I learned the oceans were formed a different way in the 60’s in Sunday School................
GROK says this is the latest guess:
“ Current Scientific Consensus (2025)Theory
Contribution
Status
Outgassing from lava/mantle
~20–40% of total water (early Earth)
Important, but not the main source
Icy asteroids & comets (late veneer)
~60–80% of total water
Dominant modern view
Why the Shift?1. Deuterium-to-Hydrogen (D/H) RatioEarth’s oceans: D/H ≈ 1.5 × 10⁻⁴
Outgassed water from Earth’s mantle: D/H ≈ 1.2–1.4 × 10⁻⁴ → close, but slightly too low
Carbonaceous chondrites (icy asteroids): D/H ≈ 1.4–1.6 × 10⁻⁴ → perfect match
Comets: D/H often 2–3× higher → too deuterium-rich (except some Jupiter-family comets like 67P)
Conclusion: Water chemically matches asteroids, not comets or purely mantle sources.
2. Noble Gases & TimingOutgassing happened early (during magma ocean phase, <100 Myr after formation).
But noble gases (Ne, Ar, Xe) in the atmosphere require late delivery by impacts — outgassing alone can’t explain them.
Icy planetesimals delivered both water and volatiles after the Moon-forming impact.
3. Zircon Evidence (Oldest Crystals)4.4-billion-year-old zircons show liquid water existed very early → some primordial water was present or outgassed.
But volume increased later via impacts.
Well, that is the Reader’s Digest version. LOL