80 research outputs found
The Origin of Nitrogen on Jupiter and Saturn from the N/N Ratio
The Texas Echelon cross Echelle Spectrograph (TEXES), mounted on NASA's
Infrared Telescope Facility (IRTF), was used to map mid-infrared ammonia
absorption features on both Jupiter and Saturn in February 2013. Ammonia is the
principle reservoir of nitrogen on the giant planets, and the ratio of
isotopologues (N/N) can reveal insights into the molecular
carrier (e.g., as N or NH) of nitrogen to the forming protoplanets, and
hence the source reservoirs from which these worlds accreted. We targeted two
spectral intervals (900 and 960 cm) that were relatively clear of
terrestrial atmospheric contamination and contained close features of
NH and NH, allowing us to derive the ratio from a single
spectrum without ambiguity due to radiometric calibration (the primary source
of uncertainty in this study). We present the first ground-based determination
of Jupiter's N/N ratio (in the range from to
), which is consistent with both previous space-based studies
and with the primordial value of the protosolar nebula. On Saturn, we present
the first upper limit on the N/N ratio of no larger than
for the 900-cm channel and a less stringent
requirement that the ratio be no larger than for the
960-cm channel ( confidence). Specifically, the data rule out
strong N-enrichments such as those observed in Titan's atmosphere and in
cometary nitrogen compounds. To the extent possible with ground-based
radiometric uncertainties, the saturnian and jovian N/N ratios
appear indistinguishable, implying that N-enriched ammonia ices could
not have been a substantial contributor to the bulk nitrogen inventory of
either planet, favouring the accretion of primordial N from the gas phase
or as low-temperature ices.Comment: 33 pages, 19 figures, manuscript accepted for publication in Icaru
Spatial Variations in the Altitude of the CH4 Homopause at Jupiter's Mid-to-high Latitudes, as Constrained from IRTF-TEXES Spectra
Peer reviewedPublisher PD
Enhanced CH absorption within Jupiter's southern auroral oval from Juno UVS observations
Reflected sunlight observations from the Ultraviolet Spectrograph (UVS) on
the Juno spacecraft were used to study the distribution of acetylene
(CH) at Jupiter's south pole. We find that the shape of the CH
absorption feature varies significantly across the polar region, and this can
be used to infer spatial variability in the CH abundance. There is a
localized region of enhanced CH absorption which coincides with the
location of Jupiter's southern polar aurora; the CH abundance poleward
of the auroral oval is a factor of 3 higher than adjacent quiescent,
non-auroral longitudes. This builds on previous infrared studies which found
enhanced CH abundances within the northern auroral oval. This suggests
that Jupiter's upper-atmosphere chemistry is being strongly influenced by the
influx of charged auroral particles and demonstrates the necessity of
developing ion-neutral photochemical models of Jupiter's polar regions.Comment: Accepted in JGR: Planet
Astro2020 Science White Paper: Triggered High-Priority Observations of Dynamic Solar System Phenomena
Unexpected dynamic phenomena have surprised solar system observers in the
past and have led to important discoveries about solar system workings.
Observations at the initial stages of these events provide crucial information
on the physical processes at work. We advocate for long-term/permanent programs
on ground-based and space-based telescopes of all sizes - including Extremely
Large Telescopes (ELTs) - to conduct observations of high-priority dynamic
phenomena, based on a predefined set of triggering conditions. These programs
will ensure that the best initial dataset of the triggering event are taken;
separate additional observing programs will be required to study the temporal
evolution of these phenomena. While not a comprehensive list, the following are
notional examples of phenomena that are rare, that cannot be anticipated, and
that provide high-impact advances to our understandings of planetary processes.
Examples include: new cryovolcanic eruptions or plumes on ocean worlds; impacts
on Jupiter, Saturn, Uranus, or Neptune; extreme eruptions on Io; convective
superstorms on Saturn, Uranus, or Neptune; collisions within the asteroid belt
or other small-body populations; discovery of an interstellar object passing
through our solar system (e.g. 'Oumuamua); and responses of planetary
atmospheres to major solar flares or coronal mass ejections.Comment: Astro2020 white pape
Possible Transient Luminous Events observed in Jupiter's upper atmosphere
11 transient bright flashes were detected in Jupiter's atmosphere using the
UVS instrument on the Juno spacecraft. These bright flashes are only observed
in a single spin of the spacecraft and their brightness decays exponentially
with time, with a duration of ~1.4 ms. The spectra are dominated by H2 Lyman
band emission and based on the level of atmospheric absorption, we estimate a
source altitude of 260 km above the 1-bar level. Based on these
characteristics, we suggest that these are observations of Transient Luminous
Events (TLEs) in Jupiter's upper atmosphere. In particular, we suggest that
these are elves, sprites or sprite halos, three types of TLEs that occur in the
Earth's upper atmosphere in response to tropospheric lightning strikes. This is
supported by visible light imaging, which shows cloud features typical of
lightning source regions at the locations of several of the bright flashes.
TLEs have previously only been observed on Earth, although theoretical and
experimental work has predicted that they should also be present on Jupiter.Comment: Accepted in JGR: Planets. 28 pages, 8 figure
Juno-UVS Observations of Io during the PJ58 Flyby
peer reviewedCurrently in its first extended mission, NASA’s Juno spacecraft has made several close approaches to Jupiter’s Galilean satellites.  The final of these very close flybys will be of Io during the perijove (PJ) 58 orbit, scheduled to occur at 17:48:35 UTC on 3 Feb. 2024, about 3h59m prior to PJ58. Juno’s Ultraviolet Spectrograph (UVS) is a photon-counting far-ultraviolet (FUV) imaging spectrograph with a bandpass of 68-210 nm, which will be used to observe Io’s numerous FUV emissions during the flyby. The circumstances of the flyby are similar to that for Ganymede during PJ34 at 16:56 UTC on 7 June 2021, with the satellite only observable for a few minutes on either side of Juno’s closest approach. We plan to record data +/-5 min (at best 20 swaths of data) about the closest approach time hoping for a significant decrease in the high radiation background due to shielding provided by Io itself.  Our observations will range from an altitude of 1500 km (closest approach) to 7820 km, giving the UVS data an expected spatial resolution of 6 to 28 km at the sub-spacecraft point.  As with the similar close flyby of Ganymede (Greathouse et al. 2022; Molyneux et al. 2022), UVS will attempt to measure reflected FUV sunlight from the surface of Io and airglow emissions from oxygen and in this case sulfur atoms. These observations will be more challenging than at Ganymede, however, since the background due to penetrating (>10 MeV) electrons at Io is expected to be a factor of 10 or more larger than at Ganymede. In this talk we will present results from the initial reduction and analysis of the UVS data obtained during the flyby of Io
Solar system Deep Time-Surveys of atmospheres, surfaces, and rings
Imaging and resolved spectroscopy reveal varying environmental conditions in
our dynamic solar system. Many key advances have focused on how these
conditions change over time. Observatory-level commitments to conduct annual
observations of solar system bodies would establish a long-term legacy
chronicling the evolution of dynamic planetary atmospheres, surfaces, and
rings. Science investigations will use these temporal datasets to address
potential biosignatures, circulation and evolution of atmospheres from the edge
of the habitable zone to the ice giants, orbital dynamics and planetary
seismology with ring systems, exchange between components in the planetary
system, and the migration and processing of volatiles on icy bodies, including
Ocean Worlds. The common factor among these diverse investigations is the need
for a very long campaign duration, and temporal sampling at an annual cadence.Comment: 10 pages, 4 figures: submitted for Astro2020 White Pape
The Io, Europa and Ganymede auroral footprints at Jupiter in the ultraviolet: positions and equatorial lead angles
Jupiter's satellite auroral footprints are a consequence of the interaction
between the Jovian magnetic field with co-rotating iogenic plasma and the
Galilean moons. The disturbances created near the moons propagate as Alfv\'en
waves along the magnetic field lines. The position of the moons is therefore
"Alfv\'enically" connected to their respective auroral footprint. The angular
separation from the instantaneous magnetic footprint can be estimated by the
so-called lead angle. That lead angle varies periodically as a function of
orbital longitude, since the time for the Alfv\'en waves to reach the Jovian
ionosphere varies accordingly. Using spectral images of the Main Alfv\'en Wing
auroral spots collected by Juno-UVS during the first forty-three orbits, this
work provides the first empirical model of the Io, Europa and Ganymede
equatorial lead angles for the northern and southern hemispheres. Alfv\'en
travel times between the three innermost Galilean moons to Jupiter's northern
and southern hemispheres are estimated from the lead angle measurements. We
also demonstrate the accuracy of the mapping from the Juno magnetic field
reference model (JRM33) at the completion of the prime mission for M-shells
extending to at least 15RJ . Finally, we shows how the added knowledge of the
lead angle can improve the interpretation of the moon-induced decametric
emissions.Comment: 20 pages, 8 figures, Accepted for publication in Journal of
Geophysical Research: Space Physics on 20 April 202
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