Mars’ Volcanic Past: Unearthing Explosive Secrets
For decades, planetary geologists have known that Mars is covered in volcanic features. The discovery of massive shield volcanoes and lava plains by missions like Mariner 9 in the 1970s revealed a planet dramatically shaped by volcanic activity. Now, new research is focusing on a less common, but equally important, aspect of Martian volcanism: explosive eruptions.
The Puzzle of Explosive Volcanism on Mars
Olympus Mons, the solar system’s largest volcano, and Alba Mons, its widest, were primarily built by relatively calm lava flows. However, a smaller portion of Martian volcanism was produced by explosive events, creating volcanic cones, pyroclastic flows, and ashfalls. Interestingly, despite Mars’ thinner atmosphere and lower gravity – conditions that theoretically should *encourage* explosive eruptions – these features are surprisingly rare.
Petr Brož, a planetary geologist with the Czech Academy of Sciences, notes that the scarcity of explosive volcanic features has long puzzled researchers. Recent discoveries, like the volcanic cones found in Mars’ Ulysses Colles region, are providing crucial clues.
Analogous Landscapes: Earth’s San Francisco Volcanic Field
To better understand these Martian features, scientists are turning to Earth for comparison. The San Francisco Volcanic Field in northern Arizona provides a striking analog. NASA’s Landsat 8 captured images of scoria cones in Arizona, which closely resemble those observed on Mars by the Mars Reconnaissance Orbiter’s Context Camera (CTX). Both locations too exhibit grabens – linear blocks of crust that have shifted downward.
These scoria cones are formed by “mildly explosive” Strombolian events, characterized by intermittent lava fountains. Although not as violent as eruptions like the one at Hunga Tonga-Hunga Ha’apai, they represent a significant departure from the predominantly effusive volcanism previously thought to dominate Mars.
What Martian Cones Notify Us
The presence of scoria cones suggests that explosive volcanism played a more significant role in shaping the Martian surface than previously understood. Researchers have identified tens to a few hundred potential cones on Mars, compared to the tens of thousands found on Earth. This disparity raises questions: was explosive volcanism simply less common on Mars, or have these features been obscured by later lava flows or erosion?
Patrick Whelley, a NASA volcanologist, emphasizes the value of studying analogous features on Earth. “Understanding similar features on Earth helps us know what to look for on Mars and interpret processes that You can’t observe directly.” SP Crater in Arizona, for example, is used for NASA astronaut geology training due to its similarities to Martian volcanic landscapes.
Beyond Scoria Cones: Super Eruptions and Future Research
While scoria cones offer insights into smaller explosive events, Mars also shows evidence of massive “super eruptions.” These events leave behind different geological signatures, such as large depressions called paterae and broad ash deposits sculpted into yardangs.
However, interpreting Martian geology requires caution. As Brož points out, features that *look* volcanic may not always be. Mud volcanoes, for instance, can mimic the appearance of scoria cones. His laboratory research suggests that mud flows on Mars can even resemble lava flows under certain conditions.
Determining the sequence of events – whether lava flows preceded cone formation or vice versa – remains a key challenge. Further research, including potential future missions to Mars, will be crucial to unraveling the planet’s complex volcanic history.
Frequently Asked Questions
- What are scoria cones? Scoria cones are steep-sided hills formed from the accumulation of volcanic fragments (scoria) ejected during explosive eruptions.
- Why is studying Martian volcanism important? Understanding Martian volcanism provides insights into the planet’s internal structure, thermal evolution, and potential for past habitability.
- How do scientists study Martian volcanoes remotely? Scientists use data from orbiting spacecraft, such as the Mars Reconnaissance Orbiter and Landsat 8, to analyze the morphology and composition of volcanic features.
- Are there active volcanoes on Mars today? Currently, there is no evidence of active volcanism on Mars, but the planet is not considered geologically dead.
Pro Tip: Planetary comparison is a powerful tool for understanding distant worlds. By studying analogous features on Earth, scientists can gain valuable insights into the geological processes that have shaped other planets.
Explore more about Mars’ geology and ongoing research at NASA’s Mars Exploration Program.
