The Martian rock

Materials World magazine
1 Aug 2018

Volcanic eruptions have been found to be the source of the Medusae Fossae rock formation on Mars.

It is the size of 20% of continental USA, and one of Mars’s largest sedimentary deposits, formed 3 billion years ago – the Medusae Fossae rock formation (MFF). While it is known when it formed, researchers are now able to determine how it was formed. 

In their study, The Density of the Medusae Fossae Formation: Implications for its Composition, Origin, and Importance in Martian History, published in the Journal of Geophysical Research, the team from the John’s Hopkins University in Baltimore, USA, reveals more information about the origin of the formation. 

‘Based on the relatively low density, lack of ice, and the previously known enrichment of volatile elements associated with volcanic emissions – chlorine and sulphur – we propose that the MFF was deposited by pyroclastic eruptions.’ 

They further expand on this, explaining how they’ve come to their conclusions. ‘Using our density estimate, the mass of the MFF is found to be two orders of magnitude greater than the largest terrestrial pyroclastic deposit, making it the largest known pyroclastic deposit in the solar system.’

It is further stated, ‘Outgassing of volatiles such as CO2 and H2O from the MFF would have substantially contributed to the Martian atmosphere and hydrosphere.’

The MFF was first discovered in the 1960s by the NASA Mariner spacecraft. According to the new research, the formation was once double its size and is unusually porous, about two thirds as dense as the rest of the Martian crust.

The new study shows the promise of gravity surveys in interpreting Mars’s rock record, according to Kevin Lewis, a Planetary Scientist at Johns Hopkins University and co-author of the study. ‘Future gravity surveys could help distinguish between ice, sediments and igneous rocks in the upper crust of the planet,’ Lewis said.

You can access the study here: