New Horizons at Io Options

[volcanopele]

I suspect that around Tvashtar we're seeing the landscape illuminated by the plume itself, as we mentioned in the original caption.

LOL, yeah, I just noticed that in the caption. Makes sense, explains why you can see surface features only in the Tvashtar region, not anywhere else.

[volcanopele]

WOOHOO! More images. Io images even!

[volcanopele]

Quick look results:

*Plume at Shango Patera Not a plume, actually Skythia MonsI am so lost, that's a plume, but it is at Amirani...
*Prometheus flow hasn't changed shape since the late 2001
*Prominent plume deposit around new lava flow at 58 South, 295 West (northern Lerna Regio). Plume no longer active (not apparent in LORRI images)

[volcanopele]

The first image set up is Ihires1. These images were acquired on Feb. 26, 2007 at 21:01 UTC. The images were acquired from a distance of 2,881,000 km and have a resolution of 14.2 km/pixel. The individual frames shown are (clockwise from upper left): a 4-msec exposure, a 20-ms exposure, a preview image from Celestia, and a 75-msec exposure.

The 4-msec exposure image reveals the albedo features visible across Io's anti-Jovian hemisphere. The persistent volcano Prometheus is visible just right of center. No major albedo changes are apparent. The plume deposit around Thor has faded from its appearance in August 2001, but the lava flows associated with Thor have not yet faded back to its pre-eruption appearance. The plume at Prometheus may have moved, creating a double ring appearance to the west of the plume source, but that maybe a phase angle effect. There was a brightening of a small region north of Volund.

The 20-msec exposure highlights the mountains visible near the terminator. The most prominent mountains include Euxine Mons (the N-S trending mountain south of Tvashtar), Capaneus Mensa (the mitten-shaped plateau south of Emakong Patera, and a plateau in the south polar region, south of Telegonus Mensae/Bactria Regio.

The 75-msec exposure highlights three plumes: Tvashtar (the prominent one in the north polar region), Amirani (visible just past the terminator southwest of Euxine Mons), and Masubi (south polar region along the dark limb).

EDIT 04/04/07: On further inspection, I found a darkening at a patera located at 56 South, 157.5 West, south of Mycenae Regio.
EDIT 04/04/07: Nevermind, that is likely to be a phase angle effect at the patera there.

[volcanopele]

The next image set up is Ihires2. These images were acquired on Feb. 27, 2007 at 01:05 UTC. The images were acquired from a distance of 2,691,000 km and have a resolution of 13.3 km/pixel. The individual frames shown are : a 3-msec exposure, a 20-ms exposure, and a preview image from Celestia.

The 3-msec exposure highlights albedo features on Io's anti-Jovian hemisphere. The most prominent albedo feature is Pele at lower left. The prominent red ring of Pele appears to be more extended to the southeast than during its previous appearances in the latter part of the Galileo mission. No other major surface changes are apparent, though I should note that the apparent darkening of the flow I mentioned in a previous post, appears to be caused by a phase angle effect (the old flow appears to be strongly forward scattering), as the flow doesn't appear darker in this image than similar phase angle images from the Galileo I32 flyby.

The 20-msec exposure highlights topographic features (and albedo features for that matter) near the terminator. Not many mountains are visible, though Tohil Mons and a mountain east of Shamash Patera can be seen southeast of Culann Patera. Plumes should also be faintly visible in this exposure. The top of the Tvashtar plume is visible. No other plumes are visible. A plume over the new flow at 58 South, 295 West should have been visible in this image along the limb at lower left had it been active and/or the exposure supported its visibility.

[volcanopele]

The final image set up is Ihires3. These images were acquired on Feb. 27, 2007 at 09:15 UTC. The images were acquired from a distance of 2,679,000 km and have a resolution of 13.3 km/pixel. The individual frames shown are : a 3-msec exposure, a 20-ms exposure, and a preview image from Celestia.

The 3-msec exposure highlights albedo features on Io's trailing hemisphere. The most prominent albedo feature in this image is Pele, the ring of red material below and to the right of center. I discussed Pele in the last post so I won't go over that again. Unlike the last couple of posts, there are a few major surface changes representing eruptions that have occurred since October 2001. The most prominent is a new dark lava flow centered at 58 South, 295 West. This flow is located along the northern margin of Lerna Regio, a bright region within Io's south polar region. This flow is surrounded by a bright material that appears to have a greater extent, particular to the north, than the bright material associated with Lerna Regio, indicating that this bright material is from this new eruption. Surrounding this new bright deposit is a partial ring of dark material, probably representing a new red ring deposit. Dazhbog Patera continues to remain prominent, 6 years since the major eruption in late 2000, and has not faded from its pre-eruption appearance, though its plume deposit may have (similar to the situation of at Thor). There is a new dark flow to the east of Dazhbog Patera, located at 51 North, 278 West. An old flow is visible there in the Galileo and Voyager imagery, so like Thor and Tvashtar, this maybe a volcanic center that uses the same channels over and over again.

The 20-msec exposure highlights topography near the terminator. Among the mountains visible are Ionian Mons (northeast of Pele), Ot Mons (southeast of Ionian Mons just past the terminator), and a mountain just past the terminator in the south polar region in western Illyrikon Regio.

[volcanopele]

Because not everyone is caught up on their Ionian geography, here are some labeled images:

[volcanopele]

Marchis et al. 2005 reported that a hotspot was observed at the flow labeled "New Flow #2" on December 28, 2001. This hotspot was observed using the Keck telescope's Adaptive Optics system. The authors state that this eruption may have started between the 23rd and 28th since the hotspot was not observed on the 23rd.

[nprev]

Getting the impression here that buying real estate on Io would be risky indeed... ...is there any part of the moon that is not subject to sudden, unexpected volcanic activity? In other words, are there geological districts that are thought to be relatively stable, such as near those tremendous mountains (what's holding them up? )

[volcanopele]

Actually, on or near mountains would be one of the worst places to build settlements on Io due to the avalanche risk. Most mountains on Io show signs of significant mass wasting, suggesting that they may not be all that stable.

The non-volcanic plains, like Colchis Regio, maybe the best places to put settlements. We haven't really seen new volcanic centers form in the 28 years that volcanoes have been monitored. This suggests to me that settlements within non-volcanic plains could be stable for quite a long time.

[volcanopele]

And I have narrowed down the date of the northern Lerna Regio eruption. It appears to have been a bright hot spot on July 15, 2005, as observed by the Marchis group working with Keck AO.

[ustrax]

The first images from MVIC have been released showing the Tvashtar hotspot and plume:

Just Beatiful!
I was playing around with the original image and found it curious that "something" appears always on a precise location, Marduk I guess (help me here volcanopele...) but I can't distinguish anything in particular in the original image...
Here it goes:

[volcanopele]

Okay, with two eruptions seen by Keck tied to surface changes, I thought I would check on an outburst observed by Marchis et al. on May 28, 2004. Their hotspot was located at 17.5 South, 6.3 West (with error bars of +/- 5 degrees) and was one of the brightest hotspots observed on Io during the interprobum. This eruption was attributed to either Angpetu Patera or Ilmarinen Patera. So, I thought I would look through the New Horizons images to see if there was a visible surface change.

First, let's take a look at the eruption site in Galileo images for context. The first image below is c0420669000r from the 11ISTOPO__01 observation. The second image is the same image, but I have labeled some of the volcanic centers seen in the observation to provide some context. The area marked 0405A is the center of the error box given by Marchis et al. for the May 2004 eruption. This spot is located in the northwestern part of the Tung Yo Fluctus lava flow, an old flow first observed by Voyager. However, keep in mind that box that the hotspot could be located in includes Angpetu, Sui Jen, and Ilmarinen Paterae.



Okay, so what do the New Horizons images show? Unforunately, the longitudes close to the sub-Jovian point have the poorest sunlit coverage during the New Horizons encounter. I've attached versions of the two online image sets that provide coverage over this eruption site: ISunMon2 and Ihires5. Looking at these two observations, it would seem that there was no surface change associated with the 0405A eruption, indicating that either the surface changes have faded since 2004, the change were small compared to other eruptions like in northern Lerna Regio, and/or there was no visible surface change associated with the eruption, akin to the Tupan eruption from March 2003, suggesting an interpatera eruption.

[volcanopele]

Stealing an idea from Emily, here is an animated gif of the Io images returned thus far showing Ionian albedo features, i.e. the short exposure images. Click on the link above for an animated gif of Europa images.

EDIT: New image added 04/04/07
EDIT: Three new images added 04/07/07
EDIT: Two new images added 04/16/07
EDIT: New image added 04/23/07
EDIT 05/01/07: Movie removed. See http://www.unmannedspaceflight.com/index.p...ost&p=89403 for updated versions.

[elakdawalla]

Oh, you beat me to it, Jason!

--Emily