For the past seven years, a leftover chunk of an old SpaceX Falcon 9 rocket has been
circling the Earth in a fairly wide orbit, having a pretty unremarkable time.
But that’s about to change on March 4th, when this rocket component is predicted to
slam into the Moon’s dark side.
The doomed component is part of a rocket that was deployed in 2015 to launch a NASA satellite
called the Deep Space Climate Observatory (DSCOVR).
Since then, the rocket’s second stage, or booster, has been floating in what mathematicians
refer to as a chaotic orbit.
Bill Gray, an independent astronomer, was the first to predict earlier this month that
the Falcon 9 would collide with the Moon.
He is one of the few persons who’s been following the rocket fragment since it took
off and also calculated the space junk’s new collision course with the Moon.
Since the DSCOVR mission, he and other amateur space trackers equipped with telescopes and
cameras have been periodically observing the object every couple of weeks or months.
After each observation, Gray would use a software program he’s developed over the last two
decades for his company, Project Pluto, to update the stage’s predicted orbit around
Earth.
Initially, the software was developed to estimate orbits for asteroids and small moons around
distant gas giants.
But lately, he’s started using the software to keep track of the things humans have made
around Earth.
Gray saw the rocket stage again a week later after it flew close to the Moon, concluding
that it would crash into the Moon’s dark side on March 4th at a speed of more than
5,500 miles per hour.
He requested help from amateur astronomers to observe the rocket, and his conclusion
was validated.
Although the actual time and location of impact may differ slightly from what Gray predicted,
there is universal agreement that a collision on the Moon will occur that day.
He stated that he has been observing this type of debris for almost 15 years, and this
is the first time we’ve had an unintentional lunar impact.
Astronomer Jonathan McDowell from the Center for Astrophysics, Harvard & Smithsonian, also
added that similar collisions may have occurred unnoticed.
At least 50 objects in deep Earth orbit were abandoned throughout the 1960s, ‘70s, and
‘80s, and were not tracked.
Currently, astronomers are picking up a few of them, but many of them cannot be found,
and as a result, it is assumed that they are not there anymore.
Maybe a couple of them hit the Moon by accident, and we just didn’t notice.
The impact of the SpaceX rocket piece, weighing four tons on the Moon, will not be visible
in real-time from Earth.
However, it will leave a crater that scientists will be able to observe using spacecraft and
satellites such as NASA’s Lunar Reconnaissance Orbiter or India’s Chandrayaan-2, thus giving
them a chance to see what materials lie beneath the surface.
Though the collision poses no danger, it is a reminder that space companies need to have
better procedures for disposing of space debris, even parts that are left in extremely high
orbits.
Most of the concern about space debris is over fragments left in lower orbits, which
can endanger satellites and the International Space Station.
Typically, companies like SpaceX will purposefully dispose of the second stages of their rockets
when they go to lower orbits.
In such situations, SpaceX will intentionally send the object down toward the Earth at an
extremely low angle so that it burns up in the atmosphere somewhere over the ocean.
That way, large pieces are less likely to survive the breakup, and those that do will
fall over unpopulated areas.
But for missions that go to the Moon or extremely high orbits such as DSCOVR, rocket stages
are occasionally left out in the wilderness after the launch is over.
Even recently, the Ariane 5 second stage that carried the James Webb Space Telescope into
orbit remained in space and is now orbiting the Sun.
According to Gray, as the US and Chinese space programs, in particular, leave more debris
in orbit, there may be more unintentional collisions into the Moon in the future.
The United States, together with international partners, is already working on a space station
to orbit the Moon.
These collisions might start to be problematic when there’s a lot more traffic in space,
hence scientists need to find a way of regulating the debris.
Maybe by disposing the debris as SpaceX is doing, it could help reduce the amount of
debris in space.