ASA Digital Art’s theory, not a published finding: the fragments came down in an ancient ocean during the Great Oxidation Event.
The event itself is well documented. Oxygen first became significant in the atmosphere about 2.43 billion years ago[1,2]. NASA’s astrobiology program places the Great Oxidation Event between about 2.4 and 2.1 billion years ago[3]. Work led by Simon Poulton at the University of Leeds found that early oxygenation was unstable for some two hundred million years and that permanent oxygenation came later than previously thought[2,1]. The episode changed the chemistry of Earth’s surface and coincided with four widespread glaciations, some of which may have covered the planet in ice for millions of years[1]. The Leeds team relabelled the interval the Great Oxidation Episode and found that permanent oxygenation followed the last major glaciation of the period; it ushered in roughly 1.5 billion years of comparative climatic stability[1,2].
Haggerty’s own model also places most carbonado falls in the ocean, though at an earlier time, during the Late Heavy Bombardment[4]. Published lead-isotope ages for carbonado are 2.6 to 3.8 billion years[4,5]. A landing near 2.4 billion years ago would therefore postdate the published ages; our timing is untested and, on present evidence, difficult to reconcile with them.
We include the idea because it frames a question rather than answers one: if carbonado did enter early oceans, what record of that passage, if any, would remain in its surface pores, which today hold low-temperature minerals of surface origin[4]?