Budgets, Carnivals, and Cryovolcanoes, Oh My!

Here are some short little news items that are hitting the interplanetary interwebs today:

• Ian Musgrave's Astroblog is this week's host for the Carnival of Space, #142 of its name.  The Carnival of Space is a collection of links to the best space blog posts from the week that was.  In this edition, learn about the launch of the Solar Dynamics Observatory, the (then) ongoing STS-130 shuttle mission to install the Cupola at the International Space Station, and why the oxidation of iron creates a positive spectral slope in the visible (aka, "Why is rust red?").
• Today, the Cassini Imaging and the Composite Infrared Spectrometer (CIRS) teams released a series of images from the November 21 encounter with Enceladus, a cryovolcanically active moon of Saturn.  This set of images includes some awesome mosaics, including one showing a series of water-rich jets erupting from fractures within the moon's south polar region and another combined with CIRS data to show thermal emission from one of these fractures, Baghdad Sulcus.  Also don't forget to check out two mosaics of Enceladus' leading hemisphere, an area not seen at high-resolution previously, and an 3D anaglyph (don't forget your red-blue 3D glasses) of a portion of Baghdad Sulcus.
• Yesterday, NASA released further details on its proposed budget for the next fiscal year, FY2011, including the breakdown for Planetary Science.  Overall, the next year will see budget increases for the Planetary program with out-years showing shallower increases, that according to Van Kane, would barely cover inflation, possibly decreasing the budget's purchasing power. The Mars program and precursor missions (mostly Lunar) will see major increases, with more modest increases over the five projected years for the Outer Planets Program (Cassini, EJSM, and ROSES, a research grant program).  Until FY2013, the budget is inline with the project needs of the Europa/Jupiter System Mission for its Phase Pre-A and A when studies will be conducted to mitigate the radiation risk further, instruments selected using an Announcement of Opportunity, and the preliminary concept design finalized.  Starting with Phase B in FY2014, the budget does start to deviate from what is required for JEO, staying in the $150 million range when it should closer to $300 million (or $425 million if one includes reserves) in FY2014 and $400 million (or $600 million if one includes reserves) in FY2015.  While a bit discouraging, keep in mind that budget projections for years so far out are...very sketchy.  I don't trust them any farther than I can throw them; who knows who could be in the White House at that point.

Link: Carnival of Space #142 [astroblogger.blogspot.com]
Link: Enceladus Rev121: Forest of Jets [ciclops.org]
Link: FY11 NASA Budget Proposal Details [futureplanets.blogspot.com]

10th Anniversary of Galileo's I27 Encounter

I almost completely forgot about this, but today (for another 2 minutes here) is the tenth anniversary of the Galileo spacecraft's I27 flyby of Io.  This encounter occurred on February 22, 2000 and was the third of three flybys of Io that took place over a four-month period between October 1999 and February 2000.  The closest approach altitude was 198 kilometers.  It was the fourth Io flyby overall by Galileo (including the one right before orbit insertion) and took place during the spacecraft's 27th orbit of Jupiter.  Galileo went on to perform three more flybys of Io between August 2001 and January 2002.

Compared to the first two flybys of this "Io campaign" section of the Galileo Europa Mission (the spacecraft's first extended mission), when spacecraft safe-mode events and instrument malfunctions limited the science return, the I27 flyby was relatively problem free.  All of the planned Io observations were acquired.  However, this did caused problems when it came to playing all that data back, as more images were planned than could be downlinked with the expectation that some data might be lost due to some spacecraft malfunction, like the other two encounters.  In which case, mission planner carefully selected which data to playback, in some cases skipping entire frames or only playing back a portion of others.  That was the case for the CHAAC_01 observation, a very high-resolution mosaic across Chaac Patera (a portion of which is shown above).  Another good example is the SOPOLE01 observation, a four-image, medium resolution mosaic that covered the southern mid-latitudes of the anti-Jupiter hemisphere, where only the first frame over Telegonus Mensae was played back in close to its entirety, while two others had 100 lines out of 800 played back.  These kinds of limits were seen in many of the SSI observations from this flyby, and that's even with three months between I27 and the next flyby, this time of Ganymede, G28.

For the other instruments on Galileo, I27 was a very exciting, with high resolution, Near-Infrared observations of Pele, revealing the location of the majority of the volcanoes thermal emission (which would be targeted by the camera in October 2001), coverage over the Chaac Patera and Camaxtli Patera region, which led to a confirmation of the connection between dark patera floor terrain and thermal emission as well as a patera covered in nearly pure sulfur dioxide ice (Balder Patera), and observations of the Prometheus and Amirani flow fields, showing the detailed thermal structure of these features.

For the camera, check out my I27 image page to see the images Galileo took during the flyby.  Among the highlights include the highest resolution images acquired of Io (covering layered terrain in Bulicame Regio, broken up by a dark promontory, a jagged fissure, boulders, and sapping channels), a 12-frame mosaic over the Chaac-Camaxtli region, and a high-resolution mosaic across the Prometheus flow field and the hummocky terrain that surrounds it. Mosaics of the Amirani and Prometheus lava flow fields showed changes since they were imaged in October 1999, providing the first direct measure of the lava coverage rate at these two prominent features.  So even though many images were only partially played back or not played back at all, an amazing array of gorgeous terrain is seen in the images that were returned.

With that, I want to leave you with a nice simulation from Celestia showing an animation of the I27 flyby (note the fly over of the Zamama plume):



Link: Galileo I27 Images [pirlwww.lpl.arizona.edu]

New URL for the The Gish Bar Times

With the second birthday for The Gish Bar Times coming up on Thursday, I want to go ahead and announce the blog's new URL: http://gishbartimes.org.  The old Blogspot URL will remain active, just redirecting you to the new site so you should never have any problems accessing the site or finding information on this site using Google.  Hopefully, people will find it easier to reach this blog by using this url.

Again, you don't need to do anything if you subscribe to the blog's RSS feed, subscribe via Google Reader, or have this site bookmarked, but certainly I would recommend changing to this new url if you like.  It looks like there are a few elements on the site that no longer work on the old gishbar.blogspot.com url, like some of the sidebar elements, like the ability to send a page to one of the social network sites like Digg or Facebook or Google Friend Connect.  I also had to recreate my blogroll.  For whatever reason, my ability to quick edit a post is gone with these custom urls.

Anyways, excuse the mess while we go through this transition to the new URL. Also allows a couple of days for the new URL to work its way through everyone's DNS listings.

Animation of the Jupiter Europa Orbiter's Four Io Flybys

Yesterday, while finishing up work on the Exploration of Io article on Wikipedia and looking for a graphic for the Jupiter Europa Orbiter (JEO), I noticed that a SPICE trajectory file for JEO had been posted online. The Jupiter Europa Orbiter is NASA's portion of the Europa/Jupiter System Mission approved last year. I can use the SPICE kernel to display the position of the spacecraft at a given time in Celestia.  The trajectory file covers the Jupiter tour portion of the current mission baseline, though obviously a number of factors between now and the arrival of JEO at Jupiter will cause changes to this baseline, including changes in the launch date (assumed as February 2020 with an arrival at Jupiter in December 2025).  So, as of right now, these provide more of an example of the types of flybys JEO can perform at Io.

I've created a little video and uploaded it to Youtube with animations from Celestia simulating each of the four Io flybys in the current tour.  You can see some of the highlights from each encounter, though note that no science is planned for the first encounter (Io-0) as it takes place right before JEO's all-important, Jupiter Orbital Insertion burn.  For Io-1, on July 9, 2026, JEO passes almost directly over the Amirani plume, and depending on how high gases from the volcano reach, it could directly sample the composition of it.  JEO can also image the north polar region of Io from an oblique angle. However, Amirani's plume is ~75 km tall, while the altitude for Io-1 is 300 km.  For Io-2, on September 3, 2026, JEO should be able to image the Pele volcano and south polar region at high resolution. In the latter case, this is the section not covered by Voyager 1 at medium resolution.  The Zamama, Marduk, Prometheus, and Pele plumes will also be visible along the bright limb near C/A.  Finally, for Io-4, JEO will pass directly over Tohil Mons providing a chance to obtain laser altimetry over a mountain we have pretty good stereo coverage already, providing a useful comparison.

I wrote up a more detailed article on the potential science from each of these encounters last February.



I hope you all enjoy!  I should point out that this video was uploaded at 720p so you can view it in high-definition, and this definitely works better if you view it full screen.

Link: Animation of the Jupiter Europa Orbiter's Four Io Flybys [www.youtube.com]

Exploration of Io article at Wikipedia

I just got finished writing up a major new article on Io over at Wikipedia covering the exploration of Io.  This article covers the discovery of Io by Galileo, the observations of Io from Earth leading up to the space age, and the spacecraft that have performed science at Io, covering the Pioneer, Voyager, and Galileo missions quite extensively, and touching a bit on the future of Io exploration.

I don't want to post the entire article here on the blog because of its length, but here is the lead section:

The Exploration of Io, one of Jupiter's four largest moons, began with its discovery in 1610 and continues today with Earth-based observations and visits by spacecraft to the Jupiter system. The Italian astronomer Galileo Galilei was the first to record an observation of Io on January 8, 1610, though Simon Marius may have also observed Io at around the same time. For the next two and a half centuries, Io remained an unresolved, 5th-magnitude point of light in astronomers' telescopes. During the 17th century, Io and the other Galilean satellites served a variety of purposes, such as helping mariners determine their longitude, validating Kepler's Third Law of planetary motion, and determining the time required for light to travel between Jupiter and Earth. Based on ephemerides produced by astronomer Giovanni Cassini and others, Pierre-Simon Laplace created a mathematical theory to explain the resonant orbits of Io, Europa, and Ganymede. This resonance was later found to have a profound effect on the geologies of the three moons. Improved telescope technology in the late 19th and 20th centuries allowed astronomers to resolve (that is, see) large-scale surface features on Io. New technologies also allowed astronomers to estimate Io's diameter, mass, and surface composition, as well as discover the moon's effect on Jupiter's magnetic field.

The advent of unmanned spaceflight in the 1950s and 1960s provided an opportunity to observe Io up-close. The flybys of the two Pioneer probes, Pioneer 10 and 11, in 1973 and 1974 provided the first accurate measurement of Io's mass and size. Measurements from the Pioneers also allowed for the discovery of an intense belt of radiation near Io as well as an Ionian ionosphere. In 1979, the two Voyager spacecraft flew through the Jupiter system. Voyager 1, during its encounter in March 1979, observed active volcanism on Io for the first time and mapped its surface, particularly the side that faces Jupiter, in great detail. The Voyagers also observed the Io plasma torus and Io's sulfur dioxide atmosphere for the first time. In order to study the Jovian study in better detail and over a longer period of time, NASA launched the Galileo spacecraft in 1989, which entered orbit in December 1995 following the first close flyby of Io by an unmanned spacecraft. Galileo orbited Jupiter until crashing into the giant planet in September 2003. In between, Galileo flew by Io six more times between late 1999 and early 2002, providing high-resolution images and spectra of Io surface, confirming the presence of high-temperature silicate volcanism on Io. Distant observations by Galileo during parts of the missions allowed planetary scientists to study surface changes on Io's surface as a result of the moon's active volcanism.

Following Galileo and a distant encounter by the Pluto-bound New Horizons spacecraft in 2007, NASA and the European Space Agency (ESA) generated plans to return to the Jupiter system and Io. In 2009, NASA approved a plan to send an orbiter to Jupiter's moon Europa called the Jupiter Europa Orbiter as part of a joint program with ESA called the Europa/Jupiter System Mission. The ESA component of the project, the Jupiter Ganymede Orbiter, is on their short list of large-scale missions to be launched in the next decade with final approval coming in 2011. While these missions will perform Io science as ancillary to their primary mission targets, the proposed NASA Discovery mission, the Io Volcano Observer, would explore Io as part of its primary mission, though this project still needs to go through a competition process to be approved. In the meantime, Io continues to be observed by Earth-based astronomers, utilizing new technologies such as adaptive optics and improved telescopes such as Keck, the European Southern Observatory, and the Hubble Space Telescope.

Again, the rest of the article can be read over at Wikipedia.  Among the things you might learn include Io's role in the drawing of the Mason-Dixon Line, post-Pioneer models of Io's surface composition, and the sampling of the Thor plume by Galileo.

Link: Exploration of Io [en.wikipedia.org]

Carnival of Space #141 @ Starry Critters

The 141st edition of the Carnival of Space, a weekly series highlighting the best in the astronomy and space blogosphere, is now online at Starry Critters, a blog dedicated to the latest images of our wonderful solar system.  You know the drill.  Some great posts on the latest shuttle launch, STS-130, Hubble observations of polar aurorae on Saturn, and a tribute to the now-stationary Mars rover, Spirit.

Link: Carnival of Space #141 [www.starrycritters.com]

Happy Valentine's Day from Io

Completely ripping off the idea from Phil Plait, I submit for your approval two heart-shaped volcanic depressions on Io.  The volcano on the left is Inti Patera, observed by Voyager 1 on March 5, 1979.  The volcano on the right is unnamed and located at 8.5°N, 71.5°W.  This feature was observed by Galileo on February 22, 2000.

Both are somewhat cardioid-shaped.  Interestingly enough, both volcanoes have similar characteristics.  Both paterae have evidence of multiple floor levels, with the lowest portion (to the upper right on Inti, to the left on the other volcano) showing the most signs of activity.  Activity at both features tends to also be confined to the outer margins of the paterae, though the volcano on the right has a lower floor that is covered almost entirely by a dark lava flow or lava lake.  The majority of both volcanoes have an albedo similar to that of their surroundings, suggesting that lava has not flowed over their floors (except for the lower portions of the floor) in a very long time (>100 years, I'd say).  Finally, both show evidence for structural control, pre-existing faults that for part of the boundary for the volcano.  This is particularly evident in the volcano on the right, with has a number of straight margins.

Again, tip of the hat to Phil Plait.  And Happy Valentine's Day!

Link: Happy Valentine’s Day. Love, Rhea [blogs.discovermagazine.com]

The Giant Book of Europa

Well, I ended up breaking down and picking up the new Europa book at the University of Arizona bookstore.  This 727-page tome by University of Arizona Press covers a number of Europa topics including its geology, the geophysics of its iceshell, its induced magnetic field, and of course, its potential to be an abode for life.  I haven't had much time to sort through it yet; I'm still trying to get through Titan from Cassini-Huygens that was sent to me last month.  However, I do like the abundant coverage of Europa geology, which holds much more interest to me than the speculation of whether Europa's sub-surface ocean contains life.  This book is edited by Bob Pappalardo, Bill McKinnon, and Krishan Khurana and each chapter has different authors that serve as a review paper for our current understanding of different topics.  Right now, I am flipping through the induced magnetic field chapter (by Krishan Khurana) since it certainly helps with understanding the recent Io results.

Yes, I know that buying a book all about Europa makes me a traitor... I know, I know...

Link: Europa (University of Arizona Space Science Series) (Hardcover) [www.amazon.com]

Infernal Io

Over the last few days, rather than updating my blog or getting around to reading those two atmospheric model papers, I have spent my free time playing either Bioshock 2 or Dante's Inferno on the Xbox 360.  Now of the two, Dante's Inferno would seem to have the most connection to Io.  Bioshock 2 is set in a dystopian underwater city in the late 1960s would probably have more connection to Europa.  EA's Dante's Inferno is a very, very, very, very, very, VERY loose adaptation of the first third of the Italian epic poem, The Divine Comedy by Dante Alighieri, written between 1308 and 1321.  The game isn't for everyone, like anyone younger than 40, with all the dead, blade-wielding, unbaptized babies and dead prostitutes with projectile anatomies you have to fight.

The original poem by Dante has been used as the source for names for several features on Io.  The names of people and places from Inferno can be used for mountains, bright regions, layered plains, and shield volcanoes.  This change came about in 2000 as a result of the previous source of names for these features - people and places from the Greek myth of Io - had become exhausted.  With the abundant number of shades (souls condemned to limbo or hell proper) and places referenced in Dante's original story, it should take quite a while before this source is exhausted.  Dante's Inferno was chosen as a source for names for Io was Io's extreme volcanic activity that in many ways share similarities with Dante's description of hell, with fire (in the form of lava) and brimstone (another word for sulfur).


To date, three feature on Io have been named after people or places mentioned in Inferno: Capaneus Mensa, Bulicame Regio, and Mongibello Mons.  Capaneus Mensa is large, mitten-shaped domical plateau in southern Bosphorus Regio in an area with a high density of mountains, such as Seth Mons to its northwest.  Capaneus Mensa is at least 5.2 kilometers tall based on shadow measurements of its eastern margin, however, stereo data from Galileo suggest a height of around 9.2 kilometers, making it one of the taller mountains on Io.  Bulicame Regio is the northern extension of Colchis Regio, a bright, equatorial region on Io's anti-Jupiter hemisphere.  Bulicame, which lies to the Isum Patera volcanic region, has a higher albedo than the rest of Colchis Regio and its morphology suggests that it might be a bright lava flow, possibly composed of sulfur dioxide.  High-resolution images taken during I27 revealed dramatic, fine-scale albedo variations across parts of Bulicame, with some evidence for layering.  Mongibello Mons is a 7-kilometer tall double ridge on Io's leading hemisphere.  A medium-resolution frame was acquired over portions of Mongibello during Galileo's I27 encounter in February 2000.  The split morphology of Mongibello is suggestive of tectonic deformation of the feature after formation, resulting in one of half of the mountain breaking off from the other half.

The original The Divine Comedy chronicles the story of Dante, a poet from Florence who has become afraid that he has lost the path to salvation as a result of his own imperfections, largely a result of the author's own sense of loss after being exiled from Florence due to political infighting among the city's ruling Guelph party.  The spirit of a dead childhood friend, Beatrice, enlists the help of the Roman poet Virgil to guide Dante through the afterlife, Inferno (hell), Purgatorio (purgatory), and Paradiso (heaven) to help get Dante on the right path (diritta via).  In Inferno, Dante and Virgil visit each of the nine circles (plus Limbo) of hell, wherein each a different sin is punished in a sort of poetic justice, e.g. fortunetellers can only see the path behind them and murderers stand within a boiling river of blood at a depth corresponding to the extent of their sins.

The names for all three of the Ionian features described above come from Inferno XIV, the 14th "chapter" or canto of the Inferno part of The Divine Comedy. In this chapter, Dante is traversing the seventh circle of hell where those who committed grave acts of violence: against people and property (in that boiling river of blood); against self, be it through suicide or wanton waste of material possessions (where the suicides are punished by becoming heavily overgrown trees); and against God, nature, or established order.  It is this last section of the seventh circle, a burning desert where those who committed violence against God (blasphemy), violence against nature (homosexuality), and violence against order (usurpers) are punished, that Dante visits in Inferno XIV.  Dante had just come out of the overgrown forest of the suicides, and he and Virgil follow along the margin between the forest and the burning desert to keep Dante from burning himself.  While following this path, he comes across Capaneus, the soul of a mythological Greek warrior who participated in the "Seven Against Thebes" siege, lying on the burning sand (oh did I mention that fiery embers are falling from the sky too...).  Capaneus, his arrogance and pride being so great, proclaimed at the gates of Thebes that not even Zeus could stop him from taking the city.  For such blasphemy, Zeus struck him down with a thunderbolt created within Hephaestus' (or Vulcan to the Romans) forge in the crater of Mount Edna in Sicily.   In Dante's conversations with Capaneus, the volcano Mount Etna is referred to as Mongibello, meaning the "beautiful mountain" in Italian.  After passing the clearly unrepentant Capaneus, Dante and Virgil reach a stream of blood connecting the Phlegethon to the frozen Cocytus in the ninth circle deep below.  The two poets later travel along the dikes that keep the blood in its channel in order to traverse across the otherwise harsh, burning desert.  Dante compares this stream to the Bulicame, a hot sulfurous spring near Viterbo from which prostitutes in the town drew their water for their own homes since they were likely prohibited from using the public baths.

With plenty of names from Dante's Inferno available for use on Io's many mountains, we should see more names and places from the poem to be added to Io's infernal surface features.  I always thought the names of the Malebranche from the eighth circle would make a good fit for Io's mountains.  Come on, don't tell me you don't want to see a Barbariccia Mensa.

Link: The World of Dante [www.worldofdante.org]
Link: Princeton Dante Project [etcweb.princeton.edu]

Carnival of Space #140 @ Lights in the Dark

The 140th edition of the Carnival of Space, a weekly series highlighting the best in the astronomy and space blogosphere, is now online at Lights in the Dark, a blog dedicated to the latest images of our wonderful solar system.  You know the drill.  Some great posts on the latest age estimate for the universe, the mechanics of black holes, and early coverage of the latest shuttle launch, STS-130.  <Schwarzenegger voice> Go there.  Go there now!!!</Schwarzenegger voice>

I should also point out that at some point this week, I will post articles on the two remaining LPSC 2010 abstracts about Io that I haven't discussed yet.  They will take just a wee bit longer for a few reasons.  First, they cover modeling of Io's atmosphere, which as usual is difficult for me to summarize.  Second, both abstracts have related papers now in press in Icarus, so I can summarize the papers, not just the 2-page LPSC abstract.  Given the above, this will make the process even longer.  Finally, in about 5 minutes I am going to head out to Gamespot to pick up Bioshock 2 and Dante's Inferno, two games that will soak up a lot of my non-work time.  So bear with me a bit on this...

Link: Carnival of Space #140 [lightsinthedark.wordpress.com]

LPSC 2010: Science Rationale for the Io Volcano Observer

For the last couple of weeks, we have been examining the Io-abstracts submitted for next month's Lunar and Planetary Science Conference.  Today we take a look at a paper submitted by Alfred McEwen and a host of co-authors from the IVO team titled, "Science Rationale for an Io Volcano Observer (IVO) Mission." For this paper, McEwen discusses the technology and science goals and objectives for the proposed Io Discovery mission.  McEwen also touches on how IVO could expand on our knowledge of Io beyond what Galileo obtained in the late 1990s and early 2000s and what the Jupiter Europa Orbiter (JEO) will get in the late 2020s.  This research will be presented as a poster at the Mission Plans and Concepts session on Tuesday, March 2.

We've discussed this proposed mission a number of times in the past. The Io Volcano Observer mission concept was first developed as part of NASA's Discovery & Scout Mission Capability Extension (DSMCE) program.  In this study, NASA hoped to get better grasp on what could be done within the Discovery/Mars Scout program cost cap if the missions were provided two, government-provided radioisotope power sources.  NASA's goal is to test the new Advanced Stirling Radioisotope Generator (ASRG) power source on one of these low-cost missions.  The ASRGs are a much more efficient power source than current RTGs, making them a smarter choice given the limited amount of plutonium available going forward.  The Io Volcano Observer (IVO) was one of nine mission concepts that were selected for further study for the DSMCE program; that study was completed back in February 2009.

For this poster, McEwen will focus on the science objectives and goals for an IVO mission, now a possible proposal for the next Discovery AO.  Some of these goals were discussed here back in September:

1. A1 - Understanding Io's current active volcanism by understanding how its active lavas and plumes are emplaced and generated.  The team plans to acquired repeated imagery of the same volcanic sites at global scales and at high-resolution (< 10 meters per pixel) in order to monitor changes at these volcanoes.  They also plan to take movies of dynamic phenomena like plumes as well as make in situ mass spectra of plume material and Io's atmosphere.
2. A2 - Understand Io's internal structure and tidal heating mechanisms.  The IVO team will use electromagnetic sounding of Io's induced magnetic field and lava temperature measurements to measure the amount of partial melting in Io's asthenosphere.  Thermal mapping in the mid-infrared (~15-20 microns) will allow the group to map Io's heat flow.  The distribution of thermal sources on Io could help distinguish the region of tidal heating in Io's mantle, whether it is in the asthenosphere or in the deep mantle close to the core.
3. B1 - Investigate the processes that form Io’s mountains and paterae and the implications for tectonics under high-heat-flow conditions that may have existed early in the history of other planets.  This will be accomplished through high resolution stereo mapping of large portions of Io's surface, with particular emphasis on areas where we already have at least medium resolution imagery, in order to look for topographic changes on a time-scale of decades (42 years between Voyager 1 and the arrival of IVO in 2021).
4. B2 - Understand how Io affects the Jupiter system.  They plan to accomplish this through in situ measurements of the composition of Ionian volcanic products, Io's atmosphere, and the plasma and neutrals in near-Io space. They also plan to study how Ionian material is lost to Jupiter's magnetosphere.  Finally, they will remotely monitor Io's sulfur dioxide atmosphere and Na-D and OI emissions.
5. B3 - Search for evidence for activity in Io's core and deep mantle by looking for an internal magnetic field in addition to the induced field discovered last year.  Resolving the conundrum of why Io can be so active and not have an intrinsic field might help us better understand how planetary magnetosphere are created.  They also plan to investigate the neutral and plasma densities and energy flows in the Io plasma torus, plus their variations over time, and characterize the ionic radiation belts in the vicinity of Io and their influence on the surface.

In addition to these science goals, a major technology goal for this mission is to study the effectiveness of the new ASRGs. One way to accomplish this is to extend the life of the mission past its primary mission of 7-8 years (including cruise to Jupiter and Io).  They could either expand IVO's orbital period to 1 year to test the ASRGs for their entire nominal lifetimes (~14 years), or they could tighten the orbits to test how well the ASRGs handle the Jovian radiation environment.  ASRGs are needed for an Io mission as the rapid flybys require fast turn times, which a non-gimbaled solar panel wouldn't support and a gimbaled solar panel may not be stable enough and too expensive for a Discovery-class mission.  The inclined orbits of IVO would result in low doses per flyby (10 krads compared to 85 krads for the average JEO flyby), so that actually wouldn't be the limiting factor for a solar-paneled Io mission, the high turn rates and high data rates during the encounters would be.

Finally, the IVO team compare the possible science generated by the Io Volcano Observer and other missions to Io: Galileo and the Europa/Jupiter System Mission.  Galileo's instruments were designed before the discovery of volcanism on Io so the camera and near-infrared spectrometer were not optimized to take advantage of this discovery, and the limited downlink bandwidth brought on by the high-gain antenna failure didn't help.  Compared to the Jupiter Europa Orbiter, IVO would fly over Io's polar regions, mapping the heat flow in those areas and performing sounding of Io's induced magnetic field.  The instruments can also be designed to specifically perform measurements needed for Io that might not be possible with those on the Jupiter Europa Orbiter, such as the near-simultaneous color imaging needed for color measurements.  JEO would accomplish some Io science that would be complementary to that of IVO, such as ground-penetrating radar and laser altimetry.  One interesting possibility is a simultaneous close-up observation with both IVO and JEO.  If IVO's mission at Jupiter and Io is extended with year-long orbits, its extended mission could overlap with the Europa/Jupiter System Mission.

Link: Science Rationale for an Io Volcano Observer (IVO) Mission [www.lpi.usra.edu]

Io Basics

Have you come to this blog looking for basic information on Io?  Well many of the posts here may seem a bit overwhelming without a bit of understanding of the main topic, Jupiter's moon Io.  In this post, I have organized a list of link that will be helpful to new visitors, as well as a list of overview posts that highlight the latest in Io science:

Overview of Io

Io is the innermost of the four large moons of Jupiter known as the Galilean satellites.  Io is a little larger than the Earth's moon but has a surface that couldn't be more different.  While the ancient surface of our moon is dominated by impact craters and large basalt "mare" provinces that are 3-4 billion years old, Io's surface is continuously being renewed, with more than 400 volcanic depressions known as a paterae and more than 130 mountains, the vast majority of which are created by tremendous compressional stresses in Io's crust.  The engine for this violent volcanic activity is tidal heating.  Io's orbit is slightly eccentric and Jupiter's gravitational pull on Io varies over the course of an Ionian day.  The moons Europa and Ganymede help to prevent Io from circularizing its orbit, keeping the heat engine in Io's mantle running.

For more information on Io and its volcanism, check out the following links:

• On Wikipedia, check out the Io and Volcanism on Io articles.  Both are featured articles on the online encyclopedia, representing some of the best content there.  Plus, I regularly review content changes to those articles in order to maintain their high quality.  I am also beginning to prepare more articles on several of Io's volcanic features, such as Pele, Masubi, and Tawhaki Vallis.
• Janet Wood created a neat site about 10 years ago on Io that is still helpful for providing an overview of Io science called Io: Jupiter's Volcanic Moon
• The USGS has a website dedicated to planetary nomenclature, or surface feature names. Their section on Io provides a list of official names used for volcanoes and mountains on Io.
• Looking for a map of Io?  Scientists at the USGS office in Flagstaff created a basemap based on Voyager and Galileo images of the satellite several years ago.  Several versions of this map can be found on their website as well as a PDF version of the color basemap with feature names added.
• Looking for images from the Voyager, Galileo, or New Horizons spacecraft?  A good place to look for officially released versions of spacecraft images is the Planetary Photojournal, which has a page for Io images.  I also have a page where I've done my own processing of the raw data from Voyager, Galileo, and New Horizons.

From the Blog

While generally I post articles related to recent news or the latest papers, from time to time I also post articles that provide an overview of a topic of Ionian research, whether it is on the formation of Io's volcanoes or the composition of its surface.  I believe these articles are of the most interest to new readers, so I've listed a few of them here:

• Formation of Paterae (volcanic craters) on Io
• Formation of Mountains on Io
• The Chemical Composition of Io
• Boösaule Montes: The Tallest Mountain on Io
• The Curious Case of Reiden Patera
• It's Not Easy Being Green: The Chaac Patera Story
• Io@400: A series of posts covering Galileo Galilei's Discovery of Io in 1610
• Astronomy from Io
• The Potential for Science at Io from the upcoming Juno mission
• Summary of the proposed Io Volcano Observer mission
• The Potential for Science at Io from the upcoming Europa/Jupiter System Mission

I hope you all enjoy you visit to the Gish Bar Times!

LPSC 2010: Modeling the Volcanic Plume of Pele

For the last couple of weeks, we have been examining the Io-abstracts submitted for next month's Lunar and Planetary Science Conference.  Today we take a look at a paper submitted by William McDoniel, David Goldstein, Philip Varghese, Laurence M. Trafton, and Benedicte Stewart titled, "DSMC Modeling of the Plume Pele on Io." For this paper, the authors modeled the plume of Pele using a curvilinear source region.  The goal is to replicate not only the extreme height of Pele's large plume, but also the elliptical shape of the red deposit it leaves on Io's surface.  This research will be presented as a poster at the Planetary Atmospheres session on Thursday, March 4.

During last year's Lunar and Planetary Science Conference, McDoniel and his colleagues reported on their computer modeling of volcanic plumes that erupt from irregularly-shaped vents, such as those that would be expected from the flow front of a lava flow.  The group uses the Direct Simulation Monte Carlo (DSMC) method for simulating the motion and properties of gas molecules within a rarefied flow like an Ionian volcanic plume.  The method was previously used with great success in 2-D space, which is appropriate for replicating the height, width, and appearance when projected against black space, by Zheng et al. 2003 for a Pele-type plume and Zhang et al. 2004 for a Prometheus-type plume.  DSMC modeling is also being used to simulate the entire atmosphere of Io as generated by sublimation and volcanism and what can happen to the atmosphere when Io is in the shadow of Jupiter. The work done by McDoniel and his colleagues at the University of Texas in the last few years has been to extend the earlier plume modeling into the third dimension in order to match the 3D shape of Ionian plumes and their non-circular deposits on the surface.  As mentioned, last year the authors examined a half-annular vent region, as opposed to the circular vent region assumed by Zheng et al.  This was done to simulate the Prometheus plume, which is generated by the interaction between warm silicate lava and surficial sulfur dioxide frost at a broad, half-circular lava flow front.  They found that such as vent geometry generated a plume that was roughly similar to one generated from a circular vent source, but with prominent jets forming along the inner concave portion of the half-annulus vent area and at the ends of convex side.  These jets had some effect on the strength of the canopy shock (the upper bright region of a plume), but the plume deposit was still roughly circular, albeit shifted in the direction of the convex side of the half-annulus source.

This year, McDoniel et al. have shifted their attention to the larger Pele plume.  The Pele plume is one of the largest on Io and was seen off and on by Voyager 1, Galileo, and the Hubble Space Telescope.  Fallout from this plume produces a large red ring that encircles the Pele volcano at a distance of 400-600 kilometers.  Two of the major features of this deposit are its elliptical shape where it is more elongated in the north-south direction and its subtle changes in shape and localized intensity over time.  McDoniel et al. used a DSMC model of the eruption conditions of Pele (sulfur and sulfur dioxide-rich gas desolving from lava fountaining at an active lava lake) and a Galileo image from the I24 encounter in October 1999 of a portion of the lava lake as a representation of the vent geometry in order to replicate the shape of the Pele plume deposit.  There simulations showed an elliptical plume deposit, with the elongation roughly perpendicular to the curvilinear line of thermal hotspots assumed to be vent sources.  Closer to the vents, the research found that jets should be created generated by the concave portions of the curvilinear line of small gas vents, including the ends of the line of vents.  The jets are associated with areas of greater deposition in the fallout region far from the vent.

What I think is most significant about this research is that it suggests that a roughly linear Pele-type plume source, like this curved line of hotspots, should produce an elliptical plume deposit.  The elongation of this deposit should be perpendicular to the trend of linear source.  Variations in intensity of the deposit are related to stronger jets resulting from deviations from the linearity of the plume source, like the concave and convex sections of the source used in the simulation.  Now, the exact source they used for their simulation may not be the source of the Pele plume, as there is a much more intense section of the Pele lava lake to its east, as seen during the I32 encounter.  Interestingly enough, this intense portion is an elongated depression that is perpendicular to the elongation of the Pele plume deposit, which is what you would expect if it is the source of the plume based on this simulation.  Variations in the deposit may result from different portions of this active region turn on or shutting off, producing jets in the plume.

Very intriguing research, IMHO!  Certainly it provides an explanation for the shape of Pele's plume and provides a possible explanation for changes in the shape and intensity of its deposit on the surface.  A more linear source would be expected from a fissure-like eruption, which is what you would expect from an explosive eruption that produces a short-term giant plume, like Grian, Tvashtar, Surt, or Dazhbog.  This may explain why at least Grian also produced an elliptical plume deposit.

Link: DSMC Modeling of the Plume Pele on Io [www.lpi.usra.edu]

LPSC 2010: Re-examining the Iothermal Gradient

For the last couple of weeks, we have been examining the Io-abstracts submitted for next month's Lunar and Planetary Science Conference.  Today we take a look at a paper submitted by Giovanni Leone, Lionel Wilson, and Ashley Davies titled, "The Geothermal Gradient of Io: Consequences for Lithosphere Structure and Volcanic Eruptive activity." For this paper, the authors modeled the structure of Io's lithosphere by calculating how its temperature varies with depth.  This research will be presented as a poster at the Igneous and Volcanic Processes session on Thursday, March 4.

Io's internal heat, generated by tidal stresses on Io's mantle, is released through volcanic activity in a process called advection.  As opposed to convection or conduction, with advection, heat is transported from a system through a warm liquid, in this case, liquid hot magma.  The model used by Leone and his colleagues was first developed in O'Reilly and Davies 1981 in order to explain how Io's lithosphere could be releasing so much heat (2.4 Watts per m²) yet still hold up Io's steep paterae walls and tall mountains.  A conducting crust would be far too warm at shallow depths and too thin to hold up these structures.  Thus, thanks to advection, all of the internal heat from the asthenosphere is released through volcanic eruptions and the lithosphere stays pretty cool except for the lower two to three kilometers of the 30-kilometer thick lithosphere, preventing viscous relaxation of Io's topography (see the craters of Saturn's moon Enceladus to see how viscous relaxation can distort topography).

For their model, Leone et al. used two equations from O'Reilly and Davies 1981 as well as improved knowledge about the chemistry and properties of Io's lithosphere to calculate the geothermal (or iothermal, if you will) gradient within the lithosphere, from the cold (100 K) surface to the lithosphere/asthenosphere interface at a depth of 30 kilometers and a temperature of 1500 K. Their inputs include estimates for the porosity of the lithosphere as a function of depth, the density of the magma, the globally-averaged, advected heat flux, radiogenic heatign rate, the magma specific heat, latent heat of crystallization, and thermal diffusivity. From these equations, the authors derived the lithospheric density, pressure, and temperature at different depths in Io's lithosphere. As expected, the lithosphere remains below the melting point of sulfur dioxide from the surface down to a depth of 21 kilometers. It remains below the melting point of sulfur until a depth of 26 kilometers. Much of the lithospheric heating takes place in the bottom few kilometers of the lithosphere.

The iothermal gradient generated by Leone's model does support the transport of magma all the way to the surface. Without any entrained volatiles, magma from the asthenosphere can rise to a depth of 23 kilometers before becoming negatively buoyant and forming magma reservoirs, assuming a pore-space fraction of 30% at the top of the lithosphere. As mentioned above, this is within the depth range of the melting point of the dominant volatiles on Io, sulfur and sulfur dioxide. These may then become entrained in the lava, allowing the magma to rise further to the surface. Leone et al. conclude that with volatile contents as low as 5% by mass, magma should be able to reach the surface using reasonable values for lithospheric porosity. With even more volatiles, such as the 10-30% suggested at some plume sites like Tvashtar, the modeled iothermal gradient would support the kinds of high eruption speeds observed at that volcano. They conclude "that there should be a positive correlation between mass eruption rate and volatile content." So it should not come as a surprise that major eruption on Io, like Tvashtar 1999/2001/2007, Thor 2001, Grian 1999, and Pillan 1997 all had volcanic plumes.  Finally, they also place a limit on the porosity of Io's lithosphere at the surface at 38% as magma could not ascend into the lithosphere above that level, the crust would be too light.

Another factor that the authors examined was the effect that changes in the advected heat flow would have have on the lithosphere.  Just as Kirchoff and McKinnon found last year, a decrease in volcanic activity but not a decrease in the amount of heat generated in the mantle (i.e. the temperature remains the same) would leading to a heating of the lower to mid-lithosphere, possibly leading to some melting.  In Leone's model, the gradient changed from a steep curve at 2.4 W/m² (remaining relatively cool until close to the lithosphere/asthenosphere boundary) to a much shallower one at 0.5 W/m².

With this model of Io's geothermal gradient, Leone and his co-authors have placed limits on the amount of pore spaces are possible in Io's lithosphere.  Their model is supported by their ability to replicate the ascent of magma to the surface, which is readily visible on Io's surface.  Their model also helps support the argument that the volatiles in Io's lava are incorporated into its magma within reservoirs in the lithosphere.  I would be interested to see how this model fits with the view that the upper 2-3 kilometers of Io's lithosphere maybe dominated by volatiles with silicates being predominant deeper into Io.

Link: The Geothermal Gradient of Io: Consequences for Lithosphere Structure and Volcanic Eruptive activity [www.lpi.usra.edu]

LPSC 2010: Comparing the Distribution of Io's Paterae

For the last couple of weeks, we have been examining the Io-abstracts submitted for next month's Lunar and Planetary Science Conference.  Today we take a look at a paper submitted by Brandon Barth, Jani Radebaugh, and Adam McKean titled, "Distribution and Comparison of Io's Paterae: Areas, Effective Diameters, and Active Volcanism".  In this paper, the authors discuss measurements of volcanic depressions on Io's surface, known as paterae, and dark paterae floor material.  The authors then studied the size-distribution of paterae across different quadrants of Io's surface.  This research will be presented as a poster at the Satellites and their Planets session on Thursday, March 4.  Last year, this group presented their research on the distribution of paterae (both in general and those with dark material on their floors) at last year's LPSC.  This year, they add the size of the volcanoes found into the mix.

For her PhD dissertation, co-author Jani Radebaugh created a database of paterae back in 2003 and 2004 based on measurements from Galileo and Voyager images, along with parallel MySQL databases of thermal hotspots and mountains.  I still remember the pizza involved, yes, even 7±1 years later... The measurements of the length and area for this database were made assuming that these patera were ellipses, however many paterae as you can see in the image above have complex shapes.  For example, Yaw Patera is shaped like a gasoline nozzle, as seen in the I27 CAMAXT01 mosaic where Yaw is the dark patera in the lower right corner.  Now, one of her students, Brandon Barth, has measured 426 paterae (minus 30 or so in the polar regions still to be measured in time for the poster session) using ArcGIS™.  This allowed Barth and the other co-authors to calculate the size and areas of these oddly-shaped volcanoes more accurately as they are able to mark the boundaries of the patera and ArcGIS does the work in calculating the area of the marked region.

From these measurements, the average effective diameter for paterae on Io is 56.8 kilometers.  Effective diameter is the size of a circle with the same area as the paterae, which aids in comparing the sizes of paterae to one another by normalizing them.  The average effective diameter found is quite a bit larger than Radebaugh et al. 2001, where it was found to be 41 km.  The authors attribute this discrepancy to the measurement techniques mentioned above employed in the different works.  This new method ensures that the entire volcano is captured in the area measurement.

The authors looked at how the size-distribution of all paterae and active paterae (those with at least some dark material on their floors) varies across Io's surface.  They determined that the anti- and sub-Jupiter quadrants of Io have more paterae than the leading and trailing quadrants.  They define these quadrants as the 90 degrees of longitude surrounding the sub-Jupiter (0°W), anti-Jupiter (180°W), leading (90°W), and trailing (270°W) points.  However, they also found that the average effective diameter for the leading and trailing quadrants was larger (63.5 km) than those found on the anti- and sub-Jupiter quadrants (52 km). A similar trend was seen in active paterae, with active paterae being larger than inactive ones on the trailing and leading quadrants and vice versa for the sub- and anti-Jupiter quadrants.  This distribution may have consequences for how Io's releases its heat since paterae are the dominant contributor to Io's total heat flow.

I am curious how much image resolution plays into this.  The resolution of images of Io from the Voyager and Galileo missions is best on the sub- and anti-Jupiter quadrants, respectively.  Better resolution would allow for better identification of paterae margins and would allow smaller paterae to be resolved.  This issue may be most acute on parts of the leading quadrant where the best images have a pixel scale of around 9 kilometers per pixel.  Such low-resolution data may cause an over-estimate of paterae margins as they are confused with nearby bright or dark flows.  I know that Shamshu Patera looks larger than it really is in the global basemap as a result of a bright flow to the south of the volcano.  So more paterae (from smaller paterae being detected) on the sub- and anti-Jupiter quadrants and larger paterae (from mis-identification of margins due to the low resolution of the available data) on the trailing and leading quadrants would be an expected result from resolution effects.  That being said, the trailing and leading quadrants do have some of the largest paterae I can think of like Loki, Dazhbog, Shamshu, and Zal so maybe there is something to this hemispheric difference in average paterae size after all.  Just looking at the poster in front of me, I can only quickly see west Tvashtar and Mentu in that ballpark on the anti-Jupiter side.

This isn't meant as a criticism of their work.  Their methodology is sound; using ArcGIS is an excellent way to measure areas of irregular surface features.  Every day conclusions are made from less than ideal data; science doesn't stop just because the effective resolution of a basemap isn't uniform.  You make do with what you have and just attempt to remain humble when in future years better images are acquired and your conclusions have to be changed.  Look at Titan - a world full of less than ideal data.  When a cryovolcano turns into just another patch of bright material surrounded by dunes, you suck it up and move on.  But you don't let methane windows, low spatial resolution data, or ambiguous terrain stop you from making interpretations and measurements.

Link: Distribution and Comparison of Io's Paterae: Areas, Effective Diameters, and Active Volcanism [www.lpi.usra.edu]