An interesting fragment of modern space exploration will soon hit the far side of the Moon. Recent observations, combined with calculations made by Project Pluto’s Bill Gray have shown that a spent Falcon 9 rocket upper stage will hit the lunar surface on March 4 at around 7:26 a.m. EST (12:26 p.m. UT) near the rim of the Hertzsprung crater. .
Unfortunately, as the unintended impact will occur on the far side of the Moon, it will not be visible to terrestrial observers. Astronomer Gianluca Masi and the Virtual Telescope Project will, however, offer two viewing sessions of the Falcon 9 booster before impact, one on February 7 and the other on February 8.
Gray first noticed the upcoming encounter in early 2022: a close flyby that took the booster within 9,600 km of the Moon on January 5 primed it for impact in March. Gray then appealed to the amateur astronomical community via the Minor Planets Mailing List (MPML) to observe the wandering thruster in an effort to determine its exact orbit. The scene is in a wide-ranging Earth orbit that currently takes it beyond the orbit of the Moon.
Keep in mind that relatively light objects like empty rocket boosters are more at the mercy of solar wind thrust than solid asteroids. Also, the booster seems to tumble. But at this point, an impact on the lunar surface is certain, although the timing may vary by about a minute, as can the exact location (by a few kilometers). Additional observations in February will help better pinpoint the time and place of impact.
The Falcon 9 upper stage was part of SpaceX’s launch of NASA’s Deep Space Climate Observatory (DSCOVR) in 2015. The DSCOVR was sent into a heliocentric orbit between the Sun and Earth, at L1 Lagrange point, which provides a fully illuminated view of the side of the Earth facing the Sun.
Although we won’t see the impact of the booster in real time as it occurs on the other side, it is entirely possible that NASA’s Lunar Reconnaissance Orbiter or India’s Chandrayaan 2, both currently orbiting and imaging the Moon, can see the crater resulting from the impact.
A Brief History of Things Hitting the Moon
While plenty of space-age hardware has hit the Moon over the years, this is the first time we know that a human-launched space artifact on a non-lunar mission has hit the Moon. involuntarily hit the moon.
The very first object to reach the lunar surface was the Soviet Union’s Luna 2 on September 13, 1959. Derelict Apollo-era boosters often also hit the Moon, and NASA’s Lunar Reconnaissance Orbiter (LRO) has documented the resulting scars.
Sometimes discarded boosters end up as “quasi-moons” instead. A spectrum of J002E3, a quasimoon spotted in 2002, showed the signature of titanium dioxide paint, which helped astronomers determine it was Apollo 12 Saturn V’s third-stage booster Observers also recently recovered another quasi-moon, which turned out to be the Surveyor 2 rocket booster.
And sometimes, missions have even intentionally sent boosters to the Moon, for the sake of science. The Lunar Crater Observational Detection Satellite (LCROSS) observed its worn Centaur upper stage when it struck Cabeus Crater in 2009, providing data that has helped scientists infer the presence of water ice on the Moon.
The LCROSS mission is a useful reference point because its impact velocity was about the same as that calculated for the Falcon 9 upper stage, about 2.5 kilometers per second (5,500 mph). But while the LCROSS’s Centaur upper stage weighed 2,300 kg (5,100 pounds), the Falcon 9 upper stage is almost double the mass, at 3,900 kg.
However, it is entirely possible that unintended impacts have occurred in the past, as boosters leaving Earth often remain in space rather than re-entering the atmosphere.
“There are at least 50 objects that were left in deep Earth orbit in the 1960s, 70s and 80s that have just been abandoned there,” Jonathan McDowell (Center for Astrophysics, Harvard & Smithsonian) told the AFP news agency. “Now we’re picking up a few…but we can’t find a lot of them and so they’re not there anymore. Probably at least a few of them hit the Moon accidentally and we don’t have just not notice.”
With the launch of a fleet of lunar missions this year, the Moon is set to become a very crowded place. SpaceX is actually launching the first Commercial Lunar Payload Services flight for Intuitive Machines and their Nova-C lander this summer. It’s ironic that SpaceX will already reach the Moon on March 4, but perhaps not as originally planned.