Thalassa (moon)
Naiad or Thalassa as seen by Voyager 2 (elongation is due to smearing)
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| Discovery | |
|---|---|
| Discovered by | Richard J. Terrile[1] and Voyager Imaging Team |
| Discovery date | September 1989 |
| Orbital characteristics[2] | |
| Epoch 18 August 1989 | |
| 50 075 ± 1 km | |
| Eccentricity | 0.0002 ± 0.0002 |
| 0.31148444 ± 0.00000006 d | |
| Inclination |
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| Satellite of | Neptune |
| Physical characteristics | |
| Dimensions | 108×100×52 km[3][4] |
|
Mean radius
|
41 ± 3 km[5] |
| Volume | ~2.9×105km³ |
| Mass | ~3.5×1017 kg (based on assumed density) |
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Mean density
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~1.2 g/cm³ (estimate)[5] |
| synchronous | |
| zero | |
| Albedo | 0.09[3][5] |
| Temperature | ~51 K mean (estimate) |
| 23.3[5] | |
Thalassa (/θəˈlæsə/ thə-LASS-ə; Greek: Θάλασσα), also known as Neptune IV, is the second innermost satellite of Neptune. Thalassa was named after sea goddess Thalassa, a daughter of Aether and Hemera from Greek mythology. "Thalassa" is also the Greek word for "sea".
Thalassa was discovered sometime before mid-September 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 5.[6] The discovery was announced (IAUC 4867) on September 29, 1989, but the text only talks of "25 frames taken over 11 days", giving a discovery date of sometime before September 18. The name was given on 16 September 1991.[7]
Thalassa is irregularly shaped and shows no sign of any geological modification. It is likely that it is a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.[8] Unusually for irregular bodies, it appears to be roughly disk-shaped.
Since the Thalassian orbit is below Neptune's synchronous orbit radius, it is slowly spiralling inward due to tidal deceleration and may eventually impact Neptune's atmosphere, or break up into a planetary ring upon passing its Roche limit due to tidal stretching. Relatively soon after, the spreading debris may impinge upon Despina's orbit.
References
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Wikimedia Commons has media related to Thalassa (moon). |
- Thalassa Profile by NASA's Solar System Exploration
- Neptune's Known Satellites (by Scott S. Sheppard)
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Generally listed in increasing distance from Neptune
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| Regular (inner) | |
| Triton | |
| Irregular | |
| See also | |
| Geography |
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- ↑ Planet Neptune Data http://www.princeton.edu/~willman/planetary_systems/Sol/Neptune/
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