Geology Before Pluto: Pre-Encounter Considerations

Pluto, its large satellite Charon, and its four known satellites represent the first trans-Neptunian Kuiper Belt objects populating the outer-most solar system beyond the gas giant planets to be studied in detail from a spacecraft (New Horizons). A complete picture of the solar nebula, and solar system formation cannot be confidently formulated until representatives of this group of bodies at the edge of solar space have been examined. The Pluto system is composed of unique lunar- and intermediate-sized objects that can tell us much about how objects with volatile icy compositions evolve. Modeling of the interior suggests that geologic activity may have been to some degree, and observations of frost on the surface could imply the need for a geologic reservoir for the replenishment of these phases. However, the putative indicators of Pluto's geologic history are inconclusive and unspecific. Detailed examination of Pluto's geologic record is the only plausible means of bridging the gap between theory and observations. In this talk I will examine the potential importance of these tentative indications of geologic activity and how specific spacecraft observations have been designed and used to constrain the Pluto system's geologic history. The cameras of New Horizons will provide robust data sets that should be immanently amenable to geological analysis of the Pluto System's landscapes. In this talk, we begin with a brief discussion of the planned observations by New Horizons' cameras that will bear most directly on geological interpretability. Then I will broadly review major geological processes that could potentially operate of the surfaces of Pluto and its moons. I will first survey exogenic processes (i.e., those for which energy for surface modification is supplied externally to the planetary surface): impact cratering, sedimentary processes (including volatile migration) and the work of wind. I will conclude with an assessment of prospects for endogenic activity in the form of tectonics and cryo-volcanism

Does Titan's Landscape Betray the Late Acquisitions of Its Current Atmosphere?

Titan may have acquired its massive atmosphere relatively recently in solar system history. The sudden appearance of a thick atmosphere may have changed Titan's global topography. This change in global topography may be expressed in the latitudinal distribution of landform types across its surface

Flow-induced dilation of skeletal muscle feed arteries: relevance to exercise hyperemia

During exercise, an increase in blood flow to working skeletal muscle is accomplished by dilation of arteries and arterioles supplying the muscle. Arterioles, located within contracting muscle, are exposed to dilatory metabolites released by the muscle; however, the mechanism by which feed arteries, located external to the muscle, dilate is still unknown. One potential mechanism for feed artery dilation is flow-induced dilation, occurring when arteries dilate in response to increased vascular wall shear stress. Shear stress is the frictional force between blood and the arterial wall, which increases when blood flow velocity increases. Data from previous in vitro experiments (8) indicate that flow-induced dilation in rat soleus feed arteries occurs at blood flow levels that are far less than normal resting blood flow in conscious rats. This data led to the conclusion that flow-induced dilation was not a plausible mechanism to explain the increase in blood flow during exercise. Furthermore, the soleus muscle is primarily composed of slow-oxidative fibers and used in maintaining posture; thus, it receives a substantial amount of blood flow at rest. We sought to test whether flow-induced dilation could contribute to exercise hyperemia in rat extensor digitorum longus muscle, primarily composed of fast-glycolytic fibers, and rat gastrocnemius, a muscle of mixed fiber type (4). The differences in fiber type of each muscle may be a factor in how the feed arteries dilate during exercise. The purpose of this study was to determine if flow-induced dilation potentially contributes to exercise hyperemia in rat extensor digitorum longus and gastrocnemius muscle feed arteries, EDLFA and GFA, respectively. In this study, blood flow was induced through the arteries and corresponding flow measurements (µl/min) were collected. The flow values were used to calculate intraluminal wall shear stress in the arteries and then compared to calculated in vivo shear stress values from previously published studies (1,2,3,7,10,11,12,13,14,15). We hypothesized that flow-induced dilation in GFA and EDLFA occurs at shear stress values lower than the shear stress normally present in non-exercising rats. This would preclude flow-induced dilation from causing the dilation of feed arteries to gastrocnemius and EDL muscles in exercise

Volcanic Constructs on Ganymede and Enceladus: Topographic Evidence from Stereo Images and Photoclinometry

The morphology of volcanic features on Ganymede differs significantly from that on the terrestrial planets. Few if any major volcanic landforms, such as thick flows or shield volcanoes, have been identified to date. Using new stereo Voyager images, we have searched Ganymede for relief-generating volcanic constructs. We observed seven major types of volcanic structures, including several not previously recognized. The oldest are broad flat-topped domes partially filling many older craters in dark terrain. Similar domes occur on Enceladus. Together with smooth dark deposits, these domes indicate that the volcanic history of the dark terrain is complex. Bright terrain covers vast areas, although the style of emplacement remains unclear. Smooth bright materials embay and flood older terrains, and may have been emplaced as low- viscosity fluids. Associated with smooth bright material are a number of scalloped-shaped, semi- enclosed scarps that cut into preexisting terrain. In planform these structures resemble terrestrial calderas. The youngest volcanic materials identified are a series of small flows that may have flooded the floor of the multiring impact structure Gilgamesh, forming a broad dome, The identification of volcanic constructs up to I km thick is the first evidence for extrusion of moderate-to-high viscosity material on Ganymede. Viscosity and yield strength estimates for these materials span several orders of magnitude, indicating that volcanic materials on Ganymede have a range of compositions and/or were extruded under a wide range of conditions and/or eruptive styles

The Thai Way of Counterinsurgency

The goal of this study is to ascertain how Thailand wages counterinsurgency (COIN). Thailand has waged two successful COINs in the past and is currently waging a third on its southern border. The lessons learned from Thailand’s COIN campaigns could result in modern irregular warfare techniques valuable not only to Thailand and neighboring countries with similar security problems, but also to countries like the United States and the United Kingdom that are currently reshaping their irregular warfare doctrines in response to the situations in Afghanistan and Iraq. The first set of COIN lessons comes from Thailand’s successful 1965-85 communist COIN. The second set comes from Bangkok’s understudied 1980s-90s COIN against southern separatists. The third set comes from Thailand’s current war against ethnic Malay separatists and radical Islamic insurgents attempting to secede and form a separate state called “Patani Raya,” among other names. Counterinsurgency is a difficult type of warfare for four reasons: (1) it can take years to succeed; (2) the battle space is poorly defined; (3) insurgents are not easily identifiable; and (4) war typically takes place among a civilian population that the guerrillas depend on for auxiliary support. Successful COINs include not only precise force application operations based on quality intelligence, but also lasting social and economic programs, political empowerment of the disenfranchised, and government acceptance of previously ignored cultural realities. Background: In 1965, communist insurgents, backed by the People’s Republic of China and the Democratic Republic of Vietnam (North Vietnam), began waging an insurgency against Thailand in order to overthrow its government and install a Marxist regime. The Thai government struggled, both politically and militarily, to contain the movement for years, but eventually, it prevailed. Its success was based on a combination of effective strategy and coordination, plus well-designed and run security, political, and economic programs, the latter nowadays called the “three pillars of COIN,” a phrase developed by David Kilcullen, a modern COIN theorist and practitioner. One of Bangkok’s most successful initiatives was the CPM program (civil-military-police), which used a linked chain of local forces, police, and the military to not only provide security for villages, but also economic aid and administrative training to rural peoples. State political programs that undercut communist political programs backed by masterful diplomacy and a constant barrage of rural works helped erode the communist position. The 1980s-90s COIN against southern separatists followed similar lines. The far South’s four border provinces, comprised of 80 percent ethnic Malay Muslims, had been in revolt on and off for decades since Bangkok annexed the area in 1902. Bangkok had waged haphazard COIN campaigns against rebel groups there for decades with mixed results. But after the successful communist COIN was up and running in 1980, Bangkok decided to apply similar ways and means to tackle the southern issue. The government divided its COIN operations into two components: a security component run by a task force called CPM-43, and a political-economic component run by the Southern Border Provinces Administrative Center, or SB-PAC. SB-PAC also had a Special Branch investigative capacity. Combined, the 80s-90s southern COIN strategy relied on extensive military intelligence networks to curb violence, civilian administrators to execute local political reforms, and local politicians to apply traditional Malay and Muslim problem solving techniques to keep the peace. These programs worked well against the multitude of southern insurgent groups that conducted sporadic attacks against government and civilian targets while also running organized criminal syndicates. By the end of the 1990s, with a dose of Thailand’s famed diplomacy and help from Malaysia’s Special Branch, Bangkok defeated the southern separatists. In January 2004, however, a new separatist movement in southern Thailand emerged – one based on ethnic Malay separatism and radical Islam. It is a well-coordinated movement with effective operational expertise that attacks at a higher tempo than past southern rebel groups. It moreover strikes civilian targets on a regular basis, thereby making it a terrorist group. Overall, it dwarfs past southern movements regarding motivation and scale of violence. Thai officials think the Barisan Revolusi Nasional Coordinate, or BRN-C, leads the current rebellion, but there are several other groups that claim to also lead the fight. Members of the insurgency are nearly exclusively ethnic Malays and Muslims. The movement demonstrates radical Islamic tendencies thought its propaganda, indoctrination, recruitment, and deeds. It is a takfiri group that kills other Muslims who do not share its religious beliefs, so it wrote in its spiritual rebel guidebook, Fight for the Liberation of Patani. BRN-C seeks to separate the four southernmost provinces of Pattani, Yala, Narathiwat, and Songkhla from Thailand in order to establish an Islamic republic. The separatists base their revolt on perceived military, economic, cultural, and religious subjugation going back to the early 1900s. And they have a point. The central government has, at different times in the past, indeed treated southerners with tremendous disdain and sometimes violence – especially those considered insurgents. But Bangkok has also instituted scores of economic and social aid programs in the south – mosque building, college scholarships, and medical aid, for example – so it has not been a continual anti-Muslim “blood fest” as government detractors have painted it. Still the maltreatment, certainly many times less than yesteryear, has provided today’s insurgents with ideological fodder for a steady stream of recruits and supporters. Combined with radical Islam, it has bonded the insurgents to a significant degree. Statistically, in the 2005-07-time frame, insurgents assassinated 1.09 people a day, detonated 18.8 bombs a month, and staged 12.8 arson attacks a month. In 2005, they conducted 43 raids and 45 ambushes. The militants target security forces, government civilians, and the local population. They have killed fellow Muslims and beheaded numerous Buddhist villagers. The insurgents’ actions have crippled the South’s education system, justice system, and commerce, and also have maligned Buddhist-Muslim relations. Overall, the separatists pose a direct threat to Thailand’s south and an indirect threat to the rest of the country. Moreover, their radical Islamic overtones have potential regional and global terrorist implications. The Thai Government spent much of 2004 attempting to ascertain whether the high level of violence was, in fact, an insurgency. To begin with, the government, led by PM Thaksin Shinawatra, was puzzled by the fact that the separatists had not published a manifesto or approached Bangkok with a list of demands. By mid-2004, however, the insurgents had staged a failed, region-wide revolt, and their prolific leaflet and Internet propaganda campaign clearly demonstrated that a rebel movement was afoot. By fall 2005, the separatists had made political demands via the press, all of which centered on secession. By 2006, a coup against PM Thaksin succeeded and the military government that replaced him instituted a new COIN strategy for the south that by 2008 had reduced violence by about 40 percent. Some of the tenets of this new strategy were based on Thailand’s past successful COIN strategies. Whether or not the government has concocted a winning strategy for the future, however, remains to be seen. This paper analyses these COIN campaigns through the COIN Pantheon, a conceptual model the author developed as an analytical tool. It is based on David Kilcullen’s three pillars of COIN. The COIN Pantheon has as its base the concept of strategy, and then as the next edifice, coordination. Three pillars of security, politics, and economics rise from these to push against the insurgent edifice. The roof is the at-risk population. By researching the specifics of all these issues for the three COINs discussed here, the Thai way of COIN emerges. Then, by measuring these results against the tenets of COIN theorists David Galula, Sir Robert Thompson, and Kilcullen, the Thai Way of COIN is more clearly illuminated

The Pinnacles of Callisto

Many regions of Callisto feature an unusual landscape consisting of rolling dark plains with interspersed bright knobs (pinnacles) and ridges. In earlier work we interpreted the dark plains as dusty, mass-wasted residue from sublimation from volatile-rich bedrock and the bright knobs (often crater rims) as water ice accumulations at locations sheltered from thermal reradiation from the dusty residue. We simulated evolution of Callisto's craters as a combination of bedrock volatile sublimation, mass wasting of the dark, non-coherent residue, and redeposition of ice, and concluded that the ice pinnacles and ridges might be underlain by tens to hundreds of meters of ice. Here we report the initial work of a new study of pinnacles addressing additional questions: 1) Is there an evolutionary sequence starting, e.g., from a cratered initial surface through growth and formation of a dust mantle and pinnacles, to eventual loss of ice to sublimation resulting in just a dark, dusty surface? 2) What determines the areal density and spatial scale of pinnacles - volatile content of bedrock, crater density, surface age, broad-scale topographic setting? 3) Are pinnacles still forming? Several observations address these questions. In a few places scattered high-albedo blocks approx. 25-60 m in diameter occur in the vicinity of large icy pinnacles. We interpret these blocks to be remnants from the collapse of tall pinnacles that were undermined by mass wasting. Some high-relief icy knobs have developed a skeletonized planform due to mass wasting by avalanching, or perhaps to seeding of new sites of ice deposition on mass-wasted ice blocks. Some areas nearly lack fresh craters with well-defined ejecta and ice-free rims. This may imply rapid transformation of fresh craters by sublimation, mass wasting, and ice reprecipitation. In other areas small sharp-rimmed craters occur which lack ice pinnacles, but the craters nonetheless lack visible ejecta sheets. Our preliminary interpretation is that mass wasting is very efficient on Callisto, or alternatively the dust cover is very thick and lacks competent coarse materials

Fresh shallow valleys in the Martian midlatitudes as features formed by meltwater flow beneath ice

Significant numbers of valleys have been identified in the Martian midlatitudes (30–60°N/S), spatially associated with extant or recent ice accumulations. Many of these valleys date to the Amazonian, but their formation during these cold, dry epochs is problematic. In this study, we look in detail at the form, distribution, and quantitative geomorphology of two suites of these valleys and their associated landforms in order to better constrain the processes of their formation. Since the valleys themselves are so young and thus well preserved, uniquely, we can constrain valley widths and courses and link these to the topography from the Mars Orbiter Laser Altimeter and High-Resolution Stereo Camera data. We show that the valleys are both qualitatively and quantitatively very similar, despite their being >5000 km apart in different hemispheres and around 7 km apart in elevation. Buffered crater counting indicates that the ages of these networks are statistically identical, probably forming during the Late Amazonian, ~100 Ma. In both localities, at least tens of valleys cross local drainage divides, apparently flowing uphill. We interpret these uphill reaches to be characteristic of flow occurring beneath a now absent, relatively thin (order 101–102 m), regionally extensive ice cover. Ridges and mounds occasionally found at the foot of these valley systems are analogous to eskers and aufeis-like refreezing features. On the basis of their interaction with these aufeis-like mounds, we suggest that this suite of landforms may have formed in a single, short episode (perhaps order of days), probably forced by global climate change

Laboratory Simulations of Mars Evaporite Geochemistry

Evaporite-rich sedimentary deposits on Mars were formed under chemical conditions quite different from those on Earth. Their unique chemistries record the chemical and aqueous conditions under which they were formed and possibly subsequent conditions to which they were subjected. We have produced evaporite salt mineral suites in the laboratory under two simulated Martian atmospheres: (1) present-day and (2) a model of an ancient Matian atmosphere rich in volcanic gases. The composition of these synthetic Mars evaporites depends on the atmospheres under which they were desiccated as well as the chemistries of their precursor brines. In this report, we describe a Mars analog evaporite laboratory apparatus and the experimental methods we used to produce and analyze the evaporite mineral suites

Equivariant volumes of non-compact quotients and instanton counting

Motivated by Nekrasov's instanton counting, we discuss a method for calculating equivariant volumes of non-compact quotients in symplectic and hyper-K\"ahler geometry by means of the Jeffrey-Kirwan residue-formula of non-abelian localization. In order to overcome the non-compactness, we use varying symplectic cuts to reduce the problem to a compact setting, and study what happens in the limit that recovers the original problem. We implement this method for the ADHM construction of the moduli spaces of framed Yang-Mills instantons on $\R^{4}$ and rederive the formulas for the equivariant volumes obtained earlier by Nekrasov-Shadchin, expressing these volumes as iterated residues of a single rational function.Comment: 34 pages, 2 figures; minor typos corrected, to appear in Comm. Math. Phy