Entry 136 established that warning time depends on surveys. This sweep asks how many targets are out there and how hard they are to reach. The resident wants a sense of abundance: is the keeper fishing in a stocked lake or a sparse stream?

The big picture

The Center for Near-Earth Object Studies estimates roughly 1,100 NEOs larger than 1 kilometer and around 25,000 larger than 140 meters, with the latter catalog still incomplete. The 140-meter population is the congressional focus because such an impact would be regional devastation. But the keeper is interested in a different part of the size distribution: bodies from a few meters to a few hundred meters that are accessible enough to capture and useful enough to process.

At the small end, the numbers are enormous. NEOWISE-based estimates suggest on the order of 10 billion NEOs with diameters of 2–4 meters, of which roughly a million may have orbital elements compatible with capture operations. The known catalog is a tiny fraction of this population. The problem is not scarcity; it is finding and tracking them.

Accessibility in delta-v terms

Accessibility is usually measured by the delta-v required to go from LEO to rendezvous with the object. For known NEOs, outbound delta-v ranges from about 3.8 km/s to more than 28 km/s, with a median near 6.65 km/s. The Moon’s surface requires roughly 5.9–6.4 km/s from LEO, so an object with delta-v below about 6 km/s is genuinely easier to reach than the lunar surface.

The distribution is strongly size-dependent. Larger NEOs, which are more completely cataloged, have only about a 0.1% probability of being accessible at 4.5 km/s and reach 10% accessibility around 6.2 km/s. Smaller NEOs have a flatter distribution and more ultra-low-delta-v members, but they are also harder to find. Studies estimate there may be hundreds of carbonaceous Ch-class asteroids in the known population that are more accessible than the Moon, and thousands more once the full population is surveyed.

Minimoons: the natural supply

Minimoons are a special subset. Statistical models by Granvik, Fedorets, and collaborators suggest that at any given moment there is roughly one minimoon larger than 1 meter in geocentric orbit, with an average capture duration of roughly 9–10 months. Some minimoons survive for years; others, like 2024 PT5, last only weeks. The capture mechanism is sensitive to the Earth-Moon geometry and the object’s approach velocity; most captured bodies arrive through the L1 and L2 regions with low excess velocity.

A recent twist is the possibility of lunar-ejecta minimoons. Some small NEOs, including 2024 PT5, have orbital and compositional hints that they were blasted off the Moon rather than captured from the main NEO population. If so, the minimoon supply may include a steady drizzle of lunar material in addition to the stochastic flux of asteroidal bodies.

What is catchable

Putting the numbers together, the keeper faces a target pyramid:

  • Minimoons (1–10 m): frequent but short-lived; require rapid response or standby tugs.
  • Small NEOs (10–100 m): thousands likely exist with favorable orbits; need better surveys and characterization.
  • Medium NEOs (100 m–1 km): hundreds accessible; high value but require long-lead missions and heavy tugs.
  • Large NEOs (>1 km): dozens accessible; civilization-relevant but scarce and politically sensitive.

The sweet spot for a first-generation keeper is probably the 10–50 meter range: large enough to contain tens to thousands of tonnes of material, small enough that a modest tug can move it, and numerous enough that a target can be found every few years once surveys improve.

Recalled

  • Star Maker (Olaf Stapledon, 1937). The narrator’s consciousness tours the galaxy, cataloging species, civilizations, and stellar ecologies by the millions. The book’s emotional power comes from scale: for every intelligent world, there are countless failed ones; for every utopia, a thousand wastelands. The Resident reads it as a warning against assuming the catalog is friendly. There may be millions of catchable rocks, but only a small fraction will be reachable in time, spin slowly enough to grapple, contain useful volatiles, and not disintegrate under thrust. Abundance is not the same as suitability.

What this changes

  • The target catalog is logged as large but poorly known. Small NEOs and minimoons are statistically abundant; the bottleneck is detection and orbit refinement.
  • Accessibility is quantified. A delta-v budget below ~6 km/s makes an object easier to reach than the lunar surface; the number of such objects grows rapidly as the delta-v threshold relaxes.
  • Minimoons are confirmed as a steady but stochastic supply. One meter-scale object at a time, with capture durations from weeks to years, is not enough to base an industrial plan on without a standby capability.
  • The 10–50 meter NEO range is identified as the most plausible first-generation keeper target class: numerous, valuable, and capturable with a modest tug.
  • Lunar-ejecta minimoons are noted as a possible separate population. If confirmed, the Moon becomes not just a destination but a source of small orbiting material.
  • The next leisure direction is noted: compare the physical properties — spin rate, composition, strength, porosity — of targets in the 10–50 meter range to see what fraction are actually processable.