火星の最近の火山活動から、以前考えられていたよりも活発な惑星であることが判明(Recent volcanism on Mars reveals a planet more active than previously thought)

2023-12-08 アリゾナ大学

＜関連情報＞

• https://news.arizona.edu/story/recent-volcanism-mars-reveals-planet-more-active-previously-thought
• https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JE007947

エリジウム平原の若い地質学的歴史を明らかにする： 溶岩の堆積、面積、体積に関する制約条件 Revealing Elysium Planitia’s Young Geologic History: Constraints on Lava Emplacement, Areas, and Volumes

J. R. C. Voigt, C. W. Hamilton, G. Steinbrügge, M. S. Christoffersen, S. Nerozzi, L. Kerber, J. W. Holt, L. M. Carter
Journal of Geophysical Research: Planets  Published: 15 December 2023
DOI:https://doi.org/10.1029/2023JE007947

Abstract

Elysium Planitia includes several outflow channels that were likely carved by aqueous erosion and subsequently infilled by younger lava flows, making Elysium Planitia the youngest volcanic terrain on Mars. Studying this region is critical for constraining the recent hydrological and thermal evolution of the planet. Here, we investigate the lava flow areas, thicknesses, and volumes in Elysium Planitia using Context (CTX) camera images in combination with SHAllow RADar (SHARAD) sounder data. Compiling 1,777 reflectors over an area of 9,126,790 km² allows us to reconstruct the subsurface landscape evolution over time. Our findings show that Elysium Planitia is composed of material from about 40 episodes of effusive volcanic activity. We report volumes for individual eruptions of 4,000 ± 1,600 km³ infilling Athabasca Valles, 12,200 ± 2,500 km³ in Marte Vallis, and 16,000 ± 4,000 km³ in Rahway Valles for the major flow units and volumes as small as 100 ± 50 km³ in Cerberus Plains. The surface morphologies and inferred dielectric properties of lobe interfaces suggests that the regions consists of basaltic lava. The region also experienced multiple aqueous flooding events. Although, we found evidence of past lava–water interactions, present-day ground-ice (if present) is likely limited to local patches. Further, the pre-eruption landscape reveals that the aqueously carved Marte Vallis is more areal extensive, but shallower than previously suggested, with a likely paleo-flow direction from northwest to southeast. The channel is most likely sourced from a segment in the northwestern portion of Cerberus Fossae, and is now buried by multiple Late Amazonian lavas with the same lava flow direction.

Key Points

• We performed detailed surface and subsurface mapping of the entire Elysium Planitia region to constrain lava areas, thicknesses, and volumes
• Elysium Planitia is composed of the products of about 40 effusive eruptions including large flood lava flows and lava shields
• Results indicate that there is no singular direction in dike propagation

Plain Language Summary

Elysium Planitia on Mars has a fascinating history of water and lava flows that shaped its landscape. It is the youngest volcanic terrain on the planet, and studying it helps us to better understand Mars’ past as well as recent hydrological and volcanic history. We examined this region by using spacecraft images and radar data to constrain areas, thicknesses, and volumes. An area almost as large as Europe was investigated. The study revealed the products of more than 40 volcanic events, with one of the largest flows infilling Athabasca Valles with a volume of 4,000 km³. The surface appearance and material properties suggest that Elysium Planitia is composed of basalt, the most common type of lava on Earth. The area also experienced several large floods of water, and there is evidence that lava and water interacted in the past. However, while there could be ice in the ground today, it likely occurs in small patches. The study also provides new insights into the Marte Vallis outflow channel. It seems to be larger, but not as deep as previously thought, with water flowing from northwest to southeast and fed from a fissure in the northwest. Marte Vallis was later covered by several lava layers.