1,092 research outputs found
Giant planets: Clues on current and past organic chemistry in the outer solar system
The giant planets of the outer solar system - Jupiter, Saturn, Uranus, and Neptune - were formed in the same flattened disk of gas and dust, the solar nebula, as the terrestrial planets were. Yet, the giant planets differ in some very fundamental ways from the terrestrial planets. Despite enormous differences, the giant planets are relevant to exobiology in general and the origin of life on the Earth in particular. The giant planets are described as they are today. Their basic properties and the chemistry occurring in their atmospheres is discussed. Theories of their origin are explored and aspects of these theories that may have relevance to exobiology and the origin of life on Earth are stressed
Photochemistry of Planetary Atmospheres
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94723/1/eost12487.pd
Book Review: Physics and Chemistry of the Upper Atmosphere
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94675/1/eost8433.pd
Saturn's Exploration Beyond Cassini-Huygens
For its beautiful rings, active atmosphere and mysterious magnetic field,
Saturn is a fascinating planet. It also holds some of the keys to understanding
the formation of our Solar System and the evolution of giant planets in
general. While the exploration by the Cassini-Huygens mission has led to great
advances in our understanding of the planet and its moons, it has left us with
puzzling questions: What is the bulk composition of the planet? Does it have a
helium core? Is it enriched in noble gases like Jupiter? What powers and
controls its gigantic storms? We have learned that we can measure an outer
magnetic field that is filtered from its non-axisymmetric components, but what
is Saturn's inner magnetic field? What are the rings made of and when were they
formed? These questions are crucial in several ways: a detailed comparison of
the compositions of Jupiter and Saturn is necessary to understand processes at
work during the formation of these two planets and of the Solar System. This
calls for the continued exploration of the second largest planet in our Solar
System, with a variety of means including remote observations and space
missions. Measurements of gravity and magnetic fields very close to the
planet's cloud tops would be extremely valuable. Very high spatial resolution
images of the rings would provide details on their structure and the material
that form them. Last but not least, one or several probes sent into the
atmosphere of the planet would provide the critical measurements that would
allow a detailed comparison with the same measurements at Jupiter. [abridged
abstract
Observations of the Io plasma torus
The short wavelength spectrography on the IUE satellite was used to obtain spectra of the plasma torus near the orbit of Io about Jupiter. Three exposures of about 8 hours each taken in March and May 1979 show emission features due to SII, SIII, and OIII. The absence of features at other wavelengths permits upper limits to be other species in the torus
Stratospheric aerosols from CH 4 photochemistry on Neptune
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95495/1/grl4442.pd
Observations of polar aurora on Jupiter
North-south spatial maps of Jupiter were obtained with the SWP camera in IUE observations of 10 December 1978, 19 May 1979, and 7 June 1979. Bright auroral emissions were detected from the north and south polar regions at H Ly alpha (1216 A) and in the H2 Lyman bands (1250-1608 A) on 19 May 1979; yet no enhanced polar emission was detected on the other days. The relationship between the IUE observing geometry and the geometry of the Jovian magnetosphere is discussed
Clouds of Neptune and Uranus
We present results on the bases and concentrations of methane ice, ammonia ice, ammonium hydrosulfide-solid, water ice, and aqueous-ammonia solution (droplet) clouds of Neptune and Uranus, based on an equilibrium cloud condensation model. Due to their similar p-T structures, the model results for Neptune and Uranus are similar. Assuming 30-50x solar enhancement for the condensibles species, as expected from formation models, we find that the base of the droplet cloud is at the 370 bars for 30 solar, and at 500 bars for 50 solar cases. Despite this, entry probes need to be deployed to only 50-100 bars to obtain all the critical information needed to constrain models of the formation of these planets and their atmospheres
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HDO And SO2 Thermal Mapping On Venus II. The So2 Spatial Distribution Above And Within The Clouds
Sulfur dioxide and water vapor, two key species of Venus photochemistry, are known to exhibit significant spatial and temporal variations above the cloud top. In particular, ground-based thermal imaging spectroscopy at high spectral resolution, achieved on Venus in January 2012, has shown evidence for strong SO2 variations on timescales shorter than a day. We have continued our observing campaign using the TEXES high-resolution imaging spectrometer at the NASA InfraRed Telescope Facility to map sulfur dioxide over the disk of Venus at two different wavelengths, 7 mu m (already used in the previous study) and 19 mu m. The 7 mu m radiation probes the top of the H2SO4 cloud, while the 19 mu m radiation probes a few kilometers below within the cloud. Observations took place on October 4 and 5, 2012. Both HDO and SO2 lines are identified in our 7-mu m spectra and SO2 is also easily identified at 19 mu m. The CO2 lines at 7 and 19 mu m are used to infer the thermal structure. An isothermal/inversion layer is present at high latitudes (above 60 N and S) in the polar collars, which was not detected in October 2012. The enhancement of the polar collar in October 2012 is probably due to the fact that the morning terminator is observed, while the January data probed the evening terminator. As observed in our previous run, the HDO map is relatively uniform over the disk of Venus, with a mean mixing ratio of about 1 ppm. In contrast, the SO2 maps at 19 mu m show intensity variations by a factor of about 2 over the disk within the cloud, less patchy than observed at the cloud top at 7 mu m. In addition, the SO2 maps seem to indicate significant temporal changes within an hour. There is evidence for a cutoff in the SO2 vertical distribution above the cloud top, also previously observed by SPICAV/SOIR aboard Venus Express and predicted by photochemical models.NASA NNX-08AE38AIRTF AST-0607312, AST-0708074Astronom
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