Constraints on the Noachian Paleoclimate of the Martian Highlands From Landscape Evolution Modeling

Abstract

The progressive degradation and loss of impact craters throughout the Noachian Period on Mars indicate prolonged erosion, rather than only a brief spike around the Noachian/Hesperian transition. The purpose of this study is to determine which suite(s) of geomorphic processes and rates best reproduce the relict Noachian landscape. We modeled the evolution of two study areas in the Martian highlands, Noachis Terra and Terra Cimmeria, to constrain the long-term erosional processes and rates that prevailed~4.0-3.7 Ga, before the valley networks formed. Our model runs indicate a very low erosion rate and inefficient runoff production during the Middle and Late Noachian Epochs. The terrestrial equivalent of 2 and 1.5 Myr worth of erosional work under arid to semiarid conditions with inefficient runoff production was required in order to replicate the landscape at Noachis Terra and Terra Cimmeria, respectively, over~300 Myr. Low areas in the landscape filled with sediments, while mass wasting and fluvial erosion were focused on crater rims and interior walls. The surface characteristics that best reproduce the observed landscape are a bedrock weathering rate around 0.0005-0.001 m/year with regolith that is 100 times more erodible than bedrock, suggesting that impact comminution and aqueous weathering produced abundant transportable material on Noachian Mars. The simulation results suggest that the Noachian paleoclimate was more arid than around the Noachian/Hesperian transition, but it supported occasional precipitation (snow or rain) that weathered surface materials and transported sediments.Plain Language Summary Evidence shows that Mars was once wetter with liquid water flowing long enough on the surface to form valley networks. Previous studies indicate that the climate responsible for valley formation was short lived, although older craters are much more degraded than can be explained by short-term climate change. A landscape evolution model was used to recreate the landforms we see at two locations on Mars, Noachis Terra and Terra Cimmeria, to estimate the possible climatic conditions responsible for shaping the topography of early Mars before the formation of valley networks (~4.0-3.7 Ga). We controlled parameters such as aridity, the weathering rate of the surface material, and how much of the precipitation contributes to surface runoff. Our model runs indicate conditions similar to those of arid to semiarid environments on Earth with a very low erosion rate and inefficient runoff during the Middle and Late Noachian Epochs. Our results also show that crater impacts and aqueous weathering produced abundant loose materials that are transportable by surface flow. A major portion of early Mars was more arid than around the time of intense valley formation, but it supported occasional precipitation (snow or rain) that weathered and transported surface sediments. Howard et al., 2005; Irwin et al., 2015; Moore & Howard, 2005). A longer-term wet climate likely would result in MATSUBARA ET AL. 2958

How Much of the Sediment in Gale Crater's Central Mound Was Fluvially Transported?

“…However, while such a value might be plausible during the intense erosion in the Early Noachian (Hynek & Phillips, 2001), it is unreasonably high after this time, at least for most places on Mars. Estimates of post-Middle Noachian erosion rates are more than an order of magnitude lower (e.g., Golombek et al, 2006;Matsubara et al, 2018). For example,~2 m of denudation was inferred in Milna crater watershed in the Margaritifer Sinus Quadrangle during a similar period of time (Buhler et al, 2014).…”

Evolution of Escarpments, Pediments, and Plains in the Noachian Highlands of Mars

“…In a hypo-fluvial regime earlier in the Noachian Period, deposition of impact ejecta exceeded fluvial and eolian denudation, leading to the net aggradation of the highland intercrater surfaces that Matsubara et al (2018) found when reproducing the topography of two study areas in a landscape evolution model (see also the Noachian craters with intact ejecta in Figures 5d, 7c, and 7d). These are transport-limited conditions in one sense, because the regolith could be transported if adequate runoff were available.…”

“…This area is more densely dissected by valley networks, and here it is useful to observe how Late Noachian to Early Hesperian channelized flow responded to older intercrater topography. This study area is one of the sites reproduced in a simulation model by Matsubara et al (2018).…”

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

“…A brief summary of the MARSSIM model is presented in this section to provide context for our simulations and inferred results for the fluvial degradation of Endeavour. The reader is referred to papers by Barnhart et al (2009), Forsberg-Taylor et al (2004, Howard (1994Howard ( , 1997Howard ( , 2007, Howard et al (2005), and Matsubara et al (2011Matsubara et al ( , 2018 for detailed discussions of model development and past applications to the fluvial history of Mars.…”

“…Fluvial period value adopted from Matsubara et al (2018) Postfluvial diffusion period values chosen after experimentation to produce lowered upper interior slopes, fill in interior channels, and maintain pediment surfaces…”