Free Astronomy Magazine November-December 2026

12 NOVEMBER-DECEMBER 2026 ASTRO PUBLISHING ogy should be here inten- tionally and be active right in our time. A more reasonable, albeit remote, possibility seems that somewhere on a rocky or icy body in the Solar Sys- tem there are the inactive remains of an extraterres- trial technology, crashed, landed, or otherwise aban- doned there for who knows how long. As one might easily imagine, the surfaces best suited to preserving alien remains for billions of years are those of bodies devoid of atmospheres, ge- ological processes, or any other phenomena capable of periodically reshaping surface environments. A promising candidate could be Callisto, Jupiter’s second- largest moon. As large as Mercury, it possesses the oldest and most unaltered surface in the Solar System; its icy, rocky crust is esti- mated to have been free of significant tectonic or vol- canic activity for approxi- mately 4 billion years. Vesta and other asteroids also exhibit surfaces unchanged for billions of years, as well as the burning Mercury and the Moon, at least partially. Our natural satellite itself could be the ideal target for searching for alien technosignatures: it’s nearby, has no atmosphere (only a thin ex- osphere), is geologically almost completely inactive, and the only phenomenon capable of altering its surface—meteorological impacts— hasn’t been intense enough to dras- tically degrade its surface structures in the last tens of millions of years. Even considering the near-constant rain of micrometeorites and solar radiation, tens of thousands of years would have to pass before the been exploited only to image the Apollo landing sites, ro- botic survey vehicles, and areas of interest for future ex- ploration. Over 98% of the lunar surface has been imaged with a resolution of just 100 m/px. To reliably distinguish an object with a resolution of 100 m/px, it must have an ex- tension of at least 400 or 500 meters (about 4-5 pixels on a side). According to visual in- terpretation criteria, an object requires at least 2 pixels to be detected, but 4 to 6 pixels are needed for certain identifica- tion. Therefore, the more than 20 million images taken so far by LRO, most of which have yet to be examined, are un- likely to reveal non-terrestrial artifacts, unless they are the size of the USS Enterprise-D from Star Trek: The Next Gen- eration . Less pessimistic might be the search for alien technology in the vast database of images produced by NASA’s Mars Re- connaissance Orbiter (MRO), which imaged approximately 2% of the red planet’s surface with the HiRISE Camera at the maximum resolution of 0.3 m/px, while the re- maining approximately 98% (from 88°N to 88°S) was imaged by the Context Camera at a resolution of approximately 0.6 m/px. However, the Martian environment is much more dynamic than the lunar one, and any small extraterrestrial arti- facts could be buried or eroded by atmospheric agents over a variable period of time. All things considered, Lazio’s provoc- ative hypothesis is unlikely to be re- futed until all the solid surfaces of the Solar System have been imaged in detail and carefully examined, an undertaking that could take many decades or even centuries. J oe Lazio enjoys a moment of relaxation while attend- ing the International Pulsar Timing Array in Banff, Calgary, Canada. [Scott Ransom] footprints of the Apollo astronauts could be erased. To make alien technology as large as the Lunar Ex- cursion Module’s ascent stage (less than 5 meters wide and weighing just over 2 tons) unrecognizable, several tens of millions of years would be needed, unless it were first struck by a large meteoroid, a highly unlikely scenario. The Moon is therefore the ideal starting point for searching for evi- dence of another technological civ- ilization. The task may seem rela- tively easy, since NASA’s Lunar Re- connaissance Orbiter (LRO), in lunar orbit since 2009 and still fully oper- ational, can image the lunar surface with a maximum resolution of 0.5 m/px. Unfortunately, that limit has !