Deep inside of an ice core located in Antarctica is a mineral that is very rare on Earth but quite common on Mars. Researchers described the brittle, yellowish/brown mineral called jarosite as being created in the same manner both on Earth and on Mars – by dust that was trapped inside of ancient ice.
It was NASA’s Opportunity rover that discovered the jarosite at several different locations on Mars back in 2004 when it drove over layers of the mineral. Scientists definitely weren’t expecting to find it as it needs water, iron, potassium, sulfate, and acidic conditions in order to form which are not easy to find on the Red Planet.
Scientists came up with several hypotheses as to how the mineral formed in high quantities on Mars such as the evaporation of tiny portions of water that contained salt and acid. However, according to Giovanni Baccolo, who is a geologist at the University of Milan-Bicocca and the lead author of the study, the alkaline basalt rocks on the crust of the planet would have gotten rid of any moisture containing acid.
Another theory that the scientists came up with was that the jarosite would have formed inside of ice that covered Mars billions of years ago. When the ice sheets grew larger, the dust would have collected inside of them which then turned into jarosite.
As for the rare occurrences when jarosite has been found on Earth, it was usually because of mining waste that had been exposed to rain and air. And the fact that it was discovered in Antarctica was something that nobody expected. In fact, Baccolo found it by accident when he was looking for minerals that could possibly show ice age cycles inside of an ice core. He discovered the jarosite inside of pockets deep down in the 1620-meter-long ice core. But it was only a tiny fragment of the mineral as it was smaller than an eyelash or a sand grain.
Additional analysis seems to indicate that the mineral forms in the same manner here as it does on Mars but it still doesn’t explain how there is so much of it on the Red Planet. Megan Elwood Madden, who is a geochemist at the University of Oklahoma but wasn’t involved with the study, stated, “On Mars, this is not just some thin film,” adding, “These are meters-thick deposits.”
Since there is a lot more dust on Mars than on Earth, Baccolo said that perhaps the reason why that planet has so much more jarosite than here is because the dust provides additional raw materials that help form the mineral. “More ash would favor more jarosite formation under the right conditions,” he said. He went on to say that he wants to perform further studies on the jarosite found in Antarctica in order to learn more about its presence on Mars. “This is just the first step in linking deep Antarctic ice with the Martian environment,” he noted.
The research was published in the journal Nature Communications where it can be read in full.