The Medusae Fossae Formation on Mars could be the result of explosive volcanic eruptions

The Medusae Fossae Formation seen by Mars Odyssey. Mars based on data from the MOLA instrument (Image NASA, modified by Chmee2)
The Medusae Fossae Formation seen by Mars Odyssey. Mars based on data from the MOLA instrument (Image NASA, modified by Chmee2)

An article published in the journal “Journal of Geophysical Research: Planets” describes a research on the Medusae Fossae Formation on Mars. A team of researchers coordinated by the Johns Hopkins University analyzed this geological formation finding its possible origin in explosive volcanic eruptions that over three billion years ago ejected ash, rock and gas. It could add important information about Mars interior and its past.

The Medusae Fossae Formation extends over 5,000 kilometers discontinuously near the equator of the planet Mars. composed of anomalous deposits of sedimentary rocks and hills whose origin has remained unknown, at least until now. What was known was the origin of the rocks, with dust and smaller debris that cemented over time and now a new research proposes a triggering cause for that process.

According to the researchers, a series of explosive volcanic eruptions that occurred more than three billion years ago generated such an amount of ash and debris to start the processes that led to the Medusae Fossae Formation. If the conclusions of the research are correct, it’s the largest explosive volcanic deposit in the entire solar system, one hundred times more massive than the largest known on Earth.

Planetary scientist Lujendra Ojha, the lead author of the study, explained that we know of no other deposit of that kind. Its existence indicates that Mars had enormous amounts of volatile gases inside it to create a deposit of the size of the Medusae Fossae Formation and that those volatile gases must have been there for long periods of time.

These conclusions were obtained by putting together data collected over decades starting with those obtained in the 1960s thanks to the Mariner space probe to end with those obtained recently thanks to the MRO (Mars Reconnaissance Orbiter) space probe, both NASA’s. Various surveys, including gravitational ones, made it possible to measure the density of the Medusae Fossae Formation, which was about two thirds of that of the rest of the Martian crust because it’s abnormally porous.

Those porous rocks must have been deposited by explosive volcanic eruptions, where magma contains large amounts of gas and explodes upward, emitting jets of ashes and rock fragments into the atmosphere. These deposits fall down to the ground and after enough time they cement into rocks.

The researchers estimate that about half of the soft rocks that deposited originally after the huge explosive eruptions that created the Medusae Fossae Formation got eroded. The valleys and hills visible today are what remained, showing above all the vastness of the territory affected by that process.

This research indicates that over three billion years ago on Mars there was a very intense volcanic activity, a result consistent with other researches. The results could be very interesting to better understand Mars interior and the processes that took place under the surface when the planet was young. The researchers used a lot of information from NASA’s archives, confirming the importance that space missions can have even after decades.

A portion of the Medusa Fossae seen by Mars Express (Image ESA/DLR/FU Berlin (G. Neukum), CC BY-SA 3.0 IGO)
A portion of the Medusa Fossae seen by Mars Express (Image ESA/DLR/FU Berlin (G. Neukum), CC BY-SA 3.0 IGO)

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