On February 18th, 2021, NASA’s Perseverance rover landed in Jezero crater on Mars. This feature was selected because liquid water may have once flowed into it, as indicated by the delta feature at its western edge. Since landing, Perseverance has been exploring the region’s geology and past habitability, including the samples it collected for eventual return to Earth. Analyzing these samples will provide new clues about Mars’ warm and watery past and address whether life once existed there.
However, the delta fan is not the only significant feature in the Jezero crater near where the Perseverance rover landed. There’s also the recently-named Jezero Mons, a mountain that dominates the southeastern horizon, identified in Perseverance rover images. According to new research, lava flows possibly originating from this mountain could have shaped the geology of the crater floor. According to their findings, the analysis of the Perseverance samples could also reveal clues about ancient Mars when it was still geologically active.
The study was led by Sara C. Cuevas-Quiñones, a PhD Planetary Science student from the School of Earth and Atmospheric Sciences (EAS) at the Georgia Institute of Technology (Georgia Tech) and Brown University. She was joined by EAS Professor Dr. James Wray, EAS Assistant Professor Frances Rivera-Hernández, and Jacob B. Adler, a Research Assistant Professor with the School of Earth and Space Exploration at Arizona State University (SESE-ASU). The paper describing their findings appeared on May 3rd in the journal Nature.
As Cuevas-Quiñones and her colleagues note in their paper, the detection of clay and carbonate minerals on Jezero Crater’s floor supports the conclusion that the sedimentary deposits on the crater’s western edge are the result of aqueous activity that took place roughly 3.8 to 3.5 billion years ago. In addition, satellite observations have revealed a set of non-sedimentary geologic materials that cover most of the Jezero crater’s floor. This includes data obtained by the Mars Odyssey‘s Thermal Emission Imaging System (THEMIS) and the Mars Orbiter Laser Altimeter (MOLA) aboard the Mars Global Surveyor.
Spectral features observed in the Jezero crater indicated the presence of olivine [(Mg, Fe)2SiO4], a mineral commonly found in igneous rocks and a primary part of Earth’s upper crust. The spectra also indicated the presence of magnesium carbonate (MgCO3) and hydrated minerals. As Prof. Wray told Universe Today via email, this constitutes evidence that Jezero Mons was once an active volcano:
Volcanoes are built ‘from the ground up’, as successive layers of lava and ash erupt and spread from the source vent; so if Jezero Mons is indeed a volcano (as we argue), then its simple presence would be evidence that it was once active, to have built up the mountain that we see looming above the crater rim today. There are also possible flows of material visible on the mountain’s northwestern flank extending down onto Jezero crater’s southeastern floor, which could have emerged when the volcano was active. And finally, there are the volcanic rocks that Perseverance encountered in its traverse across the crater floor – we can’t say for sure that those came from Jezero Mons, but they imply that there was an active volcano somewhere nearby in the region’s past! And Jezero Mons seems like the most visually apparent candidate to us.
Before the Perseverance rover landed, there were several theories about Jezero’s curious geology, ranging from lakebed sedimentary deposits, sandstone formed by wind-blown sand, or volcanic ash. However, observations by the Perseverance rover of the Séítah formation revealed lightly altered olivine cumulate rock. These minerals form when olivine crystals accumulate and settle from a magma or lava flow. These mineral deposits predate the formation of the crater’s delta features.
Similarly, the darker-toned rock unit known as the Máaz formation dominates the central crater floor, which shows spectral signatures of pyroxene, another mineral associated with volcanic outflows. As Wray told Universe Today, the presence of volcanic and aqueous activity would have had a significant impact on the crater:
“Given the clear evidence for river channels and sediment fans, before Perseverance landed some thought most of the material on the floor might have been sedimentary rocks, perhaps lake deposits. But the first rocks explored with the rover appeared pretty clearly volcanic (or at least igneous, i.e. cooled from a magma). If Jezero Mons had been identified and more widely discussed before the rover landed, then maybe this wouldn’t have been so surprising. The timing of Jezero Mons’s activity is pretty uncertain, but there is indeed evidence from the rover (and from orbital mapping of materials across the crater) that episodes of water flow and volcanism interleaved with each other over time.”
To evaluate this hypothesis, the team consulted datasets from the Mars Reconnaissance Orbiter’s (MRO) High Resolution Imaging Science Experiment (HiRISE) and other orbiter missions. Infrared hyperspectral mapping of the northern and eastern flanks of the mountain showed widespread pyroxene-bearing materials and a mixture of low- and high-calcium pyroxenes at the summit. Meanwhile, the mixing of pyroxene-rich materials and underlying bedrock was visible in several areas of the crater around the mountain’s western flank.
Similarly, the team measured the mountain’s morphometry and compared it to similarly sized volcanoes identified on Earth and Mars. While they found that most Martian shield volcanoes are significantly larger than Jezero Mons, a similarly sized mountain with a summit crater believed to have once been an explosive volcano has been observed in Thaumasia Planum. In addition, two of the first mountains identified as potential composite volcanoes—Zephyria and Apollinarus Tholi—are even more similar in size to Jezero Mons.
.png){kind=tracking}
For an Earth-based comparison, the team measured Antarctica’s Mt. Sidley, which has been identified as a potential analog for the Argyre Mons volcanic cone, but is more similar in size to Jezero Mons. As Wray noted, the timing of Jezero Mons’s activity and the origin of volcanic rocks in the crater remain open questions. Nevertheless, evidence obtained by Perseverance and orbiters that have mapped the Jezero Crater suggests that episodes of water flow and volcanism interleaved with each other over time.
“In terms of what that means for habitability, volcanic eruptions-like any natural disaster-often have immediate negative effects, but can have longer-term benefits for the evolution of ecosystems on Earth,” Wray added. “In particular, a sizable volcano so close to the Jezero crater paleolake implies subsurface heat that could have prolonged the stability of any liquid water there, a potential boon for habitability on a planet 50% farther from the Sun than Earth.”
The timing of Mars’ volcanism and its possible effect on habitability cannot be answered until a Mars sample-return mission can be mounted. Unfortunately, scientists will have to wait a while due to the cancellation of the NASA/ESA Mars Sample Return (MSR) mission. Currently, the plan is to return them via a crewed mission planned for the 2030s, though experts predict that such missions will happen no sooner than 2040. But as Wray explained, the analysis of the Perseverance samples will be a major game-changer:
“The sample return will provide major, unique insights into Jezero crater’s history, such as solving the “pretty uncertain timing” problem mentioned above: we can date igneous rocks quite precisely in Earth-based labs by measuring rare isotopes of trace elements, but this is very difficult to do with miniaturized rover instruments. Fortunately, the sample return from Jezero is exactly what NASA has planned! I can’t imagine another place on Mars from which it would be much more valuable to return samples, so I hope we get them back, whether the US continues to lead on that effort or someone else steps up instead.”
In the meantime, says Wray, another rover (or possibly a crewed mission) to the Jezero Crater would address these two questions. This mission could set down between Jezero Mons and the crater’s floor, allowing it to explore the mountain and volcanic deposits directly. The team also suggests that additional high-resolution mapping could greatly increase our knowledge of the eastern side of Jezero. This could be accomplished using existing orbital assets or by future spacecraft like the ESA’s LightShip/SpotLight mission under consideration.
Further Reading: NCBI