What Was in the Crashed Moon Rocket?

This double crater was formed on March 4, 2022, when a Chinese rocket part crashed onto the moon. But why was it a double crater?

On March 4, 2022, a plummeting rocket component generated a distinctive double crater on the moon—confirmed to be the upper stage of a Chinese carrier rocket through recent analyses. However, these analyses also reveal that this rocket stage must have borne an additional, relatively heavy payload. Only in this way can the double crater resulting from the crash be explained, as researchers report. Nevertheless, the nature of the cargo carried by the rocket for the Chang’e 5-T1 test lunar mission remains shrouded in mystery.

In February 2022, a rocket component named WE0913A gained attention for diverging from the typical space debris trajectory and heading instead towards the moon. Initially believed to be the second stage of a Falcon-9 carrier rocket, closer analysis provided clues that it was, in fact, the upper stage of a Chinese Long March carrier rocket. This rocket launched a test capsule for China’s Chang’e 5 lunar mission back in 2014.

How Did the Double Crater Occur?

During the Chang'e 5-T1 test mission,
During the Chang’e 5-T1 test mission, a launch vehicle placed a preliminary version of the lunar probe on a path that led around the moon back to Earth. Here is an image taken by the lunar module from the far side of the moon. Image: Chinese National Space Agency

However, the peculiar aspect is that when this rocket component crashed on the far side of the moon on March 4, 2022, it left behind a double crater. “This is the first time we’ve seen such a double crater after the crash of a rocket component,” says lead author Tanner Campbell from the University of Arizona. Images from NASA’s Lunar Reconnaissance Orbiter (LRO) revealed two round, nearly identical craters near the impact site, slightly overlapping.

Nevertheless, a rocket stage, even upon impact at a very shallow angle, would not leave such a double crater. It would, at most, leave an elliptical imprint, as researchers explain. “With the rocket part from Chang’e 5 T1, we know that it crashed almost vertically,” says Campbell. “To get two separate, nearly identical craters, you would need two heavy masses spatially separated from each other.”

Peculiar Flight Behavior

These brightness curves show the regular rotation of the rocket section.
These brightness curves show the regular rotation of the rocket section. Image: Campbell et al./ The Planetary Science Journal, CC-by 4.0

But what could these masses be? The upper stage of the Long March rocket consists of an almost empty shell with two 500-kilogram engines at one end. Such a stage is heavy at one end and light at the other, causing it to typically move through space in a tumbling and uncontrolled rotation due to this imbalance.

However, with WE0913A, astronomers found this to be different through photometric observation data: “This object rotated in a very stable manner along its long axis,” Campbell reports. The gravitational pulls of the moon, Earth, and sun caused the rocket stage to perform regular somersaults with little change in orientation or rhythm over the course of the lengthy flight.

Heavy Counterweight at the Front

Schematic of a Chinese Long March 3C carrier rocket, which was also used for the Chang'e 5-T1
Schematic of a Chinese Long March 3C carrier rocket, which was also used for the Chang’e 5-T1 test moon mission. Image: Shujianyang/ CC-by-sa 4.0

According to Campbell and his team, this leads to only one conclusion: The rocket component must have carried an additional, relatively heavy counterweight at its front. “While we know that the stage carried an instrument platform at its upper end, it weighed only about 14 kilograms,” Campbell reports. “That would not be nearly enough for such a stable rotation. Therefore, we believe that something else was mounted on the front.

The existence of such an additional payload would not only explain the flight behavior of the rocket component but also the double crater left by its crash on the moon.

Need for More Transparency in the Lunar Environment

Understanding the trajectories and identities of such large space debris pieces becomes increasingly crucial amid growing space activities. In Earth’s orbit, defective satellites and other debris already pose a significant problem, endangering other satellites and space missions. In the moon’s vicinity, relics from previous missions were scarce for a long time, given the limited lunar space exploration since Apollo.

However, this has drastically changed in recent years. The United States, with its Artemis mission, plans a manned return to the moon in the coming years. Russia and China also aim to bring astronauts to the moon and establish manned lunar stations by the mid-2030s. India, Japan, and European countries likewise aspire to have a manned presence on the lunar surface.

In light of these space exploration plans, according to Campbell and his team, it is particularly crucial to monitor and document rocket components and other space debris in the lunar environment. “There is significant motivation for lunar flights on both commercial and government levels,” says co-author Roberto Furfaro from the University of Arizona. “However, as we send more and more objects to the moon, we need to track their orbits and understand what happens to them there.

Source: The Planetary Science Journal