146 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
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
Unexpected Long-Term Variability in Jupiter's Tropospheric Temperatures
An essential component of planetary climatology is knowledge of the
tropospheric temperature field and its variability. Previous studies of Jupiter
hinted at periodic behavior that was non-seasonal, as well as dynamical
relationships between tropospheric and stratospheric temperatures. However,
these observations were made over time frames shorter than Jupiter's orbit or
they used sparse sampling. We derived upper-tropospheric (300-mbar)
temperatures over 40 years, extending those studies to cover several orbits of
Jupiter, revealing unexpected results. Periodicities of 4, 7 8-9 and 10-14
years were discovered that involved different latitude bands and seem
disconnected from seasonal changes in solar heating. Anti-correlations of
variability in opposite hemispheres were particularly striking at 16, 22 and 30
degrees from the equator. Equatorial temperature variations are also
anticorrelated with those 60-70 km above. Such behavior suggests a top-down
control of equatorial tropospheric temperatures from stratospheric dynamics.
Realistic future global climate models must address the origins of these
variations in preparation for their extension to a wider array of gas-giant
exoplanets.Comment: Primary file: 16 pages, 5 figures. Supplemental File (attached): 12
pages, 3 figures, 1 tabl
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
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
Emerging Capabilities for Detection and Characterization of Near-Earth Objects (NEOs)
Here we describe the status for the detection and characterization of Near- Earth Objects (NEO) with current and future observatories. A summary of the capabilities, limitations, and obtainable NEO parameters is provided. <p/
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