Publication Date:
2017-05-06
Description:
Large alluvial fan deposits on Mars record relatively recent habitable surface conditions (≲3.5 Ga, Late Hesperian - Amazonian). We find net sedimentation rate 〈(4–8) μm/yr in the alluvial fan deposits, using the frequency of craters that are interbedded with alluvial fan deposits as a fluvial-process chronometer. Considering only the observed interbedded craters sets a lower bound of 〉20 Myr on the total time interval spanned by alluvial fan aggradation, 〉103-fold longer than previous lower limits. A more realistic approach that corrects for craters fully entombed in the fan deposits raises the lower bound to 〉(100–300) Myr. Several factors not included in our calculations would further increase the lower bound. The lower bound rules out fan formation by a brief climate anomaly. Therefore, during the Late Hesperian - Amazonian on Mars, persistent or repeated processes permitted habitable surface conditions. ©2017. American Geophysical Union. All Rights Reserved.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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