Natural Lithopanspermia to Earth: Transport, Shielding, and Survival Limits for Solar-System and Extrasolar Donor Classes

[physics.gen-ph] Natural panspermia is a transport-and-establishment hypothesis, not a theory of abiogenesis. The Earth-specific question is whether any nonterrestrial donor remains competitive with terrestrial origin once launch, planetary-system escape, transit, Earth interception, atmospheric entry, terminal loading, and post-delivery establishment are imposed.

We formulate this problem as a donor-class dependent Earth-directed transport-survival kernel, supplemented by a minimum protected-depth envelope d_min(t_fl) and a survival-weighted buried-volume fraction F_bur for the low-shock spall population. The resulting hierarchy is strongly ordered under current transport and survival constraints.

Hard panspermia is physically credible only on Solar-System scales: early Mars combines demonstrated lithic exchange with Earth, low escape speed, early aqueous habitability, and a rare 10² –10⁴ yr transfer tail, whereas the more common 10⁵ –10⁷ yr martian transfer regime requires lightly shocked meter-class carriers.

Beyond the Solar System, low-v_∞ capture and long-duration survival fail simultaneously; even the Solar birth-cluster channel yields only ∼ 3 × 10⁻⁵ f_seed expected Earthseeding events, where f_seed is the conditional probability that a viable arrival establishes life on Earth.

Indigenous terrestrial origin therefore remains the default inference, early Mars is the only quantitatively serious external hard-panspermia alternative, and extrasolar or intergalactic hard panspermia is not competitive for Earth’s actual origin history. Soft panspermia is much more plausible as chemical enrichment of early terrestrial abiogenesis.

Slava G. Turyshev

Comments: 18 pages, 4 figures, 3 tables
Subjects: General Physics (physics.gen-ph)
Cite as: arXiv:2604.03916 [physics.gen-ph] (or arXiv:2604.03916v2 [physics.gen-ph] for this version)
https://doi.org/10.48550/arXiv.2604.03916
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Submission history
From: Slava G. Turyshev
[v1] Sun, 5 Apr 2026 00:53:25 UTC (63 KB)
[v2] Fri, 24 Apr 2026 00:53:54 UTC (887 KB)
https://arxiv.org/abs/2604.03916

Astrobiology, Astrogeology,