South Ray (crater)
Small lunar crater visited by Apollo 16 astronauts.
South Ray is a small lunar crater located in the Descartes Highlands, first photographed from the Moon's surface by the Apollo 16 crew. The International Astronomical Union officially assigned its name in 1973.
The Apollo 16 lunar module *Orion* touched down between North Ray and South Ray craters on April 21, 1972. Astronauts John Young and Charles Duke spent three extravehicular activities exploring the region between the two craters, using a Lunar Roving Vehicle. Their closest approach to South Ray occurred during the second EVA at station 4, known as Cinco crater, roughly 3.9 kilometers south of the landing site. Duke captured an image of South Ray from that spot using a 500-millimeter lens.
The crater measures about 700 meters across and 120 meters deep, and it features a bright system of ejecta rays. The astronauts noted that the ejecta around South Ray was extremely bouldery, and they reported that driving a rover there would have been very difficult or impossible.
South Ray cuts into the Cayley Formation, which dates to the Imbrian period, but the crater itself is much younger, belonging to the Copernican period.
Quick Facts
- Diameter
- 700 m
- Depth
- 143 m
- Formation
- Copernican
- Eponym
- Astronaut-named feature
Facts from the source article.
Lore & Background
South Ray crater is located in the Descartes Highlands of the Moon and was photographed from the lunar surface by the astronauts of Apollo 16. The Apollo 16 Lunar Module Orion landed between North Ray and South Ray craters on April 21, 1972. Astronauts John Young and Charles Duke explored the area between the craters over three EVAs using a Lunar Roving Vehicle.
The astronauts came closest to South Ray on EVA 2, at station 4 (Cinco crater), about 3.9 km south of the landing site. Duke photographed South Ray from there with a 500-mm lens. The crater is approximately 700 m in diameter and 120 m deep, with a bright system of rays of ejecta. The astronauts observed that the ejecta was very bouldery and reported it would have been difficult or impossible to drive there on their rover.
South Ray cuts into the Cayley Formation of Imbrian age, but the crater itself is much younger, belonging to the Copernican period. Its name was formally adopted by the IAU in 1973.
Reader's Guide
South Ray crater is significant as a geological feature studied during the Apollo 16 mission, the fifth human landing on the Moon. Its bright ray system and bouldery ejecta provided valuable information about impact processes and the age of lunar surface features. The crater's Copernican age indicates it is relatively young compared to the surrounding Cayley Formation, helping scientists understand the sequence of lunar geologic events. The astronauts' observations that the terrain around South Ray was too rugged for the rover highlighted the challenges of lunar exploration and influenced planning for future missions. The crater's formal naming by the IAU in 1973 cemented its place in lunar cartography. As a landmark visited by humans, South Ray remains a point of interest for lunar geology and the history of space exploration.
Did You Know?
- The crater was photographed by astronaut Charles Duke using a 500-mm lens from station 4 (Cinco crater).
- The astronauts reported that the bouldery ejecta of South Ray would have made it difficult or impossible to drive there on their rover.
Frequently Asked Questions
What is South Ray crater and where is it located?
South Ray is a small impact crater roughly 700 meters wide and 120 meters deep, sitting in the Descartes Highlands on the Moon. It was first photographed from the lunar surface by the Apollo 16 crew in April 1972.
How close did the Apollo 16 astronauts actually get to South Ray?
The Orion lunar module landed right between South Ray and its twin North Ray on April 21, 1972. During the second EVA at Cinco crater, John Young and Charles Duke drove the rover to a point only about 3.9 kilometers from South Ray's rim.
Who gave South Ray its official name and when?
The International Astronomical Union formally assigned the name in 1973. Prior to that designation, it was simply an unmarked feature in the highlands terrain.
How old is South Ray compared to the surrounding geology?
The crater itself is classified as Copernican in age, making it relatively recent in lunar history. Its rim cuts into the Cayley Formation, which is Imbrian in age, so South Ray postdates the terrain it sits on.
Why is South Ray a meaningful landmark for Apollo 16 fans?
It anchors one end of the corridor the astronauts explored across all three EVAs, with North Ray marking the other end. For fans reconstructing the mission's surface route, South Ray is the fixed reference point that brackets the entire Descartes landing area.
More in Apollo 16 1-18
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