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42nd Lunar and Planetary Science Conference (2011) 2687.pdf

ERUPTION HISTORY OF THE ELYSIUM VOLCANIC CENTRE, . T. Platz and G. G. Michael. Freie Universität Berlin, Institute of Geological Science, Planetary Sciences and Remote Sensing, Malteserstr. 74-100, 12249 Berlin, Germany ([email protected]).

Introduction: The surface of Mars has been ex- Methods: Lava flow mapping was performed in a tensively reshaped by volcanic processes. Large vol- GIS environment using HRSC and THEMIS IR day canic edifices and vast lava plains dominate the planet. imagery. Crater-size frequency determinations were Although it is generally known that volcanic activity at primarily carried out on CTX and HRSC images and various volcanic centres on Mars peaked in the Late subordinately on THEMIS VIS data. Crater measure- /Early , little knowledge exists ments and analysis was done using cratertools [4] and about the complete eruption history at individual vol- craterstats [5], respectively. Crater modelling ages canic centres. were compiled in frequency plots and cumulative prob- Estimates of the eruption frequency, associated ability density plots. volume of erupted material, and volatile release to the atmosphere at each volcanic centre on Mars would Results: A total of 133 lava flows and 6 calderas propel our understanding of global climate changes and were mapped and their formation ages determined us- atmospheric evolution, sustained heat production, melt ing impact craters. Model ages range between 3.4 Ga generation, and magma ascent. and 60 Ma. The majority of lava flow effusion oc- In our ongoing study to quantify the global volatile curred between 1-1.1 Ga. Since then activity rapidly escape during volcanic eruptions on Mars we first fo- waned with minor broad peaks at 250 Ma and 100 Ma. cused on the Elysium Volcanic Centre. The total mini- The oldest age of a buried surface underlying a lava mum volume of erupted material at the Elysium Vol- flow is 3.8 Ga. canic Centre has been estimated at >3.5×106 km3 [1]. Currently, there is no obvious time-space correla- However, to evaluate the volatile release in time, we tion apparent. However, it is observed that 9 of 10 lava also need to identify the duration of volcanic activity flows younger than 500 Ma are located at the lower and its periods along with associated volumes of flanks of the Elysium rise or at more distal reaches. erupted material. Light has now been brought into the The youngest caldera-forming events occurred at eruption frequency of the Elysium Volcanic Centre. Hecates . Here we report on the first comprehensive eruption frequency record of a single volcanic region. Interpretation: This study shows that the Elysium Volcanic Centre was active much longer than previ- Elysium Volcanic Centre: The centre consists of ously thought. Although only a small number of ex- three edifices: , , and posed lava flows were studied, it is evident that Ely- Albor Tholus. Elysium Mons is the largest and sium was active for more than 3.8 Ga. If it is inferred is located on a c.1000 km×1500 km rise. The summit that the Elysium Volcanic Centre developed following of Elysium Mons rises c.17,700 m above the surround- the Utopia impact at c. 4.1 Ga [6], then most of the ing plain to the west. Hecates and Albor Tholi are lo- Elysium rise and edifices were formed in less than 300 cated to the NNE and SSE, respectively, of Elysium Myrs. Mons at the periphery of the Elysium rise. Volcanic Further, we anticipate a genetic between Ely- material erupted from Late Hesperian to Early Amazo- sium Volcanic Centre and Elysium Planitia, where nian from the Elysium Volcanic Centre and was some of the youngest known lava flows and low shield mapped as unit AHEe [2,3]. It spreads over 110° E-W volcanoes on Mars exist. Those exposed volcanic (>3600 km) and 35° N-S (>1600 km) and covers an products are related to the Fossae system area of approx. 3.4×106 km2. which extends well into the Elysium Volcanic Centre. There, the fossae were activated at least twice enabling Approach: In order to obtain a representative set the ascent of magma to the surface. Therefore, we sug- of crater modelling ages from lava flows, mapping ef- gest that both volcanic regions share a common magma forts concentrated on proximal, medial, and distal source at depth. If true, volcanic activity preferentially reaches of the volcanic region. This approach was only migrated along the system to lower biased by the availability of suitable imagery and vary- altitudes within Elysium Planitia. Vaucher et al. [7] ing degrees of obliteration across the region. In addi- determined surface ages of lava flows and low shield tion, the formation ages of selected calderas were also volcanoes. We have reprocessed their data using the determined. Hartmann and chronology [8]. As a result, 42nd Lunar and Planetary Science Conference (2011) 2687.pdf

two peaks in activity occur at about 10 Ma and 60 Ma with the youngest material erupted at 1.4 Ma. If we take the Elysium Planitia ages into considera- tion it appears probable that Mars is still volcanically active in the broader Elysium region.

Acknowledgements: We thank P. Jodlowski and T. Lehmann for assistance in image processing and U. Wolf for selected crater counts. This work was sup- ported by the Helmholtz Association through the re- search alliance “Planetary Evolution and Life”. G.M. was supported by the German Space Agency (DLR Bonn) grant 50QM0301 (HRSC on ), on behalf of the German Federal Ministry of Economics and Technology.

References: [1] Platz T. et al. (2010) LPS XLI, Ab- stract #2476. [2] Tanaka K. L. et al. (2003) J. Geophys. Res., 108, E4, 8043. [3] Tanaka K. L. et al. (2005) U.S. Geol. Surv. Sci. Inv., Map SIM-2888. [4] Kneissl T. et al. (in press) Planet. Space Sci. [5] Mi- chael G. G. and Neukum G. (2010) Earth Planet. Sci. Lett., 294, 223-229. [6] Frey H. (2008) Geophys. Res. Lett., 35, L13203. [7] Vaucher J. et al. (2009) Icarus, 204, 418-442. [8] Hartmann W. K. and Neukum G. (2001) Space Sci. Rev., 96, 165-194.