 What, within the context of the passage, is a 'marker'?
Wherever the yacht landed, such a disparity between its documents and its crew would spark an investigation. It could have travelled at almost any speed in practically any direction for a length of time that was at least indefinite. The process would be to find a planet and check its climate and relationship to other planets, and its flora and fauna against descriptions in the Directory. It marked a first-landing spot on some planet or other, so the people could find that spot again. If they left a beacon, they may have left an identification of the planet. From time to time some thing unknown made a cry that sounded very much like a small boy trailing a stick against a picket fence, only much louder.
 A safe space for a spacecraft to land on an alien planet
 A microchip inserted into a person, designating them as a fugitive  A safe space for a spacecraft to land on an alien planet  A sound picked up on a radar that reveals the closest habitable planet  A location on the alien planet that indicates high predatory activity