Instead of the surficial geologic features, we investigate the subsurface pre-fill topography in Chryse Planitia using the morphology and distribution of buried craters. With the recent advent of high-resolution gravity models 20 and comprehensive imagery 21 and topography data 22 of the planet, we revisit the possibility of Chryse Planitia being originated as an impact basin. An impact origin for the basin has been proposed previously 9, 18, 19, but was debated since there is no clear topographic depression compared to the adjacent lowlands, the gravity signature appeared weak and non-circular and any surface feature has been removed. Chryse Planitia is a ~2000 km wide basin within the northern lowlands near the dichotomy, located at the termini of Mars’ most prominent outflow channels (e.g., Ares Valles and Kasei Valles). These features in early basin-forming impacts may be obscured by subsequent crustal relaxation and burial beneath Hesperian and Amazonian aged lava-plains and sediments, especially within the northern lowlands of Mars 16, 17. Extensive studies on the moon showed circular, positive Bouguer anomalies form in impact basins as a result of a combination of crustal thinning, uplift of the mantle beneath, and later infill of dense materials 12, 13, 14, 15. Impact basins have near-circular topographic depressions with surrounding ringed structures, and mostly show positive Bouguer anomalies in gravity data. The confirmation of these ancient basins would advance our understanding of the impactor flux in the early period before ~4 Ga and place crucial constraints on the timing of the dichotomy forming event and the thermal evolution of Mars. Alternatively, many large basins could have existed on Mars 9, 10, 11 but the evidence that commonly supports the identification of large impact basins are obscured by later resurfacing, lending some uncertainties to their identification. The observed cratering record may imply a decrease in the impactor flux during Mars’ post-accretionary phase 8. Although the Martian crust may have formed within a hundred million years from solar system formation 6, 7 during which impact flux was expected to be high, currently on Mars only four large basins (diameter >780 km) have been identified with confidence (Hellas, Argyre, Utopia, and Isidis) among which only Isidis impacted onto the dichotomy. However, the early cratering record on Mars is not as clear as the Moon and Mercury since it has been modified via erosion and resurfacing events. Large basin-forming impacts have played a major role in shaping Mars’ surface and its climate, through interactions with the hydrosphere or cryosphere 4, 5.
On Mars, a hemispheric dichotomy formed during this period, possibly as a result of one giant impact 2, 3, resulting in a dramatic elevation difference of 5–6 kilometers between the southern highlands and northern lowlands. “So the discovery of hydrated minerals (has) significant indications on the geological and water history of the region and the climate evolution of Mars,” he said.Large basin-forming impacts significantly modified planetary surfaces and crusts, especially in the first billion years of solar system history when the impactor flux was orders of magnitude higher than at present 1. Many scientists have posited that the region may once have been an ocean on the surface of mars, and Yang hopes that the rover could go on to study different layers of a crater to discovery more about the chronology of the Red Planet’s change. The use of the rover to explore a far great expanse of Mars’ surface allowed for the discovery and similar projects on Utopia Planitia will become more common. The astonishing findings exceeded researchers’ expectations of the mission, becoming the first to show the existence of hydrated minerals at the landing site. The duricrust is particularly pronounced in Utopia Planitia, suggesting that the area of Mars’ surface had the most active water cycle.Įxperts also explained that no river beds or channels of water have been found in the area, suggesting that any water has been gone for long enough to allow the planet’s surface to be sufficiently weathered for any marks to be removed. This layer is known as duricrust and could be a key signal of the presence of water on the surface of Mars in the past. 1DbTLGPxVC- Hua Chunying 华春莹 May 7, 2022 China's Mars rover #Zhurong is ready for winter on the Red Planet.
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