Mars' huge rock formations the result of explosive volcanic eruptions three billion years ago

Massive volcanic eruptions could have warmed Mars' surface sufficiently for oceans to form

A rock formation on Mars that has perplexed scientists for years, could be the result of some explosive volcanic eruptions that shot jets of hot ash, rock and gas skyward, a new study has found.

Called the Medusae Fossae Formation, the huge and unusual deposit of soft rock lies near Mars' equator, and consists of hills and abrupt mesas. It's about one-fifth of the size of the continental United States and 100 times bigger than the largest explosive volcanic deposit on Earth, according to measurements.

Scientists first observed the Medusae Fossae with NASA's Mariner spacecraft in the 1960s but never fully understood how it formed.

However, fresh research indicates that the mass was deposited during explosive volcanic eruptions on the red planet more than three billion years ago. If that's true, it would make it the largest known explosive volcanic deposit in the solar system.

It's about one-fifth as large as the continental United States and 100 times bigger than the largest explosive volcanic deposit on Earth

Not only that, but it might also give scientists some deeper understanding around the red planet's interior and its past potential for habitability.

"This is a massive deposit, not only on a Martian scale, but also in terms of the solar system, because we do not know of any other deposit that is like this," said planetary scientist at Johns Hopkins University in Baltimore, and the study's lead author, Lujendra Ojha.

The eruptions that created the deposit could have spewed massive amounts of climate-altering gases into Mars's atmosphere and ejected enough water to cover Mars in a global ocean more than nine centimeters thick, Ojha claimed.

He also added that greenhouse gases exhaled during the eruptions that spawned the Medusae Fossae could have warmed Mars's surface enough for water to remain liquid at its surface, but toxic volcanic gases like hydrogen sulfide and sulfur dioxide would have altered the chemistry of Mars's surface and atmosphere.

Both of these processes would have affected Mars's potential for habitability.

"If you were to distribute the Medusae Fossae globally, it would make a 9.7 metre thick layer," Ojha said. "Given the sheer magnitude of this deposit, it really is incredible because it implies that the magma was not only rich in volatiles [but] also that it had to be volatile-rich for long periods of time."

The new study was published in the Journal of Geophysical Research: Planets, a journal of the American Geophysical Union.