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Met Name

Met Type

Thin Sections

24.6 and 41.2 grams.   CM2

TKW ~12 kg. Observed fall 23 April 2019, Alajuela, Costa Rica.

        ^EarthSky

Steve writes:

The Aguas Zarcas meteorite fell at 9:07 PM on Tuesday, April 23, 2019. As the fireball flew above the crater of the erupting Volcan Turrialba, its transit was captured on video by government cameras, dash cams, and security cameras across the country. The meteor exploded before impact, with some pieces hitting man-made objects, roofs, and even an occupied dog house.

At 27 kg, Aguas Zarcas was the largest fall of a rare CM2 class meteorite in recent history (only 1969’s 100 kg Murchison shower was larger). CM2s contain pristinely-preserved stardust made up of materials that predate our solar system. They also contain water and organic compounds left over from the solar system’s creation, as evidenced by the “Murchison-like” odor accompanying Aguas Zarcas’ fall. And like Murchison, Aguas Zarcas exhibits an abundance of left-handed amino acids (unlike the 50:50 distribution obtained when creating them in a lab) – additional evidence of an early solar system bias similar to terrestrial amino acids. But unlike Murchison, Aguas Zarcas is also anomalous, having features uncommon in other meteorites of its type: high levels of salts; brecciation; visible chondrule-rich clasts; bright blue-green iridescence on the fusion crust; and in some cases, enough metal to adhere to a magnet.

The smaller 24.6 gram stone in today’s post (Photo 1) was collected before the rains that followed the fall; the larger 41.2 gram stone (3D crossed-eyes Photos 2 and 3) was collected post-rain and provides an obvious indication of how a fresh meteorites’ fusion crust is modified by even just a short period of time exposed to water. Both stones exhibit rollover lips on their fusion crust (including a faint secondary one seen about halfway down the lower image in Photo 1), as well as defined splatters (3D crossed-eyes Photo 4). But unlike the arguably less interesting smaller stone – which developed fusion crust all the way around by tumbling before it oriented – the larger stone’s trailing edge is more unaltered, and it features several fractures, one of which is deep enough to clearly show CAIs and chondrules below the meteorite’s surface (3D crossed-eyes Photo 5). Both stones also exhibit glassy reddish-colored silicate melt (Photo 6, with the 3D crossed-eyes Photo 7 showing a protruding chondrule ringed by this silicate material).

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