Challenges of Identifying Putative Planetary-Origin Meteorites of Non-Igneous Material - 2019

Astrogeology, Asteroids, Robots, Space Flight & Extraterrestrial Matters / Other Planets and Planetoids

Anfinogenova and Anfinogenov reported in early 2019 that the challenges of identifying planetary-origin meteorites of non-igneous composition are difficult - particularly those of sedimentary origin. Evidence for putative sedimentary-origin (sed-type) meteorites and their potential parent bodies is reviewed, suggesting that the list of candidate parent bodies for sedimentary-type meteorites includes, but is not limited to: Mars, Enceladus, Ganymede, Europa, Ceres, Vesta, and other hypothetical planets that existed between the orbits of Mars and Jupiter in the past.

The extraterrestrial origin and probable parent body for sed-type meteorites should be assessed based on multiple lines of evidence, and not solely limited to tests of oxygen and noble gas isotopes, whose signatures may undergo terrestrial contamination and which may exhibit significant heterogeneity within both the Solar System and parent cosmic bodies. The observed fall of a cosmic body, evidence of hypervelocity fall, signs of impact, presence of fusion crust, melting, and/or shock deformation features in impactor fragments should be considered as priority signs of meteoritic origin.

The authors concluded that:

• the macroscopic signs of a geologically-fresh hypervelocity pipe/groove-like impact associated with "John’s" Rock,
• the presence of microscopic deformation lamellae, a fusion crust-like glassy surface on some fragments,
• the location of this boulder near the epicenter of the 1908 Tunguska catastrophe, and
• its starkly different mineralogy compared to the regional geology represent extraordinary evidence for its meteoritic origin.

Studying the subject rock sample may contribute to gaining insights into both the 1908 Tunguska phenomenon and into hitherto unexplored physics of small-scale impacts in unconsolidated or poorly consolidated targets. Dozens of pseudo-meteorites found in Antarctica and mentioned in the Meteoritical Bulletin Database maybe tossed away based upon an erroneous assumption that sed-type meteorites cannot exist. Maybe, ‘a time to gather stones’ has come. Considering the abundance of liquid water in the Solar System, the field of Astrobiology and future missions exploring the Solar System may benefit from identifying planetary-origin meteorites with non-igneous compositions.