What happens when a SpaceX rocket hits the moon?

The Background: Space Junk on a Collision Course

In early March 2022, a piece of a SpaceX Falcon 9 rocket, specifically the upper stage from the 2015 Deep Space Climate Observatory (DSCOVR) mission, is on an unguided trajectory towards the Moon. This object, designated as object 2015-007B, is not the first man-made object to impact the lunar surface, but it is notable for being the first piece of space junk from a private company's mission to do so unintentionally. Its impending collision, expected around March 4, 2022, has drawn attention from astronomers and space agencies alike, prompting observations and discussions about the growing problem of orbital debris.

While the rocket's booster stage was designed to re-enter Earth's atmosphere and burn up, the DSCOVR mission's upper stage was sent on a trajectory that placed it in a chaotic orbit around the Earth and Moon. After years of drifting, gravitational tugs from both celestial bodies have altered its path, setting it on a collision course with the Moon. This event highlights the long-term consequences of space missions and the challenges of managing objects left behind in orbit.

The Mechanism: An Uncontrolled Lunar Impact

The SpaceX Falcon 9 rocket's upper stage, weighing approximately 4,000 kilograms (8,800 pounds), has been in orbit for nearly seven years. Unlike satellites or spacecraft intentionally sent to crash into the Moon, this piece of hardware is no longer under control. Its trajectory is dictated by the complex gravitational forces of the Earth and Moon, as well as residual thrust from its original mission. As it approaches the Moon, these forces will accelerate it, leading to an impact at an estimated speed of 2.5 kilometers per second (about 5,600 miles per hour).

Astronomers, including those at NASA and the SETI Institute, plan to use telescopes, such as the Lunar Reconnaissance Orbiter (LRO) and ground-based observatories, to observe the impact. The goal is to document the event and analyze the resulting ejecta – the material thrown up by the impact. While the exact location of the impact is difficult to pinpoint precisely due to the object's uncontrolled nature, it is expected to occur on the far side of the Moon, making direct visual observation from Earth impossible. However, the LRO may be able to capture images of the impact site afterward.

Who is Affected and How: A New Crater and a Growing Problem

While the direct impact on Earth is negligible, the Moon will gain a new, albeit small, crater. The estimated size of this crater is likely to be around 10 to 20 meters (30 to 60 feet) in diameter. This event does not pose any threat to lunar exploration or existing lunar infrastructure. However, it serves as a stark reminder of the increasing amount of space debris in Earth's orbit and beyond.

The primary concern is the long-term sustainability of space activities. As more missions are launched, the risk of collisions between active satellites and defunct objects increases. This can lead to the creation of more debris, a phenomenon known as the Kessler Syndrome, which could render certain orbits unusable. The unintentional lunar impact of the SpaceX rocket part underscores the need for better tracking, regulation, and disposal methods for space hardware. For ordinary people, this means that the future of space exploration and utilization could be jeopardized if debris management is not addressed proactively.

What Happens Next: Monitoring and Policy Considerations

Following the impact, astronomers will analyze data from telescopes and lunar orbiters to study the resulting crater and ejecta. This will provide valuable information about the composition of the rocket stage and the dynamics of lunar impacts. The event is also likely to reignite discussions among space agencies, private companies, and international bodies about establishing stricter guidelines for space debris mitigation. This could include requirements for de-orbiting stages of rockets after their missions or developing technologies for active debris removal.

Future outcomes depend on the willingness of stakeholders to implement these measures. If robust international agreements and technological solutions are adopted, the risk of future uncontrolled impacts and orbital congestion can be significantly reduced. Conversely, inaction could lead to a more cluttered space environment, increasing the cost and complexity of future space missions. The long-term implication is that a failure to address space debris could limit humanity's ability to use space for scientific, commercial, and defense purposes.