RISING MOON
Splish splash
A DAY BEFORE FIRST QUARTER, the Moon shows us a face of thirds. The south is a crowded, cratered mess that quickly morphs into the equatorial slate gray seas, whose large frozen waves are known as wrinkle ridges. Venture up to the northern third, where the smoothness is punctuated by a handful of large identifiable craters.
On Oct. 11, the ramparts of Aristoteles lie aglow in the rising Sun, mostly emerged from the terminator. One Earth day later, we can see this marvelous, complex crater fully lit. Craters half its 50-mile size boast cleaner lines and a simpler peak, but Aristoteles’ features suffered much more during the greater energy release of a larger impact. In moments of good seeing, there is a lot of structure to see here.
Splattering back down after the blast, the vast amount of excavated soil spreads a large apron around Aristoteles, creating an uncountable number of small secondary craters. You can only see them flit in and out of view in the slanted light near lunar sunrise or sunset. By the 13th, the higher lunar Sun has erased these shadowlets from view. The inner crater walls, weakened from the impact, have slumped into a series of terraces. Millions of years later, lava welled up from underneath, flooding the inside — but not quite enough to cover the peaks at the center.
Return for a look around Full Moon and pop in a filter to cut down on the glare. Sweeping in a gentle arc of dark gray across the lunar north is Mare Frigoris. Aristoteles has been transformed to an oval of light material, paired with the smaller, more circular crater Eudoxus just to the south. What a change solar noon brings!