Electric Neptune

[StefanR]

Triton — Biggest Moon of Neptune
Description:

Triton is the biggest of Neptune’s thirteen known moons. This moon is suspected to have been captured by Neptune, which would explain its highly unusual orbit and rotation. One of the only bodies in the solar system to have a retrograde orbit, Triton also rotates at an angle of 157° to the axis of Neptune’s rotation. This means that the poles and equator alternately face the sun during rotation, most likely causing dramatic changes in seasons. When the Voyager 2 flew by in 1989, Triton’s South Pole was facing the sun. An ice cap of frozen nitrogen and methane was found on Triton’s South Pole when Voyager 2 visited.

http://sos.noaa.gov/datasets/solar_system/triton.html


On this page is a 4MB movie available.

[StefanR]

The nature of Neptune’s increasing brightness: evidence for
a seasonal response

Abstract
Hubble Space Telescope (HST) observations in August 2002 show that Neptune’s disk-averaged reflectivity increased significantly since
1996, by 3.2
0.3% at 467 nm, 5.6
0.6% at 673 nm, and 40
4% in the 850–1000 nm band, which mainly results from dramatic
brightness increases in restricted latitude bands. When 467-nm HST observations from 1994 to 2002 are added to the 472-nm ground-based
results of Lockwood and Thompson (2002, Icarus 56, 37–51), the combined disk-averaged variation from 1972 to 2002 is consistent with
a simple seasonal model having a hemispheric response delay relative to solar forcing of 30 years (73% of a full season).

Introduction
Neptune’s equatorial plane is inclined 29° to its orbit
plane, which subjects it to seasonal solar forcing during its
164.8-year orbit of the Sun. The resulting local variation in
incident sunlight is similar in fractional amplitude to that on
the Earth, but the absolute variation is 900 times smaller and
the rate of change is an additional factor of 165 slower.
Remarkably, there is now evidence that Neptune is responding
measurably to this weak forcing. A clear trend of increasing
brightness since 1980 has emerged from diskaveraged
ground-based observations (Lockwood and
Thompson, 2002) and from spatially resolved Hubble Space
Telescope (HST) observations in 1996 and 1998 (Sromovsky
et al., 2001d). Here we describe new HST observations
in 2002, which confirm a continuing increase in
Neptune’s reflectivity and establish new constraints on its
spectral and spatial characteristics. We show that the recent
increase is mainly produced by changes in restricted latitude
regions and that the long-term variation follows a simple
phase-shifted seasonal model.

Clearly
some variation in Neptune’s spectrum is required to explain
the near-IR results discussed in the previous paragraph.
However, it does not seem likely that the effect at short
wavelengths could be large enough by itself to explain the
entire discrepancy. Another potential source for unusual
brightness changes is the heightened solar activity near the
end of 1957 when the largest-ever monthly mean sunspot
number was observed (sunspot data from ftp://ftp.ngdc.
noaa.gov). Sunspot number was anticorrelated with Neptune’s
brightness during the 1972–1980 period when it
seemed to be associated with 2–3% variations in brightness
(Lockwood and Thompson, 1986). But during 1950–1961,
the B-filter observations of a steadily increasing brightness
contain no evidence of a 1957 minimum that would have
been obvious had the same correlation been present then as
during 1972–1980. Thus, the B observations during 1950–
1960 seem inconsistent with both seasonal and solar responses.
An alternate possibility is that these earlier broadband
measurements are in error, either due to instrumental
anomalies or analysis errors. In fact, Jerzykiewicz and
Serkowski (1966) themselves raise this issue by pointing
out that “The steady decrease of the instrumental coefficient
A8 in the years 1950–1960 . . . throws some doubt on the
reality of the changes in Neptune’s brightness.” A clear
resolution of this discrepancy remains to be found.
It should be noted that the discrepancies between the
seasonal model and the observations are mainly with observations
that are minor in effect or made in different spectral
bands and that very good agreement is obtained with the
best-calibrated and most spectrally homogeneous diskaveraged
observations. Thus, seasonal forcing remains a
plausible explanation for Neptune’s main brightness variation,
although a firm understanding of the complete variation and
all its contributing factors and spectral variation remains to
be established. Achieving that understanding will probably
require a much longer record of observations and more
detailed investigations of physical mechanisms. If the seasonal
model is correct, Neptune should continue to brighten
at 467 nm for almost another two decades.

http://hubblesite.org/pubinfo/pdf/2003/17/paper.pdf

Maybe someone can find a way of taking some of the images from this PDF. Some could be handy later on.

[StefanR]

Mass loss of N2 molecules from Triton by magnetospheric plasma interaction

Abstract

Previous investigations of sputtering of molecular nitrogen from Triton's atmosphere lead to estimates of escape rates of about 1021 N2 molecules s−1. Here, the erosion of Triton's nitrogen atmosphere resulting from sputtering due to different plasma populations and particles from Neptune's magnetosphere is investigated. This investigation shows that sputtering from Triton's nitrogen atmosphere could lead to N2 escape rates during the plasma sheet crossing on the order of 5 × 1024 s−1. This calculation shows that sputtering of Triton's nitrogen atmosphere by magnetospheric particles is an efficient nonthermal escape mechanism, similar to Saturn's large satellite Titan, and is an additional important process for the power input of the Neptune aurora. The N2 escape rates should be in a good agreement with the measured H+/N+ ion ratio in Neptune's magnetosphere. The excess energy of the sputtered particles leads primarily to escape and supply to the Neptune system rather than to ballistic orbits. Sputtering will yield, however, a small N2 corona on Triton.

link

[StefanR]

Stimulated desorption of atoms and molecules from bodies in the outer solar system

Laboratory data is needed on electronically-induced desorption from low-temperature solids: ices, organics, hydrated salts, glasses and certain minerals. Many bodies in the outer solar system are bombarded by relatively intense fluxes of fast ions and electrons as well as solar UV photons. This can cause both changes in their optical reflectance as well as desorption of atoms and molecules from their surfaces. Stimulated desorption produces Na and K 'atmospheres' above the 'rocky' surfaces of the moon and Mercury and H2O, H2 and O2 'atmospheres' about icy outer-solar system bodies. Since theses bodies contain other surface materials, direct detection by spacecraft or remote detection by telescopes of the desorbed atoms and molecules can be used, along with laboratory data, to determine the surface composition and geological processes occurring on distant bodies. This paper describes the relevance of stimulated desorption to the ambient neutrals and plasma in Saturn's magnetosphere, in preparation for CASSINI's arrival, and to the production of atmospheres on the moons of Jupiter being studied by the Galileo spacecraft.





I Introduction

An exciting period of exploration of the outer solar system is underway by spacecraft, by remarkably improved ground-based observations and by orbiting telescopes: International Ultraviolet Explorer (IUE) and Hubble Space Telescope (HST). These studies have revolutionized our understanding of the solar system revealing a kaleidoscope of unusual worlds. Because of the low surface temperatures, typically < 130K, ice is the 'rock' in the outer solar system. That is, excluding the four giant planets and Io, it is the structural and thermal properties of ice that determines the surface geology of many objects from the orbit of Jupiter outward (Burns and Matthews, 1986). Therefore, understanding the radiation chemistry of and desorption from ice or low-temperature hydrated minerals is critical. Other more volatile molecular species, such as N2, O2, CO, CO2, NH3, CH4, and SO2 form atmospheres and polar 'ices' or can cause the surface to be geologically active. Io, a moon of Jupiter, is an exception. Owing to its tidal interaction with Jupiter, Io is volcanically active and has lost its water and other light volatiles. Because of this, frozen SO2, a volcanic gas on earth, covers Io's surface (Burns and Matthews, 1986).

Since most small, outer solar system bodies, with the exception of Titan, have either no atmospheres or tenuous ones, their icy surfaces are exposed to the solar UV and to the local plasma causing desorption as well as physical and chemical alterations (Johnson, 1990; 1998). During the Voyager I tour of the outer solar system, W.L. Brown, L.J. Lanzerotti and colleagues at AT&T Bell Labs measured the ejection of molecules induced by energetic ion impact of ice. They discovered that the sputtering from low-temperature ices by fast, light ions is determined by the electronic excitations produced in the ice, rather than by knock-on collisions (Brown et al., 1978) and, hence, is an electronically-stimulated-desorption process. This exciting discovery opened a new field of study. Below the relevance of desorption to a few outer solar system bodies is described; for extended descriptions see Johnson (1990; 1996; 1998).



II Desorption from Solar System Bodies

The samples collected during the Apollo missions show the lunar surface is modified by the impacting solar-wind ions (~ 1 keV/u H+ and He++) and by energetic solar particles (Taylor, 1982). This aspect of planetary physics has recently been revived by the observation of Na and K 'atmospheres' around Mercury and the Moon (Potter and Morgan, 1985; 1988). Such atmospheres are produced by stimulated-desorption (the ions, electrons and UV photons) of these atoms from the rocky surfaces (Madey et al. 1998). The sodium atmosphere has been seen to extend to ~ 5 lunar radii from the moon's surface (Flynn and Mendillo, 1993), providing an impressive manifestation of desorption.

Similarly the ions trapped in the Jovian and Saturnian magnetospheres bombard the surfaces of the embedded moons. These ions are energetic (Fig.1) producing a neutral desorption flux of ~ 1011 molecules/cm2/s. Although this is much smaller than typical laboratory sputtering rates, the exposure times are long. The application of laboratory data to the erosion of grains has shown that the icy, main rings of Saturn are transient ( ~ 108 yrs). Of current interest is a ring of micron-sized ice grains called the E-ring, lying outside the main rings in the region where the plasma trapped in Saturn's magnetosphere is relatively intense. Desorption rates based on laboratory data (Shi et al., 1995) place an upper limit on the survival of these charged ice grains (Jurac et al. 1995) of about 1000 years. Therefore, the E-ring must have a source, presumably a relatively recent massive impact or volcanic activity on the moon Enceladus

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-97331999000300008&lng=&nrm=iso&tlng=

[StefanR]

The plasmasphere of Neptune

Abstract.
We examine the plausible existence of Neptune's plasmasphere- and study the drift of
particles inside it. Using the 08 magnetic field model [Comemey et aZ., 19911 and assuming a
uniform solar wind convection electric field, the plasma convection time and refilling time are
calculated in a Euler potential coordinate syste[mH o et aL, 19971. The plasma density and refilling
time at the equilibrium state are first calculated, and the location of the plasmapause is set to be
where the refilling time and convection time are equal. The refilling time as a function of ion speed
is then recalculated along field lines, and the plasma density and temperature are obtained by
directly integrating the local ion distribution function over the range of speeds for which the
refilling time is less than the convection time. The density calculated using this model shows sharp
drop-offs at approximately 3.25 to 4.5 RN on the zero magnetic scalar potential surface, a
boundary taken to be the plasmapause. Our calculated density compares fairly with the observed
density along the Voyager trajectory within about 5 RN. Ion temperature is also calculated along the
field line with results which indicate that high-speed tails of the distribution function might be
needed to explain the high observed temperature measured along the Voyager 2 trajectory. Drift
trajectories and speeds of 90" pitch angle particles inside the plasmapause are calculated. Particles
of energy above tens of eV are gradient drift dominated, and the drift paths of this class of particles
are essentially the minimum B contours that are similar to Acuiia et aZ.'s [1993] calculations.
Atmospheric precipitation otfh e J = 0 particles may provide an explanation for the UV emissions,
as an alternative to the "monoprecipitation" suggested by Puranicas and Cheng [ 19941. Drifts of
low-energy particles are strongly affected by the gravitational andc entrifugal forces, and because
of the largely tilted dipole and the large higher components of magnetic field, the resultant drift is
nonaxisymmetric and quite complicated.

According to Ness et d ' s [ 1989] OTD (Offset Tilted Dipole) model, Neptune has a dipole
axis tilted about 47" from the rotation axis. Together with the 113" angle the rotation axis made
with the Neptune-Sun direction during the Voyager 2 flyby to the planet, the large tilted angle
results in an “Earth-like” and a “pole-on” magnetic field configurations at two extreme positions
during each revolution of the planet as the rotation axis, the dipole axis and the Neptune-Sun
direction all lie in the same plane [Ness et al., 1989; Selesnick, 19901. These two extreme
positions represent the upper and approximately the lower limits of the efficiency of coupling
between the solar wind and the convection over the polar cap, and the strong modulation of the
convection electric field in the Neptunian magnetosphere causes a cumulative effect like the
acceleration of particles in a cyclotron[S elesnick, 19901.

Since Neptune has an Earth-like position and Earth has a plasmasphere, and while in the
pole-on position, solar wind magnetosphere coupling at Neptune this is weakest and the likelihood
to form a plasmasphere is highest, Neptune should also have a plasmasphere. The existence of a
plasmasphere at Neptune is also supported by the Voyager 2 Plasma Wave Instrument (PWS),
which detected whistler signals with large dispersions [Gurnett et aZ., 19891 that require dense
plasma path lengths along field lines.

Further arguments for the existence of a Neptunian plasmasphere can be made as follows:
Neptune has a region, extended to about three planetary radii (1 RN = 24,765 km), dominated by
the gravitational force, and in this region the ionospheric plasma refilling surpasses the solar wind
driven convection,L emaire [1974] has used the critical distance, “Roche Limit,” beyond which the
refilling time quickly increases, to define Earth’s plasmapause. Earth’s plasmasphere defined in
this way has a size of 5.8 RE, a value not too far from the actual observed average values. For
Neptune, assuming a spin axis-aligned dipole as a rough estimate, the critical distance of Neptune
is 3 RN. However, because of the larger gravity and the lower ionospheric temperature of Neptune
[Tyler et aZ., 19891, the plasma distribution in the plasmasphere differs from that of the terrestrial
plasmasphere in that the plasma density gradient along a field line from the ionosphere to the
equatorial plane is quite large. As a result of the low plasma density of ionospheric origin along the
field line in the low magnetic latitude region, the incoref a spela sma refilling time with increasing L
shell is not so fast as in the terrestrial magnetosphere, and hence the actual size of the Neptunian
plasmasphere might be larger than the above estimate of at 3 RN.

In this paper, based on the competition of plasma. refilling with the solar wind driven
convection, we construct a model of plasmasphere at Neptune. We also study the particle drift
motions inside the plasmasphere. The magnetic field model we use of are various calculations is the
08 model [Connerney et al. 19911, and for representing it the a and p (Euler potentials)
coordinates [Ho et al., 19971 are used. The 08 model, including the dipole, quadrupole and
octupole of the field, has been used to study field geometry invariants d arnifdt shells [Acuiia et al.,
19931, and aurora in association with W emissions [Puranicasa nd Cheng, 19941.

This paper is structured as follows. In section 2, we calculate the plasma density
originating from the ionosphere, assuming an equilibrium state, i.e., a full Maxwellian distribution
everywhere on the concerned field lines. We then proceed by comparing the solar wind driven
convection time with the plasma refilling time to estimate the size of the plasmasphere, as an
approximation. Next, for a more accurate calculation, we consider the local dynamic accessibility
of particles in the refilling process.T his is followed by a more meticulous study of the dynamics of
ions along the field lines. To do this, we calculate the refilling time of the ions that can access a
certain point on a field line. By integrating the local ion distribution functoiovne r the rangeo f ion
speeds that correspond to a refilling time less than the convection time, the ion density and
temperature can be obtained. The location of the plasmapause is thus determined to be where the
densities show sudden drop-offs. In section 3, we compare the calculated plasma densities and
temperatures witht he Voyager Plasma Science Experiment (PLS) measurements. In secti4o,n w e
calculate the particle drift paths and drift velocities inside the plasmasphere of Neptune. Finally,
discussion and conclusions are given in section 5.

5. Discussion and Conclusions
Based on the fact that the refilling time of the ionospheric ions is less than the solar wind
driven convection time within a few planetary radii, we set out to argue for the existence of a
plasmasphere at Neptune and proceeded to estimate its size, density, and temperature. The
existence of a plasmasphere at Neptune is supported by the fact that Voyager2 PWS detected large
dispersive Whistler waves, suggesting large densities along field lines. Other evidence is the lack
of report on the day-night asymmetries in plasma density. Such density asymmetries have been
used as an argument for a convection-dominated magnetosphere at Uranus. In the case of Uranus,
convection domination, and hence the lack of a plasmasphere ,may be supported by the theoretical
argument that solar wind particles can penetrate easily into the inner magnetosphere because of the
near alignment of the spin axis and the solar wind flow. The penetration, however, may not be
achieved so readily if the inner flux tubes are filled by interhemispherical plasma flow in a
timescale that is short compared to the convection time, in fact, sharp plasma edges were observed
at Uranus which may be explained by the reduction of the electric field in the inner region that thus
provides some sort of "shielding" [WoZf, 19831. The method used in this paper can be applied to
Uranus to determine if it has a plasmasphere.

In the first approximation, the plasma was assumed to be in an equilibrium state, and the
boundary at which the plasma refilling time equals the solar wind driven convection time is taken to
be the plasmapause.The plasmasphere so obtained has a size of about 7 planetary radii on the zero
magnetic scalar potential surface, which is obviously overestimated, indicating an equilibrium state
of plasmaspheric plasma to be a poor assumption.

In more accurate calculations, we have taken the effect of accessibility of ions from the
ionosphere to a certain point on a field line due to both the potential barrier resulting from the
gravity and centrifugal force and the requirement of the local refilling time to be less than the solar
wind driven convection time. By calculating the time to fill a flux tube from the ionosphere to a
specific point on the field line for the ions which are able to cross the potential barriers and
comparing with the convection time, the accessibility of the ionospheric ionso f various speeds to
that particular point was determined.The density and temperature of the plasma at the local point
were then obtained by integrating over all the ions that are accessible to the concerned point. By
this we found that Neptune has a plasmasphere which has its boundary located between3 .25 and
4.5 RN on the zero magnetic scalar potential surface.

The calculated H+ densities and temperatures/ were compared with the Voyager 2
observations. The measured density minima at about 3 RN inbound and 5 RN outbound were
roughly the location of the plasmapause we calculated. The plasma density drops exponentially
with distance inside the plasmasphere because of the large gravity of Neptune, and the sudden
density drop-offs at the plasmapause we calculated have magnitudes a few orders lower than the
ionospheric density. The Neptunian plasmasphere is therefore quite different from Earths
plasmasphere, which has a density that does not decrease appreciably with distance until the dropoff
at the plasmapause. The high temperatures observed may result from the high-speed tails of the
ions escaping from the ionosphere. Other sources of plasmas such as solar wind particles and
plasmas originating from Neptune's moons and rings, as well as various heating processes, may
also contribute to the measured bulk plasma parameters.

We also calculated the particle drifts. Only 90" pitch angle particles are considered in this
paper, which simplifies the problem to two-dimensions by removing bounce motions.D ue to the
high nondipole magnetic components, particles very near the planed to not execute complete 360"
drifts, similar to Acuiia et aZ.'s E19931 results given on the minimum B contours. Energetic 90"
pitch angle particles precipitate into the atmosphere along them agnetic equator on the planetary
surface, providing an alternate explanation for Paranicas and Cheng's [ 1 9941 "monoprecipitation."
In the range of 2 - 4 RN, particles of energies of 100 eV and above drift at the speeds that are
comparable to the solar wind driven convection speeds, of the order of a few m/s . The drifts of
particles of lower energies are strongly affected by the gravitational and centrifugal forces, and
constrained to the surfaces where the first invariant of the particles is maximum on each field

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/20374/1/98-1317.pdf

[StefanR]

Large Satellites:
Active Worlds and Extreme Environments

The 17 large and medium-size satellites of the outer planets, shown to scale, are worlds in their
own right. The Galilean satellites of Jupiter (top row) are (from left) Io, whose surface is constantly renewed by active
volcanoes tinged with sulfur allotropes; Europa, which probably possesses a liquid water ocean beneath its ruddy ice skin;
Ganymede, a moon bigger than the planet Mercury, possessing a rutted surface of dirty ice and an internally generated
magnetic field; and Callisto, a moon with an ancient cratered surface whose interior is only weakly differentiated. Saturn’s
family of bright icy moons (second row) consists of Mimas, Enceladus, Tethys, Dione, and Rhea; cloud-shrouded Titan has
an atmosphere rich in organics and possibly seas of methane; and two-toned Iapetus shows one face as bright as snow and the
other as black as coal. The five major uranian satellites (third row) are Miranda, Ariel, Umbriel, Titania, and Oberon. Each
displays a dirty-ice surface and some tectonic activity, but the bizarre world of Miranda—with its exotic jumble of surface
terrains suggesting that it may have been totally disrupted in the past and put back together at random—steals the show.
Neptune’s sole large satellite (fourth row), Triton, is coated with exotic ices tinged pink by organic molecules; nitrogen
geysers spew high into its tenuous atmosphere. Courtesy of NASA/JPL.

Of the six large outer-planet satellites—Io, Europa, Ganymede, Callisto, Titan, and Triton—all are larger than
Pluto and two are larger than Mercury; in addition, there are 11 medium-sized satellites (Figure 5.1; Table 5.1).
Each planet-sized satellite is unique:
• Io is intensely volcanically active,
• Europa may have a layer of subsurface water greater in volume than all of Earth’s oceans combined,
• Ganymede has an intrinsic magnetic field,
• Callisto is largely undifferentiated,
• Titan has a thick atmosphere rich in organic compounds, and
• Triton has active, geyserlike eruptions.
The large satellites have bizarre life cycles, influenced by orbital evolution and tidal heating, revolutionizing
concepts based on the terrestrial planets. They are rich in volatile species such as H2O, SO2, N2, CH4, CO2, and
perhaps NH3, creating a rich diversity of processes and environments. The 11 medium-sized satellites are also
unique worlds, and they may provide essential information about the origin and evolution of satellite systems.

WHY DO WE CARE ABOUT LARGE SATELLITES?
Why are these large satellites worthy of national and international exploration and research? One good reason
is that advancing basic research about physical processes in fields such as volcanology and meteorology may
eventually provide benefits that will improve our lives. Another is that such interesting worlds inspire our youth
and students to excel in mathematics and science. But the most compelling motivation is to understand the origin
and destiny of life. Water is essential to life as we know it, and the large icy satellites may contain the largest
reservoirs of liquid water in the solar system. Outside Earth, Europa may be the best place in the solar system to
search for extant life. Titan provides a natural laboratory for the study of organic chemistry over temporal and
spatial scales unattainable in terrestrial laboratories. Perhaps teeming with life or perhaps sterile today, these
worlds do contain the basic ingredients for life. Knowing whether they do or do not harbor life is equally
important. The origin and evolution of satellite systems also provide analogs for understanding extrasolar planetary
and satellite systems, some of which may be abodes for life.

Triton
Four separate ices have been identified spectroscopically on Triton’s surface: N2, CH4, CO, and CO2.43,44
The latter three species (except perhaps CO2) exist partially in solid solution with N2, the main constituent. More
complex organic molecules are also expected to be present as a result of photolysis and radiolysis. Triton’s surface
temperature of approximately 38 K creates an atmosphere in vapor pressure equilibrium with the ices, which is
highly responsive to heating changes associated with solar insolation and the variable photometric and compositional
properties of the surface. As a result, the atmosphere experiences large-scale sublimation, transport, and
recondensation of N2, CO, and CH4. Another unique characteristic is Triton’s geyserlike plumes that entrain dark
dust and rise 8 km above the surface.45 A diffuse haze pervades the atmosphere; it probably consists of the
condensation of hydrocarbons created by photochemistry. Discrete clouds, likely condensed N2, are present near
the poles.

Magnetospheric Processes and Interactions

Sputtering/Implantation

The large satellites of the gaseous giant planets spend all or most of their time in the corotating magnetospheres
of these planets. The interaction of satellite and corotating plasma modifies the satellites’ surfaces and
atmospheres and leads to a net loss of volatile materials to the magnetospheres. At the present time, Io is known
to lose more than a ton per second of volatile material (mostly S and O) to Jupiter’s magnetosphere.51 Similarly,
Europa is losing its icy surface at the rate of ~2 cm per million years (Myr) to Jupiter’s magnetosphere.52
Ganymede’s magnetic field partially shields the equatorial regions from plasma bombardment. However, it is
estimated that the polar regions of Ganymede lose an average of 8 mm/Myr of ice from sputtering.53 Callisto, in
a more benign radiation environment, loses <0.4 mm/Myr of ice to sputtering. The plasma bombardment of icy
surfaces results in the implantation of S derived from Io’s torus into the crusts of icy satellites.54 The irradiation
of icy satellite surfaces also results in the production of H2, O2, H2O2, and other stable oxides that get embedded
in the ices and also form tenuous atmospheres near the surface.55 The irradiation of other ice contaminants such
as C and S produces CO2, SO2, and H2SO4. The radiolysis of the surface by magnetospheric particles continuously
cycles S between SO2, H2SO4, and polymer S forms.56 At Europa, the fast recycling of the crust (believed to occur
over a time scale of 100,000 to 10 million years) may deliver oxidants from the surface to the subsurface ocean.57
These oxidants could fuel life in the absence of sunlight.

Style of Plasma Interaction

The type and strength of satellite/magnetospheric interaction depends on the satellite’s size, surface composition,
and electrical conductivity, the presence or absence of an internal magnetic field in the satellite, and the
density, composition, and speed of the interacting plasma. Based on these factors, three distinct types of interactions
have been observed. In the nonconducting type of satellite/plasma interaction, as in the case of Callisto,
the magnetospheric plasma slams into the satellite and is absorbed, but sputters some volatile material off the
satellite’s surface.
A second type of interaction, called the conducting-satellite/plasma interaction, is best illustrated by Io and
Europa. Because of a well-developed ionosphere at Io and large plasma pickup near Europa, most of the
magnetospheric plasma is diverted around the moons. Only a small fraction of the incoming plasma flux strikes
the moons and sputters volatile materials off the surface. The strong Alfvén wing currents generated in the
interaction are closed in the ionosphere of Jupiter where they generate visible footprints (see Figures 4.3 and 4.4).
The third type of interaction is epitomized by Ganymede, which generates its own internal magnetic field.58
Ganymede’s magnetic field is strong enough that it creates a minimagnetosphere of its own in Jupiter’s magnetosphere,
partially shielding the satellite from plasma bombardment. The interaction between Ganymede’s magnetosphere
and Jupiter’s magnetosphere is similar to the interaction between Earth’s magnetosphere and the solar
wind, in which magnetic reconnection plays a key role.
Curiously, the other three Galilean satellites were found not to have internal fields at present. However, it is
likely that some or all of the other large moons of the solar system were endowed with an internal magnetic field
at some time in their evolution.

Induced Fields

Europa, Ganymede, and Callisto. Magnetic observations from the vicinities of Europa, Ganymede, and Callisto
show that all three moons generate electromagnetic induction fields in response to the rotating field of Jupiter.59,60 The
magnetic signatures are consistent with the presence of subsurface electrically conducting shells in these bodies.
Detailed analyses for Europa and Callisto suggest that liquid subsurface oceans with thicknesses exceeding a few
kilometers could account for the enhanced subsurface conductivities.61 Geological and geophysical lines of
evidence are consistent with liquid subsurface oceans within Europa and Ganymede. However, the presence of
electromagnetic induction from geologically inactive Callisto was indeed a surprise.
Titan. The only spacecraft to make in situ observation of the interaction of Titan with Saturn’s magnetosphere was
Voyager 1, which flew through the plasma wake of Titan. No appreciable internal magnetic field was observed
(surface field strength <30 nT).62 The main pickup ion is N+, and the integrated surface pickup rate is ~1024 ions
per second. The geometry of the flyby was not suitable to infer the presence or absence of an electromagnetic
induction signature, so magnetic measurements cannot yet speak to the question of an ocean within Titan.

UNIFYING THEMES AND KEY SCIENTIFIC QUESTIONS
FOR LARGE SATELLITE EXPLORATION
The Large Satellites Panel evaluated and organized key scientific questions around four major themes that, in
its opinion, best capture the most important scientific questions pertinent to large satellites. They are as follows:
• Origin and evolution of satellite systems. Tidal heating and orbital evolution have led to complex histories
for some large satellites. Satellite systems may form and evolve in ways analogous to planetary systems but are
much more accessible for detailed study than are extrasolar planetary systems.
• Origin and evolution of water-rich environments in icy satellites. Evidence for water within the icy
Galilean satellites has led to a new paradigm for the potential habitability of planetary systems. Europa offers the
greatest potential for finding life, because the subsurface water may interact with the surface and the silicate mantle.
• Exploring organic-rich environments. Although organic materials are common in the solar system, only
Earth and Titan allow the study of organic chemistry in the presence of a thick atmosphere, a solvent, and a solid
surface. Titan may enable study of the conditions leading to the origin of life.
• Understanding dynamic planetary processes. We can best understand physical processes by observing
them in action, and satellites such as Io, Titan, and Triton offer a broad range of current activity, from the interiors
to the surfaces, atmospheres, and magnetospheres

http://128.183.114.83/miscellaneous/jupiter/NRC_SSB_Reports/Solar_System/118-150.pdf

[flyingcloud]

Huge Pressures Melt Diamonds On Planet Neptune
http://www.sciencedaily.com/releases/20 ... 091937.htm

As a bonus to science, researchers Marcus Knudson, Mike Desjarlais, and Daniel Dolan discovered a triple point at which solid diamond, liquid carbon, and a long-theorized but never-before-confirmed state of solid carbon called bc8 were found to exist together.

“Liquid carbon is electrically conductive at these pressures, which means it affects the generation of magnetic fields,” says Desjarlais. “So, accurate knowledge of phases of carbon in planetary interiors makes a difference in computer models of the planet’s characteristics. Thus, better equations of state can help explain planetary magnetic fields that seem otherwise to have no reason to exist.”

[StefanR]

When the comet Shoemaker-Levy 9 hit Jupiter sixteen years ago, scientists all over the world were prepared: instruments on board the space probes Voyager 2, Galileo and Ulysses documented every detail of this rare incident. Today, this data helpsThe "dusty snowballs" leave traces in the atmosphere of the gas giants: water, carbon dioxide, carbon monoxide, hydrocyanic acid, and carbon sulfide. These molecules can be detected in the radiation the planet radiates into space.

In February 2010 scientists from Max Planck Institute for Solar System Research discovered strong evidence for a cometary impact on Saturn about 230 years ago (see Astronomy and Astrophysics, Volume 510, February 2010). Now new measurements performed by the instrument PACS (Photodetector Array Camera and Spectrometer) on board the Herschel space observatory indicate that Neptune experienced a similar event. For the first time, PACS allows researchers to analyze the long-wave infrared radiation of Neptune.

The atmosphere of the outer-most planet of our solar system mainly consists of hydrogen and helium with traces of water, carbon dioxide and carbon monoxide. Now, the scientists detected an unusual distribution of carbon monoxide: In the upper layer of the atmosphere, the socalled stratosphere, they found a higher concentration than in the layer beneath, the troposphere. "The higher concentration of carbon monoxide in the stratosphere can only be explained by an external origin", says MPS-scientist Paul Hartogh, principle investigator of the Herschel science program "Water and related chemistry in the solar system". "Normally, the concentrations of carbon monoxide in troposphere and stratosphere should be the same or decrease with increasing height", he adds.

The only explanation for these results is a cometary impact. Such a collision forces the comet to fall apart while the carbon monoxide trapped in the comet’s ice is released and over the years distributed throughout the stratosphere. "From the distribution of carbon monoxide we can therefore derive the approximate time, when the impact took place", explains Thibault Cavalié from MPS. The earlier assumption that a comet hit Neptune two hundred years ago could thus be confirmed. A different theory according to which a constant flux of tiny dust particles from space introduces carbon monoxide into Neptune’s atmosphere, however, does not agree with the measurements.

In Neptune’s stratosphere the scientists also found a higher concentration of methane than expected. On Neptune, methane plays the same role as water vapor on Earth: the temperature of the socalled tropopause - a barrier of colder air separating troposphere and stratosphere - determines how much water vapor can rise into the stratosphere. If this barrier is a little bit warmer, more gas can pass through. But while on Earth the temperature of the tropopause never falls beneath minus 80 degrees Celsius, on Neptune the tropopause's mean temperature is minus 219 degrees.

Therefore, a gap in the barrier of the tropopause seems to be responsible for the elevated concentration of methane on Neptune. With minus 213 degrees Celsius, at Neptune’s southern Pole this air layer is six degrees warmer than everywhere else allowing gas to pass more easily from troposphere to stratosphere. The methane, which scientists believe originates from the planet itself, can therefore spread throughout the stratosphere.

http://www.mpg.de/english/illustrationsDocumentation/documentation/pressReleases/2010/pressRelease201007161/


Still I think, although I couldn't quite trace the argument shooting down the influx from outside-hypothese, that there is is room for sputtered material migrating from for instance Triton to flow and seed the stratosphere of Neptune. This in relation with:

Triton
Four separate ices have been identified spectroscopically on Triton’s surface: N2, CH4, CO, and CO2.43,44
The latter three species (except perhaps CO2) exist partially in solid solution with N2, the main constituent. More
complex organic molecules are also expected to be present as a result of photolysis and radiolysis. Triton’s surface
temperature of approximately 38 K creates an atmosphere in vapor pressure equilibrium with the ices, which is
highly responsive to heating changes associated with solar insolation and the variable photometric and compositional
properties of the surface. As a result, the atmosphere experiences large-scale sublimation, transport, and
recondensation of N2, CO, and CH4. Another unique characteristic is Triton’s geyserlike plumes that entrain dark
dust and rise 8 km above the surface.45 A diffuse haze pervades the atmosphere; it probably consists of the
condensation of hydrocarbons created by photochemistry. Discrete clouds, likely condensed N2, are present near
the poles.
......
Magnetospheric Processes and Interactions

Sputtering/Implantation

The large satellites of the gaseous giant planets spend all or most of their time in the corotating magnetospheres
of these planets. The interaction of satellite and corotating plasma modifies the satellites’ surfaces and
atmospheres and leads to a net loss of volatile materials to the magnetospheres. At the present time, Io is known
to lose more than a ton per second of volatile material (mostly S and O) to Jupiter’s magnetosphere.51 Similarly,
Europa is losing its icy surface at the rate of ~2 cm per million years (Myr) to Jupiter’s magnetosphere.52
Ganymede’s magnetic field partially shields the equatorial regions from plasma bombardment. However, it is
estimated that the polar regions of Ganymede lose an average of 8 mm/Myr of ice from sputtering.53 Callisto, in
a more benign radiation environment, loses <0.4 mm/Myr of ice to sputtering. The plasma bombardment of icy
surfaces results in the implantation of S derived from Io’s torus into the crusts of icy satellites.54 The irradiation
of icy satellite surfaces also results in the production of H2, O2, H2O2, and other stable oxides that get embedded
in the ices and also form tenuous atmospheres near the surface.55 The irradiation of other ice contaminants such
as C and S produces CO2, SO2, and H2SO4. The radiolysis of the surface by magnetospheric particles continuously
cycles S between SO2, H2SO4, and polymer S forms.56 At Europa, the fast recycling of the crust (believed to occur
over a time scale of 100,000 to 10 million years) may deliver oxidants from the surface to the subsurface ocean.57
These oxidants could fuel life in the absence of sunlight.

http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?p=6549#p6549

blobs of material that rise from depth and penetrate through a surface layer. This suggests that Triton's crust is layered. Some of the smooth deposits at right may be volcanic in origin. Plumes (or Geysers) One of the biggest surprises about Triton was the discovery of atmospheric plumes in the spotted southern hemisphere of Triton. These plumes reach heights of 8 kilometers and are blown laterally by winds in the extremely thin atmosphere (!). They can be traced for several hundred kilometers. The origin of these plumes is still a matter of debate. They may be the result of solar heating of a thin frozen nitrogen layer, or of melting of volatiles near the surface by internal heat.

http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?p=6346#p6346

Hubble also spied two small satellites, named Mab and Cupid. One of the satellites shares an orbit with the outermost of the new rings. The satellite is probably the source of fresh dust that keeps replenishing the ring with new material knocked off the satellite from meteoroid impacts. Without such replenishment, the dust in the ring would slowly spiral in toward Uranus. Collectively, these new discoveries mean that Uranus has a youthful and dynamic system of rings and moons.
......
"We think that dusty rings in general are sustained by impacts," de Pater said. "The rings of Jupiter exist because small meteorites continuously bombard the moons in Jupiter's system."
Study co-author Heidi Hammel of the Space Science Institute in Ridgefield, Connecticut, added that Uranus has been "the unappreciated underdog of the outer solar system for too long.
"It is refreshing to see such dynamic change and exciting evolution in the rings and the planet."

http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?p=6099#p6099

The maps show evidence for asymmetrical patterns, due tothe existence of CO jets. Analysis of the spectra and their velocity shifts shows thatthere is a spiral CO jet rotating in a plane almost perpendicular to the sky plane.This is the rst time that rotating jets are observed for parent molecules. We havedeveloped a 3-D model simulating rotating spiral jets of CO gas......

................

Thrill seekers may want to hitch a ride on the giant comet Hale-Bopp, but they would fail vehicle emission tests miserably. When it was the same distance from the Sun as Earth, Hale Bopp produced carbon monoxide (CO) emissions equal to that given off by 5.5 billion cars every day.

.....................

a puzzle about the nature and distribution of elemental carbon and carbonaceous material in its nucleus and coma. The nucleus is darker even than coal (albedo <4%)1, suggesting that its volatile ices contain a few per cent of carbonaceous material in the form of graphitic or amorphous carbon.The very high abundance of light elements in the coma dust2, 3, particularly H, C, N and O, suggests the presence of a significant organic component. The emission feature near 3.4 m also implies the presence of organic material in the dust 4–6. But the parent species for the primary carbon-containing material that have been identified so far (such as CO, CO2 and CH4) are not present in sufficient quantities to account for all of it. Here we propose that an additional contribution from carbon suboxide (C3O2) in the coma dust and the nucleus material is consistent with the observational data

....................

Jupiter's atmosphere still contains remnants of a comet impact from a decade ago, but scientists said last week they are puzzled by how two substances have spread into different locations.....
...
The highest concentration of carbon dioxide, however, has shifted away from the latitude of the impact. It is most prevalent poleward of 60 degrees south and decreases abruptly, toward the equator, north of 50 degrees south. Another smaller spike in its presence occurs at high northern latitudes, around 70 to 90 degrees north.
Perhaps the two chemicals got distributed at different altitudes, and are being moved around by different currents, Flasar told SPACE.com. Or maybe the formation of the carbon dioxide was more complex than thought. He said it might have involved carbon monoxide first moving away from the impact area and then interacting with other substances at higher latitudes before being converted to carbon dioxide.

http://www.thunderbolts.info/forum/phpBB3/viewtopic.php?p=336#p336


So there is the presence of CO and CH4 and all such as named above, are possible to get from sputtering whether from comets,moons or asteroids. Even mixing of these compounds on gasgiants are not as predictable as was thought. Etc, etc......

[mharratsc]

Still I think, although I couldn't quite trace the argument shooting down the influx from outside-hypothese, that there is is room for sputtered material migrating from for instance Triton to flow and seed the stratosphere of Neptune.

I think it proves that these scientists are not required to sit in the same rooms with each other and talk, read each other's work, or in any other way attempt to stay current with other discoveries in not only other disciplines, but with the work that others are doing with the same satellite!

One guy is adamant about this material only being able to be brought in via the 'Comet Express', while others are taking measurements on the amount of sputtered material they are observing transiting the two bodies... rediculous. Yet- even the guys who are measuring the material being sputtered off the moons is careful to avoid mentioning HOW sputtering occurs in the first place!

Meh.

[nick c]

This thread is a composite of the following threads:
Glowing Neptune
Huge Pressures Melt Diamonds On Planet Neptune
The Triton-Neptune interaction