The brittle mineral with brown color is rare on Earth, but surprisingly abundant on Mars. Geologists have now discovered it under Antarctic ice, suggesting that the mineral is formed when dust is trapped under ice deposits. In other words, glaciers not only existed on Mars, but also contributed to the geological composition of the planet.
Jarosite was detected by three martyrs (Spirit, Opportunity and Curiosity). It is a hydro-sulphate – and watery comes from the Greek word meaning water because jarosite forms in the presence of water. Water is not only necessary for its formation, but also to preserve it. When Martians discovered it on the Red Planet, it was a strong nod to a wet past. Now researchers have also found it in Antarctica; deep in Antarctica.
The discovery comes from the Talos Dome Ice Core (TALDICE) project in East Antarctica, a European research project. The project looks at any signs indicating the climate of our planet, but a team of researchers led by Giovanni Baccolo of the University of Milano-Bicocca in Italy also learned something about Mars’ climate.
The mineral needs very specific conditions to form: it needs water (but not too much of it) and acidity – not exactly conditions you can now find on the Red Planet. When the mineral was first found on Mars in 2004, it initially confused researchers. Thereafter, it kept popping up, indicating that the first discovery was not accidental and gave the geologists the task of finding out how the mineral originated on Mars.
Here on earth, jarosit is not so common. We know that it can occur due to low temperature acid weather of ferrous minerals, and as a product of zinc refining (which of course is not something you would expect on Mars). The cold, acid weathering theory therefore seemed more likely, but the smoke gun has been missing until now.
The mechanisms behind the formation of jarosite have been theorized, but never seen before, either on Earth or beyond. The samples of jarosite were found in a Talos ice core more than 1000 meters (3,281 feet) below the ice. The crystal weathering indicates that the minerals formed there (and the ice was actually undisturbed for 250,000 years), so this is probably where the minerals formed – the smoke gun.
“Based on our understanding of the environmental conditions of deep ice, we interpret jarosite as the product of defense in England,” the researchers write in their paper.
‘Its formation requires acidic conditions, a limited activity of liquid water and the presence of ferrous materials. The deep section (> 1000 m) of TALDICE can meet such requirements. ”
Since jarosite is now so common on Mars, it probably means that the planet must have had large masses of ice that formed the surface – and recent research agrees. Separate studies indicate that Mars, like the Earth, had multiple periods of icing, and that Mars experienced dramatic climatic fluctuations throughout its history. As the ice sheets grew over time, dust would have accumulated, forming jarosite in soft bags.
But there is still a long-standing question.
Antarctic research has exposed a thin film of jarosite and only in one place (so far), but Mars has a thick dimension of meters, so the conditions for the formation of jarosite should have been much better on Mars. This can perhaps be explained by dust: Mars is much dustier than Earth, and more ‘seeds’ for jarosite would have formed.
The study was published in the journal Nature communication.