The Geologic Map of the MTM 45302 quadrangle in Northeastern Tempe Terra on Mars.

We present our work on developing the 1:1M scale geologic map of a quadrangle of Mars in the Northeastern Tempe Terra region, next to the transition between Martian highlands and lowlands. The MTM 45302 quadrangle covers an area of about 200 by 300 kilometers, centered at 302.5°E, 42.5°N. We based our mapping on data from NASA’s Mars Global Surveyor, Mars Odyssey,  Mars Reconnaissance Orbiter, the ESA’s Mars Express, and CNSA’s Tianwen-1.

The regional topography in the area dips towards the northeast, with a total elevation decrease of about 2000 meters. We defined three plateau units in the area, with morphologies of wide, gently-dipping flat surfaces bounded by cliffs.  Moderate resolution imagery shows spots with evidence of layering within the plateaus units. Crater size frequency distribution indicates ages of 3.9 to 3.4 Ga for the plateau units. The three mapped units are separated stratigraphically by erosional unconformities, cross-cutting craters, and linear features. The middle and most extensive plateau unit is cut by parallel elongated valleys oriented NNE-SSW, exposing mounds, pitted terrain, fan deltas, and inverted channels in the lower plateau unit. The mapped channel axes are often associated with the trend of the valleys formed by the erosion of plateaus. Wrinkle ridges are present on each plateau unit, and their tectonic expression is confined to each relative unit. In the south portion of the quadrangle, ENE-WSW trending linear tectonic features of the Tempe Terra system cut through all the units. Craters in the MTM exhibit pedestal, radial, single- and multi-layer ejecta morphologies, and different infill styles. Several crater floors contain curvilinear ridges and troughs. We are currently reviewing the interpretation of the mapped features, their stratigraphic relationship and building hypotheses on the geologic evolution of the area, preparing the final geologic mapping product.

Besides the purpose of describing the evolution in space and time of the area, our mapping project serves as a context for a companion study about the presence of ice in the shallow Martian crust, observed from imaging spectroscopy at a spatial resolution of about 20 meters per pixel.  The area of our map also contains six ~0.5 - 2 km diameter, relatively recent impact craters with similar thermal inertia and crater morphology characteristics, including radial ejecta which exhibit unusually bright thermal inertia at night. Furnari et al. (2024)  studied one of these craters using spectral analysis, highlighting an anomalously large abundance of seasonal water ice on the ejecta, offering new insights on ice variation in the Martian ground. Additionally, crater analysis by Gou et al. (2024) in the lowlands Chryse Planitia region to the southeast of our study area posits that craters with multi-layer ejecta at this latitude indicate the presence of subsurface volatiles. 

The stratigraphic and structural relations of the geologic features mapped in this work provide the key to reconstruct the geologic evolution of processes that occurred on Mars in an area where the southern highlands are transitioning to the northern lowlands.  Evidences for ice-related processes in the geologic history, combined with the instrumental record of ice in relatively recent craters, suggests that this region likely hosted ice in the past and potentially in the present.

 

Acknowledgements: This work is supported by the ASI-INAF Mars Exploration agreement  2023-3-HH 0.

References: Furnari et al., 2024, Study of the seasonal water ice in the ejecta of a small crater on Mars. Congresso di Scienze Planetarie, Bormio, Italy, 5-9 Febbraio 2024;  Gou et al., 2024, Paleoenvironment implications of layered ejecta craters in the Chryse Planitia, Mars, Icarus, Volume 410, 115918.