{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"8ac290ccb16d125b41d1a3762fda910dc305a61a9ca97e3a3580fac502c75c2c","created":"2026-10-03T07:18:03Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"4595dd10f2a8f6f6ba747f30e3a52a3ed8e464655a5d283a68f95adb2491d9c5","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"earth.solar-system-dynamics.late-bombardment","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"Moon rocks brought back by Apollo showed many impact melts about 3.9 billion years old, suggesting a sudden burst of impacts. It may instead be the tail of a steadily declining impact rate, sampled unevenly.","posed_since":"1974","precise":"Determine whether the inner Solar System impact flux between 4.5 and 3.8 Gyr ago had a transient increase (a terminal cataclysm about 3.9 Gyr ago) or declined monotonically, accounting for the dominance of Imbrium ejecta in Apollo samples and for impact-age resetting. An answer is an impact-flux history with uncertainties from lunar, meteoritic and Martian chronology.","problem_ref":null,"references":"","settled_by":"Secure radiometric ages for several intermediate-age basins (for example Nectaris and Serenitatis) with confirmed sample provenance, which together with the 4.25 Gyr South Pole-Aitken age fix the shape of the basin-formation rate.","status_note":"Chang'e-6 samples (returned 2024) date the South Pole-Aitken basin to about 4.25 Gyr (Xu and Chen 2025, National Science Review), which leaves about 350 Myr between the oldest and youngest large basins and argues against a single cataclysm about 3.9 Gyr ago; the shape of the 4.25 to 3.8 Gyr flux, including any late uptick, remains debated.","title":"Was there a late heavy bombardment spike about 3.9 billion years ago?","topic_ref":"b929a620dac9f17771effc8b71b936420a6fad08ab629dcf3f51f65829dd7067"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"423cd296d90c1e150049de56fbb6759f668a85a07a5b93112c6a5b0af55ac2cd","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"a48465558b1d520aa1f60af362cc6e18f19205354da7fbe2b538df2e17d68047","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"uyoxqm0_K7umoNnaNcySDFjA0f9Zz61vfi1hWW33fZ4I2o2YMg-653TlqffC1W7okgB-aNpRewj-iQ8Ci0JgCw"},"schema":"pubphys.envelope/1"},"record_hash":"423cd296d90c1e150049de56fbb6759f668a85a07a5b93112c6a5b0af55ac2cd","leaf_index":1365}