SETI Institute Weekly Colloquium - Upcoming Speakers
Abstract: Current theories suggest that portions of interstellar compounds should eventually be incorporated into the comets, "asteroids" and planets of new planetary systems. Astronomical observations point to processes such as the formation of comet and asteroid belts, familiar to our solar system, as likely occurring in many star systems. As with comets and asteroids, the formation of organic compounds around new-formed stars might be a common process. The only laboratory items available for the study of a wide range of primordial organic-chemical processes are carbonaceous meteorites.
Among the most interesting features (and relevant to origin of life studies) of carbonaceous meteorites are the enantiomer excesses possessed by some of their organic compounds. While the majority of indigenous meteoritic compounds are racemic, i.e., their D/L enantiomer ratios are 50:50, some of the more unusual amino acids contain slightly more of one enantiomer - usually the L. In addition, initial analyses of some meteoritic sugar derivatives (sugar acids) revealed significant enantiomer excesses of the D enantiomers.
A question of relevance from such studies is: did extraterrestrial sources aid in the beginning of life’s homochirality? This presentation will include the results of recent analyses of enantiomer ratios of meteoritic compounds as well attempts at laboratory re-creation of such excesses.
If the forces that acted on organic compounds (and/or their precursors) in the early Solar System are common, then specific laboratory experiments may indicate whether enantiomer excesses in organic compounds are available for the origin of life in a multitude of planetary systems.
Abstract: The debate about whether or not Mars ever had life upon it centers on the issue of water.
Was there water on Mars? If so, where has it gone? One of the explanations for the water loss focuses on the idea that the solar wind is removing the water by acceleration ionospheric ions and removing them from Mars.
The problem is complicated by a variety of features: the presence of crustal magnetic fields on the surface of Mars, the photo-chemistry taking place in Mars' atmosphere/ionosphere, and the solar activity (EUV flux and solar wind behavior), and finally the small size of Mars. These features make for a very non-linear interaction which in many regions has little to do with fluid dynamics but rather plasma kinetics.
In this talk a discussion of these issues as well as results of kinetic plasma simulations with data comparisons will be presented. Dr. Brecht will also discuss how the results from the ongoing MAVEN mission at Mars can be used to test the presented plasma simulation predictions.
Abstract: Rosetta is the third cornerstone mission of the European Space Agency's (ESA) Horizon 2000 Programme. It's goals are to examine some of the original material of the solar system with a comprehensive evaluation of the minearologic, isotopic, and organic constituents of a comet; understand how the body works as a machine to absorb and re-radiate energy from the sun; and understand more about the origins of the solar system.
In this talk, I'll explain the science background of some of the mysteries of comets including pros and cons about why we think comets might have brought Earth's water, concepts regarding missing nitrogen in the outer solar system, and material the comet is made of (CAIs & IDPs). The talk will include early images of the comet's activity. I'll set the stage for the landing and walk through the 60 hours of time spent on the comet's surface. Finally I'll present an overview of initial findings.
Abstract: The Rosetta Lander, Philae, landed on 67P/Churyumov Gerasimenko on 12 November 2014. Before this could happen, a landing site had to be selected within just 2 months, based on data from the Rosetta Orbiter instruments and analyses on flight dynamics and illumination profiles. Philae was programmed to perform a First Scientific Sequence, immediately following touch down, and then enter its long term science mode.
The paper will report on the actual landing and the very first results. The landing was successful, though the operational sequences had to be modified ad hoc: Philae did not anchor upon first touchdown at 15:34:06 UTC but rebounded at least once, finally settling - fully operating all the while - at a place not ideal for long-term science. A wealth of science data has been received.
Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI.
Abstract: 3-D models can help explore the possible roles of rotation, atmosphere and ocean dynamical transports, cloud feedbacks and sea ice-albedo feedbacks in determining the habitability of a range of planetary environments. Using recent modifications to the Goddard Institute for Space Studies (GISS) IPCC AR5 General Circulation Model (GCM) we have explored the Inner Edge of the habitable zone (HZ) of our Solar System. We find that while Venus is currently outside the HZ, it may have been close to or within it early in Solar System history when the solar luminosity was lower and an ocean may have been present. The GISS GCM maintains habitable equilibrium surface temperatures for a solar constant 40% stronger than present day Earth (comparable to the Faint Young Sun at Venus' orbit) even if Venus rotated as rapidly as Earth early in its history. Stratospheric water vapor concentration is an order of magnitude smaller than the classical water loss limit for this simulation. We have also explored the parameter space in models with slower rotation rates. Our results are based on an atmosphere coupled to a 100m mixed layer ocean with no ocean heat transport. We are currently running the same experiments with with a fully coupled dynamic ocean. Negative cloud feedbacks due to increasing high, thick clouds in the tropics as the planet warms appear to be the stabilizing mechanism, along with maintenance of subsaturated water vapor by the general circulation.
The habitable zone (HZ) is the region around a star in which liquid water could exist on a planetary surface. Although 1-D models have been traditionally employed in HZ studies, recent investigations using 3-D models incorporate more realistic physics and self-consistently calculate both the effects of clouds and relative humidity. However, both parameters remain poorly understood, especially as applied to planetary atmospheres near the inner edge of the HZ. Thus, 1-D models remain indispensable for recognizing major trends and patterns that can then be analyzed more fully with more sophisticated models. I will present an updated 1-D climate model, coupled with results from other 1-D and 3-D studies, to assess the sensitivity of our Solar System’s inner edge to changes in surface relative humidity and clouds. This novel relative humidity parameterization self-consistently calculates surface relative humidity and assumes tropospheric relative humidity gradually increases with temperature. These results show that treating relative humidity more realistically moderately increases the width of the habitable zone. Lastly, I discuss certain caveats regarding the effects of clouds on the inner edge boundaries.
Hydrothermal fields on the prebiotic Earth are candidate environments for biogenesis. We propose a model in which molecular systems driven by cycles of hydration and dehydration in such sites undergo chemical evolution and selection in a dehydrated surface phase followed by encapsulation and combinatorial selection in a hydrated phase. This model is partly supported by recent science, and lies partly in the realm of speculation including a hypothesized pathway for the parallel evolution of the functional machinery of life. Complex models like this present challenges for science in the 21st century and we will describe a new technology to enable the simulation of such models.