Many volcanos on Mars and Venus are morphologically comparable to terrestrial volcanos above mantle plumes. This similarity extends to chemistry and petrology – the nakhlite martian meteorites are like some post-shield magmas above Earth plumes.

Nakhlites are augite-rich igneous rocks [1,2], most of which represent magma compositions [3]. They crystallized at ~1.35 Ga [4], and are enriched in incompatible elements [2]. Had the nakhlites formed on Earth, they would be called ankaramites [5,6].

The nakhlites’ young ages restrict their source to a few central volcanoes, inferred to represent mantle plumes [7]; most of Mars’ basaltic surfaces are > ~3.0 Ga [8]. The impact crater that launched the nakhlites off Mars must appear fresh – nakhlites cosmic ray exposure ages are only ~11 Ma [9]. A likely source crater is Kotka, on the flanks of the Elysium volcano [10], which represents a long-lived (and active [11]) mantle plume.

On Earth, plume shield lavas are typically tholeiitic and un- to slightly-enriched in incompatible elements [12]. Post-shield lavas are distinct, being enriched in incompatibles [13] and commonly in augite [14,15], and were derived from long-term depleted sources [13]. Nakhlite lavas fit this model, and also have elevated Nb/Y [5,7] which is (on Earth) characteristic of ‘rejuvenated’ post-shield plume lavas. Thus, mantle plumes on Earth and Mars share some similar magmatic products, and must also share similar mantle compositions and structures.

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