Click for full image.
Cool image time! The photo to the right, cropped and reduced to post here, was taken on June 4, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It captures one of the many deep straight fissure canyons that make up the feature dubbed Cerberus Fossae in the center of Mars’ volcano country.
The crack is called a graben, and happens when the ground is either stretched from pressure from below, or when two adjacent large blocks of material move sideways relative to each other.
What makes this particular graben interesting are two features. First, the overlapping break suggests something complex took place at this spot when the crack separated. Second, the crack cut across the foot of an older frozen lava flow, meaning it has to be younger than that flow.
The overview map below provides a clue when that lava flow might have occurred, while also suggesting this crack in Cerberus Fossae might be much younger than expected.
The white cross marks the location of this crack and flow, at the western end of Cerberus Fossae and just beyond the north edge of the Athabasca Valles flood lava, hypothesized by some scientists [pdf] to be the youngest large flood lava event on the Red Planet. They estimate it occurred less than 600 million years ago, covering an area about the size of Great Britain in only a matter of weeks.
This spot is also not far from another feature scientists think might be a volcanic eruption only 50,000 to 210,000 years old.
The location is also close to where InSight’s seismometer has detected its largest Earthquakes, as indicated by the white splotches on the map.
Moreover, for the cracks of Cerberus Fossae to cut across older features is not unusual. See this April 2021 cool image for just one other example.
All these facts strongly suggest that the crack itself is relatively very young. The abrupt steepness of the canyon walls as well as the sharpness of its rim further reinforces this supposition. If the fissure was old, there would have been time for the rim and canyon to soften.
This data thus suggests that some very dramatic volcanic events on Mars have happened in the relatively recent past. The underground pressure required to stretch and crack the surface as extensively as it has been in Cerberus Fossae is not trivial. More important, that there is accumulating evidence it is young means that large scale volcanism might very well still be active on Mars. Events might be well spaced out in time, but they can still occur.
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