Calibrating the Martian Cratering Chronology: An In Situ Dating Mission
- Paper number
IAC-08.A3.3.A10
- Author
Dr. Jeffrey Plescia, Johns Hopkins University Applied Physics Laboratory, United States
- Coauthor
Dr. Tim Swindle, The University of Arizona, United States
- Year
2008
- Abstract
One of the most critical aspects of understanding the geologic, climatological and biologic history of Mars is the absolute timing of events. Presently, only a relative chronology has been established using the frequency of craters on different surfaces (higher frequencies indicate older ages). Attempts to correlate the lunar cratering chronology (established by dating Apollo and Luna samples from known locations with well-defined crater frequencies) to the martian rate have large uncertainties. For example, the youngest major volcanic surface (Cerberus Plains) have model ages ranging from a few million years to hundreds of millions of years.
To calibrate the absolute cratering chronology for Mars, an absolute radiometric age must be determined for an igneous rock from a known location with a well-defined crater frequency. The site must be geologically simple such that the age indicates the surface emplacement age and the area must not have experienced significant post-emplacement modification that would disturb the cratering statistics or alter the samples. Target sites include Lunae Planum, eastern Tharsis plains, and the Cerberus Plains.
The approach to this problem for the Moon has been to date returned samples. However, a Mars sample return is expensive and challenging and may well be focused on objectives such as the sedimentary history or exploration of a site with the potential of preserving biotic processes. A more promising approach to establishing the chronology is to determine the radiometric ages using an in situ experiment. While in situ techniques are less precise than terrestrial analyses, in situ precisions of 10-20
A mission with the objective of determining a radiometric age would be relatively simple and need survive only a short time. A number of samples would be acquired from bedrock to ensure that a statistically significant age has been determined. Various techniques have been proposed and are under development including K/Ar and Rb/Sr. After acquisition the chemistry and mineralogy of the sample needs to be determined and the radiogenic isotopes measured to calculate the age. Limited mobility would be advantageous to ensure that bedrock is obtained, assure a variety of chemical compositions, and avoid the problem of surface aeolian cover. In addition to providing information on the absolute timing of events, such a mission would provide critical information on the petrology and geochemistry of large-scale igneous units on Mars and help constrain the planet’s thermal and magmatic history.
- Abstract document
- Manuscript document
IAC-08.A3.3.A10.pdf (🔒 authorized access only).
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