Volcano Olympus Mons is visible upper left of centre in this picture of Mars. At the centre are the three Tharsis volcanoes including Alba Mons. Credit: Stocktrek Images/ Getty Images

Alba Mons, an active volcano on Mars, has been continuously spewing lava for the last 500 million years, planetary scientists at the National Geophysical Research Institute (NGRI) in Hyderabad report11. The volcano’s activity has migrated from its north to its south over time, according to their analysis using NASA images.

Previous research suggested that volcanism on Mars is episodic. Now geologists Vivek Krishnan and Senthil Kumar from NGRI report that Alba Mons has been erupting non-stop for at least the last 500 million years.

“The volcanic activity in the Alba Mons region is not extinct. Our study indicates that in recent times it has shifted south to the Ceraunius Fossae (CF) graben system”, Kumar, a Principal Scientist at NGRI told Nature India.

The Tharsis region of Mars is home to the largest and oldest volcanoes in the solar system and has remained active for over 4 billion years. The NGRI study suggests that long-lived and active magma chambers, and subcrustal magma underplating — possibly fed by a mantle plume — are present beneath the region's volcanoes.

The researchers say volcanic activity in the region may have triggered the formation of boulder avalanches on the slopes of volcanoes, and impact craters aged a few tens to thousands of years. “There are long-lived magma sources and active mantle plume just a few kilometers below the surface,” Kumar said.

The researchers analysed data and surface features of the planet to find that in the last 500 million years, northern Tharsis witnessed continuous lava flows, tectonic activity leading to several generations of grabens (a graben is a depressed block of the crust), and formation of thousands of pits and pit-chains.

“These suggest the presence of long-lived and active magma chambers, interconnecting dikes to the surface, and subcrustal magma possibly fed by a mantle plume,” Kumar says.

For their study, the researchers dated 1,089 lava flows, and mapped 988 grabens and 1,138 boulder falls. Theya also studied 4,322 simple and 1,459 complex pits. This elaborate dating revealed the variation in the rates of magmas intruding through the dikes. “These (magma chambers and underplating) gradually migrated southward toward the CF region as the Alba plume migrated," they write. The migration of this mantle plume is clearly reflected in volcanic and tectonic records, the researchers say.

Lionel Wilson, Emeritus Professor of Earth and Planetary Sciences at the Lancaster University in the UK says the NGRI research provides a picture of the history of two of the major volcanic provinces of Mars. It sheds light on both the formation of features by eruptions and their later modification due to eruptions, earthquakes and fault movements, he says.

“The results make it clear that the interior of Mars has remained dynamic into more recent geological times than many people expected,” he told Nature India.

The recent detection of marsquakes by the Insight probe, coupled with these new research findings, suggest that it may be possible to observe a volcanic eruption on Mars, Wilson said.