While the surface of Mars looks relatively unchanging now, it wasn’t always so. The tallest mountain in the Solar System is Olympus Mons, a giant shield volcano on Mars that reaches 21.9 km (13.6 miles) high, 2.5 times higher than Mount Everest here on Earth. Ancient lava flows surround the volcanic caldera, evidence of an active time.
New images from ESA’s Mars Express show how these lava flows created extremely sharp cliffs, as high as 7 km (4.3 miles) in some areas, which suddenly collapsed in mind-boggling landslides. One of these landslides occurred several 100 million years ago when a chunk of the volcano broke off and spread across the surrounding plains. If we could look back in time and see as it happened, it was certainly a very dramatic and turbulent epoch on Mars.
Olympus Mons, located at the northwest edge of the Tharsis Montes region on Mars, was appropriately named. Based on readings obtained by the Mars Orbiter Laser Altimeter (MOLA), an instrument aboard NASA’s Mars Global Surveyor (MGS), this mountain is the tallest in the Solar System, standing 21.9 km (13.6 mi) tall – about two and a half times the height of Mount Everest (8.85 km; 5.5 mi). According to current estimates, this extinct shield volcano formed during Mars’ Hesperian Period (ca. 3.7 to 3 billion years ago), which was characterized by widespread volcanic activity and catastrophic flooding.
This coincides with a period when Mars had a denser atmosphere, a warmer environment, and flowing water on its surface. This included a global ocean that spanned much of the northern hemisphere, known today as the Northern Lowlands, encompassing Olympus Mons. According to a recent study led by researchers from the Centre National de Recherches Scientifique (CNRS), features found on the slopes of Olympus Mons indicate that it could have been a massive volcanic island where volcanic eruptions flowed into the ocean, similar to ones found on Earth.
However, a research team led by ETH Zurich recently analyzed a cluster of more than 20 recent marsquakes, which revealed something very interesting. Based on the location and spectral character of these events, they determined that most of Mars’ widely distributed surface faults are not seismically active. Nevertheless, most of the 20 seismic events observed originated in the vicinity of Cerberus Fossae, a region consisting of rifts (or graben). These results suggest that geological activity and volcanism still play an active role in shaping the Martian surface.
Earth is a geologically active planet, which means it has plate tectonics and volcanic eruptions that have not ceased. This activity extends all the way to the core, where action between a liquid outer core and a solid inner core generates a planetary magnetic field. In comparison, Mars is an almost perfect example of a “stagnant lid” planet, where geological activity billions of years ago and the surface has remained stagnant ever since.
But as indicated by the many mountains on Mars, which includes the tallest in the Solar System (Olympus Mons), the planet was once a hotbed of volcanic activity. And according to a recent NASA-supported study, there is evidence that thousands of “super-eruptions” happened in the Arabia Terra region in northern Mars 4 billion years ago. These eruptions occurred over the course of 500-million years and had a drastic effect on the Martian climate.
Back in March, NASA’s InSight lander detected two large quakes from a geologically active region of Mars called the Cerberus Fossae. Now, using imagery from the Mars Reconnaissance Orbiter, which circles the red planet at an altitude of about 300km, researchers have discovered that the Cerberus Fossae region holds the most recent evidence of volcanic activity ever seen on Mars.