683 research outputs found
Effect of cell separation on gene expression and DNA methylation profiles in intestinal epithelial cells
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Experimental and simulation efforts in the astrobiological exploration of exooceans
The icy satellites of Jupiter and Saturn are perhaps the most promising places in the Solar System regarding habitability. However, the potential habitable environments are hidden underneath km-thick ice shells. The discovery of Enceladus’ plume by the Cassini mission has provided vital clues in our understanding of the processes occurring within the interior of exooceans. To interpret these data and to help configure instruments for future missions, controlled laboratory experiments and simulations are needed. This review aims to bring together studies and experimental designs from various scientific fields currently investigating the icy moons, including planetary sciences, chemistry, (micro-)biology, geology, glaciology, etc. This chapter provides an overview of successful in situ, in silico, and in vitro experiments, which explore different regions of interest on icy moons, i.e. a potential plume, surface, icy shell, water and brines, hydrothermal vents, and the rocky core
Charge Separation and Isolation in Water and Ice Particles on Strong Impacts
Tarrasó, Olga;Fuente Fuente, Carlos;Reventós, Manue
Models of dust around Europa and Ganymede
We use numerical models, supported by our laboratory data, to predict the
dust densities of ejecta outflux at any altitude within the Hill spheres of
Europa and Ganymede. The ejecta are created by micrometeoroid bombardment and
five different dust populations are investigated as sources of dust around the
moons. The impacting dust flux (influx) causes the ejection of a certain amount
of surface material (outflux). The outflux populates the space around the
moons, where a part of the ejecta escapes and the rest falls back to the
surface. These models were validated against existing Galileo DDS (Dust
Detector System) data collected during Europa and Ganymede flybys.
Uncertainties of the input parameters and their effects on the model outcome
are also included. The results of this model are important for future missions
to Europa and Ganymede, such as JUICE (JUpiter ICy moon Explorer), recently
selected as ESA's next large space mission to be launched in 2022
The three-dimensional structure of Saturn's E ring
Saturn's diffuse E ring consists of many tiny (micron and sub-micron) grains
of water ice distributed between the orbits of Mimas and Titan. Various
gravitational and non-gravitational forces perturb these particles' orbits,
causing the ring's local particle density to vary noticeably with distance from
the planet, height above the ring-plane, hour angle and time. Using
remote-sensing data obtained by the Cassini spacecraft in 2005 and 2006, we
investigate the E-ring's three-dimensional structure during a time when the Sun
illuminated the rings from the south at high elevation angles (> 15 degrees).
These observations show that the ring's vertical thickness grows with distance
from Enceladus' orbit and its peak brightness density shifts from south to
north of Saturn's equator plane with increasing distance from the planet. These
data also reveal a localized depletion in particle density near Saturn's
equatorial plane around Enceladus' semi-major axis. Finally, variations are
detected in the radial brightness profile and the vertical thickness of the
ring as a function of longitude relative to the Sun. Possible physical
mechanisms and processes that may be responsible for some of these structures
include solar radiation pressure, variations in the ambient plasma, and
electromagnetic perturbations associated with Saturn's shadow.Comment: 42 Pages, 13 Figures, modified to include minor proof correction
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 time‐varying 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 wind‐magnetosphere 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 re‐enter Saturn‐s magnetosphere IMF direction and solar wind compression arrival time can be derivedPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99078/1/grl50604.pd
Using Dust from Asteroids as Regolith Microsamples
More robust links need to be forged between meteorites and their parent bodies to understand the composition, diversity and distribution of the asteroids. A major link can be sample analysis of the parent body material and comparison with meteorite data. Dust is present around all airless bodies, generated by micrometeorite impact into their airless surfaces, which in turn lofts regolith particles into a "cloud" around the body. The composition, flux, and size distribution of dust particles can provide insight into the geologic evolution of airless bodies. For example, the Cassini Cosmic Dust Analyzer detected salts and minerals emitted by plumes at Enceladus, evidence for a subsurface ocean with a silicate seafloor. Dust analysis instruments may enable future missions to obtain elemental, isotopic and mineralogical composition of regolith particles without returning the samples to terrestrial laboratories
Galileo dust data from the jovian system: 2000 to 2003
The Galileo spacecraft was orbiting Jupiter between Dec 1995 and Sep 2003.
The Galileo dust detector monitored the jovian dust environment between about 2
and 370 R_J (jovian radius R_J = 71492 km). We present data from the Galileo
dust instrument for the period January 2000 to September 2003. We report on the
data of 5389 particles measured between 2000 and the end of the mission in
2003. The majority of the 21250 particles for which the full set of measured
impact parameters (impact time, impact direction, charge rise times, charge
amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in
radius), most of them originating from Jupiter's innermost Galilean moon Io.
Their impact rates frequently exceeded 10 min^-1. Surprisingly large impact
rates up to 100 min^-1 occurred in Aug/Sep 2000 when Galileo was at about 280
R_J from Jupiter. This peak in dust emission appears to coincide with strong
changes in the release of neutral gas from the Io torus. Strong variability in
the Io dust flux was measured on timescales of days to weeks, indicating large
variations in the dust release from Io or the Io torus or both on such short
timescales. Galileo has detected a large number of bigger micron-sized
particles mostly in the region between the Galilean moons. A surprisingly large
number of such bigger grains was measured in March 2003 within a 4-day interval
when Galileo was outside Jupiter's magnetosphere at approximately 350 R_J
jovicentric distance. Two passages of Jupiter's gossamer rings in 2002 and 2003
provided the first actual comparison of in-situ dust data from a planetary ring
with the results inferred from inverting optical images.Comment: 59 pages, 13 figures, 6 tables, submitted to Planetary and Space
Scienc
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