Explosive Volcanoes Created Mysterious Martian Rock Formation

A new study reveals that explosive volcanic eruptions likely created the Medusae Fossae Formation, a massive and unusual rock deposit on Mars. The formation, located near the planet's equator, has puzzled scientists since its discovery in the 1960s. The study, led by Lujendra Ojha of Johns Hopkins University, suggests that the formation was created by volcanic eruptions over 3 billion years ago.

The Medusae Fossae Formation is one of the largest explosive volcanic deposits in the solar system, covering an area about one-fifth the size of the continental United States. Its unique composition and structure, revealed through gravity data from Mars orbiters, indicate that it is highly porous and not composed of ice, as previously thought. This porosity suggests that the rock was formed by explosive volcanic activity, where gas-rich magma erupted and deposited ash and rock.

The study highlights the impact of these eruptions on Mars's early environment. The volcanic activity could have released large amounts of greenhouse gases, potentially warming the planet enough to allow liquid water on the surface. However, toxic gases like hydrogen sulfide and sulfur dioxide would have also altered the planet's atmosphere and surface chemistry, influencing its habitability.

Ojha and his team used a combination of radar and gravity data to determine the density of the Medusae Fossae, finding it to be significantly less dense than the rest of the Martian crust. This supports the idea that the formation was created by volcanic ash that later cemented into rock. Over time, much of the original deposit has eroded, leaving the hills and valleys seen today.

The findings suggest that Mars's interior is more complex than previously understood, with a need for large amounts of volatile gases to create such a massive deposit. The study also demonstrates the value of gravity surveys in understanding the composition of Mars's crust, offering new insights into the planet's geological history.