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Martian spherules
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<p>Martian spherules (also known as hematite spherules, blueberries, & Martian blueberries) are small spherules (roughly spherical pebbles) that are rich in an iron oxide (grey <a href="/facts/Hematite/716YBzGr">hematite</a>, α-Fe2O3) and are found at <a href="/facts/Meridiani_Planum/JHh5qLA5">Meridiani Planum</a> (a large plain on Mars) in exceedingly large numbers. </p> <p>These spherules were discovered on the Martian day that NASA's <a href="/facts/Mars_Exploration_Rover/74WxIsHS">Mars Exploration Rover</a> <a href="/facts/Opportunity_rover/MEC0VIuy"><i>Opportunity</i></a> landed at <a href="/facts/Meridiani_Planum/JHh5qLA5">Meridiani Planum</a>. (At NASA's Mission Control building that was January 24, 2004.) They are grey but look bluish next to the ubiquitous rusty reds on Mars, and since the first spherules found in Eagle Crater were 3–6 mm in diameter, the <a href="/facts/Opportunity_rover/MEC0VIuy"><i>Opportunity</i></a> team quickly called them "blueberries". </p><p>Martian blueberries are either embedded or loose. That is, Martian blueberries are either embedded in the large body of sediments of <a href="/facts/Meridiani_Planum/JHh5qLA5">Meridiani Planum</a>, or they are loose blueberries that lie directly on outcrops of the sediments or lie on top soils spread over the Meridiani sediments. The size of these spherules varies by location and elevation across the <a href="/facts/Meridiani_Planum/JHh5qLA5">Meridiani Planum</a>. </p><p>Martian blueberries are rich in the iron oxide hematite, but determining how rich they are in this iron oxide has proven difficult. (more below). The formation of blueberries required aqueous chemistry and involved flows of acidic, salty, liquid water over the <a href="/facts/Meridiani_Planum/JHh5qLA5">Meridiani Planum</a> and over two geological epochs. </p>