Earth's temporary satellites as potential space mission targets

Earth's temporary satellites (Granvik et al., 2012) are small asteroids that occasionally become trapped as Earth's companions. At any given time, the largest temporary moon has a diameter of ~75 cm, and the moon with a diameter  of 3 m is captured once every 10 years. On average, a captured temporary moon makes three revolutions around the Earth over a period of 9 months (Fedorets et al., 2017).

Both the transfer from the main asteroid belt and Lunar ejecta are two plausible solutions for the origin of Earth's temporary satellites. Temporary satellites are a key population for distinguishing between the main-belt and Lunar origin of asteroids in Earth's immediate vicinity (Jedicke et al., 2025, Alessi & Jedicke, 2026). Temporary moons would therefore be ideal targets for studying the population of very small asteroids, about which very little information is known. Moreover, due to their low delta v and relatively long residence in Earth's vicinity, temporary satellites are outstanding test mission targets in the emerging field of asteroid mining (e.g. Granvik et al., 2013). Finally, temporary moons provide opportunities to train for navigation around individual boulders which have been observed floating, e.g. in the vicinity of asteroid Bennu during the visit of the OSIRIS-ReX mission.

So far, only two temporary satellites have been discovered, both by the Catalina Sky Survey.  LSST is expected to discover temporary satellites on a more regular interval, currently expected to be 1-4 year (Fedorets et al. 2020a). With LSST, not only will it be possible to understand the population of Earth's temporary satellite as a population, but also to narrow the size-frequency distribution gap in the NEA population at 1-10 metres between asteroid survey and bolide data (e.g., Chow & Brown, 2025). However, due to narrow observational windows of Earth's temporary satellites, additional observations and sieving through LSST alerts will be required for their physical characterisation in addition to LSST baseline.

In this presentation, I will discuss the expected discovery methodology of Earth's temporary moons, and consider ideas for their in situ exploration.

References:

Granvik, M., Vaubaillon, J. & Jedicke, R. (2012), Icarus 218, 262 – 277.

Granvik, M. et al. (2013), ’Earth’s Temporarily-Captured Natural Satellites – The First Step Towards Utilization of Asteroid Resources’, in V. Badescu, ed., ‘Asteroids. Prospective Energy and Material Resources’, Springer, pp. 151 – 167.

Fedorets, G., Granvik, M. & Jedicke, R. (2017), Icarus 285, 83 – 94.

Fedorets, G., Granvik, M., Jones, R. L., Jurić, M. & Jedicke, R. (2020a), Icarus 338 113517.

Chow, I & Brown, P. G. (2025) Icarus 429 116444.

Jedicke, R. et al. (2025), Icarus 2025 438 116587

Alessi, E. M. & Jedicke, R. (2026) Icarus 455 117109