Climate Forcing of Ripple Migration and Crest Alignment in the Last 400 kyr in Meridiani Planum, Mars

Abstract

The plains ripples of Meridiani Planum are the first paleo‐aeolian bedforms on Mars to have had their last migration episode constrained in time (to ~50–200 ka). Here we test how variations in orbital configuration, air pressure, and atmospheric dust loading over the past 400 kyr affect bedform mobility and crest alignment. Using the National Aeronautics and Space Administration Ames Mars Global Climate Model, we ran a series of sensitivity tests under a number of different conditions, seeking changes in wind patterns relative to those modeled for present‐day conditions. Results indicate that enhanced sand drift potential in Meridiani Planum correlates with (1) high axial obliquity, (2) a longitude of perihelion (Lp) near southern summer solstice, and (3) a greater air pressure. The last pulse of westward plains ripple migration likely occurred during the most recent obliquity (relative) maximum, from 111 to 86 ka. At Lp coinciding with southern summer solstice, the Mars Global Climate Model produced a westward resultant drift direction, consistent with the observed north‐south plains ripple crest alignment. However, smaller superposed ripples, aligned NNE‐SSW, are consistent with a strengthened northern summer Hadley return flow, occurring when Lp coincided with northern summer solstice. The superposed NNE‐SSW ripples likely formed as the axial obliquity decreased during the last relative maximum and Lp swung toward northern summer, from 86 to 72 ka. The timeline of bedform activity supports the proposed sequence of CO2 sequestration in the south polar residual cap over the past 400 kyr.

Ancient Stratigraphy Preserving a Wet‐to‐Dry, Fluvio‐Lacustrine to Aeolian Transition Near Barth Crater, Arabia Terra, Mars

“…Given the scale of the paleo‐dune field discussed in this work, and the consistency in preserved transport direction over >100 km, the ~90° difference between modern and ancient transport requires a regional‐scale difference in atmospheric conditions between today and ancient Mars at the time of this paleo‐dune field. Regional‐scale changes in the dominant sand‐transporting winds could be caused by changes in obliquity, atmospheric density, composition, or solar insolation (Fenton et al, ; Newman et al, ).…”

Patterns in Mobility and Modification of Middle‐ and High‐Latitude Southern Hemisphere Dunes on Mars

“…These boundary conditions can change over time and create shifting cryospheric and aeolian environments (e.g., Brothers & Kocurek, 2018). For example, studies have turned to variations in orbital parameters of Mars to explain climate change; Martian obliquity, which varies with a periodicity of 10 4 -10 5 years and which can strongly influence insolation and change atmospheric density and wind strengths (Brothers & Kocurek, 2018;Haberle et al, 2003;Head et al, 2003;Laskar et al, 2004), likely serves as a cyclical climate forcing agent influencing the formation and stabilization of dune fields and sand sheets (e.g., Ayoub et al, 2014;Brothers & Kocurek, 2018;Fenton et al, 2018;Laskar et al, 2004;. Since we can assume that these dune fields originally accumulated in an environment in which sand availability and wind transport capacity allowed sand saltation and dune accumulation, we can also interpret, in accordance with Fenton and Hayward (2010), the morphological shift to SI values >1 as a potential indicator of climate change postdating the formation of the dune fields.…”

“…Thus, our combined observations of high-latitude dune mobility and modification may reflect a recent shift in the climate to activate or stabilize these dune fields. For example, studies have turned to variations in orbital parameters of Mars to explain climate change; Martian obliquity, which varies with a periodicity of 10 4 -10 5 years and which can strongly influence insolation and change atmospheric density and wind strengths (Brothers & Kocurek, 2018;Haberle et al, 2003;Head et al, 2003;Laskar et al, 2004), likely serves as a cyclical climate forcing agent influencing the formation and stabilization of dune fields and sand sheets (e.g., Ayoub et al, 2014;Brothers & Kocurek, 2018;Fenton et al, 2018;Laskar et al, 2004;.…”

“…Multiple studies have now revealed present-day movement of sand by the wind and migration of bedforms (dunes and ripples collectively) in some environments in the current Martian climate and~6-mbar atmosphere (e.g., Banks et al, 2015;Banks et al, 2017;Bourke et al, 2008;Bridges et al, 2010Bridges et al, , 2012Bridges et al, , 2013Chojnacki et al, 2011Chojnacki et al, , 2014Chojnacki et al, , 2015Chojnacki et al, , 2017Chojnacki et al, , 2018aChojnacki et al, , 2018bFenton, 2006;Silvestro et al, 2010Silvestro et al, , 2011Silvestro et al, , 2013Silvestro et al, , 2016Sullivan et al, 2008). Dune field and sand sheet formation, activity, and stabilization, on both Earth and Mars, are driven by factors such as sediment availability and wind transport capacity, potentially initiated by changes in climatic conditions (e.g., Ayoub et al, 2014;Fenton et al, 2015Fenton et al, , 2018Kocurek, 1998;Kocurek et al, 2007;Kocurek & Lancaster, 1999;Runyon, Bridges, Ayoub, et al, 2017;Silvestro et al, 2015).…”

Degradation of Endeavour Crater Based on Orbital and Rover‐Based Observations in Combination With Landscape Evolution Modeling

“…The orientation of the interior mound and trough is also consistent with mesoscale atmospheric modeling over Endeavour that shows a dominant wind regime with winds coming from the east to the southeast for multiple hours each sol (Chojnacki et al, ; Fenton et al, ). In addition, Fenton et al (, ) have shown that longer‐term regional‐scale easterlies are predicted to be the dominant sediment‐moving winds, consistent with the north‐south oriented crest lines associated with wind‐blown ripples that cover much of the Meridiani plains (Arvidson et al, ).…”