When two full Moons fall in the same month, as is the case this August, the second is known as a Blue Moon. When a week boasts two Moon landings, the second is called…well, no one knows; such a one-two punch has never happened before. But there is a decent chance that will change in the coming days.

Chandrayaan-3, an Indian mission, blasted off on July 14th. It arrived in lunar orbit three weeks later, having taken a fuel-efficient but slow approach to leaving Earth. It has spent the days since lowering its orbit towards the tight, circular loop from which its lander will attempt a touchdown on August 23rd. Luna 25, a Russian probe, did not blast off until August 10th. But it took a more direct route, reaching lunar orbit on August 16th. Its operators plan to get it to the surface on August 21st, shortly after dawn at its landing site.

That landing site, like Chandrayaan-3’s, will be at a much higher latitude than any previous landing, about 600km from the Moon’s south pole. The region is of interest because there may be water ice below the surface—or even, in craters where the Sun never rises above the horizon, sitting at the surface as frost.

Scientists want to understand how and when that ice arrived. Earth’s ice caps contain records of past events; so may the lunar ice, assuming the probes can find it. Proponents of lunar settlement see ice as a potential source of oxygen, water and rocket propellant. An American mission due to launch in November aims to land on the edge of a crater called Malapert, which is closer to the pole even than the Indian and Russian sites and contains some of the enigmatic permanently shadowed regions. Researchers in both America and China are looking at Malapert as a candidate for human exploration.

Success is not guaranteed. Russia has not run a successful interplanetary mission since the fall of the Soviet Union. Yuri Borisov of Roscomos, the Russian space agency, has said he thinks Luna 25 has a 70% chance of success. India may be more confident, in part because of past failure. In September 2019 Chandrayaan-2 was just a couple of kilometres from the surface when it malfunctioned and subsequently crashed.

Details of what went wrong have never been made public, but ISRO, India’s space agency, has presumably learned from the experience. If it succeeds, India will become the fourth country, after America, the ussr and China, to have pulled off a landing. If Russia succeeds, it will be repeating something its antecedent once superpower treated as routine. The second landing, if it is the second, will be the true first.