Effective January 1, 2011, LPI seminars will be held on Fridays.
LPI seminars are held from 3:30–4:30 p.m. in the Lecture Hall at USRA, 3600 Bay Area Boulevard, Houston, Texas. Refreshments are served at 4:30 p.m. For more information, please contact Georgiana Kramer (phone: 281-486-2141; e-mail: email@example.com) or Patricia Craig (phone: 281-486-2144; e-mail: firstname.lastname@example.org). A map of the Clear Lake area is available here. This schedule is subject to revision.
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Every significant wave of technology which sweeps society - the jet aircraft, the atomic age, the PC, the internet, is preceded by a long period of development which is largely invisible to all but a few technologists who often themselves cannot foresee where their creations might lead. Nearly 50 years into the space age, space remains a ponderously slow, expensive activity which is at most marginally relevant to the great majority of people. Whether space will remain a niche technology for science and warfighting, or if it will usher in a new era in human life, depends on our ability to create utility - to produce value for people - in space. To date this search for utility has produced much less than we like to admit.
Utility is only a recent mandate for space. I will examine the other directions people have pursued in space to date. I will then point out some of the low-utility (but high visibility) uses we have made of space, uses which do not create utility even equal to their cost and hence are not sustainable in the long term. I'll conclude with discussion of new technologies and applications which might deliver on the promise of utility and how microspacecraft are contributing to these attempts.
One of the premier areas of scientific return from Hubble Space Telescope observations of the solar system has been studies of the Galilean satellites of Jupiter. This talk will present highlights of those studies, which include discoveries of the molecular oxygen atmospheres of Europa and Ganymede, the discovery of auroral emissions at the poles of Ganymede, the quantitative characterization of Io's atmosphere, volcanic plumes and electrodynamic interaction with magnetospheric plasma, and the detections of ozone and sulfur dioxide in the surfaces of Europa, Ganymede and Callisto.
Zircons preserve the best record of U-Pb age and oxygen isotope composition of magmatic events. Compositions are preserved even through high grade metamorphism and hydrothermal alteration. A systematic study of magmatic zircons from all ages of rock shows more primitive oxygen isotope ratios (5-7.5) in the Archean, and has has led to the discovery of the oldest recognized piece of the Earth, a 4.404 Ga detrital zircon from the Jack Hills, Western Australia. The high oxygen isotope ratio of the core of this crystal (7.4), the presence of inclusions of SiO2, and the REE compositions suggest that it came from continental crust that was enriched in the heavy isotopes of oxygen by interaction of liquid water with the magma-protolith at the surface of the Earth. Thus low temperature conditions prevailed approximately 150 m.y after the formation of the Earth and 50-100 m.y. after the formation of the core and the Moon. These conclusions contrast with accepted ideas about the early hot Earth
Locating sites on Mars that have high potential to capture and preserve biomarkers is a major focus of the Mars exploration program. The current Mars exploration strategy calls first for orbited infrared spectral instruments to identify locations with key minerals to determine the most favorable landing sites to explore for a Martian fossil record, and for sample return. This places the productivity of infrared remote sensing in the critical path of this exploration strategy. However, the current infrared data set, being collected by the 1996 Mars Global Surveyor Thermal Emission Spectrometer (TES), has been less productive than hoped in identifying key mineral deposits such as chert and carbonates. Terrestrial remote sensing measurements can provide information on the conditions that must be present for TES to identify the desired minerals in the field environment. I will discuss what the terrestrial measurements indicate about the ability of the current and planned instruments to identify the desired minerals, and the implications for implementing the current Mars exploration strategy.
The Beta-Atla-Themis region of Venus contains the highest concentration of coronae and other volcanic features observed on Venus, along with a number of rift structures. Gravity models can constrain the relative importance of crustal and mantle structures in supporting these geologic features. The crustal thickness map provides an integrated history of volcanism in this region. The mantle density anomaly map indicates areas that are related to hot upwellings or cold downwellings. These results indicate that a number of large coronae and rifts in this region occur over regions of hot mantle, indicating that these structures are probably still geologically active. Other coronae that were once volcanically active now exist over mantle of average temperature, indicating a minimum of 100 million years of cooling since these features formed. Contrary to some past work, there is little evidence for cold downwellings on the margins of large coronae in this region.
Recent advances in encounter theory have allowed the very early identification and analysis of asteroid-Earth collision possibilities, even those with very low impact probabilities. The problem hinges on two issues. First, it is necessary to actually detect any impacting trajectories that are compatible with the available astrometric observation set. Linear methods are reliable only for detecting impacting trajectories at uncomfortably high probabilities of impact (~0.1%). Thus nonlinear search methods are necessary to ensure the earliest detection of a threatening encounter, which is the key element of any hazard mitigation strategy. After a potential collision is detected it becomes necessary to compute the probability of impact in order to assess the risk posed by the collision in question.
The theoretical tools needed to automatically and robustly monitor the ever-changing asteroid catalog for threats to the Earth are now available and such a system is presently under development at JPL.
From an analysis of over 8000 MOC images acquired from MGS, a unique terrain that is interpreted to be a uniform mantle undergoing dissection has been identified and mapped. Based on the implied physical properties, global distribution limited to the latitude bands 30°-60° N and S, and Earth analogs, this terrain delineates regions of a loess mantle recently cemented with ice. The formation of this ice-rich mantle on orbital time scales (100,000 yrs) has important implications for volatile storage and transport, near surface processes, and the evolution of terrains on Mars. The identification of this terrain, its inferred properties, the importance of its distribution, and implications for Mars will be discussed.
Dr Ng is leader of the team responsible for the sampling drillbits onboard the ESA Beagle 2 Mars 2003 Lander, and other micro-sampling research projects into planetary subsoil, surface, and zero gravity samplings. There are two types of sampling tools on the Beagle 2: (1) ROCK CORER & GRINDER and (2) MOLE SUBSOIL SAMPLER. The ROCK CORER is the size of a cigarette box; weighs 420gm; able to core/grind rock powder and deliver samples into GCMS for in situ examination. The RIND GRINDER is fitted on the front of the rock corer; able to grind 3mm thickness/30mm square of rind surface for APX examination; and able to change surface area. The MOLE SAMPLER is the size of a pencil sharpener; attached to the tip of the Russian's mole; able to retrieve soil samples and deliver them into GCMS for in situ examination, and self cleanse its jaws after each operation. My team is going to perform the first tele robotic planetary rock coring on Mars. All the MEEs will be displayed for hands-on inspection.
Geomorphic evidence for water on Mars implies significant volcanic outgassing of water, a conclusion which contrasts sharply with the low magmatic mater contents inferred for igneous martian meteorites. Pyroxene cores in Shergotty crystallized at depth and thus offer the possibility of recording water prior to loss on ascent or eruption. Zoning patterns of soluble trace elements in pyroxenes support loss of water prior to formation of pyroxene rims, and the results of new hydrous and anhydrous crystallization experiments suggest pre-eruptive water contents of ~1.8 wt. %. This water content is also similar to that estimated from the occurrence of amphibole in Shergotty melt inclusions. These results appear to reconcile geologic and petrologic constraints on the planet's outgassing history. Fractionation paths for wet Shergotty magma also can produce andesitic magma having similar composition to that found on Mars, and the relative efficiency of this process may explain the hemispheric proportions of andesite found by Mars Global Surveyor.
A geochemical introduction to the composition, origin, and evolution of planetary atmospheres.
On the basis of 16sRNA gene sequencing analysis, as well as energetic considerations, the general consensus of opinion is that life probably evolved in the environment of hydrothermal vents characterised by steep chemical and temperature gradients. This would imply that the last universal common ancestor (LUCA) was a chemolithotrophic organism, obtaining both its energy and its carbon from inorganic sources, such as inorganic chemicals and CO2, respectively. However, by the time we have any record of early life (3.75 b.y.?? or 3.45 b.y.) it seems to have already diversified into a variety of habitats: or had it? We find extensive microbial mat formation in shallow water environments, on top of lava flows, and in littoral reaches. But even in these shallow water/littoral regions, there is evidence for pervasive hydrothermal seepage. Were these organisms, therefore, still hyperthermophiles? At the same time, the association of extensive mat formation (tabular stromatolites) with shallow water/littoral habitats provokes the question as to whether the Early Archaean organisms of the Barberton and Pilbara greenstone belts were also photosynthetic. If so, were they anoxygenic or oxygenic? The fact that the actual locations of the domal stromatolites are restricted to the mouths and surfaces of hydrothermal vents clearly links chemistry (nutrients), heat, and photosynthesis. This might support a hypothesis of chemotaxis as a precursor for photosynthesis. The overall evidence for anoxygenic conditions at this period points to the photosynthesis (if it is such) being anoxygenic, rather than oxygenic.
Given the zircon evidence for oceans by 4.4 b.y., life could have originated on Earth sometime before that date and flourished despite a spike in bolide impacts between 4.1-3.85 b.y. Although it was widespread in shallow water environments on top of protocontinents by 3.45 b.y., it was still thermophilic, chemotrophic and maybe photosynthetic (anoxygenic). What does this imply for life elsewhere in our solar system?
- A cold start to life is unlikely (i.e. no origin of life on asteroids);
- Are protocontinents necessary? û Probably not. Any hydrothermal system in (shallow?) water would do, e.g. Noachian impact crater lakes on Mars
- Life could have originated on early Europa
- We would still be dealing with some form of prokaryotic organisms.
Bedded evaporites on Earth are mainly deposited in basins on continental platforms. These basins form and are episodically flooded by seawater in response to plate tectonics. Such an environment has probably never existed on Mars. Still, if early Mars did possess a liquid hydrosphere, with the water largely provided by volcanism, then its hydrosphere, like Earth's, must have been saline (i.e., a brine). Later, as Mars lost water from its atmosphere and began to freeze down, initially dilute brines would have become greatly concentrated by evaporation and fractional crystallization involving surface ice. This would have caused their salinity to increase in the direction of eutectic (minimum-melting) compositions (e.g., Brass, 1980), with freezing points as low as 221 K even for simple ternary brines (NaCl-CaCl2-H2O). The brines would have become viscous liquids, denser than ice or pure water, that would have sunk into and reacted with the fractured regolith, displacing less saline waters already there. This is where the evaporites went, and where they probably still are (along with any later-crystallized salts).
Unmanned lunar exploration programs were conceived in the late 1950s. Although the Ranger and Surveyor programs were started prior to the announcement of Apollo, they soon succumbed to the need to support Apollo. They were reduced in scope, both in types of experiments and number of flights to save money, and reconfigured to provide the early information required to give confidence for the designs of Apollo hardware on the drawing boards. Lunar Orbiter, although proposed at a later date, also was modified and became primarily an Apollo support program. However, the photographic coverage was expanded on the last two missions to include potential post-Apollo landing sites and the final mission was designed to cover as much as possible of the still poorly photographed parts of the Moon, including the backside. Soviet unmanned missions during this timeframe added information and eventually a small amount of sample was returned. The more recent Clementine and Lunar Prospector spacecraft have added new information, however, they were not launched as part of an ongoing, comprehensive plan of lunar exploration.
Apollo, at its inception, had very modest scientific objectives. Collect a few samples, perhaps take some photographs and deploy some experiments (with emphasis on "perhaps"), and complete President Kennedy's mandate without losing any astronauts in a risky venture. By 1964 this view had changed and, little by little, our ability to conduct exploration greatly expanded culminating with the final three "J" missions.
Mars exploration has had a much different evolution. Beginning with the Mariner and Viking missions, unmanned exploration has taken a much more careful and complete evolutionary approach than the unmanned missions that led up to the first Apollo landings. In addition to those already completed or underway, a continuing suite of missions had been proposed by NASA and only time will tell if they will be successfully carried out. Unmanned Mars missions that include small rovers and sample return may resolve the major reason to conduct costly Mars exploration, the unequivocal discovery of life forms. If found, one might ask, is it necessary to continue to explore the red planet? If life forms are not found in returned Mars samples, or for whatever reason samples cannot be returned, then the need, in the minds of some, to continue Mars exploration will still exist.
As we look to the future of Mars exploration, what may be the drivers? A political imperative such as shaped lunar exploration will probably not be established. Human exploration, setting foot on Mars surface just to understand its history and evolution (comparative planetology), will be a hard sell under any circumstances because of cost. Colonization is still science fiction. But what if the search for life becomes a compelling reason and the case is made that only humans on the ground can assure that an answer will be found? Should we prepare for such an eventuality, and if so, what further groundwork needs to be done and how can we apply the lessons from Apollo to help assure success?
Using the Moon to occult the Sun, the Clementine spacecraft used its navigation cameras to map the inner zodiacal light at optical wavelengths over elongations of 3-30 degrees from the Sun. The zodiacal light is sunlight that is reflected by interplanetary dust, so these images provide information on the spatial distribution of this dust over heliocentric distances of about 10 solar radii to the orbit of Venus. A simple model is applied to the data where it is assumed that the zodiacal light is due to three dust populations having distinct inclination distributions. These populations are: low-inclination dust from asteroids and Jupiter-family comets, higher-inclination dust from Halley-type comets, and an isotropic cloud of dust from Oort Cloud comets and interstellar sources. This modeling then yields estimates of the relative contributions to the interplanetary dust cross-section from asteroids, comets, and interstellar dust sources, as measured in the ecliptic as well as at higher latitudes. These results for the inner solar system are extrapolated out to the asteroid belt and yield an upper limit on the mass of the light-reflecting asteroidal dust that is equivalent to a 10 km asteroid. A similar extrapolation of the isotropic dust cloud out to Oort Cloud distances yields a mass equivalent to a 30 km comet (although this mass estimate is quite uncertain). Since the flow of interstellar gas and dust ultimately strips these wide-ranging Oort Cloud dust grains from the solar system, these finding suggests that the Sun and perhaps other stars may have vast but tenuous stellar dust tails.
Liquid water is a metastable substance that eventually evaporates or freezes in any unsaturated atmosphere. It is sufficiently stable to be of more than passing significance on Earth. And neither does physics preclude the transient presence of water on Mars, though it is a forbiddingly cold and dry place. Therefore the well-known Mars Global Surveyor images of apparently recent gullies, with morphological characteristics consistent with formation by liquid water, were justifiable cause for excitement. Moreover, the gullies preferentially appear on cold, high-latitude, pole-facing slopes that are known to harbor frozen volatiles. This talk revisits the simple explanation that the gullies are formed by seasonal meltwater, and concludes that it is plausible. It will be shown that the stability and lifecycle of water on Mars would be similar to water in comparably cold places on Earth. Seasonally wet soil may have been a feature of Mars throughout its history, possibly providing an ecological niche for the survival of hypothetical ancient martian organisms.
The oxygen fugacity of the martian basalts QUE 94201, Dar al Gani 476, EET 79001 (lithologies A and B), Zagami, Shergotty and Los Angeles have been determined by analysis of Fe-Ti oxides and olivine-pyroxene-spinel. They range from ~3 log units below the Quartz-Fayalite-Magnetite (QFM) buffer to QFM - 1. Oxygen fugacity in martian basalts correlates with 87Sr/86Sr, 143Nd/144Nd and La/Yb ratio, indicating that the mantle source of the basalts is reduced and that assimilation of crust-like material controls the oxygen fugacity. This allows constraints to be placed on the oxidation state of the martian mantle, and on the nature of assimilated crustal material. The assimilated material may be (1) products of early and extensive hydrothermal alteration of the martian crust, or (2) amphibole- or phlogopite-bearing basaltic rock within the crust. In either case, water may play a significant role in the oxidation of basaltic magmas on Mars, although it may be secondary to assimilation of ferric iron-rich material.
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