The composition of Martian blueberries using new mass balance analysis method

What is it about?

The NASA rover Opportunity found spherules (little blob-balls), each with a large composition fraction of the iron oxide mineral hematite (Fe2O3). The NASA scientists nicknamed the spherules "blueberries." These blueberries were the single most prominent feature found on the surface of Mars by the rover in over fourteen years of this rover's exploration of the Meridiani Planum. There are vast numbers of Martian blueberries both as loose lag deposits on the surface and underneath embedded in a huge geological formation. This geological formation has a surface area of >100,000 square kilometers (larger than Lake Superior, roughly equal to England). The loose blueberries have an average surface density of the order of 1 per square centimeter. Several previous papers (between 2004 and 2008) attempted to give a quantified composition of the blueberries. However, none of them could make any stronger statement than the hematite content in Martian blueberries is somewhere between 24 wt% and 100 wt%. This paper introduces a new data analysis method called "searching mass balance." The paper finds a more information-rich, narrower, and high range for the hematite content in Martian blueberries: To do this, the paper applies (a) this new analysis method, (b) the standard dataset from the rover's APXS instrument, and (c) the previously published result that no siliceous material could be detected in Martian blueberries by the rover's mini-TES instrument. The searching mass-balance analysis for Martian blueberries carried out composition calculations in 13,366,080 test cases over 10 blueberry samples. This analysis found 348,797 blueberry compositions consistent with the mini-TES instrument's non-detection of siliceous material. In all 348,797 composition solutions (compatible with no or low siliceous material), the hematite content was between 79.5 wt% and 99.85 wt%. Further, in most of these consistent solutions, the hematite content was between 86 wt% and 96 wt%.

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Why is it important?

By adding the context of two additional facts, the importance of the result that blueberries at the Meridiani Planum becomes clear. The first of these additional facts is the known result that no other location on Mars has surface hematite levels or surface areas remotely close to the iron-bearing formation of the Meridiani Planum. The second is that the hematite levels in Martian blueberries are nearly identical with the highly improved iron-ore pellets input to modern blast furnaces and direct reduction furnaces: Blueberries on and under the Meridiani Planum are an almost perfect iron-ore that could be picked up by robots and placed into direct reduction furnaces. All that is needed to consider building the first science station on Mars at the Meridiani Planum are demonstrations that the sponge iron produced by direct reduction furnaces can be turned into steel and then into working steel components by robots operating suitable equipment.