Sunday, January 3, 2016

W-40

-Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath----------------------------------------------------------
 W-40...............................2         .47.6W 2.1N.....40 km-.....    ..T56--40
Radar T56 image.
  .....
Circular dark floor, surrounded by bright ejecta deposit with strong radial drainage. Small gap to west, perhaps due to adjacent smaller crater now gone, allows dark dunes onto crater floor. No sign of a central peak. 
Click image to enlarge it.

NL4 & 5

-Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath----------------------------------------------------------
 NL5...............................2 ......140.6W 12.1N......30 km-.......T56--
 NL4........................ ......2 ......141.8W  11.0N.....22 km-.......T56--
Neish and Lorenz craters #5 (top) and #4. T56 Radar image.
Dark floors surrounded by narrow bright rims and one crater diameter ejecta deposit. Builds up high enough to stop dunes. Dunes penetrate missing rim segment and enter floor of #4. 

References:
2012: Neish, C. D., and Lorenz, R. D. Titan’s global crater population: A New assessment.  Planet. Space Sci., 60(Jan.), 26–33. doi: 10.1016/j.pss.2011.02.016.

Saturday, January 2, 2016

Veles

Cat #------Name----Certainty---Long---  Lat-----Diameter---Radar Swath---------------------------------------------------------   
None     ..Veles         .. 2        137.3W 2N        45 km         T58

Rougly hexagonal shaped feature with slightly bright rim and dark floor. Hint of central structures in middle of crater floor. Also weaker hint of ejecta deposit about 1 to 1.5 crater diameter swide. Classed as a Large Ringed Feature in IAU nomenclature.

Selk

Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath--------------------------------------------------------- 
NL1 .......... Selk ................198W   7N ..........80 km .......T36
VIMS colored image and geologic map from Soderblom et al (2010)
Radar T36 (left) and mosaic of unidentified images (right)
from USGS Titan map.

Broad, flat floor. Bright rim. VIMS shows 3 or 4 separate peak masses, only one near crater center. 
Rare case where VIMS image is sharper than radar.

This is NL1 of Neish and Lorenz (2012).





References:
2010: Soderblom, J. and others. Geology of the Selk impact crater region from Cassini VIMS observations. Icarus 208, 905-912. 

2010: Martin, E. Decoding a Titan CraterPlanetary Society post

2012: Neish, C. D., and Lorenz, R. D. Titan’s global crater population: A New assessment.  Planet. Space Sci., 60(Jan.), 26–33. doi: 10.1016/j.pss.2011.02.016.




Friday, January 1, 2016

Mystis

Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath---------------------------------------------------------   
None       Mystis-----  1  --       193.4W 0.3N--20 km--    
A bright, but narrow rim encircles a dark floor. The crater appears on a bright blob that is about two times the crater diameter and thus gives the impression that it is ejecta. I don't know that it is. 

A smaller version of Mystis is below it, and with a little imagination another smaller bright ring is just above this one. A third possible crater is one Mystis diameter to its left, on dark terrain, rather than eject-like bright material. Are all of these impact craters? Any?

Nath

Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath--------------------------------------------------------
None--      Nath- --        2         7.7  30.5S-- -95 km------T50 HiSAR
Poorly depicted feature, classed as a "Large ringed feature" rather than a crater in IAU nomenclature system. But bright rim and dark floor are very similar to accepted craters Soi and Forseti - I consider it an impact crater. At this resolution, no evidence for central peak, and as for many other dark-floored craters the rim is unbroken so the dark fill must have come from aeolian deposition.

Momoy

Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath---------------------------------------------------------   
None      Momoy-----  2  --       44.6W 11.6N--478 & 28 km--     T77

Is this a two-ring crater? The outer circle could be the edge of an ejecta deposit, but the fact that it stops and diverts the dunes coming from the west documents that it is a raised relief structure - a crater rim. The smaller inner rim is rounded. This concentric ring structure is unique on Titan. 

Using radar foreshortening of opposing crater walls, Neish et al (2013) estimated the crater depth as 680 m +/-100 m. As I understand their paper, 680 m is the depth to the floor of the smaller crater; the rim height and crater depth of the outer ring are not known. 


References:
2013: C.D. Neish, R.L. Kirk, R.D. Lorenz, V.J. Bray, P. Schenk, B. Stiles, E. Turtle, K. Mitchell, A. Hayes, and the Cassini RADAR Team. Crater topography on Titan: Implications for landscape evolutionIcarus 223, 82-90.

Paxsi

Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath---------------------------------------------------------   
None     Paxsi-----1  --     341.2W 5N--  120 km--  T108
Above: Discovery images from VIMS.

Below: T108 Radar image showing bright-rimmed, crater with dark floor. Crater is elongated north to south, and central peak complex is significantly offset to south. Center of peak is circular and bright, surrounded by apron of fainter material with radial lineations - perhaps due to downslope movement.

At bottom left is another bright-rimmed, dark-floored feature that may be another impact crater.









Publications:
Buratti, B.J. and 9 others (2012) A newly discovered impact crater in Titan's Senkyo: Cassini VIMS observations and comparison with other impact features. Planetary and Space Science 60, 18-25.

Beag

Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath---------------------------------------------------------   
None      Beag-----  2  -- 169.6W 34.7S--27 km--     T98
Apparently complete elevated rim with possible faint radial streaks to west and east that may be ejecta. Interior is nearly filled with broad, circular bright zone, separated from rim in many places by a dark moat. Very unusual interior.

Afekan

Cat #------Name----Certainty---Long---...Lat-----Diameter---Radar Swath--------------------------------------------------------
None.....Afekan-----1.........200.3W 25.8N...15 km........T43

Completely rimmed crater surrounded by radially lineated ejecta. Small but bright central peaks and mostly dark floor, with streaks and broader, more amorphous bright deposits.

This is NL2 of Neish and Lorenz (2012).

Hano

-Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath----------------------------------------------------------
 28-----      Hano-----   2            344.7W 40.2N-N110 km----------T16---
T84 + T104 Radar Mosaic
Mountainous, bright, apparently jagged rim. Dark floor. with broad arc of bright/rough terrain on south side. Strange chain of about six craters?? across floor - is this an artifact or real? If real, only a breakup of an incoming projectile is a known explanation. 

Forseti

Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath--------------------------------------------------------
5---          Forseti-- --  1         10.5W   5.7N-- -139 km----------T23, T84 HiSar and T113 Seg 7-

Soi

-Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath----------------------------------------------------------
 4----           Soi--       -   1        139.6W 22.7N---- -75 km------....T16--
Bright jagged-looking rim, with dark floor, and apparent ejecta. Said to be extremely degraded, but the rim is complete and a hint of a central peaks exists. Main degradations appears to be infilling of the floor by materials similar in radar reflectivity to exterior surroundings.

Sinlap

-Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath------------------------------------------------------
 2-----        Sinlap---      1          16.1W  N11.3-----79 km-------- T03---

First crater discovered on Titan. Similar in appearance to craters on Earth, Moon and Mars that have had aeolian deposition of sediments reduce original depth. Broad flat floor with bright streaks and northern third dusted with brightness. Strangely, VIMS indicated bright spot in center but higher resolution radar shows no central peak.
Close-in dark halo in radar, with broader brighter ejecta beyond. The 2008 Le Mouelic paper finds evidence for "the presence of an area enriched in water ice around the main ejecta blanket.   
    Image from Le Mouelic et al (20018)

Publications: 
2008: Le, Mouelic, S.; Paillou, P.; Janssen, M. A.; Barnes, J. W.; Rodriguez, S.; Sotin, C.; Brown, R. H.; Baines, K. H.; Buratti, B. J.; Clark, R. N.; Crapeau, M.; Encrenaz, P. J.; Jaumann, R.; Geudtner, D.; Paganelli, F.; Soderblom, L.; Tobie, G.; Wall, S. Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data. Journal of Geophysical Research E: Planets, 113 (abstract).

Ksa

Cat #------Name----Certainty---Long---Lat-----Diameter---Radar Swath-----------------------------------------------------------
1-----        Ksa---          1          65.4W 14.0N---- -30 km--------T17--      
--------
Ksa is perhaps the freshest and most lunar-like impact crater on Titan. It has a complete elevated rim with dark floor and a bright nearly circular central peak. The crater   has an extensive ejecta deposit that overlies older terrains, including somewhat bright dunes to the bottom-right. But dark dunes embay and cover the ejecta to the left. A dark river apparently cuts thru the ejecta on the right. Both above and below Ksa there are delicate radial lineations showing that original deposition features of the ejecta have not yet been eroded away. Ksa is either a very young crater, or erosion/modification processes on Titan - other than cover by dunes - is very slow.