New Horizons at Io Options

[volcanopele]

Since the New Horizons Jupiter Encounter thread is already getting pretty long, I decided to create a thread dedicated to New Horizons' observations of the most interesting object in the solar system: Io. Info on upcoming observations comes from the jupiter_timeline_static.xls document john_s posted, and the preview images are from Celestia (note that each image is scaled so that the pixel scale is ~correct, and represents a smaller FOV than LORRI)

Today, February 24, New Horizons conducts three observations of Io with the LORRI camera as well some observations of Io's atmosphere with ALICE. These observations have the lowest phase angle for Io of the entire encounter. Phase angle continues to increase as NH approaches Jupiter and Io.


The first observation, ISunMon1, shows Io's sub-Jovian hemisphere (Clat=5.5 S, Clon=340.2 W) from a distance of 7,856,307 km. The resolution with LORRI would be 38.8 km/pixel. Pele is on the limb at lower right and Masubi is on the limb at lower left. Ra Patera is near center.


The second observation, ISunMon2, also shows Io's sub-Jovian hemisphere (Clat=5.5 S, Clon=15.1 W) from a distance of 7,575,510 km. The resolution with LORRI would be 37.5 km/pixel. The Tvashtar plume might be poking above the limb at upper left.


The third observation, ISunMon3, shows Io's leading hemisphere (Clat=6.0 S, Clon=84.7 W) from a distance of 6,627,459 km. The resolution with LORRI would be 32.8 km/pixel. The Zamama plume might be visible just above center on the left limb.

It only gets better from here. Not sure how NH downlink works, but there is a DSN window right after the last Io observation, hopefully at least one frame from each observation will be returned. Maybe they can do the Huffman window right around where Io is... Tomorrow contains four more observations of Io, highlighting Pele and an eclipse.

[volcanopele]

Thought I would take a look into Shango, perhaps the most interesting new lava flow observed in this image.

Here is a view of Shango Patera from Galileo:



The color data is from the C21 encounter in July of 1999, and the higher resolution gray-scale data is from the I24 flyby in October of 1999. Shango Patera, its associated yellow-colored flows, and the near-by mountain, Skythia Mons, are in the zoomed in image at left. Shango Patera was only observed as active once during the entire Galileo mission, as a weak emission source during an SSI eclipse observation. From the looks of the Galileo color image above, it certainly doesn't look active: very little dark material can be seen. The patera is covered mostly in greenish material, the flows appear to be covered in yellow sulfur. The flows looks kinda like the Thor flows in the years before it blew its top in 2001. However, it looks like at some point in the recent past, the patera over flowed, and lava flowed to the south and south west in several, discrete flow lobes

Here is a zoomed in image from NH (with labels):



Again you see Shango Patera, but it is now much darker and has two lobes. The northern lobe I presume is the patera and its immediate surroundings to the south. The southern lobe represents the two southern branches of the associated lava flows seen in the Galileo image (NOT the Southwestern flows). Like Thor in 2001, when Shango erupted, lava followed previously emplaced flows, rather than carving out a new path, though the details of the old and new flows may be different, we just have to resolution to tell. Does that mean that the conduits that fed the south western flows were cut off? A clue can be found in the Galileo images. In the earlier images, bright material surrounded the ends of the southern flows, but not the southwestern flows, suggesting that the southern flows had sublimated sulfur that were then deposited just outside the edges of the flows. Prometheus does the same thing here: http://pirlwww.lpl.arizona.edu/missions/Ga...prometheus.html . This suggests that the southwestern flows have been dormant long enough for both the flows and the flow margins to be covered over in sulfur, while the flow margins (or the SO2 anyways) of the southern flows had not, suggesting that the southwestern flow conduits had been closed off prior to Galileo.