Today it is well known that Mars is cold, dry, and geologically dead planet. But billions of years ago, when she was young, its atmosphere was denser, and the surface was liquid water. Millions of years ago, the planet also possessed of volcanic activity, which led to the formation of massive faults and mountains like mount Olympus, the largest volcano in the Solar system.
Until recently, scientists believed that Martian volcanic activity is controlled by sources other than tectonic movements, which was not the planet for billions of years. But after studying samples of Martian rocks, a team of scientists from Britain and the United States came to the conclusion that in the past Mars was even more volcanically active than previously thought.
Their study, conducted under the leadership of Benjamin Cohen from the Centre SUERC, was published in Nature Communications. The researchers analyzed volcanic past of Mars, using samples of Martian meteorites.
On Earth the majority of volcanic processes is the result of the operation of plate tectonics, which, in turn, is ensured by convection in the Earth’s mantle. But on Mars the most part of volcanic activity is the result of mantle plumes, which represent highly localized upwellings of magma, rising from deep mantle. This is because the surface of Mars remained motionless and cool over the last few billion years.
Because of this, Martian volcanoes (though morphologically similar to shield volcanoes of the Earth) grew to much larger sizes than their terrestrial counterparts. For example, mountain Olympus is not only the largest shield volcano on Mars, but in the Solar system. The highest mountain on Earth — Everest — elevation 8,848 meters, mount Olympus is nearly three times higher, 22 km.
For their study, Dr. Cohen and his colleagues used radioscopic Dating methods that are commonly used to determine the age and rate of eruptions on Earth. However, such methods have not previously been used for evaluation of shield volcanoes on Mars. As a result, the panel study samples of the Martian meteorite was the first extensive analysis of the growth of the Martian volcanoes.
Six of the samples they examined, known as nakhlite class of Martian meteorite that formed from basaltic magma about 1.3 billion years ago. They came to Earth some 11 million years ago after it had been wiped off the face of Mars as the result of impact. After analyzing Martian meteorites, scientists were able to uncover information about 90 millions years volcanic past of Mars.
As explained by Dr. Cohen in the press release of the University of Glasgow:
“From previous studies we know that meteorites-nality represent volcanic rocks and the development of methods of absolute Dating in recent years has made nakhlite ideal candidates that will help us learn more about volcanoes on Mars”.
The first step was to demonstrate that the samples of the rocks were truly Martian in origin, and that the team was able to confirm by measuring their effects on cosmogenic radiation. It turned out that the rocks were thrown from the surface of Mars 11 million years ago, likely as a result of the impact on the planet’s surface. And then they used high-precision radioscopic method of Dating known as 40Ar/39Ar.
The mass spectrometer allows to determine how much argon has accumulated in the samples — it is the result of natural radioactive decay of potassium. The results of the analysis showed that the volcanic history of Mars did not go the way of the earth.
“It turned out that nality formed in at least four eruptions in the past 90 million years. This is a sufficiently long period for the volcano and much longer than usual live earth’s volcanoes, which, as a rule, active for several million years. And that’s just scratching the surface of the volcano, as a very small amount of rock was ejected from the impact crater. The volcano was supposed to be much longer.”
In addition, the scientists were able to narrow the list of volcanoes that were made for these samples. Previous studies conducted by NASA, has revealed a few candidates for possible source Nolita. However, only one of the seats consistent with their results, in terms of the age of volcanic eruptions and shock that could throw the samples into space.
This particular crater (currently unnamed) is located in the volcanic plains of Elysium Planitia, located about 900 kilometers from the summit of the volcano Elysium Mons, 12.6 kilometer tall. It is 2000 kilometers North from the place where now is Curiosity. At the disposal of NASA there are, therefore, remarkably detailed satellite images of this particular crater.
“It has a width of 6.5 kilometres and saved the emission of fragments. We could see a few horizontal stripes on the walls of the crater, which indicated the formation of layers of rocks, each layer is interpreted as a single lava flow. The study has given us a clear picture of the history of Nahodka meteorites and in turn, the largest volcanoes in the Solar system”.
In the future, when Mars will leave manned crews, we will clear up the picture even more. Given that Mars, like Earth, is a planet earth-like, understanding of its geological history will ultimately improve our understanding of how the formed solid planets of the Solar system.
The first to study a meteor, born in the Martian volcano
Ilya Hel