SpaceX rocket set to crash into Moon; astronomers prepare for rare event

Discarded Falcon 9 upper stage will strike the lunar surface on August 5, helping researchers study impact physics and future risks from space debris

A discarded SpaceX Falcon 9 rocket stage is set to crash into the Moon on Wednesday in an unplanned but closely watched event that scientists say could provide rare insights into lunar impacts, space debris and the safety of future missions to the lunar surface.

 

The roughly 3.9-tonne upper stage, left adrift after launching Firefly Aerospace's Blue Ghost-1 and Japan's ispace Hakuto-R Mission 2 lunar landers in January 2025, is expected to strike the Moon at around 8,700 kmph near the Einstein Crater on the Moon's western limb at 6:35 am UTC (12:05 pm IST) on August 5.

 

Unlike previous intentional lunar impacts carried out by space agencies for scientific experiments, this collision is accidental. Yet astronomers are treating it as a unique natural experiment because the rocket's trajectory and impact site are known in advance, allowing telescopes and lunar orbiters to observe the event in real time, according to a report by Space.com.

 

Researchers expect the impact to excavate a crater about 27 metres (90 feet) wide while throwing up a plume of dust and debris that could rise as high as 100 km above the lunar surface before settling back. Nasa's Lunar Reconnaissance Orbiter and South Korea's Danuri lunar orbiter are expected to image the impact site before and after the collision to assess the crater and the distribution of ejecta.

 

How did the rocket land in the Moon's orbit?

 

SpaceX's Falcon 9 boosters have flown to space dozens of times but the upper stage that pushes payloads into orbit is expendable, and the company typically steers it back into the atmosphere for a controlled burn-up shortly after each launch. 

 

That routine cleanup wasn't an option for the rocket that carried the Blue Ghost and Resilience lunar landers, since reaching such a distant drop-off point consumed nearly all of the stage's remaining propellant. With no fuel left to guide it home, the roughly 4,000-kg stage was left drifting in a high-Earth orbit that crosses the Moon's path, as per a new study on its eventual impact, led by Benjamin Fernando of Los Alamos National Laboratory.

 

Why scientists are excited

 

For planetary scientists, the event is less about the impact flash than the cloud of debris it produces. Because the Moon has virtually no atmosphere, the ejecta can be tracked much more accurately than on Earth, helping researchers refine computer models of impact dynamics and better understand the Moon's surface and subsurface composition. 

 

The observations are also expected to sharpen predictions of how future impacts could affect spacecraft, habitats and other infrastructure planned under upcoming lunar exploration programmes.

 

“Watching this one gives us a rare chance to open up ejecta-plume science and calibrate those models against a real event, which matters for every future thing we deliver to the moon," William Jo from the University of Texas, Austin was quoted as saying by Space.com.

 

The collision also comes as concerns over space debris are expanding beyond Earth orbit. As Nasa's Artemis programme, China's lunar plans and a growing number of commercial missions target the Moon, scientists say discarded rocket stages and other hardware could become a hazard if not properly managed. 

 

While space agencies have deliberately crashed spacecraft into the Moon in the past, uncontrolled impacts of modern commercial rocket stages remain uncommon.