SETI Institute Weekly Colloquium - Upcoming Speakers
We are poised to take advantage of a remarkable confluence of technological advances and scientific opportunity. For the first time, very fast, wide bandwidth, high-gain, low noise near-infrared avalanche photo diode (APDs) detectors are available and reasonably priced. We are designing and constructing a new SETI instrument to search for direct evidence of interstellar communications via pulsed laser signals at near-infrared (900 - 1700 nm) wavelengths. The new instrument design builds upon our past optical SETI work, and is the first step toward a new, more versatile, and more sophisticated generation of very fast optical and near-infrared pulse search devices.
Dr. Wright will discuss the advantages of SETI searches at near-infared wavelengths. She will also present the instrument layout, including an overview of the opto-mechanical design, detector selection and characterization, signal processing, and integration procedure. Finally, Dr. Wright will describe our initial observational setup and search strategies for SETI targets and other astronomical studies.
It has been proposed that in Gale Crater, where the Curiosity rover landed in August 2012, lakes developed to various depths after the large central mound (informally referred to as Mt. Sharp) had evolved to a form close to its current topography. Using a combination of CTX and HiRISE imagery and CTX, HiRISE and HRSC topography, we have documented a sequence of rising and falling lake levels, thereby providing a possible relative timeline of the hydrologic events within Gale crater. Assuming that the entrance canyon deposits (the canyon which the Curiosity rover will ascend once it reaches Mt. Sharp) records a back-stepping sequence of fans and deltas, then a corresponding hydrologic sequence is suggested. After the formation of a gilbert-type delta exiting an 84-km long incised valley (Farah Vallis) that drains 270,000 km2 to the south of Gale, and a corresponding lake with an average depth of 700 meters, the inflow of water from Farah Vallis fell or ceased. The lake level dropped considerably, to an elevation at least below the entrance canyon deposits. At a later time, local precipitation drove gully erosion of the Gale rim, and amplified by renewed Farah Vallis runoff, caused a rising lake level that produced deltas on the western rim of Gale and the entrance canyon deposits on Mt. Sharp. This hydrologic system shut down sufficiently abruptly that the deltas did not cut down as the lake evaporated. The time gap between these two lake forming events, perhaps driven by different hydrologic systems, is not yet established. Fan deposition around Gale crater, including the Peace Vallis fan near the rover’s landing site, likely occurred after these large lakes disappeared. This has implications for understanding regional paleo-climates on Mars after the Noachian, as well as providing context for the geology and sedimentology along the Curiosity rover traverse.
Abstract: Since its launch in 2009, NASA's Kepler Mission has transformed our knowledge of exoplanetary system demographics. Kepler's primary mission goal-- to quantify the occurrence rate of habitable zone Earth-size planets around Sun-like stars-- has a clear connection to astrobiology. However, in addition to its planet-finding capabilities, the Kepler data may also be used to study other questions of astrobiological interest. In this talk, I will discuss my work on two such ongoing projects: the quantification of the stellar flare rate, which influences planetary habitability through its influence on atmospheric photochemistry and escape; and the detection of anomalous stellar variability as a form of signal-agnostic optical SETI. Both of these lines of research employ machine learning techniques, making them applicable to the current and future large datasets that now dominate the astronomical landscape.
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: 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.
Abstract: 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.