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Scientists have long suspected that Mars is geologically “dead,” but new spacecraft observations suggest the Red Planet’s volcanoes are merely sleeping.
That means that Olympus Mons, the extinct Martian volcano that at around 16 miles (26 kilometers) above the surrounding Martian plains is the largest mountain in the solar system, may in fact be a slumbering giant.
The observations were made with the European Space Agency (ESA) mission ExoMars Trace Gas Orbiter (TGO) as it studied volcanic fissures along the Alba Mons region of the Red Planet. Alba Mons is in the Tharsis region of Mars, the same area that is home to Olympus Mons. While the latter is the tallest volcano in the solar system, at 374 miles (600 km) across, about the size of Arizona, the Alba Mons region is the largest volcano when considering surface area.
TGO detected gas containing hydrogen chloride making its way to the surface of Mars through the Alba Mons fissures. The same gas is commonly found escaping from magmatic vents on Earth, with the compound coming from hot magma beneath the surface. Detecting it on Mars is a sign of dormant Martian volcanism.
Orbital imagery had previously shown some volcanoes appear to have been active within the last few million years, and seismometers have detected the rumbling of “marsquakes,” both implying the Red Planet is volcanically active. However, eruptions and lava flows have been conspicuous by their absence.
“Our findings suggest that Mars has retained enough internal heat to support volcanic activity until recently, and possibly still does,” team co-leader and scientist at the Space Research Centre of the Polish Academy of Sciences, Daniel Mège, said in a statement sent to Space.com via email. “The TGO was able to find the smoking gun. It was like looking for a needle in a haystack.”
Evidence of dormant Martian volcanism is rising
Mège and colleagues were first alerted to something strange happening on Mars when they noticed spikes of hydrogen chloride during Martian summer and on the northern hemisphere of the Red Planet. That is both a time and place at which hydrogen chloride shouldn’t be detected.
The gas usually peaks in the northern hemisphere during winter on Mars, disappearing in the summer. This variation is connected to the water and dust cycle on Mars. An exception to the rule occurs over volcanic fissures on the flanks of the Alba Mons volcano, in early summer.
The TGO followed up on this by detecting fresh and narrow fissures, in some cases hundreds of feet long, in the Alba Mons region. A clear sign of volcanism.
“It’s truly amazing that it spotted a handful of molecules from a perhaps intermittent source, whilst moving continuously along its orbit to monitor the whole Martian atmosphere,” Mège said.
The team thinks that these gases have been rising from the interior of Mars during the Martian winter, becoming blocked by ice. When this ice sublimates, changes directly from solid to gas, during summer, the gas is released, prompting spikes in hydrogen chloride seen by the TGO.
“Looking at the spatial distribution of the seeping, it became instantly obvious to me that there was something volcanic behind it, but it had to be demonstrated,” said Mège. “A huge part of the work consisted of examining all the possible chemical processes going on in the Martian atmosphere.
“We needed to be rigorous, critical and creative to explain the presence of hydrogen chloride. The data were complex, but also excellent brain food.”
Implications for life on Mars?
Mège and colleagues theorize that the gas is connected to “volcanic plumbing” in the form of a dormant magma chamber under the surface of Mars.
Regions like this could become hotspots (pun not intended) in the search for life on Mars. That is because magmatic gases like hydrogen chloride would have been more abundant in the past, creating a thicker Martian atmosphere and warmer climate.
Not only would this have led to liquid water covering much of the Martian surface, but when lava bubbled through the Martian crust and met groundwater, warm habitable niches ideal for microbial life could have been forged.
“Looking for Martian life in the seeping fissures of the Alba Mons region would make a lot of sense. If hydrothermal systems are active, they could contain the ingredients and energy needed for microorganisms to develop, and shield microorganisms from the hostile and changing environment above the surface,” Mège concluded.
The team’s research was published in the journal Science Advances on Wednesday (Nov. 4).
