Apollo astronauts paid only brief visits to the Moon – but they left it a little warmer than they found it.
During two of NASA’s 1970s lunar missions, astronauts set up experiments probing the flow of heat through the soil. But until now, only data from 1971–74 had been analysed. A team led by Seiichi Nagihara at Texas Tech University in Lubbock has unearthed and examined the records from 1975–77. Those measurements show that temperature increases documented over the course of the earlier period continued until the end of the experiment, with changes occurring as deep as one metre below the lunar surface.
The warming of the lunar soil was probably caused by the astronauts themselves. The crews’ landers, boots and rover disturbed the lunar surface, which darkened the soil and allowed it to absorb more of the Sun’s heat.
Future lunar missions should take this effect into account when designing heat-flow probes, the authors say.