Planetary Science Seminar - spring-2021
Distant Activity of Comet C/2011 KP36
April 2, 2021
noon - 1 p.m.
zoom
Presented By:
- Ariel Graykowski - UCLA
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Comets are the carriers of the most primitive, volatile-rich materials in the solar system, and when they enter the terrestrial planet region, they quickly lose their material via sublimation. However, some active comets have been observed beyond the water-ice sublimation zone. In this talk, I will review the potential mechanisms that can cause distant activity in comets and I will analyze a case study of distantly active, long-period comet C/2011 KP36.
From Deep Springs to Mars
April 2, 2021
noon - 1 p.m.
zoom
Presented By:
- Taylor Dorn - UCLA
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Barchan dunes are found in many sand seas on Earth and are pervasive across the surface of Mars. While mainly associated with deserts, these dune morphologies can be found anywhere there is a uniform wind direction and low sediment availability; including deserts, fluvial channels, and potentially playas. In this talk, I will discuss ongoing research in Deep Springs, California focused on determining how barchan shaped features are created seemingly in the absence of active sediment transport on the lake and how these results might provide insights on the equatorial layered deposits on Mars.
MESSENGER's View of Hollows on Mercury; Links to the Planet's High Volatile Content.
April 9, 2021
noon - 1 p.m.
zoom
Presented By:
- David Blewett - APL, Johns Hopkins University
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Observations by the MESSENGER spacecraft led to the discovery of an unusual landform on Mercury, named “hollows”. Hollows are shallow irregular depressions that appear to form by a process of volatile loss, similar to “sublimation degradation” known on icy surfaces. Hollows are a geomorphological manifestation of the unexpectedly high content of moderately volatile elements in Mercury’s crust.
New Constraints on the Origin, Geologic Setting, and Global Distribution of Martian Periodic Bedrock Ridges.
April 16, 2021
noon - 1 p.m.
zoom
Presented By:
- Jonathan Sneed - UCLA
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We show that Periodic Bedrock Ridges (PBRs), decameter-scale erosional bands oriented transverse to the dominant wind direction, are a global phenomenon occurring throughout a wide range of geologic settings and elevations on Mars. PBRs often interact with loose-sediment Transverse Aeolian Ridges, and in at least some cases, share a common genetic relationship.
Identification of Potential Mantle Rocks Around the Lunar Imbrium Basin
April 23, 2021
noon - 1 p.m.
zoom
Presented By:
- Jordan Bretzfelder - UCLA
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Basin‐forming impacts expose material from deep within the interior of the Moon, though no definitive samples of the lunar mantle have been returned to Earth. Previous studies have reported remotely detected locations which have been postulated to contain mantle‐derived material, but none are mineralogically consistent upon study with multiple techniques. To locate potential remnants of the lunar mantle, we searched for early‐crystallizing minerals using data from the Moon Mineralogy Mapper (M3) and the Diviner Lunar Radiometer (Diviner).
To Cool is to Keep: Residual H/He Atmospheres of Super-Earths and sub-Neptunes
April 23, 2021
noon - 1 p.m.
zoom
Presented By:
- William Misener - UCLA
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Super-Earths are predicted to have accreted nebular H/He envelopes before disk dispersal, which were subsequently lost through a hydrodynamic wind driven by the hot, underlying core. I will show how loss of the primordial atmospheres can be incomplete due to the thermal coupling of the core and atmosphere and discuss the observability of these thin remnant hydrogen envelopes.
Lunar and Planetary Data Visualization and Analysis Using NASA’s Solar System Treks Portals
April 30, 2021
noon - 1 p.m.
zoom
Presented By:
- Brian Day - Ames
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NASA's Solar System Treks (https://trek.nasa.gov) online portals for lunar and planetary mapping and modeling provide web-based suites of interactive visualization and analysis tools to enable mission planners, planetary scientists, students, and the general public to access mapped data products from past and current missions for a growing number of planetary bodies. This presentation will provide an overview of the portals and their capabilities.
New Horizons Found That Pluto Has Abundant Hypervolatiles and Arrokoth Has Abundant Methanol - What Does This Tell Us About KBO Formation & Evolution?
May 7, 2021
noon - 1 p.m.
zoom
Presented By:
- Casey Lisse - APL, Johns Hopkins University
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TBD
Magnetic Field Generation in Earth, Mars, and Rocky Exoplanets
May 14, 2021
noon - 1 p.m.
zoom
Presented By:
- Peter Driscoll - Carnegie Institute for Science
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I will discuss how the history of core convection in rocky planets is reflected in their magnetic fields, from Earth to Mars and (potentially) rocky exoplanets. I will also discuss how magnetic field intensities are expected to be limited by the thermal and electrical conductivities of the lower mantle and core, how magnetic fields can limit atmospheric escape, and the prospects for detecting exoplanet magnetic fields by radio cyclotron emission.
Wrinkle Ridges on Mars
May 21, 2021
noon - 1 p.m.
zoom
Presented By:
- Kobe Wang - UCLA
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Wrinkle ridges are common geomorphological features on surfaces of rocky solar-system bodies such as Mercury, Venus, the Moon and Mars. Current studies attribute the origin of wrinkle ridges to volcanic or tectonic processes. Recent documentation of widely occurring glaciated landforms adjacent to the wrinkle-ridge terrains on Mars raises an alternative possibility that the ridges may have formed as recessional moraine ridges. In this talk, I will be presenting evidence from morphological mappings and satellite images taken from Mars Reconnaissance Orbiter to show features that resemble glaciated landforms in wrinkle ridge field at SE Tharsis plateau, Mars.
Modeling the Accumulation of Secondary Craters on Mars and the Moon
May 21, 2021
noon - 1 p.m.
zoom
Presented By:
- Tyler Powell - UCLA
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Secondary craters are formed from the high-velocity ejecta of larger primary craters. The influence of secondaries on the accuracy of crater chronology has been heavily debated. In this work, we: 1) use a global catalog of Martian and Lunar craters to constrain the size-frequency and spatial distribution of secondaries produced by several large primaries; and 2) model secondary accumulation with time, accounting for spatial clustering. We show that the on Ga timescales, secondaries likely dominate the global size-frequency distribution for sub-kilometer scale craters on the Moon and Mars. However, most secondaries are distributed close to their parent primary, and the contribution of distant secondaries to a typical surface is much lower than suggested by the global average.
Geomorphologic Evidence for Thrusting and Glaciation on Pluto's Largest Moon, Charon
May 28, 2021
noon - 1 p.m.
zoom
Presented By:
- Hanzhang Chen - UCLA
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Charon's tectonic history was interpreted to have a global extension regime. However, our systematic photo-geologic mapping results indicate the existence of substantial compression and modification of glaciation, which suggest a more complex evolution history.
Fluvial Features on Titan and Earth: Lessons from Planform Images in Low-Resolution SAR
May 28, 2021
noon - 1 p.m.
zoom
Presented By:
- Julia Miller - UCLA
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The Cassini-Huygens mission produced unprecedented images of Titan's surface, revealing river networks strikingly similar to those on Earth. However, the Cassini dataset has low spatial image resolution and image quality compared to data used to map channels on Earth. In this talk, I will discuss how Earth analogues are used to better understand the biases that result from low-quality image data, as well as the geomorphologic metrics likely to be robust when applied to Titan's channels.
TBA
June 4, 2021
noon - 1 p.m.
zoom
Presented By:
- Dave Paige - UCLA
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TBA