While most volcanic and tectonic activity on Mars occurred during the first 1.5 billion years of its geologic history, recent volcanism, tectonism and active seismicity in Elysium Planitia reveal ongoing activity. However, this recent pulse in volcanism and tectonics is unexpected on a cooling Mars.

A new study by University of Arizona scientists presents multiple lines of evidence revealing the presence of a giant active mantle plume on present-day Mars. The study challenges current beliefs about the geodynamic evolution of Mars with a report of discovering an active mantle plume that pushes the surface upwards, causing earthquakes and volcanic eruptions.

Jeff Andrews-Hanna, associate professor of planetary science at the LPL, said: “We have strong evidence that mantle plumes are active on Earth and Venus, but this is not expected on a small and supposedly cold world like Mars. Mars was most active 3 to 4 billion years ago and the prevailing view is that the planet is essentially dead today.”

Adrien Broquet, a postdoctoral research associate at the UArizona Lunar and Planetary Laboratory, said: “An enormous amount of volcanic activity early in the planet’s history built the tallest volcanoes in the solar system and covered most of the northern hemisphere in volcanic deposits. The little activity that has occurred in recent history is typically attributed to passive processes on a cooling planet.”

The Elysium Planitia Plain, located in the northern lowlands of Mars near the equator, caught the attention of scientists due to some surprising activity. Elysium Planitia has experienced significant eruptions over the past 200 million years, unlike other volcanic zones on Mars that have not experienced significant activity in billions of years.

Andrews Hanna said: “Previous work by our group found evidence in Elysium Planitia for the youngest known volcanic eruption on Mars. It caused a small explosion of volcanic ash about 53,000 years ago, which is essentially yesterday in geological time.”

The Cerberus Fossae, a series of young fissures stretching more than 800 miles across the surface of Mars, is the source of the volcanism in Elysium Planitia. Recently, NASA’s InSight team found that nearly all marsquakes come from this area. Although the young age of this volcanic and tectonic activity had been established, the cause was still unknown.

Broquette said, “We know Mars has no plate tectonics, so we investigated whether the activity we’re seeing in the Cerberus Fossae region could be the result of a mantle plume.”

 active mantle plume
Artist’s impression of an active mantle plume — a large blob of warm and floating rock — rising from deep inside Mars and pushing up Elysium Planitia, a plain in the planet’s northern lowlands.Adrien Broquet & Audrey Lasbordes

The scientists discovered evidence of a similar sequence of events on Mars when they examined the features of Elysium Planitia. One of the highest places in the vast northern lowlands of Mars, its surface has been raised by more than a mile. The existence of a mantle plume is consistent with the updraft being supported deep within the globe, according to analyzes of small fluctuations in the gravitational field.

Additional measurements supported the theory that something pushed the surface up after the craters formed by revealing that the bottom of impact craters sloped toward the plume. When scientists finally used a tectonic model for the region, they found that the only explanation for the expansion that created the Cerberus Fossae was the existence of a massive plume 2,500 miles across.

Broquette said, “In terms of what you expect to see with an active mantle plume, Elysium Planitia ticks all the right boxes. The finding poses a challenge to models used by planetary scientists to study the thermal evolution of planets. This mantle plume has an area of Mars affected roughly equivalent to that of the continental United States. Future studies will have to find a way to account for a huge mantle plume that was not expected there.”

“We used to think that InSight landed in one of the most geologically boring regions on Mars – a nice flat surface that should roughly represent the lowlands of the planet. Instead, our research shows that InSight landed right on top of an active plume.”

“Having an active mantle plume on Mars is a paradigm shift for our understanding of the geological evolution of the planet, similar to when analyzes of seismic measurements during the Apollo era showed that the moon’s core was molten.”

Scientists noted, “Their findings may also have implications for life on Mars. The region studied has experienced liquid water flooding in its recent geological past, though the cause has remained a mystery. The same heat from the plume that fuels the ongoing volcanic and seismic activity could also melt ice to cause the floods — triggering chemical reactions that could sustain life deep underground.”

Andrews Hanna said: “Microbes on Earth thrive in environments like this, and that could happen on Mars as well. The discovery goes beyond explaining the puzzling seismic activity and resurgence of volcanic activity. Knowing that there is an active giant mantle plume beneath the surface of Mars raises important questions about how the planet evolved. We are convinced that the future holds more surprises.”

Magazine reference:

  1. Broquet, A., Andrews-Hanna, J.C. Geophysical evidence for an active mantle plume beneath Elysium Planitia on Mars. Wet Astron (2022). DOI: 10.1038/s41550-022-01836-3