…ed in a 4.1 billion-year-old zircon" . Proc. Natl. Acad. Sci. U.S.A . 112 (47): 14518–4521. Bibcode : 2015PNAS..11214518B . doi : 10.1073/pnas.1517557112 . ISSN 1091-6490 . PMC 4664351 . PMID 26483481 . Early edition, published online before print. ^ Tyrell, Kelly April (18 Decem…