Click for full image.
Cool image time! The photo to the right, cropped to post here, was taken on May 3, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a remarkably fractured crater that lies only a few miles to the southeast of where the now-inactive Phoenix lander put down back in 2008, at the very high latitude of 69 degrees north.
Phoenix was purposely sent to this high latitude to find out what the ground and atmosphere was like there. It found the following:
Phoenix’s preliminary science accomplishments advance the goal of studying whether the Martian arctic environment has ever been favorable for microbes. Additional findings include documenting a mildly alkaline soil environment unlike any found by earlier Mars missions; finding small concentrations of salts that could be nutrients for life; discovering perchlorate salt, which has implications for ice and soil properties; and finding calcium carbonate, a marker of effects of liquid water.
Phoenix findings also support the goal of learning the history of water on Mars. These findings include excavating soil above the ice table, revealing at least two distinct types of ice deposits; observing snow descending from clouds; providing a mission-long weather record, with data on temperature, pressure, humidity and wind; observations of haze, clouds, frost and whirlwinds; and coordinating with NASA’s Mars Reconnaissance Orbiter to perform simultaneous ground and orbital observations of Martian weather.
Below is an overview map showing the location of both this crater and the Phoenix lander.
The white cross indicates the location of both Phoenix and this crater. The giant shield volcano Alba Mons, about 1,500 miles to the south, lies north of the Tharsis Bulge where Olympus Mons and the line of three other giant volcanoes are found.
Because the fractured crater is so close to Phoenix’s landing site, the ground and atmospheric conditions should be quite similar, and can act to help explain what we see. Thus, the white material in the cracks is probably frost — both water ice and dry ice — since the picture was taken in the spring, and the Sun is only beginning to warm the surface.
The cracked surface suggests two possibilities to my ignorant eye. One, the impact hit a hard surface (slab rock) lying on top of softer material (ice). Thus, the ground cracked. More likely however these fractures occurred much later, after the impact, and reflect the changes caused by the seasonal fluctuations of temperate and atmosphere. The higher salt content in the soil could also help cause these kinds of cracks, as conditions can sometimes cause it to push up from below.
The full image reinforces this second hypothesis. The crater is surrounded by an apron of material, also fractured, that is probably melted and refrozen ice, splashed in a wave by the original impact.
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