2005 and subsequently cooled by 0.5˚C; modeled subsurface ocean temperature increased by 2–2.5˚C in central and then northwest Greenland during 1997–2005 and stabilized thereafter, while it increased after 2005 by <0.5˚C in north Greenland. Comparisons with in situ measurements off the continental shelf in the Labrador and Irminger Seas indicate that the model initial conditions were 0.4˚C too warm in the south but the simulated warming is correctly reproduced; while measurements from eastern Baffin Bay reveal that the model initial conditions were 1.0˚C too cold in the northwest but the simulated ocean warming brought modeled temperature closer to observations, i.e. the simulated warming is 1.0˚C too large. At several key locations, the modeled oceanic changes off the shelf and below the seasonal mixed layer were rapidly transmitted to the shelf within troughs towards (model-unresolved) fjords. Unless blocked in the fjords by shallow sills, these warm subsurface waters had potential to propagate down the fjords and melt the glacier fronts. Based on model sensitivity simulations from an independent study (Xu and others, 2012), we show that the oceanic changes have very likely increased the subaqueous melt rates of the glacier fronts, and in turn impacted the rates of glacier flow.

scholarly journals On realistic size equivalence and shape of spheroidal Saharan mineral dust particles applied in solar and thermal radiative transfer calculations

2011 ◽  
Vol 11 (9) ◽  
pp. 4469-4490 ◽  
Author(s):  
S. Otto ◽  
T. Trautmann ◽  
M. Wendisch
Keyword(s):  
Land Surface ◽  
Mineral Dust ◽  
Single Scattering ◽  
Radiative Heating ◽  
Dust Particles ◽  
Axis Ratio ◽  
Solar Cooling ◽  
Prolate Shape ◽  
Spheroidal Model

Abstract. Realistic size equivalence and shape of Saharan mineral dust particles are derived from in-situ particle, lidar and sun photometer measurements during SAMUM-1 in Morocco (19 May 2006), dealing with measured size- and altitude-resolved axis ratio distributions of assumed spheroidal model particles. The data were applied in optical property, radiative effect, forcing and heating effect simulations to quantify the realistic impact of particle non-sphericity. It turned out that volume-to-surface equivalent spheroids with prolate shape are most realistic: particle non-sphericity only slightly affects single scattering albedo and asymmetry parameter but may enhance extinction coefficient by up to 10 %. At the bottom of the atmosphere (BOA) the Saharan mineral dust always leads to a loss of solar radiation, while the sign of the forcing at the top of the atmosphere (TOA) depends on surface albedo: solar cooling/warming over a mean ocean/land surface. In the thermal spectral range the dust inhibits the emission of radiation to space and warms the BOA. The most realistic case of particle non-sphericity causes changes of total (solar plus thermal) forcing by 55/5 % at the TOA over ocean/land and 15 % at the BOA over both land and ocean and enhances total radiative heating within the dust plume by up to 20 %. Large dust particles significantly contribute to all the radiative effects reported. They strongly enhance the absorbing properties and forward scattering in the solar and increase predominantly, e.g., the total TOA forcing of the dust over land.

scholarly journals Dust in the Solar System

1989 ◽  
Vol 44 (10) ◽  
pp. 877-882 ◽  
Author(s):  
H. Fechtig
Keyword(s):  
Solar Irradiation ◽  
Dust Particles ◽  
Normal Density ◽  
Dust Grains ◽  
Cometary Dust ◽  
In Situ Experiments ◽  
Asteroidal Belt ◽  
Comet Halley ◽  
Cometary Origin

Abstract Properties of cometary dust particles are better known since the space missions to Comet Halley. Their properties (densities, atomic composition) are compared with relevant observations from lunar microcraters and in-situ experiments. At 1 AU in the eliptic, 2/3 of the dust grains are normal density particles, presumably of asteroidal origin and irregularly shaped, while the remaining 1/3 are low density particles, presumably of cometary origin, but due to solar irradiation in a processed state (corresponding to “Brownlee”-particles). Beyond the asteroidal belt only black cometary dust grains are observed which have recently been released from comet nuclei orbiting on highly eccentric trajectories.

Nanodust detection with Cassini CDA - Implications for DESTINY+ and Interstellar Probe

2021 ◽  
Author(s):  
Ralf Srama ◽  
Jon K. Hillier ◽  
Sean Hsu ◽  
Sascha Kempf ◽  
Masanori Kobayashi ◽  
...  
Keyword(s):  
High Resolution ◽  
Impact Ionization ◽  
Cosmic Dust ◽  
Hypervelocity Impact ◽  
Dust Particles ◽  
Interstellar Space ◽  
Mass Spectrometers ◽  
High Resolution Mass ◽  
Resolution Mass

&lt;p&gt;The Cosmic Dust Analyzer (CDA) onboard Cassini characterized successfully the dust environment at Saturn from 2004 to 2017. Besides the study of Saturn&amp;#8217;s E ring and its interaction with the embedded moons, CDA detected nanoparticles in the outer Saturn system moving on unbound orbits and originating primarily from Saturn&amp;#8217;s E-ring. Although the instrument was built to detect micron and sub-micron sized particles, nano-sized grains were detected during the flyby at early Jupiter and in the outer environment at Saturn. Fast dust particles with sizes below 10 nm were measured by in-situ impact ionization and mass spectra were recorded. What are the limits of in-situ hypervelocity impact detection and what can be expected with current high-resolution mass spectrometers as flown onboard the missions DESTINY+ or EUROPA? Is the sensitivity of Dust Telescopes sufficient to detect nano-diamonds in interstellar space? This presentation summarizes the current experience of in-situ dust detectors and gives a prediction for future missions. In summary, current Dust Telescopes with integrated high-resolution mass spectrometers are more sensitive than the CASSINI Cosmic Dust Analyzer.&lt;/p&gt;

scholarly journals Relationship between the Optical Properties and Chemical Composition of Urban Aerosol Particles in Lithuania

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Julija Pauraite ◽  
Kristina Plauškaitė ◽  
Vadimas Dudoitis ◽  
Vidmantas Ulevicius
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Organic Aerosol ◽  
Single Scattering ◽  
Chemical Compositions ◽  
Spectra Analysis ◽  
Average Value ◽  
Aerosol Mass ◽  
In Situ Investigation

In situ investigation results of aerosol optical properties (absorption and scattering) and chemical composition at an urban background site in Lithuania (Vilnius) are presented. Investigation was performed in May-June 2017 using an aerosol chemical speciation monitor (ACSM), a 7-wavelength Aethalometer and a 3-wavelength integrating Nephelometer. A positive matrix factorisation (PMF) was used for the organic aerosol mass spectra analysis to characterise the sources of ambient organic aerosol (OA). Five OA factors were identified: hydrocarbon-like OA (HOA), biomass-burning OA (BBOA), more and less oxygenated OA (LVOOA and SVOOA, respectively), and local hydrocarbon-like OA (LOA). The average absorption (at 470 nm) and scattering (at 450 nm) coefficients during the entire measurement campaign were 16.59 Mm−1 (standard deviation (SD) = 17.23 Mm−1) and 29.83 Mm−1 (SD = 20.45 Mm−1), respectively. Furthermore, the absorption and scattering Angström exponents (AAE and SAE, respectively) and single-scattering albedo (SSA) were calculated. The average AAE value at 470/660 nm was 0.97 (SD = 0.16) indicating traffic-related black carbon (BCtr) dominance. The average value of SAE (at 450/700 nm) was 1.93 (SD = 0.32) and could be determined by the submicron particle (PM1) dominance versus the supermicron ones (PM > 1 µm). The average value of SSA was 0.62 (SD = 0.13). Several aerosol types showed specific segregation in the SAE versus SSA plot, which underlines different optical properties due to various chemical compositions.

scholarly journals High-Resolution Observations of Transport and Exchange Processes in Mountainous Terrain

Atmosphere ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 457 ◽  
Author(s):  
Stefan Emeis ◽  
Norbert Kalthoff ◽  
Bianca Adler ◽  
Eric Pardyjak ◽  
Alexandre Paci ◽  
...  
Keyword(s):  
Complex Terrain ◽  
Mountainous Terrain ◽  
Full Spectrum ◽  
Spatiotemporal Information ◽  
Exchange Processes ◽  
Atmospheric Dynamic ◽  
In Situ Observations ◽  
Measurement Strategies ◽  
Mesoscale Processes

Mountainous areas require appropriate measurement strategies to cover the full spectrum of details concerning the energy exchange at the Earth’s surface and to capture the spatiotemporal distribution of atmospheric dynamic and thermodynamic fields over them. This includes the range from turbulence to mesoscale processes and its interaction. The surface energy balance needs appropriate measurement strategies as well. In this paper, we present an overview of important experiments performed over mountainous terrain and summarize the available techniques for flow and energy measurements in complex terrain. The description includes ground-based and airborne in situ observations as well as ground-based and airborne remote sensing (passive and active) observations. Emphasis is placed on systems which retrieve spatiotemporal information on mesoscale and smaller scales, fitting mountainous terrain research needs. Finally, we conclude with a short list summarizing challenges and gaps one faces when dealing with measurements over complex terrain.

scholarly journals Chemical composition of groundwaters in the Hornsund region, southern Spitsbergen

2012 ◽  
Vol 44 (1) ◽  
pp. 117-130 ◽  
Author(s):  
Tomasz Olichwer ◽  
Robert Tarka ◽  
Magdalena Modelska
Keyword(s):  
Chemical Composition ◽  
Ion Exchange ◽  
Shallow Groundwater ◽  
Mineralogical Composition ◽  
Deep Groundwater ◽  
Exchange Processes ◽  
Groundwater Circulation ◽  
Initial Chemical Composition ◽  
The University ◽  
Intermediate System

Chemical composition of groundwaters was investigated in the region of the Hornsund fjord (southern Spitsbergen). The investigations were conducted during polar expeditions organized by the University of Wroclaw in two summer seasons of 2003 and 2006. Three zones of groundwater circulation: suprapermafrost, intrapermafrost and subpermafrost, were identified in areas of perennial permafrost in the region of Hornsund. The zone of shallow circulation occurs in non-glaciated (suprapermafrost) and subglacial areas. In this zone, the chemical composition of groundwater originates from initial chemical composition of precipitation, mineralogical composition of bedrock, oxidation of sulphides and dissolution of carbonates. The intermediate system of circulation is connected with water flow inside and below perennial permafrost (intrapermafrost and subpermafrost). In this zone, the chemical composition of groundwater is mainly controlled by dissolution of carbonates, ion exchange processes involving Ca2+ substitution by Na+, and oxidation of sulphides under oxygen-depleted conditions. The subpermafrost zone (deep groundwater circulation) occurs in deep-tectonic fractures, which are likely conduits for the descent of shallow groundwater to deeper depths. In this zone, the groundwater shows lower mineralization comparing to intrapermafrost zone and has a multi-ion nature Cl–HCO3–Na-Ca–Mg.

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