1999 Fiscal Year Final Research Report Summary
Study on the rampart craters
| Project/Area Number |
10640402
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KURITA Kei University of Tokyo, Graduate School of Science, Associate Professor, 大学院・理学系研究科, 助教授 (00111451)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Mars / Crater / Rampart / ejecta / impact / planetary surface |
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| Research Abstract |
The rampart crater, which is found only on Mars is a peculiar type of crater. The morphological features resemble to those of terrestrial pyroclastic flows and lahars. It shares a nature of gravity current. In this study we have investigated geomorphological features of this rampart crater based on the high resolution images taken by Viking Orbiters.
We found ;
1) The onset diameter of rampart crater clearly exists in Chryse Planitia. Also there exist regional variations of the onset diameter, which indicate variation of depth to the hydrous (or permafrost) layer.
2) Fresh rampart craters exihit the double lobate structure. It consists of an inner thick lobe and an outer thin lobe. This finfing is contradictory to the previous studies, which stated the single lobate type is typical. We consider that the previous studies underestimated erosion process, which may sweep out the outer thin lobe.
3) The order of deposition of these two lobes was determined. The inner thick lobe deposited first, then the outer thin lobe deposited. These findings set a crucial constraint for the formation mechanism of the rampart crater., because a single impact event should result in double deposition processes of ejecta. We propose a simple mechanism for the formation of these two lobes.
4) The structure of multilobed rampart crater is interpreted as a modification of the double lobate type.
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