Japan's first-ever lunar landing didn't have the most auspicious beginning. SLIM (Smart Lander for Investigating Moon) reached the Moon early this year, but it came to rest on its nose with the solar panels at an inconvenient angle. That early misstep is in the past, as the probe proves it has real staying power on the Moon. The Japan Aerospace Exploration Agency (JAXA) confirms that SLIM has awoken after its third lunar night cycle, and it's still got more to give.
As interest in the Moon has ramped up after decades of focus on low-Earth orbit, we often hear about the limits imposed by long lunar nights. Space agencies and private aerospace firms usually caution as they work toward landings that their hardware is only designed to last a few days or weeks—night on the Moon lasts for the equivalent of two Earth weeks. Although we think of the Moon, and space in general, as frigid, it experiences wild temperature swings. On the Moon, temperatures range from 250 degrees Fahrenheit during the day to -200 Fahrenheit at night (about 120 to -130 degrees Celsius). It can be even colder in shadowed craters, too.
SLIM was not designed for these conditions, which makes its continued survival all the more amazing. On X (formerly Twitter), JAXA says that it has been in communication with SLIM after the end of the recent lunar night cycle. The craft's awkwardly positioned solar panels have been able to recharge the batteries, which have vastly outperformed their expected life. Low temperatures are particularly hard on batteries, which can become too damaged to store a charge after weeks on ice.
SLIM is not only alive, it's been able to snap new images of the lunar surface. JAXA shared one from right after the craft awoke. The image is extremely bright and shows almost no shadows because it was taken just after the night ended. If this continues, SLIM's design could give hints to other engineering teams aiming to design long-term lunar hardware. That will be necessary as NASA, the ESA, and others work toward building a long-term human presence on and around the Moon.
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JAXA didn't have any of that in mind when it created the SLIM mission. This spacecraft was launched to conduct short-term surface operations and test a new precision landing system. The system worked by scanning the lunar surface and matching that feed to high-resolution mapping data in nearly real-time. SLIM eventually landed just 180 feet (55 meters) from the target. That's much better than other landers, which can be off by several miles. However, a last-minute engine failure caused SLIM to pitch forward, landing on its nose. SLIM is making up for that with its longevity.
JAXA says it will continue to monitor SLIM to understand better what elements of its design have helped it survive this long. The designers did not anticipate it would last through even one night cycle, so for all we know, it will keep surprising us for a while longer.
