The following is an article I wrote in 2015 for my mineral society’s newsletter. It was submitted to the annual American Federation of Mineral Societies’ Bulletin competition and it won the 1st Place in the 2016 Written Features category.
Jarosite. I had never heard of it, but it is a secondary mineral found in the oxidized zones of sulfide deposits. It is formed by the reaction of dilute sulfuric acid in groundwater, typically altering from pyrite. The key word in that description is groundwater, and the reason it is key is because this mineral was just found on Mars by the Curiosity Mars rover.
Back in January, the Mars rover was looking for a rock to drill to expose fresh surfaces for examination. The rock that was chosen was named “Mojave” displayed many slender features approximately the size of rice grains that appeared to be crystals. The scientists running the rover wanted to determine the mineral represented in the hopes that it would provide clues to the history of Mars. Were they salt crystals left by a drying lake, or were they volcanic in origin?
Whatever they were, minerals tell a story, and the scientists wanted to hear the story these minerals had to tell. So, on January 13, the rover began drilling. The drill essentially is a hammer and chisel, and the Curiosity team had no way of controlling the force of the hammering. The “Mojave” rock shattered under the percussive force. While this eliminated drilling for samples, the freshly broken rock faces did present an opportunity to study unweathered surfaces up close under the rover’s hand lens.
The rover was redirected to an alternate site, “Mojave II.” The software was upgraded to allow for control over the percussive force of the drilling. On the lowest setting, the rover was able to penetrate the rock and acquire the needed samples.
Upon analysis by the rover’s Chemistry and Mineralogy (CheMin) instrument on the rover, it was determined that the crystals were jarosite. This was not a complete surprise to the Curiosity team as previous Mars surveys had suggested the presence of the mineral, but having confirmation was important.
The presence of jarosite would indicate that Mars did previously have a groundwater supply at some time. But more importantly, it confirmed to rockhounds everywhere that we could someday have samples from other worlds, possibly even mineral species that do not exist on Earth. Space… the final frontier.