Carnival of Space #92 @ The Launch Pad

The next Carnival of Space, Edition #92, is now online at The Launch Pad, a blog at the X-Prize Foundation. Check that out for more on the failed launch of the Orbiting Carbon Observatory (I still want to see an Orbiting Barium Observatory).

Become a Fan of Io

Do you use Facebook? Do you like Io? Well, become a Fan of Io on the popular social networking website. I had considered creating such a page on Facebook for a while now, but as you can see, someone did if for me, and that's fine with me.

What use is a "Fan" page on Facebook? Well, it provides some functions of a web forum, allowing people to discuss news and opinions with some of the Web 2.0 functions of users adding their own photos, links, and videos (I'm guessing just embedded stuff from Youtube and the like).

You can also become a friend of Europa, but why would you do a silly thing like that? ;-)

Link: Facebook | Io [www.facebook.com]

Pillan Color Data from Galileo Orbit I27

The other day I posted a link to Ted Stryk's version of a color image acquired of Pillan and nearby features during the I27 encounter in February 2000. At right is my version.

Admittedly, it is a little rattier, but that's what I had to work with from the data set that was returned to Earth. This represents part of a frame from 27ISGLOCOL01, a planned three-color, four-frame mosaic of Io's anti-jovian and trailing hemisphere acquired a few hours after the I27 flyby. Unfortunately, there just wasn't enough time to downlink all the data that was acquired during the flyby before the G28 Ganymede flyby in May 2000. And this GLOCOL01 observation took the brunt of these data volume hits, though for a number of observations only partial frames could be returned. So at the end of the day, this contingency color mosaic was stripped down to these three partial color frames over Pillan. To make things worse, the near-infrared 756 nm filter image (used here for red) had several data cutouts, which unfortunately couldn't be filled by additional passes through the tape recorder on Galileo.

Compare this partial frame from data acquired four months earlier after the I24 flyby (October 1999) and 1.5 months earlier from the E26 orbit (January 2000). One thing that is apparent to me are the two new dark spots at Reiden Patera, near bottom center in the I27 frame above. This again shows activity at Reiden was confined to the margins of the patera, indicated that either Reiden was a large lava lake with fresh eruptions occurring where the lava crust breaks up where it interacts with the patera wall, or that Reiden's vents were limited to the fault lines that shaped the patera.

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

The Gish Bar Times One-Year Anniversary

Today marks the first birthday for the Gish Bar Times. You can check out the original Welcome message that I posted a year ago this very minute. Despite the lack of a spacecraft at Io during this past year, and there won't be until Juno arrives in 2016, this past year has been pretty exciting with the Outer Planet Flagship Mission contest, a legitimate proposal to send a dedicated mission to Io, and further processing work on Galileo images of Io.

I want to thank all of you for visiting the blog on a regular basis. Your support has really helped spur me to try to write interesting posts on the science and exploration of this exciting, but often forgotten moon of Jupiter. When I started this blog last year, I didn't quite know if a blog about a single moon of Io would work or would find many readers. It took a while for me to really find my voice and write these more substantive posts, but I have grown more and more satisfied by what I've done with place.

When I started this blog, my goal was to talk more about the science side of Io, talking about new volcanic activity observed by ground-based observers, astro-photography posted online, and new papers. In the last year, I was definitely drawn more and more to the exploration side, with quite a few posts dedicated to future approved and proposed missions. In the next year, I'm not sure if there will be quite the level of future mission news now that the flagship mission has been selected. The IVO concept study should be wrapping up in the next few months, but I am not sure how much more it will change from the December 2008 Io Workshop presentation.

So what can you expect from this blog over the next year? Well, it is clear to me that I can't quite sustain this readership in the future by focusing ENTIRELY on Io. Now don't get me wrong, this is an Io blog. It will always be an Io blog. Much of the in-depth coverage on this blog will be dedicated to Io. So, paper summaries and reprocessed images will be about Io. However, to keep the blog fresh, I think it would be a good idea to broaden the topics covered here. So, I will also talk about the other objects in the Jovian system...including Europa if I have to. I will also post on news related to planetary volcanism (on Titan, Mars, Venus, or major eruptions on Earth). I think this will help sustain the viability of this blog in the long term and maintain interest when there isn't much to talk about regarding Io.

Anyways, thanks for reading this little missive. Go ahead and post comments to this post and let me know what you think of this idea.

Paul Schenk on the OP Flagship Selection

Paul Schenk, a planetary scientist from the Lunar and Planetary Institute in Houston, Texas, has a nice post on Unmannedspaceflight.com with his thoughts on last week's EJSM selection. I agree with what he said there, for a lot of planetary scientists, there is a lot that can be done in the Jupiter system, and as he mentions, in the wake of Galileo's successful failure, there is a lot that needs to be done in terms of Jupiter science.

For those who would have preferred the Titan mission, come on, you got EIGHT more years to hopefully look forward to from Cassini. Check out John Spencer's post on the Planetary Society Blog for more info on all the craziness that will happen with Cassini during its Extended-extended mission. The XXM includes 56 flybys of Titan and 12 flybys of Enceladus. I mean, that's more than we have done up to this point. To be honest, I also get excited about the flybys of the little rocks. Maybe it is the excitement of seeing a new world upclose that I've kinda lost from seeing Titan, Dione, Enceladus, etc. images all the time. We got a flyby of the small moon Helene coming up next March during the first extended mission, and during the XXM we have another one of Helene (providing coverage of the unilluminated hemisphere from the first Helene flyby) as well as flybys of Telesto and Methone. So while Titan will not get a flagship mission until the 2025-2035 time frame, the next decade will still be a great time to do Saturn system research.

Right above Paul's post over at UMSF, Ted Stryk posted his version of a partial color frame from Galileo's I27 flyby showing Pillan, Reiden, and parts of the Pele plume deposit. I should probably process my own version of that. That is definitely on my To-do list for tomorrow evening.

Link: Paul Schenk's post at UMSF.com [www.unmannedspaceflight.com]

OPAG March Meeting Agenda

The agenda for next month's OPAG meeting has been posted online. The Outer Planet Assessment Group reports to NASA's Planetary Science Subcommittee on issues related to the exploration of Outer Solar System. The agenda has quite a few interesting items, including presentations by Alfred McEwen on the Io Volcano Observer, Curt Niebur on the current status of the OP flagship program (in the aftermath of EJSM's downselection), and Ron Greeley and Curt Niebur on community participation in EJSM.

I will not be at this meeting, but the powerpoint files for most presentations should be posted online shortly after the meeting. The meeting is scheduled for March 9 and 10 in Bethesda, Maryland.

Link: OPAG March 2009 Meeting Agenda [www.lpi.usra.edu]

Paper: Formation of Mountains on Io

The second Io paper posted Saturday on the journal Icarus's Articles in Press page is titled, "Formation of mountains on Io: Variable volcanism and thermal stresses". The authors for this paper are Michelle Kirchoff and Bill McKinnon from the Lunar and Planetary Institute in Houston and Washington University in St. Louis. This paper takes a look at the geophysics behind the formation of mountains on Io and why there is a global scale anti-correlation between mountain and volcanic paterae. In a nutshell, they find that variations in volcanic activity can vary the level of thermal stresses in Io's lithosphere, which in concert with subsidence stress (a compressive stress that increases with depth resulting from the high resurfacing rate), leads to the formation of thrust faulting and mountains if that volcanic activity decreases.

Crustal subsidence stress from volcanic resurfacing is one of the dominant compressive stressors on the Ionian lithosphere, but subsidence stress is insufficient to produce thrust faults that reach the surface as each time a fault is formed and moves, the subsidence stress global is that much more reduced. In order for a mountain or a cluster of mountains to be formed at a particular location, a "focusing" mechanism is required. Three hypotheses have been put forth for these mechanisms:

• Jaeger et al. 2003 suggested that mantle plumes impinging on the base of the lithosphere could locally increase the compressive stress at a particular location, resulting in thrust faulting and mountain formation. Kirchoff and McKinnon call this hypothesis "plume-modified subsidence."
• Tackley et al. 2001 suggested that global mantle upwellings and downwellings produce tensile and compressive stresses in the crust. Upwellings results in tensile (extentional) stress on the lithosphere due to crustal thinning and stretching, producing increased volcanic activity. Downwellings result in compressive stress on the lithosphere, producing increased mountain formation. This model was developed in response to the obsevation that while some paterae abut mountains and thus there maybe some local correlations between mountains and volcanic pits, globally these features are anti-correlated. The authors of this paper call this hypothesis "Convection-modified subsidence".
• McKinnon et al. 2001 suggested that decreases in volcanic activity on a regional scale (and thus decreasing the transport of heat from the interior to the surface), could result in heat building up at the base of the lithosphere, causing it to melt. The increase in thermal stresses caused by this melting result in the propagation of thrust faults closer to the surface and would thus support mountain formation (also known as orogenesis). Kirchoff and McKinnon call this hypothesis "thermal-stress-modified subsidence".

The authors examined the viability of the "thermal-stress-modified subsidence" hypothesis by modeling temperature and stress levels within the lithosphere, first assuming a steady-state resurfacing rate (which, according to the O'Reilly and Davies 1981 heat pipe model, is directly related to heat flow; the advective escape of heat from Io's interior). They then increased or decreased that resurfacing rate by 50% and 100% to see how this affected the temperature and stress levels. Kirchoff and McKinnon looked at both cases where the asthenospheric heating rate and resurfacing rate are coupled and uncoupled. In the coupled case, a decrease in resurfacing rate is the result of a decrease in the local asthenospheric heating rate. In the uncoupled case, the local asthenospheric heating rate stays the same while the amount of heat that is advected to the surface (through volcanism) is varied.

• In the coupled case, the thickness of the lithosphere is maintained. Temperatures in the lithosphere increase, causing the region in compressive failure (where stresses surpass Byerlee's Rule) to become larger and more shallow. Eventually the temperatures and stress levels reach a steady state.
• In the uncoupled case, decreasing the resurfacing rate increased heating at the base of the lithosphere, leading it to melt and increasing temperatures throughout the lithosphere (though convection all the way to the surface remains negligible). Over 0.5-1 million years, the crust thins. The resulting thermal stress decreases the depth at which thrust faults could form and propagate. The more the resurfacing rate is reduced, the greater the effect. Increasing the resurfacing rate causes cooling at the base of the lithosphere, thickening it. No steady state is achieved, eventually something has to give, like an increase in volcanic activity.
• The authors also looked at a case where the lithosphere is 50 km thick, instead of 25 km. This just increases the time it takes for the lithosphere to thin enough to bring the brittle compressive zone close enough to the surface to support orogenesis.

Kirchoff and McKinnon ignored the effects of warm intrusions (which are likely important in formation of paterae) and assume that old lava flows completely cool before the next is laid down and the presence of a partially molten asthenosphere. The thermal effects of the first two are likely negligible as they don't seem to be a major component of the heat flow (heat flow estimates at longer and shorter wavelengths are consistent). The third is consistent with most modern tidal heating models for Io given volcano distribution. They also found that changing crustal rheologies (dry basalt, peridotite, or "komatiite") doesn't greatly change the modeling results. Eruption temperature estimates are consistent with dry basalt with greater iron and magnesium (olivine) content.

The authors then compared their results to the other models. For the plume-modified subsidence hypothesis, stress caused by an impinging mantle plume was not significant compared to crustal stresses. Because tidal heating is focused in the asthenosphere (or upper mantle), heat "plumes" should be downwellings, not upwellings, according to Tackley et al. 2001. For the convection-modified subsidence hypothesis, compressive stress on the lithosphere from mantle downwellings are too small to focus mountain formation. Maximum lithospheric stress are only a few kPa, compared to hundreds of MPa needed for compressive failure.

Finally, the authors examine a potential local cycle of mountain and volcano formation. First, greater volcanic activity increases the resurfacing rate (and thus the subsidence rate). This causes greater compression at depth, which constrains the deep conduits between volcanoes and their deep magma reservoirs, lowering the level of volcanic activity. This does nothing to the level of asthenospheric heat and temperatures increase throughout the lithosphere, leading to melting at its base. This melting causes thermal stresses to propagate to shallower depths, causing compressive failure between 10-20 km, where thrust faults could propagate to the surface, forming mountains. The formation of these faults and mountains relieves the subsidence stresses and thermal stresses in the lithosphere, leading to extension. This then allows magma to ascend to the surface through newly opened conduits as well as form batholiths which can helps deform mountains, such as by fracturing them. Increasing volcanic activity leads to a thickening of the crust back to its normal level. Unlike the view from McKinnon et al. 2001, volcanism does not need to complete shut down for this model to work.

One potential consequence of this cycle is that areas with high numbers of mountain should be beginning to increase their level of volcanic activity, perhaps increase the number of active paterae that abut mountains compared to areas with more paterae but fewer mountains.

Link: Formation of mountains on Io: Variable volcanism and thermal stresses [dx.doi.org]

Carnival of Space #91

The Next Big Future blog has the 91st Edition of the Carnival of Space: Europa, water on Mars, and Dawn, oh my! Definitely worth checking out!

Paper: Io's Dayside SO2 Atmosphere

As I pointed out yesterday, two papers were added to the journal Icarus's Articles in Press. The first that I want to summarize here is titled, "Io's Dayside SO₂ Atmosphere." The authors of this paper are Lori M. Feaga, Melissa McGrath, and Paul D. Feldman. The authors of this paper examined far-ultraviolet data acquired by the STIS instrument on the Hubble Space Telescope between 1997 and 2001 to see what this dataset can tell us about the density of Io's atmosphere and how it varies across Io's disk.

During the Galileo mission, the Hubble Space Telescope was tasked at various times between 1997 and 2001 with observing Io during the telescope's Space Telescope Imaging Spectrograph (HST/STIS). Feaga et al. took a look at the data in the range of the H_I Lyman-α line (around 1216 Å or 121.6 nm) and studied the spatial and temporal variations of that spectral line's emission from Io's surface. This research builds on previous work by Feldman et al. 2000 that found that the level of emission in this far-ultraviolet spectral line is related to the column density of the atmosphere. Gaseous sulfur dioxide is a continuum absorber in this region of the spectrum, so as the column density of the SO₂ in Io's atmosphere increases, less of the Lyman-α emission from the sun reaches the surface and is reflected back into space for the HST to observe it. Looking at an example image above, the dark regions on Io's disk (marked by the white circle) are places where Io's atmospheric SO₂ is densest and bright areas are where gaseous SO₂ is less dense. Feldman et al. 2000 found that Lyman-α emission from Io peaks at the satellite's mid-latitudes and is lowest within the equatorial region, suggesting a latitudinal dependence on the density of Io's atmosphere.

This new paper by Feaga et al. continues the research started in the 2000 paper by looking at the more complete HST/STIS dataset covering a greater longitude range than the earlier work by Feldman et al. This allowed the authors to look into spatial and temporal variations in the SO₂ column density. The authors found that Io's atmosphere, in addition to the latitudinal dependence also seen in the earlier work, was densest and had the greatest latitudinal extent on Io's anti-Jovian hemisphere (particularly at the longitude range of Bosphorus Regio) and was narrower in latitudinal extent and less dense on Io's sub-jovian hemisphere. The greatest SO₂ column density was seen near 140° at 5 x 10¹⁶ cm^-2. However, they do note some limitations for their method for deriving SO2 column densities. For example, the densities near the equator are often high enough that the amount of signal from the surface is quite low, low enough to be effected by some of their data reduction procedures, such as removing the Lyman-α emission from the interplanetary medium and removing the effect of albedo variations on Io's surface (their albedo map comes from a nearby wavelength range and was scaled to the extected brightness range expected at 1216 Å). They found few examples of major changes in the density and extent of Io's atmosphere, suggesting that the atmosphere is stable over periods of five years or more.

The authors also looked at how their gaseous SO₂ map with the distribution of volcanic hot spots and plumes as well as the distribution of sulfur dioxide frost on Io's surface as found by Doute et al. 2001. They argue that from these comparisons that their results best support a volcanically-driven atmosphere, as the equatorial and anti-jovian concentrations of gaseous SO₂ is best comparable with their map of hotspots and plumes. However, it should be noted that their map is still consistent with the distribution of large-grained SO₂ as found by Laver and de Pater 2009. In a sublimation-driven atmosphere, SO₂ frost in the warmest regions of Io (the equatorial regions) would be the source, so the Laver and de Pater map maybe more relevent for comparison. In addition, in a volcanically-driven atmosphere, I would have expected more examples of changes as the result of variations in volcanic activity, though a few possible examples were found at Pele and Prometheus.

Finally, the authors looked at how their data compares to other measurements made by other researchers. They found that their distribution map is similar to what others have found with Io's anti-jovian hemisphere having a greater latitudinal extent and column densities of SO₂ gas than the sub-jovian hemisphere and with greater SO₂ column densities near the equator compared to the mid-latitudes and polar regions. They found that column density numbers, particularly in the equatorial regions, tended to be lower than other authors, such as Jessup et al. 2004 and Moullet et al. 2008. The authors suggest that the low signal-to-noise ratio within the equatorial region may make some of the measurements lower limits, though they may not be consistent with some results from Spencer et al. 2005, which predicts much higher column densities at mid-latitudes than what was found in the HST/STIS data.

Link: Io's Dayside SO₂ Atmosphere [dx.doi.org]

Weekly Recap

Wow, last week was insane. We had more visitors last week than we have ever had in a month, almost 1,000. Thanks to everyone who stopped by and I hope I can keep some of you around to learn a thing or two about Io. It was also a busy week in terms of posts thanks to the selection of the Europa/Jupiter System Mission as the next Outer Planet flagship mission. So let's take a look at last week in review:

• As I just said, the big news of the week was the Outer Planet Flagship mission downselection announcement. With the Europa/Jupiter System Mission selected, we can now look forward to the next 10 years of mission development and Io observations in the mid-2020s. Last week, we touched on the potential for Io science from ESA's contribution to the mission, the Jupiter Ganymede Orbiter. We also looked at an example of science the Jupiter Europa Orbiter would obtain while in orbit around Europa. This could include constraining the thickness of Europa's water ice shell (though some of these results, such as of Europa's tides with the Laser Altimeter, maybe limited by our knowledge of the satellite's deep interior).
• We also looked at press coverage of the EJSM selection.
  
• With EJSM approved, we took at look at how the downselection would effect the Io Volcano Observer proposal as well as the Io science questions that still remain.

This week should be a bit quieter than last week, obviously, as I really don't see any external news coming that will generate posts. However, I plan to post summaries of two papers posted on the Icarus website yesterday, including one covering HST observations of Io's atmosphere that I will be posting later today. The Gish Bar Times also turns one year old on Wednesday, so we might do something special for that :)

Two New Io Papers In-Press

There are two new Io-related papers just posted to Icarus's Articles-in-Press page. In Press articles are papers that have been approved for publication but have not found a spot in the printed journal. The first paper, Io's dayside SO₂ atmosphere by Lori M. Feaga, Melissa McGrath, and Paul D. Feldman, covers Hubble Space Telescope observations of Io's atmosphere in the UV. The second paper, Formation of mountains on Io: Variable volcanism and thermal stresses by Michelle R. Kirchoff and William B. McKinnon, reports on modeling of Io's lithosphere and how its tectonics varies as a result of volcanic variability.

I'll post summaries of these two papers here tomorrow and Monday.

Outstanding Science Questions at Io

Eric posted a few comments yesterday which provided a great suggestion for a blog post. What are the outstanding science questions that remain following Galileo and New Horizons? Can these questions be answered by the Jupiter Europa Orbiter (and Io Volcano Observer)? While better understanding Io's potential habitability by native lifeforms is certainly not one of them, there are at least five I can list here.

Before I do that, I want to point out Van Kane's post on his blog giving some of his closing thoughts on the Flagship mission selection. He pointed to my last post on how the selection of Europa as the target for that mission might effect the Io Volcano Observer and noted that the instruments could be more finally tuned to better answer questions at Io. That idea has crossed my mind. If the cost of IVO can't be brought in line with the Discovery mission cost cap, one potential alternative is to submit beefed up versions of some of IVO's instruments, particularly RCam and the Thermal Mapper, for the JEO Instrument Announcement of Opportunity. RCam's radiation-hard color push-broom camera could be just as effective at observing small-scale features on Europa as it could for determine eruption temperatures on Io. Additional bandpasses on Thermal Mapper compared to the Thermal Imager in JEO's model payload could also be useful for Jupiter on JEO. However, you do still lose the spatial coverage that would be provided by IVO, which would help it be more robust against variability in Io's volcanic activity. For example, what if Amirani was inactive in the mid-2020s?

So with that out of the way, here are five of the top (in my mind) outstanding science questions at Io:

1. What is the composition of Io's lava's?
2. What is the typical eruption temperature for Io's volcanoes? These first two questions are quite related. Following Galileo, there was consensus that Io's primary lavas were composed of basalt, a silicate lava rich in iron and magnesium and common on the terrestrial bodies in the solar system. However, the exact composition was very poorly constrained by the available data (dark at visible wavelengths, an absorption at 1 micron consistent with iron, and estimated lava temperatures in mafic to ultramafic range). The eruption temperature could be related to the amount of partial melting in Io's mantle. And of course temperature is related to the composition of Io's lavas. Generally the higher the magnesium level, the more mafic it is, the greater the liquidus temperature (and thus the eruption temperature). Understanding the effect of superheating during the ascent of the magma is also important. These questions can be answered through the measurement of Io's thermal emission in the 0.7-1 micron range (like from a near-infrared spectrometer or RCam on IVO) and by looking for absorption and emission features in the near-infrared that are consistent with materials in Io's lava, such as the Christiansen Feature.
3. Is tidal heating on Io steady-state or time-variable? One of the potential implications of measurements of Io's heat flow is that Io may be pumping out more heat from its interior than it currently receives from tidal heating as a result of its orbital resonances with Europa and Ganymede. This would indicate that Io is cooling down from a period of much greater tidal heating in its past. A potential way to test this is by high-resolution tracking of the position of Io and Europa over time. One of the mission goals for JEO is to provide this kind of tracking to better constrain the orbital evolutions of Io and Europa. IVO's polar orbits would allow for better thermal emission mapping of Io's polar regions, which are thought to be much warmer than they should be given the lower solar angles.
4. How are Io's two major structural landforms, paterae and mountains, formed? Various models following Voyager and again after Galileo have been produced to explain how paterae and mountains form on Io. Sub-surface radar sounding and high-resolution, low sun imaging could go a long way toward looking at the tectonic mechanisms behind how these intriguing features are formed. JEO would provide the sub-surface sounding, while IVO (and JEO to an extent, but longitude coverage would be limited) could provide imaging of a variety of mountains and paterae.
5. Does Io have an internal magnetic field? This question may have been answered as a no by Galileo, but closer encounters at different latitudes with a magnetometer-equipped spacecraft would help put this issue to bed. Understanding Io's magnetic environment would help with our understanding of Io's deep interior.

Obviously, there are certainly more than just these five. These five also reveal my geology bias as there are certainly a lot of remaining questions regarding Io's interaction with Jupiter's magnetosphere and about Io's atmosphere.

How EJSM affects the Io Volcano Observer

With a mission now planned for the Jupiter system in the 2020s, how will the Io Volcano Observer proposal be affected? Would a dedicated Io mission even be necessary?

The Io Volcano Observer and the Jupiter Europa Orbiter would conduct complimentary science. Both spacecraft have high-resolution cameras capable to studying Io's surface in fine detail during flybys as well as monitoring Io's global volcanic activity from a distance. Both can conduct mass spectroscopy of Io's atmosphere and plumes as well as observe Io's thermal inertia. The Jupiter Europa Orbiter would be capable of acquiring observations not currently in IVO's baseline payload such as near-infrared spectroscopy, ground-penetrating radar, laser altimetry, and particle and plasma analysis. So seemingly, the Io Volcano Observer would not be necessary. Not so fast.

The Jupiter Europa Orbiter's instruments are designed to study Europa, with bandpasses of the various instruments and their functionality driven by that requirement. Studying the other bodies in the Jupiter system, while a level 1 science requirement, really is just gravy for the mission. JEO's unique instrumentation, such as the Ground-penetrating radar, can answer quite a few questions that IVO can't. However, the design of the payload for IVO has been defined to specifically answer questions at Io. For example, the camera on IVO would be capable of observing volcanic activity with multiple filters with less than 0.1 seconds between color frames. This allows fairly accurate measurement of the lava temperatures at Io's volcanoes. This can constrain the amount of partial melting in the mantle needed to support the eruption temperature observed. The band passes on the Thermal Mapper, rather than being selected to search for warm spots on an icy world, will be selected to explore different volcanic processes on Io of different ages as well as looking at the silicate composition of these flows.

Also, don't forget that IVO will perform at least seven Io flybys during its 1.5-year primary mission (starting in early 2021), three more than the encounters planned for JEO. In addition, IVO has enough margin in its radiation shield to support seven more encounters, which could be spaced out by as much one year apart to help study the long-term life time of IVO's power source, the two Advanced Sterling Radioisotope Generators (ASRGs). This extended mission could help fill the gap between IVO's primary mission which ends in late 2022 and JEO's arrival in late 2025. This provides the potential for spacecraft monitoring of Io covering almost eight years, similar to Galileo's time at Jupiter.

While the Jupiter Europa Orbiter will perform quite a bit of science at Io, since the instruments are not optimized for Io science, there is still a need for a dedicated mission like Io Volcano Observer. Potentially JEO could allow IVO to trim some costs by reducing some of the redundancy, like the magnetometer instrument. However, the priority for an Io mission may go down in comparision to other potential Discovery-class missions with the EJSM arrrive only a five years later than IVO.

Roundup of News Articles about EJSM

Quite a few news articles have been posted online about the selection of the Europa/Jupiter System Mission as the next Outer Planet Flagship Mission. Many of these report on a telecon between NASA officials and a few members of the press yesterday about this announcement. Perhaps the most interesting new news from this telecon is that the flagship mission is currently not fully funded (though budget projection in the last year have taken into account the flagship mission), though according to Space.com, "NASA is setting aside about $10 million to continue studying design challenges for its Jupiter Europa orbiter."

• Russia, Europe and NASA explore ocean depths of Jupiter’s Europa from the Russian website Pravda. Looks like the Russians are continuing to push their desire to send a lander to Europa.
• It's all systems go for Europa from the Los Angeles Times. The article focuses a bit on the local angle via the Jet Propulsion Laboratory.
• NASA Puts Money on Mission to One of Jupiter's Moons from the Washington Post
• Bold New Missions to Jupiter and Saturn Planned from Space.com
• Europa Selected As Target of Next Flagship Mission from Slashdot (yeah my first approved slashdot article)
• Europa wins next big planetary mission from Nature
  

What's next for the Europa Jupiter System Mission

The news of the Outer Planet Flagship downselection is beginning to reverberate across the internet and planetary science community. Jim Green, the directory of the Planetary Science Division at NASA, has posted a message to the Science Community on the OPF website. The Planetary Society has also issued a statement on this announcement. You can check that out on Emily Lakdawalla's blog. Also, check out the thread on at UMSF if you wish, though feel free to leave a comment here with your reaction to this news.

Now that the Europa Jupiter System Mission has been selected, what's next for a mission whose launch (nominally) doesn't take place for another 11 years?

Pre-Phase A
Starting today (or last year about this time, depending on how you look at it), EJSM enters Pre-Phase A. Spacecraft development is generally defined in different stages, or phases, of progress, running from Phase A through Phase F. During Pre-Phase A, mission planners will be looking to further refine the mission concept and working on risk mitigation. From now until January 2011, work will be performed on further defining the mission goals of the EJSM, though the Final Reports states that since so much has gone into defining the goals of a Europa mission already, these are not likely to change. Neither are the definitions of the types of instruments that will be needed, though further refining maybe needed in the run up to an instrument Announcement of Opportunity, to be released by NASA in December 2010. So, the majority of the planning work over the next two years will be performed on risk mitigation, particularly with respect to planetary protection and radiation-hardening. Planning done now could be used to save money in the future (particularly in Phase A) and help reduce the chance for cost over runs.

For the Jupiter Ganymede Orbiter, that spacecraft is now in the running for the European Space Agency's Cosmic Visions L-class mission. That's right, despite this downselection, the contest isn't over for JGO. Though JEO is safe, it was selected and it enters Pre-Phase A. The Jupiter Ganymede Orbiter will be squaring off against two astronomy missions: XEUS, an X-ray telescope that will search for black holes and examine the structure of clusters of galaxies, and LISA, a constellation of three spacecraft that will act as a gravitational wave observatory. As currently outlined by ESA, the three missions will be narrowed down to two in October and November of this year. These two missions will then be in a "competive definition phase" during 2010 and 2011, with the downselection to one mission taking place in November 2011. Even then, the decision to proceed with the selected mission "will depend on the financial situation of the programme." So the Jupiter Ganymede Orbiter has a long road ahead of it.

Phase A
During the next stage of development, Phase A, the instruments will be selected and reviewed. According to the final report, a NASA Instrument Announcement of Opportunity is planned in December 2010 with proposals due in March 2011 and payload selected in September 2011. Keep in mind that the instruments outlined in the various reports published for this concept study were model payloads, basically providing a rough idea of what the mission team is looking for out of a particular instrument. Further refinements during Pre-Phase A could obviously change what they are looking for. For example, the mission team may want different frequencies for the Ice-Penetrating Radar than what is outlined in the Final Report. Phase A ends once all the instruments have been selected, reviewed, and approved by NASA HQ.

Looking Forward
With the end of Phase A expected in October 2013, the moves on to the the other phases. During Phase B, which will run about 20 months from October 2013 through June 2015, more detailed designs will be developed for both the spacecraft and the various parts of the spacecraft with preliminary design reviews in late 2014 and early 2015. In Phase C, running for 30 months from June 2015 through December 2017, the various parts and instruments will go through one final review in late 2015 and early 2016 before actually being built. Software and avionics will be developed and integrated and the mission plan and trajectory will start to reach a final state. In Phase D, the various parts and instruments will actually be assembled into a working spacecraft in early 2018. This will be then be followed by rigorous testing to make sure all the spacecraft's parts are working the way they should be and that the spacecraft can handle launch and the environment of space. Finally JEO will be delivered to Kennedy Space Center in Florida in August 2019 and from there it will be launched on a Atlas V in March 2020.

So, now the real work begins (and that was just a very coarse summary above).

EDIT 02/19/2009 1:40am: Corrected the launch vehicle from Delta IV to an Atlas V. Sorry about that.