Lunar Reconnaissance Orbiter Camera

Korolev X and Z

Oblique view of Korolev Z, Korolev X, and melt flow that links them
Sharing a melt flow: visible in the right part of this oblique image is the bright wall of Korolev Z crater, the source of a 12.5-kilometer-long dark melt flow that drapes across the ancient floor of the degraded crater Korolev X. South is to the left. The image covers an area measuring about 20 kilometers from left to right and 40 kilometers from bottom to top. NAC image M1168158470LR [NASA/GSFC/Arizona State University].

More than any other individual, Sergei Pavlovich Korolev (1907-1966) was responsible for early Soviet rocket and space successes. He was the mind behind Sputnik 1, the first artificial Earth satellite (4 October 1957), and Vostok 1, the first spacecraft to carry a human into Earth orbit (cosmonaut Yuri Gagarin, 12 April 1961). Korolev also inspired space exploration in the United States: had the Soviet Union not scored those early space firsts, President Dwight D. Eisenhower might not have created NASA and President John F. Kennedy might not have directed NASA to land a man on the Moon before the end of the 1960s decade.

Sergei Pavlovich Korolev, Chief Designer of the early Soviet space program
Sergei Korolev, the Chief Designer of the Soviet space program, was one of the most influential figures in 20th-century history; during his lifetime, however, his identity was a Soviet state secret. Image credit: Wikipedia

The craters of the Moon are mostly named for scientists and engineers, with some celebrated explorers and male and female first names from many cultures thrown in for variety. An ancient, battered basin on the Moon's farside hemisphere honors Korolev. Within and near the 423-kilometer-wide basin lie smaller craters also named for Korolev but set apart by a following letter. Today's Featured Image is part of an oblique Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) image pair that takes in 27. 1-kilometer Korolev X (200.56°E, 0.56°N) and Korolev Z (200.48°E, 1.15°N). At 17.7 km wide, Korolev Z is only a little smaller than the city of Moscow.

Korolev Z partially overlaps Korolev X, so we know that Korolev Z is younger. Steep crater walls and fresh impact melt are also signs of Korolev Z's relative youth. Over time, impacts large and small will grind the melt deposits to dust and nearby impacts and moonquakes will make the steep walls slump.

The most remarkable geologic feature of Korolev X is a large impact melt flow that originated in Korolev Z. The asteroid or comet impact that excavated Korolev Z was violent: in less than a second it released enough energy to press down its floor, turn its rocks to lava, and collapse the kilometers-wide wall separating it from older, deeper Korolev X.  When the floor of Korolev Z rebounded, molten rock surged over the collapsed wall into Korolev X, then flowed downhill for 14 kilometers before it cooled and solidified. The molten rock flood descended more than 1.5 kilometers as it coursed from north to south.

Grab your red and blue glasses to explore Korolev X and Z and the melt flow they share in the anaglyph 3D image strip below. Below that, be sure to zoom in on our large-size Featured Image - it is packed with small details.

anaglyph image of Korolev X and Korolev Z
Anaglyph image strip, 50.3 kilometers long by 11.6 kilometers wide, composed of LROC NAC image pairs M1122289179RL and M112282070RL [NASA/GSFC/Arizona State University].

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