Martian spherules
abundant spherical hematite inclusion, found in situ embedded in a sulfate salt evaporitic matrix or also loose on the surface, discovered by Opportunity at Meridiani Planum on Mars
Martian spherules (also known as hematite spherules or blueberries) are small spherules (roughly spherical pebbles) that are rich in an iron oxide (grey hematite, α-Fe2O3) and are found in exceedingly large numbers at Meridiani Planum, a vast Martian plain.
These spherules were discovered on the Martian day (sol) that NASA's Opportunity rover, part of the Mars Exploration Rover program, landed at Meridiani Planum. 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 Opportunity team quickly called them "blueberries".
Martian blueberries are either embedded or loose. That is, Martian blueberries are either embedded in the large body of sediments of Meridiani Planum, 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 Meridiani Planum.
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 Meridiani Planum and over two geological epochs.
Initial discovery
Discovery from orbit
From 14 September 1997 to 29 April 1998, the Mars Global Surveyor spacecraft collected spectral data with its Thermal Emission Spectrometer (TES) instrument as the spacecraft entered its science phase orbit.
The public source identifies “Martian spherules” as abundant spherical hematite inclusion, found in situ embedded in a sulfate salt evaporitic matrix or also loose on the surface, discovered by Opportunity at Meridiani Planum on Mars. This brief keeps that definition visible, then builds a research path around Martian, spherules and abundant.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jan 27, 2026. The linked authority identifier is Q3310161. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1997 and 1998.
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This entry incorporates text from “Martian spherules” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.