* Astronomy

Blobrana · L

RE: Triton

Blobrana · L

Title: A 3D general circulation model for Pluto and Triton with fixed volatile abundance and simplified surface forcing
Authors: Angela Zalucha, Timothy Michaels

We present a 3D general circulation model of Pluto and Triton's atmospheres, which uses radiative-conductive-convective forcing. In both the Pluto and Triton models, an easterly (prograde) jet is present at the equator with a maximum magnitude of 10-12 m/s and 4 m/s, respectively. Neither atmosphere shows any significant overturning circulation in the meridional and vertical directions. Rather, it is horizontal motions (mean circulation and transient waves) that transport heat meridionally at a magnitude of 1 and 3 x 10^7 W at Pluto's autumn equinox and winter solstice, respectively (seasons referenced to the Northern Hemisphere). The meridional and dayside-nightside temperature contrast is small (<5 K). We find that the lack of vertical motion can be explained on Pluto by the strong temperature inversion in the lower atmosphere. The height of the Voyager 2 plumes on Triton can be explained by the dynamical properties of the lower atmosphere alone (i.e., strong wind shear) and does not require a thermally defined troposphere (i.e., temperature decreasing with height at the surface underlying a region of temperature increasing with height). The model results are compared with Pluto stellar occultation light curve data from 1988, 2002, 2006, and 2007 and Triton light curve data from 1997.

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Blobrana · L

Does Triton Have a Subsurface Ocean?

Triton was discovered in 1846 by the British astronomer William Lassell, but much about Neptunes largest moon still remains a mystery. A Voyager 2 flyby in 1989 offered a quick peak at the satellite, and revealed a surface composition comprised mainly of water ice. The moons surface also had nitrogen, methane, and carbon dioxide. As Tritons density is quite high, it is suspected that it has a large core of silicate rock. It is possible that a liquid ocean could have formed between the rocky core and icy surface shell, and scientists have investigated if this ocean could have survived until now.
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Blobrana · L

Anniversary of William Lassell's Discovery of Neptune's Moon Triton in 1846

Blobrana · L

Title: Reassessing the origin of Triton
Authors: E. Nogueira, R. Brasser, R. Gomes

Agnor & Hamilton (2006) demonstrated that the disruption of a binary was an effective mechanism to capture Triton. The subsequent evolution of Triton's post-capture orbit could have proceeded through gravitational tides. The study by Agnor & Hamilton (2006) is repeated in the framework of the Nice model to determine the post-capture orbit of Triton. After capture it is then subjected to tidal evolution. The perturbations from the Sun and the figure of Neptune are included. The perturbations from the Sun acting on Triton cause it to spend a long time in its high-eccentricity phase, usually of the order of 10 Myr, while the typical time to circularise to its current orbit is some 200 Myr. The current orbit of Triton is consistent with an origin through binary capture and tidal evolution, even though the model prefers Triton to be closer to Neptune than it is today. The probability of capturing Triton in this manner is approximately 0.7%. Since the capture of Triton was at most a 50% event -- since only Neptune has one, but Uranus does not -- we deduce that in the primordial trans-Neptunian disc there were 100 binaries with at least one Triton-sized member. Morbidelli et al. (2009) concludes there were some 1000 Triton-sized bodies in the trans-Neptunian proto-planetary disc, so the primordial binary fraction with at least one Triton-sized member is 10%. This value is consistent with theoretical predictions, but at the low end. If Triton was captured at the same time as Neptune's irregular satellites, the far majority of these, including Nereid, would be lost. This suggests either that Triton was captured on an orbit with a small semi-major axis a < 50 R_N (a rare event), or that it was captured before the dynamical instability of the Nice model, or that some other mechanism was at play. The issue of keeping the irregular satellites remains unresolved.

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Blobrana · L

Triton's Summer Sky of Methane and Carbon Monoxide

According to the first ever infrared analysis of the atmosphere of Neptune's moon Triton, summer is in full swing in its southern hemisphere. The European observing team used ESO's Very Large Telescope and discovered carbon monoxide and made the first ground-based detection of methane in Triton's thin atmosphere. These observations revealed that the thin atmosphere varies seasonally, thickening when warmed.
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Blobrana · L

Panning Across Triton's Surface [HD]

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Blobrana · L

Un ciel dété de méthane et de monoxyde de carbone sur Triton

Selon la toute première analyse dans l'infrarouge de l'atmosphère de Triton, une des lunes de Neptune, l'été bat son plein dans son hémisphère sud. En utilisant le Very Large Telescope de l'ESO, l'équipe européenne comprenant des chercheurs du Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique (INSU-CNRS, Observatoire de Paris), qui a mené cette étude, a découvert du monoxyde de carbone et a observé, pour la première fois depuis le sol, du méthane dans la fine atmosphère de Triton. Ces observations ont révélé que cette fine atmosphère varie de manière saisonnière, s'épaississant quand elle est réchauffée en été.
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Blobrana · L

Discovery of carbon monoxide on Triton

IAUC 9071 (Subscription)

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Blobrana · L

This view of the volcanic plains of Neptune's moon Triton was produced using topographic maps derived from images acquired by NASA's Voyager spacecraft during its August 1989 flyby.

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Credit: NASA/JPL/Universities Space Research Association/Lunar & Planetary Institute

The surface of Triton is very rugged, scarred by rising blobs of ice (diapirs), faults and volcanic pits and lava flows composed of water and other ices. The surface is also extremely young and sparsely cratered, and could be geologically active today. This scene is on the order of 500 kilometres across and is taken from a new flyover movie across the equatorial region of Triton commemorating the Voyager anniversary of the Triton flyby. Vertical relief has been exaggerated by a factor of 25 to aid interpretation.

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