Falcon 9 Impact! | Lunar Reconnaissance Orbiter Camera

The box in the center of the image highlights two small craters; the lower crater formed on August 5th (6:35 UTC) when a SpaceX Falcon 9 upper stage, impacted the Moon. The inset (lower left) shows details of the new crater, enlarged three times. The LROC image (M1541091337R) was acquired 6 days after the impact as the NASA Lunar Reconnaissance Orbiter (LRO) passed over the site at an altitude of 90 kilometers [NASA/GSFC/Intuitive Machines].

Using estimated latitude-longitude impact coordinates provided by the NASA JPL Center for Near-Earth Object Studies (CNEOS) Solar System Dynamics (SSD), the Korea Aerospace Research Institute (KARI) Korea Pathfinder Lunar Orbiter (KPLO, also known as Danuri) mission operations team planned a sequence of images to search for the newly formed impact crater. A few hours after the impact event, Danuri was commanded to point the high-resolution LUTI camera at the predicted site and acquire an image. A few hours later, the KARI team received the image and compared it to images acquired before the impact. And there it was, a new crater on the Moon!

LROC Narrow Angle Camera image before (M1370003265R) and after (M1541091337R) the booster impact. Images enlarged 5x, north is up, each image is 120 meters wide [NASA/GSFC/Intuitive Machines].

The KARI team relayed their updated coordinates, allowing the LROC team to refine their imaging sequence planned for 11 August. On the 11th, LROC acquired five images, one every 117 minutes, the time it takes to orbit the Moon. For the first image, LRO slewed 23° to the west; next, the spacecraft slewed 11° to the west; the third image required only a 4° slew, this time to the east, as the ground track had migrated past the impact site. The fourth and fifth images required east-looking slews of 17° and 28°, respectively. Thirteen and a half hours after the fifth image was acquired, LRO slewed 68° to the east to acquire an oblique view (see below).

Animated GIF of the before (M1370003265R) and after (M1541091337R) images of the booster impact site. Images enlarged 3x, north is up, image width is 400 meters [NASA/GSFC/Intuitive Machines].

The new crater (19.4759°N, 266.7138°E, 511 meters elevation) is 18 meters in diameter and is less than 3 meters deep (constrained with a shadow measurement). The distinctive V-shaped ejecta pattern on the south side of the crater is consistent with natural impactors hitting the Moon at low angles relative to the surface. In this case, the booster impacted at about 31° from horizontal; the forbidden zone (bright area on the south side of the crater) seen here is consistent with low-angle natural impacts. Other spacecraft impacts, such as the large Apollo Saturn S-IVB stage craters, do not always follow the same rules as natural impacts. This deviation may be due to the relatively odd mass distribution within a rocket. Upon impact, most of the booster consists of empty fuel tanks with a very heavy engine at one end. The final shape of the crater and the distribution of ejecta might be affected by the orientation of the booster upon impact (i.e., heavy end down, on its side, light end down, or somewhere in between). If the heavy end hits first, perhaps the crater and ejecta behave more like a natural event.

Why the mixed dark and bright ejecta? The Moon is covered in a layer of soil, known as regolith. Over time, the top portion of the regolith is constantly bombarded by the solar wind, galactic cosmic rays, and micrometeorite impacts. These external forces tend to darken and redden the regolith to a depth of roughly 50 centimeters. As an asteroid, or rocket body, first contacts the regolith, particles are jetted out at high velocity. As the body buries itself and explodes, it throws out deeper subsurface material, forming an ejecta blanket around the crater rim. In the Falcon 9 crater, the darker, streaky material was likely derived from the mature upper 50 centimeters of the regolith. In contrast, the brighter material near the crater rim came from the deeper, immature portion of the regolith (>50 centimeters below the surface).

With a nearly constant solar incidence angle, these images show the utility of collecting multiple observations with a range of viewing angles. The darker area in the upper-left image is rougher than the surroundings, and the brighter area in the lower-right image is less mature than the surrounding material. Images are ordered from upper left to lower right by time acquired and descending phase angle (indicated on each panel): M1541077306L, M1541084321L, M1541098353R, and M1541105368R. Each panel is enlarged two times and is 320 meters wide [NASA/GSFC/Intuitive Machines].

Although the Sun angle changed little (incidence angles 67° to 71°) during the image sequence, the groundtrack distance between these sequential orbits required a broad range of slew angles, resulting in a...