Zhurong rover data indicates existence of ancient northern ocean on Mars

The scientific evidence was collected using the Zhurong rover's multispectral camera (MSCam). As many as 106 sets of panoramic images were captured by the navigation and terrain cameras. These images captured the surface morphology and structural characteristics of the region's rocks. 

The official statement reveal a "paleo-ocean area in the northern lowlands formed a special marine sedimentary geological unit known as the Vasitas Borealis Formation (VBF)."

According to the analysis of these images, the "exposed rocks featured bedding structures." These rocks appear to be distinct from the common volcanic rocks found on many parts of Mars' surface. Furthermore, these bedding structures differed from the other bedding structures formed by aeolian sand deposition. Additionally, the structures also indicated bidirectional flow characteristics, which are represented through the layers of the rock that the cross-bedding overlap.

"This bidirectional water flow pattern is usually formed by the fluid action with periodic flow direction changes, which is not common in eolian and fluvial environments but is common in the littoral-shallow sea environment of Earth," noted the statement.

As a result, the observed sedimentary rock structures could have formed during the regression of the northern plain paleo-ocean.

Mars is currently a barren, cold desert, but liquid water may have flowed on its surface billions of years ago. This research sheds new light on Mars' early history and may lead to finding potential clues of ancient life forms.

The School of Earth Sciences at China University of Geosciences in Wuhan led the new study. The results have been reported in the journal National Science Review. 

Study abstract:

Decades of research using remotely-sensed data have extracted evidence for the presence of an ocean in the northern lowlands of Mars in the Hesperian (∼3.3 Ga), but these claims have remained controversial due to the lack of in situ analysis of the associated geologic unit, the Vastitas Borealis Formation (VBF). The Tianwen-1/Zhurong rover was targeted to land within the VBF near its southern margin and has traversed almost 2 km southward toward the interpreted shoreline. We report here on the first in situ analysis of the VBF that reveals sedimentary structures and features in surface rocks that suggest that the VBF was deposited in a marine environment, providing direct support for the existence of an ancient (Hesperian) ocean on Mars.