PAPER 6 OF THE LEF SERIES
The Craters
Craters Without Asteroids
Abstract
In the LEF model deep material was ejected through openings in the young Earth's envelope, and part of it returned to the outer shell that later rose with the forming Moon. We ask whether such material could arrive fast enough to crater and shock the target. In a central-gravity approximation without drag, material ejected radially and returning to the same radius lands at a relative speed equal to its ejection speed. At 5 km/s the flight lasts about 28 minutes and lands about 1,032 km to the west; an ideal head-on basalt landing gives a contact pressure of 45.6 GPa. A kilometre-sized body crossing a 100-bar vapour atmosphere keeps about half its speed. The source is the maria, the openings over feed domes of Paper 5. The ground around them carries their iron, from 6.9 wt% FeO near the edge to 3.1 wt% at 100–150 km. Read as external impactors, today's craters would leave 2–6% foreign material in the upper 5 km of the crust. The measured siderophile content is 0.9–2%, and where ruthenium isotopes are measured they are terrestrial. The longitudes record how the craters fell. The trailing half (90°E) is more crowded: about 250 craters of 20 km and more per million km², against 140–175, with the maria and South Pole–Aitken removed. The leading half carries more central peaks, lower jagged rims and rougher floors. Within each crater one composition runs from centre to rim, consistent with a crater filled by the material that made it.
Keywords: Moon; lunar craters; impact cratering; siderophile elements; ruthenium isotopes; crater asymmetry; ejecta; lunar origin
How to cite
Duran, Z. (2026). The Craters: Craters Without Asteroids. Paper 6 of the LEF series. https://lef-model.com/paper06.html