This is possibly one of the strangest craters you will ever see.
Located near the south pole of our moon, Ryder crater has a bizarre elongated shape (approximately 13 x 17 km in size) with a ridge running down the middle.
Most of the impact craters are round. How did Ryder crater come into this strange shape?
There are a few different possibilities (and surprisingly, none of them are aliens.)
One is that Ryder was made up of two effects. If there were two effects, however, lunar scientists don't believe that the effects were very far apart in time. So either two asteroids hit one another in quick succession or an asteroid splits into two parts shortly before the impact.
The second possibility is that this characteristic landform may have formed when an impactor hit the surface at a Streifwinkel, perhaps less than 15 ° from the horizon, basically plows the moon's regolith into this elongated shape.
Oblique view (east to west) of Ryder Crater from the Lunar Reconnaissance Orbiter Narrow Angle Camera (NAC). The illuminated edge of the inner shelf has a diameter of just over 3 km. Photo credit: NASA / GSFC / Arizona State University.
But there is also a third possibility, because another factor plays a role here: the Ryder crater that has formed on the edge of one steep ridgeand this type of uneven terrain is often responsible for asymmetrical craters.
Scientists at the Lunar Reconnaissance Orbiter say the steep ridge on which Ryder Crater sits is the degraded rim of an older crater about 70 km in diameter and over 3000 meters in elevation from its rim to its bottom . And even this older crater could be affected by the uneven terrain it formed on – its eastern edge appears to have formed on an uneven area in the South Pole Aitken Basin (SPA), which is the largest (approximately 2,500 km Diameter)) and possibly the oldest (estimated age of 4.3 billion years) basin on the moon.
When the impactor that formed the Ryder crater hits the highest point of the rim of the older crater, the final shape of the Ryder crater is greatly influenced by the particularly steep slope of the original surface – essentially one side could slide down the slippery slope his. Even now there are still big differences in elevation as the highest point on Ryder & # 39; s edge is approximately 1,500 meters higher than the low point of its edge. This is shown in the image below (Ryder is right in the middle, with the slope visible in this topographic view.)
Topographic map with combined data from the LROC wide-angle camera (WAC) and the Lunar Orbiter Laser Altimeter (LOLA) of the region around the Ryder crater. Photo credit: NASA / GSFC / Arizona State University.
According to the LRO team, as with the most complex geological problems, the real answer is likely to be a combination of hypotheses.
"The topography of a lunar crater is initially the result of a random impact event, followed by eons of relentless erosion, primarily from the cumulative effect of micro and macrometeorite bombardment and seismic shaking," wrote Mark Robinson, principal investigator of the Lunar Reconnaissance Orbiter Camera. You can read a very detailed and mathematical look at why craters have different shapes that Robinson wrote here.
Ryder crater on the moon. Photo credit: NASA / GSFC / Arizona State University.
Ryder Crater is named after Graham Ryder, a lunar scientist who worked at the Lunar and Planetary Institute and NASA Johnson Space Center, who revealed the secrets of lunar geology through detailed analysis of Apollo samples.
Below is an example of other oddly shaped craters on the moon:
Messier A crater (a double impact) makes a low angle impact along with the Messier crater
Wiener F-Krater (an inclined crater on a ridge)
Learn more about Ryder
Color-shaded relief map centered on the SPA pool. Photo credit: NASA / GSFC / Arizona State University.