Does our neighboring planet still have the remains of its former fire? This now suggests a discovery: A dark deposit around a crevice in the surface of Mars could be the trace of an explosive eruption that only occurred in the last 53,000 to 210,000 years. The InSight probe has also previously detected underground seismic activity in the area. Mars could therefore still be volcanically active, which also increases the possibility of life-friendly conditions underground, say the scientists.
Our neighboring planet was once downright “hot-blooded” – the remains of the sometimes gigantic volcanic cones and rock deposits on its surface testify to this. But these traces of volcanism are largely ancient: Most of the volcanism on the Red Planet occurred three to four billion years ago – later it boiled less and less. It has so far been assumed that small eruptions occurred until about three million years ago. But the current study now points to much more recent activities: “The structure in our sight could be the youngest volcanic deposit that has been documented on Mars so far,” says lead author David Horvath from the University of Arizona.
A dark deposit in sight
Horvath and his colleagues discovered the structure on satellite images of the Elysium Planitia region in the area of the “Cerberus Fossae” fracture zone. It is an approximately 13-kilometer-wide, dark deposit that surrounds a roughly 30-kilometer-long crevice in the underground with a strikingly uniform pattern. “When we first noticed this deposit, we knew it was special,” says senior author Jeff Andrews-Hanna University of Arizona. “The deposit was unlike anything that had been discovered in the region or even on all of Mars so far”. The features suggested that it might be the trace of an explosive eruption – a burst of material propelled by expanding gases, much like opening a shaken soda bottle.
“This phenomenon overlays the surrounding rock formations and appears to be a relatively fresh and thin deposit of ash and rock,” reports Horvath of the results of the investigation. Scientists therefore assume that it was caused by a pyroclastic eruption. Through so-called stratigraphic analyzes of the surface structures in the area, the scientists were also able to narrow down when the deposit occurred. Accordingly, it is possibly only between 53,000 and 210,000 years old. “If we were to compress the geological history of Mars into a single day, it would have happened in the very last second,” says Horvath.
Co-author Pranabendu Moitra suggests that the explosion was either triggered by gases already present in Martian magma or that it occurred when the magma came into contact with permafrost in the Martian subsurface. “The ice melts into water, mixes with the magma and evaporates, causing a violent explosion of the mixture,” says Moitra. The process could have been triggered by the tremors of an impact: the trail of the volcanic eruption is only about ten kilometers from the young crater called Zunil. “Albeit speculative, it seems possible that the impact triggered the volcanic eruption,” says Moitra.
There is a rumble underground in the region
Another peculiarity of the location in the area of the Cerberus Fossae is even more interesting: this region is the focus of a discovery by NASA’s InSight probe, which has been investigating seismic activity on Mars since 2018. InSight has detected two marsquakes whose epicentres were located in the region around the Cerberus Fossae. There were already suspicions that these quakes could be due to the movement of magma underground. The location of the young trace of volcanism seems to fit in with this. “The age of this deposit suggests that there might still be volcanic activity on Mars, and it is fascinating that the Marsquakes discovered by the InSight mission came from the Cerberus Fossae,” says Horvath.
As he and his colleagues emphasize, knowledge about volcanism on Mars also has a role in assessing the question of whether there could be microbial life in the subsurface of the planet. “The interplay of rising magma and the icy substrate of this region could have created favorable conditions for microbial life relatively recently and thus increase the possibility of existing life in this region,” says Horvath.
So it seems clear: The exciting region and the presumably most recent trace of a volcanic eruption on Mars will now continue to be the focus of science.
Source: University of Arizona, Articles: ICARUS, doi: 10.1016 / j.icarus.2021.114499