Moon Triton Research Articles

Experimental study of the NaCl–H 2O system up to 28 GPa: Implications for ice-rich planetary bodies

Recent studies have hypothesized that high-pressure H 2O polymorphs, specifically Ice VI and Ice VII, make up a significant portion of the interiors of select outer planets and their moons; most notably the Galilean satellites, Saturn's Titan and possibly Neptune's moon Triton as well as potential H 2O-rich extra-solar bodies. Several of these bodies have been conjectured to contain subsurface salty H 2O waters; therefore, any potential ice phases in the interior of these satellites could have interacted extensively with the salty oceans. Raman spectroscopy and synchrotron radiation have been used previously to study the bonding structure and unit cell parameters of pure Ice VII. However, no data exist on the effect of salts on the unit cell parameters and volume of solid H 2O at high pressure. To obtain pertinent data for use in planetary physics, it is important to understand the effect of impurities on H 2O at high pressure. The NaCl–H 2O system was chosen as a first order approximation of H 2O-rich planetary bodies. The unit cell parameters and OH stretching frequencies of Ice VII formed from 5 and 10 wt.% NaCl–H 2O solutions were studied in detail up to 27 GPa at 298 K by using a diamond anvil cell, synchrotron X-ray radiation and Raman spectroscopy. The data indicate that, over the range in pressure and temperature of this study, the maximum solubility of solutes in Ice VII was not pressure dependent. Our data suggest that the maximum concentration of NaCl that can be incorporated into Ice VII at 298 K is 7.5 ± 2.5 wt.% (or 2.4 ± 0.8 mol% NaCl). Ice VII formed from a 5 wt.% NaCl–H 2O solution has a density that is up to 5% greater at any given pressure relative to the density of Ice VII formed from pure H 2O. Additionally, the bulk modulus, 26.2 ± 1.4 GPa, was found to be approximately 10–20% greater relative to Ice VII formed from pure H 2O. Relative OH stretching frequency shifts from Ice VII formed from the NaCl–H 2O solutions were compared to Ice VII formed from pure H 2O. Ice VII formed from a 5 wt.% NaCl–H 2O solution shows a systematic increase of approximately 15 rel cm −1 in the OH stretching frequency relative to pure Ice VII for any given pressure. We hypothesize that the incorporation of Na + and Cl − into the body centered cubic structure of Ice VII results in systematic variations in the intensive thermodynamic properties of Ice VII formed from low salinity solutions. These new data will provide an improved first order approximation of high-pressure H 2O phases found within H 2O-rich bodies and should be used to model the density profiles of H 2O-rich bodies.

Monitoring active volcanism with the Autonomous Sciencecraft Experiment on EO-1

The ability to monitor and rapidly react to remote detection of volcanic activity has been greatly improved through use of the Autonomous Sciencecraft Experiment (ASE), an advanced software application installed on a spacecraft in Earth orbit. ASE is a NASA New Millennium Program experiment demonstrating science-driven autonomous command and control of a spacecraft. Flying on the Earth Observing-1 ( EO-1) spacecraft, ASE successfully detected thermal emission from the Mt. Erebus lava lake on 7 May 2004, having analyzed a Hyperion hyperspectral data product on board the spacecraft. EO-1 was re-tasked by ASE to obtain a follow-up observation 7 h later and sent a notification of detection of volcanic activity to the ground. The entire process was carried out autonomously. Initial acquisition to receipt on the ground of the positive detection took less than 3 h, a process that without ASE would have taken weeks. The ASE Thermal Classifier has detected several styles of effusive volcanic activity: active lava lakes, pahoehoe flow fields, open channel flows and lava domes. ASE successfully demonstrated that science-driven spacecraft operation greatly enhances science return per returned byte through the identification of the most valuable data, allowing prioritization of downlink products and the discarding of null data sets. This technology has applications on missions elsewhere in the solar system. Modified thermal classifiers can be used for detecting and monitoring active volcanism on the jovian satellite Io, the neptunian moon Triton, and searching for active volcanism on Mars and icy satellites. The success of ASE is an incentive for future instrument and mission designers to consider on-board data-processing requirements (especially data storage capacity, number of processors and processor speed, and RAM) in order to take advantage of this flight-proven technology.

Watching meteors on Triton

The thin atmosphere of Neptune's moon Triton is dense enough to ablate micrometeoroids as they pass through. A combination of Triton's orbital velocity around Neptune and its orbital velocity around the Sun gives a maximum meteoroid impact velocity of approximately 19 km s −1, sufficient to heat the micrometeoroids to visibility as they enter. The ablation profiles of icy and stony micrometeoroids were calculated, along with the estimated brightness of the meteors. In contrast to the terrestrial case, visible meteors would extend very close to the surface of Triton. In addition, the variation in the meteoroid impact velocity as Triton orbits Neptune produces a large variation in the brightness of meteors with orbital phase, a unique Solar System phenomenon.

Neptune's Icy Cold Satellite Comes to Life

Planetary scientists are now realizing that Neptune9s moon Triton, is still showing signs of life. The realization is all the more startling because it is based on reanalyses of 10-year-old observations. Triton9s meager heat from lingering radioactive decay, researchers assume, can still melt its interior of exotic ices to produce lavas or otherwise reshape and renew the surface. Recent telescopic observations even hint that geologic activity has made itself evident in recent years.

Lensing by Triton's Atmosphere

When a planetary object passes between an observer and a distant star, the planet9s atmosphere can refract the starlight to cause a or temporary focusing of the light. In his Perspective, Hubbard discusses results reported in the same issue by Elliot et al. in which a central flash was seen for Neptune9s moon Triton. By carefully studying the nature of the flash, one can learn a great deal about the atmospheric properties of the moon. These new results suggest that Triton9s atmosphere is complex and dynamic.

D.P. Cruikshank (ed.): Neptune and Triton. University of Arizona Press, Tucson, 1995. 1249 Seiten (mit 2 Kartenbeilagen). Preis: 135.00 us‐$, ISBN 0‐8165‐1525‐5.

Astronomische NachrichtenVolume 317, Issue 3 p. 174-174 Buchbesprechungen D.P. Cruikshank (ed.): Neptune and Triton. University of Arizona Press, Tucson, 1995. 1249 Seiten (mit 2 Kartenbeilagen). Preis: 135.00 us-$, ISBN 0-8165-1525-5. JÜRgen Rendtel, JÜRgen Rendtel PotsdamSearch for more papers by this author JÜRgen Rendtel, JÜRgen Rendtel PotsdamSearch for more papers by this author First published: 1996 https://doi.org/10.1002/asna.2113170303AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume317, Issue31996Pages 174-174 RelatedInformation

The Origin and Composition of Pluto and Charon: Chemically Uniform Models

AbstractObservations of the Pluto-Charon system using the Hubble Space Telescope are soon to provide another test of the modern Laplacian theory of solar system origin. According to this theory, Pluto, Charon and Neptune’s moon Triton are condensed remnants of the gas ring which was shed by the proto-solar cloud at Neptune’s orbit, and from which Neptune formed. Each body should have the same bulk chemical composition provided that the influence of secondary events such as physical collision can be neglected. Here we report a model for the time-dependent, surface-catalysed production of CH4, solid carbon C(s) and CO2 within the outer layers of the proto-solar cloud. This model is used to determine the condensate mix which best fits the Voyager 2 spacecraft measurements of Triton’s mean density. We suggest that Triton is a chemically homogeneous structure consisting, by mass, of 44.2% anhydrous rock, 2.1% graphite, 33.0% water ice and 20.7% dry ice (i.e., solid CO2 ice, of which a fraction nearly 2/3 is present as the clathrate hydrate CO2·5.75 H2O). On the basis of this composition, the individual mean densities of Pluto and Charon are predicted to be 2.02 ± 0.02 g/cm3 and 1.94 ± 0.02 g/cm3, respectively, assuming a mean surface temperature of 35 K. The mean density of the combined system is predicted to be 2.01 ± 0.02 g/cm3.

Volatile processes in Triton's atmosphere and surface

The August, 1989 Voyager encounter with the Neptune system provided the fundamental information required to understand the volatile budget and transport processes on Neptune's large moon Triton. The discovery of nitrogen in Triton's atmosphere at a surface pressure of roughly 15–20 microbars, and surface temperature of 35–40K, combined with earlier ground-based spectra. strongly indicate that the atmosphere is supported by extensive deposits of surface nitrogen frosts, which are moved seasonally through the atmosphere in response to varying insolation. Likewise, Voyager and ground-based data support the notion that methane frost exists on the surface and is resupplying the atmosphere. The simplest model of global volatile transport, in which the albedo of the frost is constant, illustrates heuristically some interesting aspects of this system but does not reproduce the frost distribution seen by Voyager. Instead, models in which the nitrogen deposits have variable albedo, caused by grain size changes or contaminants, must be invoked. The grain growth properties and thermodynamics of pure nitrogen may also determine the radiating properties of the nitrogen frosts, which must be accounted for in the transport models. Finally, simple sublimation of nitrogen from the lit pole is not the only means of transport through the atmosphere: the detection of plumes above the surface may indicate the operation of moist convective processes which affect the transfer of both mass and energy from summer to winter regions.

Voyager 2's Encounter with the Gas Giants

It was 3:40 am Pacific daylight time, 25 August 1989. I had watched with fascination a video display of Voyager 2's radio signal after the spacecraft had passed through Neptune's thick atmosphere, and for the last 90 minutes I had been attempting to nap in a sleeping bag on the floor of my office at JPL. My computer had just awakened me with a reminder that the first of 23 high-resolution pictures of Neptune's moon Triton was about to appear on the small monitor on my desk. The adjacent office was crowded with a dozen or so of my coworkers excitedly anticipating the same pictures. The first image appeared on my screen; boisterous cheering simultaneously erupted from next door. All thoughts of sleep fled, and for the next two hours I, along with dozens of other Voyager personnel and millions of interested onlookers around the world, exulted in the amazing scenes being transmitted by a small robot more than 4.4 billion km (4.1 light-hours) away. Humanity was seeing for the first time the surface features of the most distant moon in our solar system.

Voyager Visits Uranus and Observes Rings and Moons

Last January, having survived the hazards of interplanetary space, previous close encounters with Jupiter and Saturn, four Administrations and numerous budget cycles, Voyager 2 passed within 107 000 kilometers of the planet Uranus. The data collected on its historic flyby took 2 hours and 45 minutes to reach radiotelescopes on Earth, 2.8 billion kilometers away. And while the aptly named Voyager coasts off to an encounter with Neptune and its large moon Triton in August of 1989, the Voyager scientists will be busy analyzing their precious data for clues to the origin and evolution of the Uranian system. In January of 1987 the world's scientific community will be granted full access to the Voyager 2 Uranus data. Until then they will have to be satisfied with the Voyager team's preliminary conclusions, which were published last month.