Date: Monday 03-Feb-2020
Speaker: Christian Eistrup (UVA)
Title: From Protoplanetary Disk to Exoplanet Atmospheres and Comets - The Chemical Link
Exoplanets are ubiquitous, and exoplanetary science is now pushing to constrain the atmospheric compositions of exoplanets. This quest will be further aided by the next generation of facilities, such as the JWST and ground-based ELTs. Linking the observed composition of exoplanet atmospheres to where and how they formed in their natal protoplanetary disks often involves comparing the observed exoplanetary atmospheric carbon-to-oxygen (C/O) ratio to a model of a disk midplane with a fixed chemical composition. In this scenario, chemical evolution in the midplane prior to and during the planet formation era is not considered. The C/O ratios of gas and ice in the disk midplane are simply defined by icelines of volatile molecules such as water and CO in the midplane. However, kinetic chemical evolution during the lifetime of the gaseous disk can change the relative abundances of volatile molecules, thus altering the C/O ratios of the planet-forming material. In my chemical evolution models, I utilize a large network of gas-phase, grain-surface and gas-grain interaction reactions, thus providing a comprehensive treatment of chemistry. In my talk, I will show how such chemical reactions can cause the chemical composition in the disk midplane to evolve, and how this affects the C/O ratios of the gas and solid material that form planets and comets. I will argue that chemical evolution in both gas and ice in the disk midplane needs to be addressed when linking the chemical makeup of observed exoplanet atmospheres to how the exoplanets formed in their natal disks, as well as for understanding ice compositions in Solar System comets.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 10-Feb-2020
Speaker: Nathan Roth (GSFC)
Title: Nature vs. Nurture - The Hypervolatile Content of Short-Period Comets
Understanding the evolution of the solar system, as well as its current volatile content, requires knowledge of the initial conditions present in the protosolar nebula. As some of the first objects to accrete in the protosolar nebula, cometary nuclei are among the most primitive remnants of solar system formation. Their composition provides a record of the chemistry and thermodynamical processes present in the protosolar nebula at the time of planet formation, and characterizing their inventory of nucleus ices can provide valuable insights into nascent solar system conditions.
However, it is not clear whether (and if so, to what extent) repeated close encounters with the Sun play a role in setting the present-day measured composition of volatiles in periodic comets. Measurements of the most volatile molecules systematically observed in comets, the “hypervolatiles” CO, CH4, and C2H6, via high-resolution near-infrared spectroscopy, may offer a path to disentangling evolutionary from natal effects in such comets. Unfortunately, complete hypervolatile inventories of periodic comets are rare owing to the difficulty of such observations. I will provide an overview of near-infrared spectroscopy of comets to date, and will discuss the implications of recent work analyzing the hypervolatile composition of three short period comets: 2P/Encke, 21P/Giacobini-Zinner, and 45P/Honda-Mrkos-Pajdusakova.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 24-Feb-2020
Speaker: Nour Raouafi (JHU/APL)
Title: Parker Solar Probe - Breaking New Boundaries in Space Exploration
Launched on 12 Aug. 2018, NASA’s Parker Solar Probe is venturing closer to the Sun than any other spacecraft, mapping the last unvisited regions of the solar system. The spacecraft successfully incorporates technological breakthroughs to attain new science: PSP crossed a technological barrier by protecting sensitive spacecraft and payload components from intense solar photon radiation. Parker is primarily an exploration mission, and the data returned so far is a treasure trove that holds potential for breakthrough discoveries. It is breaking new boundaries of space exploration by flying halfway between Mercury and the Sun. Parker is writing a new chapter of space research by revolutionizing our understanding of this mysterious region by answering long-standing questions that puzzled scientists for decades: how the solar wind plasma is heated and accelerated and solar energetic particles accelerated and transported throughout the heliosphere.
On 4 Feb. 2020, PSP will have completed four of its planned 24 elliptical orbits around the Sun. The first three orbits have the same perihelion (i.e., shortest distance to the Sun) of 25 million kilometers or 35.7 Rsun (Rsun = 1 solar radius = 695,000 km) from the center of the Sun, which occurred on 6 Nov. 2018, 4 Apr. 2019, and 1 Sep. 2019, respectively. The second Venus gravity assist was performed on 26 Dec. 2019, after which the orbit perihelion will decrease to 27.8 Solar Radii. The analyses of science data from the first two orbits show new phenomena and plasma properties not seen before in the solar wind. I will provide an overview of the mission’s status after four solar encounters and the first discoveries as well as the outlook of the mission for the upcoming solar encounters.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 02-Mar-2020
Speaker: Dina Bower (UMD/GSFC)
Title: Detecting Life in Our Solar System with Raman Spectroscopy: Earth, Mars, and Ocean Worlds
The search for life in our solar system is based mainly on our understanding of life on Earth, and the instruments we use to find that life must be as simple and reliable as possible. Raman spectroscopy is a laser-based vibrational spectroscopy technique that is an information-rich, non-contact, non-destructive method for identifying and characterizing compounds such as minerals, volatiles, and carbonaceous materials in a wide variety of terrestrial and planetary materials. The versatility of Raman spectroscopy and recent technological advances has established the technique as a useful tool for laboratory analyses, in situ field measurements, and for upcoming life detection missions on the surface of Mars and future missions on Ocean Worlds. For the past several years, I have used Raman spectroscopy to understand the evolution of geologic materials through time and to characterize biosignatures in modern and ancient rocks. In this talk, I will go through some of these studies and how they relate to planetary science. I will show the differences and similarities between Raman spectroscopy used in a laboratory setting in comparison with field work in planetary analog environments, as well as the necessity of combining both applications. Lastly, I will show some examples of how Raman spectroscopy complements other analytical techniques in the characterization of astrobiologically-relevant materials.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 09-Mar-2020
Speaker: Harrison Agrusa (UMD)
Title: The Excited Spin State of Didymos B Induced by the DART Impact
NASA’s Double Asteroid Redirection Test (DART) is designed to be the first demonstration of a kinetic impactor for planetary defense against a small body impact hazard. The target is the smaller component of the binary asteroid 65803 Didymos. I will present results from a suite of high-fidelity Full Two-Body Problem (F2BP) simulations that explore the parameter space of possible dynamical outcomes. Due to their irregular shapes and tight separation of both bodies, the system exhibits highly non-Keplerian behavior and strong spin-orbit coupling. This leads to peculiar dynamical outcomes including large free and forced librations. In some cases, the secondary's spin evolution becomes chaotic and can even break from the 1:1 spin-orbit resonance.
I will also discuss how Didymos B's internal structure may affect its post-impact libration state and the degree to which this may be measured with ground-based radar observations or with the ESA's newly approved follow-up mission, Hera. If the post-impact libration can be measured to sufficient precision, it may provide an effective way to measure Didymos B's moments of inertia.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 23-Mar-2020
Speaker: Sarah Moran (JHU) (POSTPONED UNTIL FALL)
Title: Clouds and Haze of sub-Neptune Worlds from the Lab
Little experimental laboratory work has been done to explore the properties of photochemical hazes formed in exoplanets, despite their role in atmospheric chemistry and their subsequent possible impact on observations, both for those of current observatories like Hubble and in the future with JWST and ground-based observatories. I will present results of the composition of haze particles produced from exoplanet laboratory studies in the JHU PHAZER laboratory. Many complex molecular species with general chemical formulae CwHxNyOz were detected in the haze particles, including those with prebiotic applications, such as the formulae for amino acids, nucleobases, and simple sugars. I will discuss the implications of these chemical measurements as they compare to existing atmospheric models of exoplanet photochemistry. Additionally, the experimental exoplanetary haze analogues exhibit diverse physical properties, which may help us understand their role as potential cloud condensation nuclei and their role in subsequent atmospheric evolution. Finally, I will discuss how we can apply what we’ve learned from the laboratory into atmospheric models for existing and future observations of sub-Neptune-sized exoplanets.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 30-Mar-2020
Speaker: Laurent Pueyo (STScI)
Title: Collecting direct observational cues of the formation and evolution of giant planets
Self-luminous, wide separation, young sub-stellar objects (aka, “directly imaged planets”) form a critical subset of the low mass ratio binary population for which it is possible to determine atmospheric properties from thermal emission. Their locus in the age vs mass vs semi-major axis parameter space makes them the perfect laboratory to study the boundary between giant planet and stellar binary formation. Theoretical predictions posit these two processes yield significantly different atmospheric compositions, mass distribution, and overall orbital architectures. Orbital arcs are readily available with direct imaging observations, and signatures of chemical composition can in principle be observed via the emergent spectra. I will first review past and ongoing efforts (such as the Gemini Planet Imager Exoplanet Survey) aimed at securing these observables. I will explain the scientific motivation underlying these projects, discuss some of their technical challenges and highlight key recent results. I will then focus on current limitations and present a near future roadmap based on a combination of coarse observations of large samples of stars with HST and exquisite interferometric observations of the most promising sources.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 06-Apr-2020
Speaker: Giada Arney (GSFC)
Title: The Search for Life
After millennia of wondering whether humanity is alone in the universe, future observatories will enable the search for habitability and life on dozens of nearby worlds. But how would we detect and recognize life on an exoplanet? How can we discriminate between true biosignatures and abiotic “false positives”? In this talk, I will provide examples of guiding principles of life detection on exoplanets in the context of the recent National Academy of Sciences Exoplanet Science Strategy and Astrobiology Science Strategy community documents. I will discuss these strategies in the context of the LUVOIR mission concept currently being considered by the astrophysics decadal survey. A detailed study of the orbital parameters, atmospheric compositions, surface properties, and temporal variability of many rocky planets in the habitable zones of different stars will reveal environmental conditions for a diversity of worlds at different stages of evolution, and potentially usher in a new era of comparative astrobiology. To meet this challenge in the coming decades, astrobiologists are thinking critically now about what we must do to prepare, which includes thinking on what we know about life detection from Earth, how and why star-planet interactions matter, and how we can prepare for the detection of novel biosignatures.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 20-Apr-2020
Speaker: Erin May (JHU/APL) (POSTPONED UNTIL FALL)
Title: Observability of exoplanets
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 27-Apr-2020
Speaker: Joe DeMartini (UMD) (POSTPONED UNTIL FALL)
Title: Asteroids
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 04-May-2020
Speaker: Adeline Gicquel-Brodtke (UMD) (POSTPONED UNTIL FALL)
Title: Comet 67P/Churyumov-Gerasimenko
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 11-May-2020
Speaker: Tim Stubbs and Dave Glenar (GSFC/UMBC) (POSTPONED UNTIL FALL)
Title: Lunar studies
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
