Date: Monday 25-Jan-2021
Speaker: Jose Aponte (GSFC/Catholic Univ)
Title: Organic Astrochemistry 101: Meteorites and the Origins of Life on Earth
Carbonaceous chondrites (carbon-rich meteorites) represent some the oldest and most primitive pieces of material formed in the Solar System; indeed, they could even be older than the Sun itself. These carbon-rich meteorites may have delivered an important concentration of organic compounds and water to the primitive Earth. Multiple organic classes, including those required for life (e.g. amino acids, carboxylic acids, nucleobases and polyols) have been identified from carbonaceous chondrites, providing valuable insights into the chemical inventory of the early Solar System, the primordial synthesis of organic matter, and the question of how life appeared on Earth.
Amino acids constitute the basic building blocks of all protein-based living organisms on Earth and thus, they are among the most intriguing and studied meteoritic organic compounds found. Homochirality (predominance of the L enantiomer) in terrestrial biological proteins is a fundamental feature of life as we know it. L-enantiomeric excesses have been observed in some meteoritic amino acids, raising interesting questions about a potential link between meteorites and terrestrial homochirality. In addition, the stable isotopic compositions (D, 13C, 15N) of meteoritic organic compounds provide information on their formation mechanisms and histories. Contrasting the distribution, chirality and isotopic composition of meteoritic organic compounds in a wide range of carbonaceous chondrites provide important insights on the composition and environments of the protosolar nebula, the meteorite parent bodies, and may well provide clues about their synthesis and survival during the formation of our Solar System.
I will present results from our extensive investigation on the abundance and molecular distribution of amino acids, and other biologically relevant molecules extracted from meteorites. We will discuss their potential prebiotic origins and relevance to the emergence of life on Earth. We will also review the importance of sample return missions and our future findings after the analysis of asteroid samples brought to the Earth by JAXA’s Hayabusa2 (December 6, 2020) and NASA’s OSIRIS REx (September 24, 2023).
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 01-Feb-2021
Speaker: Dr. Laura Mayorga (JHU/APL)
Title: The Jupiter System: An Exoplanet Testbed
The Universe has shown it is capable of creating some truly alien planetary systems which will remain as simple specks of light next to their comparatively bright and blazing host stars. However, unlike our observations of the storms and clouds on Solar System planets, atmospheric or surface features remain unresolved on exoplanets as the light we detect is a hemispherical average. Thus, observations of planetary bodies in our Solar System with exoplanet-like observational methods are the only way we can understand how unresolved features manifest in exoplanet observations. With future direct imaging missions, we can finally image planets separate from their host stars as we have in the Solar System for centuries. However, exoplanets will be typically observed at partial illumination angles and from non-equatorial perspectives, which is an unusual Solar System perspective. I’ll present observations of Jupiter and the Galilean satellites as exoplanet analogs and discuss future avenues for providing the benchmark data needed to place exoplanets in Solar System context.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 01-Mar-2021
Speaker: Jegug Ih (UMD)
Title: Understanding the inverse problem of exoplanetary atmospheric retrievals
In characterizing exoplanets, the transmission, emission, and reflected light spectra of their atmosphere have been the primary observable data. The inverse modeling of these data, or “retrievals”, has allowed for extracting information about the physical properties and processes encoded in the observed atmospheric spectrum. One key problem of using atmospheric retrievals is that, since it relies on physical models that make certain assumptions about the atmosphere, the resulting characterization depends on particularities of the model. An incomplete theoretical model will lead us to draw spurious conclusions about the observed planet. With the launch of James Webb Space Telescope and its first observation just around the corner, it is imperative that we establish what we can accurately deduce from these observations. I will highlight some key work in the literature towards this aim and present my work addressing the issues of instrumental systematics and parametrization in retrievals. I will also discuss comparative planetology as a complementary alternative that overcomes some problems of retrievals.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 08-Mar-2021
Speaker:
Title: LPSC Practice Talks
Abstract
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 22-Mar-2021
Speaker: Maggie Thompson (UCSC)
Title: Terrestrial Planet Atmospheres: Their Outgassing Origins and Potential Biosignatures
The next phase of exoplanet science will focus on characterizing exoplanet atmospheres, including those of low-mass, terrestrial planets. In this talk, I will discuss two ongoing projects that seek to better understand the origins of and potential biosignatures in terrestrial exoplanet atmospheres.
The first project is motivated by the fact that, at present, there is no first-principles understanding of how to connect a planet’s bulk composition to its initial atmospheric properties. Since terrestrial exoplanets likely form their atmospheres through outgassing, a novel step towards building such a theory is to assay meteorites, the left-over building blocks of planets, by heating them to measure their outgassed volatiles. Our Solar System presents a wide variety of meteorite types, including carbonaceous chondrites which are believed to be representative of the bulk material in the solar nebula during planet formation. To inform the initial chemical composition of terrestrial planet atmospheres, I will present the results of outgassing experiments in which we heated carbonaceous chondrite samples to 1200 ℃ and measured the abundances of released volatiles (e.g., H2O, CO, CO2, H2, H2S) as a function of temperature and time. We also performed complementary bulk element analysis on the samples before and after the heating experiments to monitor outgassing of heavier elements (e.g., Mg, P, S, Ca, Mn, Fe). I will discuss how these experimental results compare to thermochemical equilibrium models of outgassing from the same types of chondrites and how these experiments can help improve atmospheric models.
The second project focuses on methane, a potential biosignature gas for terrestrial exoplanet atmospheres. As we move into the era of JWST and ELTs, a comprehensive understanding of possible biosignatures that may be detected with the next generation of ground and space telescopes is warranted. While some biosignature gases, such as oxygen and phosphine, have recently been reviewed in depth, these will likely be extremely difficult to detect with JWST. In contrast, while it has not been thoroughly reviewed, methane at Earth-like biogenic fluxes is one of the only biosignatures that may be readily detectable with available near-term instruments. I will present our preliminary work on a comprehensive review of methane biosignatures and false positives.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 29-Mar-2021
Speaker: Casey Honniball (GSFC)
Title: Lunar Surface Hydration: A view from Earth
Hydration on the lunar surface was first reported in 2009 by three spacecraft and manifested as a strong absorption at 3 µm. The hydration at 3 µm is produced by hydroxyl (OH) attached to metal cations and/or molecular water (H2O). Measurements of the 3 µm band were revolutionary but the returned spacecraft data have limitations in wavelength coverage, spatial resolution, global coverage, and lunar time of day. To bridge the gap, we use two Earth based observatories to characterize the true nature of the 3 µm band and to unambiguously detect molecular water. Using the SpeX infrared cross-dispersed spectrograph at the NASA InfraRed Telescope Facility (IRTF) at Maunakea Observatory we address diurnal variability of the 3 µm band and with the NASA/DLR Stratospheric Observatory For Infrared Astronomy (SOFIA) we observe the Moon at 6 µm where a purely H2O feature is exhibited.
Observations with the IRTF reveal total water (OH + H2O) abundances ranging from 0 to ~500 ppm H2O. From this new data set with improved thermal removal, we find diurnal variations of the 3 µm band along with variations with latitude and composition. We observe a decrease in abundance with increasing lunar local time, an asymmetric trend about the equator that favors the South, and higher abundances in highland regions. Data from SOFIA of the Clavius crater and surrounding region reveal abundances of ~100 to 412 ppm H2O from the 6 µm emission band that we attribute to molecular water on the Moon. All spectra acquired at the Clavius region exhibit a 6 µm emission band. We are unaware or any other lunar material that may exhibit an isolated 6 µm band. This is the first direct, unambiguous detection of H2O on the Moon outside the permanent shadows at the lunar poles.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 5-Apr-2021
Speaker: COSMO Meet Format Discussion - Terrestrial Planet Accretion
Title: Formation of Venus, Earth, and Mars: Constrained by Isotopes
For this whole group discussion, we will be considering constraints on the many flavors of accretion models provided by isotopic measurements in the Solar System and the arguments for and against each model proposed by Lammer et al. (2020). Please read (or at least skim for key points most related to your field of work) the paper before our PALS meeting so that you can bring something to the discussion table.
Lammer, H., Brasser, R., Johansen, A., Scherf, M., and Leitzinger, M. 2021. Foramtion of Venus, Earth, and Mars: Constrained by Isotopes. Space Sci Rev, 217, 7, https://doi.org/10.1007/s11214-020-00778-4.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 12-Apr-2021
Speaker: Adrienn Luspay-Kuti (JHU-APL)
Title: The source of O2 in comet 67P/Churyumov-Gerasimenko
The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument onboard the Rosetta spacecraft has measured molecular oxygen (O2) in the coma of comet 67P/Churyumov-Gerasimenko (67P) in surprisingly high abundances. These measurements mark the first unequivocal detection of O2 in a cometary environment. The large relative abundance of O2 in the coma of 67P despite its high reactivity and low interstellar abundance poses a mystery for its origin in comet 67P, and potentially other comets. Since its first detection, there have been several hypotheses for the production and origin of O2 in 67P. These hypotheses cover a wide range of contradicting possibilities from in situ production mechanisms to various primordial or protosolar nebula origins, and are limited by the current state of analysis of O2 measurements that, thus far lack appropriate geographical and extended temporal resolution. I will present results from our systematic analysis of Rosetta ROSINA data and resolve the issue of source for O2 detected in the coma of 67P. Our results provide a consistent explanation to the observed O2 outgassing over time relative to the major cometary species, and provide strong constraints on the possible origin of cometary O2.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 19-Apr-2021
Speaker: Rick Cosentino (GSFC/UMD)
Title: Convective storms, waves, and super-rotation in the atmospheres of Jupiter and Saturn
Super-rotation, or atmospheric circulation faster than a planet's rotation, is common to almost every atmosphere in the solar system. Atmospheric waves are a source of momentum that can transfer energy throughout a planet. Earth possesses an equatorial jet stream that changes direction approximately every two years in response to waves and convection. In 2016, there was an unprecedented disruption of this jet, called the Quasi-biennial Oscillation (QBO), likely associated with the effects of climate change. We have observations of other stratospheric oscillations in Jupiter and Saturn that according to theory are similar in nature to the QBO but operate on longer timescales. As we continue long-term monitoring of the outer planets, we are beginning to observe patterns in their atmospheres and explore their climatology. This talk will introduce these phenomena from a highly comparative planetology perspective.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 26-Apr-2021
Speaker: Ludmilla Kolokolova (UMD)
Title: Multi-messaging in cometary science
Multi-messaging in astronomy means “the coordinated observation and interpretation of disparate "messenger" signals.” (Wikipedia). Usually this refers to the information that comes from different types of physical “messengers”, e.g., electromagnetic radiation, gravitational waves, neutrinos, etc. However, the messengers can be just different types of electromagnetic radiation or different properties of the electromagnetic radiation. For example, to receive a consistent picture of the properties of cosmic dust or planetary atmospheres and surfaces, it is good to combine information obtained in UV, visible, IR, and microwave spectral ranges. One can receive even more accurate characteristics of the objects considering different techniques, e.g., photometry, spectroscopy, polarimetry, characteristics of the returned samples, and in-situ mission data.
In this talk I consider how multi-messaging is used to study properties of cometary dust by combining information that comes from photometry, spectra, and polarization. Comets C/2014 A4 (SONEAR) and C/2011 KP36 (Spacewatch) will be considered as examples, and the obtained “multi-messaging” data will be interpreted using a computational model of the dust as an ensemble of polydisperse porous, rough spheroids. The results allow us not only to describe properties of the dust in different coma features (jets, shells, etc.), but also to explore the dust evolution with the distance from the nucleus. I will also introduce an interactive online database of the pre-calculated dust properties that can be used for other studies.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 3-May-2021
Speaker: Guangwei Fu (UMD)
Title: A study of diverse exoplanet atmospheres from hot Jupiters to hot Neptunes
Every planet is special just like every child. With thousands of exoplanets discovered to date, we have seen an incredibly more diverse landscape of exoplanets compared to our solar system planets. To better understand exoplanets we need to collect and study large datasets to form statistically robust insights similar to how we have learned about stars and galaxies. I will talk about atmospheric studies of individual hot Jupiters and hot Neptune exoplanets and how they are connected to our understanding of exoplanet atmospheres at large.
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
Date: Monday 10-May-2021
Speaker: Dana Louie (GSFC)
Title: Simulated Follow-up Observations of TESS Discoveries with JWST and Ground-based Multi-band Photometric Instruments
The approaching launch of the James Webb Space Telescope (JWST), coupled with the recent all-sky search of the Transiting Exoplanet Survey Satellite (TESS), heralds a new era in exoplanetary atmospheric characterization, with TESS projected to detect over one thousand transiting exoplanets smaller than Neptune, and JWST offering unprecedented spectroscopic capabilities. In this talk, I will begin by providing background on the TESS mission and the TESS follow-up observing program (TFOP) as it relates to exoplanet discoveries. Next, I will discuss my recent work in simulating TESS follow-up observations. First, predictions show that TESS will detect thousands of astrophysical false positives that mimic exoplanet discoveries by also producing periodic decreases in starlight. A common scenario occurs when light from the target star blends with that of nearby eclipsing binary stars. Thus, TESS discoveries must be validated as true exoplanets using additional instruments or techniques. I designed software codes to predict how well two multi-band photometry instruments can discriminate between blended eclipsing binary false positives and true exoplanets. Second, I simulated JWST transmission spectroscopy observations of the anticipated TESS planet yield and compared the results to simulated transmission spectroscopy observations of already known exoplanets. My most significant finding is that several hundred TESS 1.5 to 2.5 Earth radii sub-Neptunes can be observed at higher signal-to-noise than currently known similarly-sized exoplanets. The large number of TESS planets amenable to atmospheric characterization in this radius regime will allow astronomers to investigate questions concerning exoplanet demographics, such as the origins of the so-called “Fulton gap.”
For further information contact PALS coordinator Dr. Lori Feaga at feaga@astro.umd.edu or (301)-405-1383.
