On the broad Martian equatorial plain called Elysium Planitia, a huge swath of dark material has been hiding a secret, one that could upend our beliefs about the recent history of Mars.
In research published in April in Icarus a team led by David Horvath of the Planetary Science Institute used Mars Reconnaissance Orbiter (MRO) images to study rocky debris in the Cerberus Fossae fissures, finding evidence of volcanism on Mars — and what’s more, the Martian eruption happened so recently that ancient humans were already roaming the Earth.
The volcano in Cerberus Fossae scattered rock and volcanic ash across the planet’s equatorial plain 50,000 years ago. It’s the latest piece of evidence that a fissured, lava-crusted region of Mars called Cerberus Fossae may still be volcanically active.
And that, in turn, could be very interesting news for the search for life on Mars.
What’s new — Cerberus Fossae was already known for wide ancient lava flows, cracked and fissured by a long history of eruptions and tectonic movement. Most of those lava flows are around 500,000 to 2.5 million years old, which makes them some of the youngest volcanic eruptions on Mars.
Horvath and his colleagues noticed a dark layer of rock and ash and realized that it was even younger than those relatively fresh lava fields, with debris lying on top of the volcanically carved region. The area also has fewer meteor craters than nearby terrain — which means it’s been lying on the surface of Mars, exposed to impacts, for a lot less time. Based on that crater-counting method, it’s about 50,000 years old.
In human terms, 50,000 years sounds like a long time ago, but for a volcano, it’s barely a short nap. "I think if you think about Mars and compress the whole history of Mars into a single day, this would represent kind of that last second, so it's extremely recent,” Horvath tells Inverse. “A lot of times we think of Mars as more dormant and not really volcanically active, but this really raises that potential."
How they did it — Horvath and his colleagues pored over high-resolution satellite photos to understand the shape and structure of the rocky deposit. They also turned to images taken in several different wavelengths, outside the spectrum of visible light, to investigate what all that rock was actually made of, based on how the material absorbed and reflected different wavelengths of energy.
They concluded that around 53,000 years, a magma chamber beneath the lava plains of Cerberus Fossae erupted with incredible violence, blasting ash and rock 10 kilometers high into the Martian sky. That plume of material, rich in a mineral called pyroxene, buried the surrounding landscape under tens of centimeters of dark rock and volcanic ash.
Here’s the background — The debris from one recent eruption isn’t the only clue that the Martian ground beneath Cerberus Fossae may still be restless. About 1,600 kilometers away, NASA’s InSight lander has measured several dozen Marsquakes since 2018. Bruce Banerdt, principal investigator on NASA’s InSight Lander, and his colleagues have managed to pinpoint the epicenters of four of those quakes, and they all came from an area very close to Horvath’s volcanic deposit.
“And then there's another dozen or more that appear to be from the same area, we can't say for sure,” Banerdt tells Inverse. “We know that they come from that distance, and we know that they have a wave signature that's similar to the ones that we know are from that area, so it's a reasonable inference that these things are from that area as well.”
According to computer models, InSight’s collection of Marsquakes behaves like they could have come from magma flowing deep beneath the Martian surface.
If there is magma brewing beneath Cerberus Fossae, it’s probably lurking deep in the Martian crust, tens of kilometers beneath the surface, according to Horvath. It would be difficult for a shallower reservoir of magma to stay hot and fluid for such a long period of time between the youngest lava flows and the explosive eruption 50,000 years ago. Magma deeper in the crust, closer to the planet’s hot mantle, would have a better chance.
In the long run, geologists need more data to tell the tale.
“It kind of raises that possibility and makes it possible that there’s maybe extant life at present.”
Why it matters — An eruption happening that recently could mean that there’s still magma flowing up from the depths of Mars beneath Cerberus Fossae.
Banerdt has been looking for signs of seismic activity on Mars since the lander arrived at the Red Planet in 2018. Banerdt, who is not involved in the study, says this means that Mars is still volcanically active in geologic terms.
Banerdt tells Inverse that an area would be inactive if magma reservoirs weren’t feeding from below and little seismic activity. “If the conditions are still possible that something should or would happen in the future, we would consider it to be active,” he says — and Cerberus Fossae might well meet those conditions.
And that, in turn, could have interesting implications for how we understand Mars: as not a dead world but an active one — and one that could have recently hosted life, and might still.
- The structure of nearby impact craters hints at ice just beneath the surface of Cerberus Fossae.
- Geologists have studied several craters in the area, and they suggest that when those ancient meteors struck the Martian surface, the ground compressed and rebounded as if there was ice lying not far beneath the surface.
- Where there’s ice and heat, there’s usually water.
“If there is subsurface ice and if there is subsurface movement of magma bodies, this might be a place where heat from the magma melts ice to make water aquifers and potential habitats,” California Institute of Technology planetary scientist Bethany Ehlmann tells Inverse.
If a magma chamber beneath Cerberus Fossae erupted as recently as 50,000 years ago, hardy extremophile microbes might have flourished there in the fairly recent past. They might even still be around if the area is still volcanically active.
“Mixing that heat source and this water definitely raises the potential that you could have had at least a recent habitable region, and possibly something that could have maybe extended into the present day,” says Horvath. “It kind of raises that possibility and makes it possible that there’s maybe extant life at present.”
Horvath says he considers Elysium Planitia in general “definitely one of the top places to go to look for life at present or well-preserved life in the possible recent past.”
What’s next — Here on Earth, scientists who want a better look at the ground beneath seismically active areas may hike into the field with dozens of seismometers to study an area just 10 or 20 kilometers wide. That array of seismometers can then measure seismic waves from dozens of angles, distances, and directions. Geoscientists use those measurements to build models of what underground structures and fault systems look like.
On Mars, however, geologists are working with just one seismometer so far: the one aboard InSight. Martian geologists won’t get really high-resolution seismic data until someday in the future, when astronauts arrive on Mars to do field geology surveys. “That's maybe not complete science fiction, but it's getting pretty close, I think,” says Banerdt. Uncrewed missions could provide more detail in the meantime, however.
“In terms of understanding an active area like Cerberus Fossae, if you could put down maybe 3 or 4 seismometers in the region, maybe a few hundred kilometers apart, you could start to pinpoint a little bit about where these quakes are occurring, and possibly even be able to start finding out where the fault planes are,” Banerdt says.
That could help geologists understand how – and how much – energy is being released under Cerberus Fossae. And those hypothetical future instruments could also measure how much heat is flowing through the Martian ground – something InSight has tried, with no luck, to do.
Horvath suggests that this explosive outburst may not have been an anomaly for Cerberus Fossae, either. Other rocky deposits may lie buried under lava, where radar observations could probe beneath the surface to look for them. Horvath and his colleagues are also looking through existing MRO data for the rocky aftermath of other fairly recent eruptions.
“I think InSight right now definitely gets us our best look into that subsurface to really determine if there is still activity,” says Horvath.
Abstract: Volcanic activity on Mars peaked during the Noachian and Hesperian periods but has continued since then in isolated locales. Elysium Planitia hosts numerous young, fissure-fed flood lavas with ages ranging from approximately 500 to 2.5 million years (Ma). We present evidence for a fine-grained unit that is atypical of aeolian deposits in the region and may be the youngest volcanic deposit yet documented on Mars. The unit has a low albedo, high thermal inertia, includes high‑calcium pyroxene-rich material, and is distributed symmetrically around a segment of the Cerberus Fossae fissure system in Elysium Planitia. This deposit is superficially similar to features interpreted as pyroclastic deposits on the Moon and Mercury. Unlike previously documented lava flows in Elysium Planitia, this feature is morphologically consistent with a fissure-fed pyroclastic deposit, mantling the surrounding lava flows with a thickness on the order of tens of cm over most of the deposit and a volume of 1.1–2.8 × 107 m3. Thickness and volume estimates are consistent with tephra deposits on Earth. Stratigraphic relationships indicate a relative age younger than the surrounding volcanic plains and the Zunil impact crater (~0.1–1 Ma), with crater counting suggesting that the deposit has an absolute model age of 53 ± 7 to 210 ± 12 ka. This young age implies that if this deposit is volcanic then the Cerberus Fossae region may not be extinct and that Mars may still be volcanically active. This interpretation is consistent with the identification of seismicity in this region by the Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) lander, and has additional implications for astrobiology.