Mest Ceresglobalmapping.Pdf

Scott C. Mest1 1Planetary Science Institute, Tucson, AZ 1 David A. Crown 2School of Earth & Space Exploration, R. Aileen Yingst1 Arizona State University, Tempe, AZ 1 Daniel C. Berman 3JHU-APL, Laurel, MD 2 David A. Williams 4 3 NASA JPL, California Institute of Debra L. Buczkowski Technology, Pasadena, CA Jennifer E.C. Scully4 5MPI for Solar System Research, Thomas Platz1,5 Göttingen, Germany H. Hiesinger6 6 J.H. Pasckert6 Institute for Planetology, WWU, Münster, Germany A. Neesemann7 7 Ralf Jaumann8 Freie Universität, Berlin, Germany Thomas Roatsch8 8DLR, Berlin, Germany Frank Preusker8 9UCLA, Los Angeles, CA, USA Andreas Nathues5 Carol A. Raymond4, 9 Christopher T. Russell Planetary Geologic Mappers Meeting/Planetary Data Workshop June 12-15, 2017 Outline

 Objectives

 Background

 HAMO-phase mapping

 Global mapping datasets

 Methodology (scale, feature sizes, unit identification)

 Current state of the map / Mapping highlights

 Publication and archiving  Cerean Chronostratigraphy

 Ongoing work

This work is supported by the NASA Dawn at Ceres Guest Investigator Program.

June 12-15, 2017 PGMM/PDW 2 Objectives

Through mapping, we are …evaluating the global geology of Ceres where important spatial and temporal relationships between geologic processes are preserved. …characterizing and analyzing stratigraphy of mapped geologic units …addressing outstanding science questions regarding the nature and stratigraphy of its impact record, potential past (cryo)volcanic activity and other geologic processes.

Specific scientific objectives of this investigation include:  Evaluate the timing and sequence of impact events by characterizing the spatial and temporal relationships between impact craters and other surface materials.  Evaluate the nature of surface materials via assessment of surface and feature morphology, and unit extent and distribution.  Determine relative ages of mapped units and features via analysis of crater size-frequency distribution statistics and stratigraphic relations (e.g., superposition, cross-cutting); develop a cerean time-stratigraphic system.

June 12-15, 2017 PGMM/PDW 3 HAMO-phase mapping plan

 Construct geologic map at 1:2.5M scale. • Build upon Survey map [Buczkowski et al., 2016, Science, v353] using HAMO data (FC base, DTM, color maps), and informed by LAMO images (for unit characterization)

 Evaluate global geologic history and develop cerean time-stratigraphic system • Relative ages determined from stratigraphic relationships (superposition, cross-cutting, embayment). • “Absolute” ages estimated from lunar- and asteroid-based chronologies; both will be reported.

 Publish map, map text, and timescale in a journal (e.g., Icarus)

 Archive geologic map and ancillary data layers (e.g., linear feature map, impact crater location map, lobate feature map) with PDS

June 12-15, 2017 PGMM/PDW 4 Global datasets

 Framing Camera mosaic Clear filter  map base

Survey mosaic HAMO mosaic (400 m/pixel) (140 m/pixel)

VENDIMIA HANAMI Occator PLANITIA PLANUM Kerwan

Urvara Yalode

June 12-15, 2017 PGMM/PDW 5 Supplemental datasets - topography

 FC-derived DTM (~137 m/pixel) • Used to identify geologic structures, characterize relationships between geologic units and topography  Surface exhibits ~15 km in relief (+7.5 km, knobs in north; -7.5 km, floor of Urvara) • Broad expanses of low-lying terrain – shaped largely by impacts (e.g., Vendimia Planitia) • Areas of elevated terrain – “high” areas composed of knobs and crater rims (eg., Hanami Planum)

HAMO DTM

VENDIMIA HANAMI

Occator PLANITIA PLANUM Kerwan

Yalode Urvara

June 12-15, 2017 PGMM/PDW 6 Supplemental datasets - spectral Spectral data is used to (a) assist in mapping unit contacts, and (b)  FC Color (0.44-0.96 μm) provide useful and unique compositional information in unit – Color filter maps (DLR) descriptions that can help – Color ratio maps - Ceres Color Composite maps (MPS) Ceres Color Composite A: R=965/750, G=750, B=440/750 distinguish geologic units.

June 12-15, 2017 PGMM/PDW 7 Supplemental datasets - spectral Spectral data is used to (a) assist in mapping unit contacts, and (b)  FC Color (0.44-0.96 μm) provide useful and unique compositional information in unit – Color filter maps (DLR) descriptions that can help – Color ratio maps - Ceres Color Composite maps (MPS) Ceres Color Composite A: R=965/750, G=750, B=440/750 distinguish geologic units.

June 12-15, 2017 PGMM/PDW 8 HAMO-based point and linear features  Linework length > 20 km  Crater diameter > 20 km

Y U

June 12-15, 2017 PGMM/PDW 9 HAMO-based contacts and units  Unit area > 100 km2

Y U

June 12-15, 2017 PGMM/PDW 10 HAMO-based geologic map  Regional units (ct, s) unconstrained by topography  Color data useful for estimating extents of proximal ejecta of “fresh” craters

FC HAMO DTM

FC color CCC A

June 12-15, 2017 PGMM/PDW 11 Impact craters

 Most pervasive features on Ceres  Sizes range from limits of FC resolution to largest craters, e.g., Kerwan (280 km), Yalode (260 km), Urvara (170 km)  Morphology – well-preserved, degraded, and buried  Well-preserved craters Gaue (80 km) • rims nearly circular and raised above surrounding terrain • small craters (D<15 km) are bowl-shaped • larger well-preserved craters display steep walls, slump terraces along their walls, scalloped rims • Some display flat floors, some floors fractured (e.g., Occator and Dantu); most contain hummocky floor deposits, debris lobes on their floors • Most have well-preserved ejecta deposits  Degraded craters • irregularly shaped • Rims are rounded and at or near level of surrounding terrain Dantu (126 km) • Most nearly filled

June 12-15, 2017 PGMM/PDW 12 Rayed craters  (D>30 km) Azacca, Dantu, Haulani, Occator  (D<30 km) Cacaguati, Kupalo, Oxo, Takel  Well-preserved rims and ejecta  Steep walls, terrace deposits, lobate deposits  Smooth floors; fractures  High albedo rays in ejecta, bluish in CCC-A  Stratigraphically important impact structures; represent some of youngest impacts on Ceres

June 12-15, 2017 13 PGMM/PDW Urvara and Yalode  170 km and 260 km in diameter  Extensive ejecta deposits; smooth and rugged (Urvara), hummocky (Yalode)  Structures (troughs, grooves, secondary chains) within Yalode ejecta help reveal extent  Relatively smooth floor deposits; fractures, grooves  Stratigraphically important impact structures

June 12-15, 2017 PGMM/PDW 14 Urvara and Yalode  170 km and 260 km in diameter  Extensive ejecta deposits; smooth and rugged facies (Urvara), hummocky and etched? textures (Yalode)  Structures (troughs, grooves, secondary chains) within Yalode ejecta help reveal extent  Relatively smooth floor deposits; fractures, grooves  Stratigraphically important impact structures

June 12-15, 2017 PGMM/PDW 15  Smooth and featureless; superposed by craters and secondary craters Smooth material  Moderate albedo  Underlaying hummocky texture in west  No clear source, emplacement process

June 12-15, 2017 PGMM/PDW 16 Cratered terrain  Covers most of Ceres’ surface  Rugged surfaces formed by structures and deposits of impacts  Moderate albedo

June 12-15, 2017 PGMM/PDW 17 Chronostratigraphy of Ceres

 Organizing major geologic events that are separated in time into distinct time- stratigraphic periods  Relative ages determined from stratigraphic relations  Superposition, cross cutting, embayment  Key relationships missing, e.g., between major impact events and smooth material

 Absolute model ages determined from calculating crater size-frequency distribution statistics  Counts from a number of Dawn Science Team sources  Ages from Lunar-derived Model (LDM) and Asteroid-derived Model (ADM) will be reported.

June 12-15, 2017 PGMM/PDW 18 Chronostratigraphy of Ceres

 Major referents to be used to define Chronostratigraphic Series:  Azacca crater materials – represents base of “Era of rayed craters”  Urvara Formation  Yalode Formation  Kerwan smooth material  Cratered terrain – represents oldest known crust

Preliminary absolute model ages (based on sub-sets of unit areas) derived for major geologic units used to represent the cerean chronostratigraphic time periods.

June 12-15, 2017 PGMM/PDW 19 Chronostratigraphy of Ceres

Preliminary geologic timescale based on absolute model ages derived for referents.  Ages being recalculated for full unit areas - Results will inform us if sub-unit areas should be counted to smaller diameters

 Considering combining Urvaran and Yalodean Tanaka et al. (1992) Mars

Crater-Density Absolute-Age Range Range N(D) = no.>D/106 (Myr) km2 Epoch N(1) N(2) N(5) N(16) LDM ADM Azaccan Y Y -- -- 110-0 38-0 Urvaran Y Y Y -- 160-110 100-38 Yalodean -- Y Y Y 840-160 180-100 KerwananJune 12-15, 2017-- Y Y Y 2,500-840 PGMM/PDW2,400-180 20 Pre-Kerwanan -- -- Y Y 4,600-2,500 4,600-2,000 June 12-15, 2017 PGMM/PDW 21