Smashing Stuff Into The Moon.... For Science???? Transcript, AI Summary & Key Points

00:04 Hello, it's Scott Manley here. A couple of days ago, a spent SpaceX Falcon 9 upper stage hit the moon near Einstein crater. Telescopes on Earth caught the plume and analyzed it. They found evidence of sodium and lithium ions, and lunar orbiters are already imaging the impact site. This has been in the news a lot, and it was not planned by SpaceX. The stage was used to deploy lunar probes, and it's just by sheer luck that it ended up hitting the moon rather than burning up in Earth's atmosphere, but there's been some

00:31 people who appear to be unhappy with a discarded piece of trash smashing into the moon. I mean, to be clear, this was blown out of proportion by an eager media. And if people are really concerned about space trash, then maybe they should give more credit to an organization trying to make a 100% reusable launch vehicle. Now, if the people complaining knew the history of humanmade lunar impacts, they might have a different perspective.

00:54 There's more than a hundred things that have hit the moon to date. Although, some of them were designed to do this. Some of them were accidentally done doing this. Others intentionally crashed after completing another mission, and quite a few landed softly, or as I like to say in this case, boringly. Because the moon's gravitational field is lumpy, most spacecraft abandoned in orbit will eventually smash into the moon.

01:15 So, let's try to talk about all the human-made lunar impacts in one video. And so, to start with, we rewind to 1959, Luna 2, the first one. On 13th September 1959, the Soviet Luna 2 became the first human-made object to reach another world. Now, it's called Luna 2, but you should be clear that this wasn't the second Luna mission, more like the sixth.

01:37 There were three failed missions before the Luna 1 flyby and another failed mission after Luna 1, which was supposed to be an impactor, but missed. Luna 2 hit the moon about 19° north of the equator on the near side between the craters Archimedes and Aristales. The probe masked about 390 kg and it hit at a roughly 3.3 km/s. Its third stage booster shot followed shortly afterwards.

02:02 So the Soviet Union got not just the first impact but the second impact on the moon with one mission. On the way to impact, it delivered some modest size. There wasn't any detectable lunar magnetic field or radiation belt. It was far more about the prestige and propaganda value of this achievement. And it carried a memorable political payload. It carried two spherical pennants made of stainless steel pentagons engraved with USSR September 1959.

02:27 They were designed to explode just before impact. And the idea being that some of the shrapnel would slow down enough that the pieces would survive the landing, scattering a handful of these emblems across the surface. Now whether any of these survived the hyper velocity collision is doubtful, but Kushchev handed Eisenhower a replica as a cold war souvenir.

02:47 Luna 2 proved that we could hit the moon on purpose. The US would eventually catch up with the Soviet Union in the smashing into the moon game with Ranger 4 being the first NASA spacecraft to reach the moon and it would have a TV camera. And while the launch and orbit insertion was successful, it failed to deploy solar panels and it ran out of power before it impacted the far side of the moon.

03:08 On April 26th, 1962, Ranger 5 would miss the moon completely. Ranger 6 would deploy the panels and fly to the moon as planned, but the TV camera failed to operate, which meant they didn't return any real data prior to impacting the Sea of Tranquility on February 1964. And while we didn't get images in the 1960s of this, we do have a 21st century image of the impact site from the Lunar Reconnaissance Orbiter, making this the oldest man-made crater that we have an image of.

03:37 The crater from the small spacecraft is about 15 mters in diameter. The first successful Ranger mission was Ranger 7 which descended into Mar Cognitum on July 31st, 1964 with its TV cameras beaming back a series of images getting closer and closer to the surface. It impacted with a speed of 2.61 km/s with the last image being taken about 500 m above the surface.

04:02 And you can see where the transmission was interrupted by the impact. Perhaps the most important result from this mission was the images showed a surface which in some areas was smooth enough to land on. Meaning that this whole Apollo mission thing might just work. Rangers 8 and 9 would continue the tradition providing early images of the lunar surface in the minutes before they hit the surface.

04:22 No doubt valuable at the time. Ranger 9 even had images broadcast live on TV as it descended towards its impact. It would be the last of the Ranger probes as NASA realized that the only getting a few minutes of useful life from a survey spacecraft was suboptimal. The Ranger spacecraft would be replaced by the lunar orbiter program which ran from 1966 to 1968, launching five lunar satellites which would make photographic survey of the moon using highquality photographic film which would then be developed on board,

04:53 scanned, and then transmitted back to Earth. While these were all placed into lunar orbit, they would ultimately impact the moon after the mission was complete. Some of the lunar orbiters even managed to image the impact craters left by their predecessors. Now, over in the Soviet Union, they'd been trying to build lunar landers. Many had failed during launch or had failed to make course corrections.

05:16 But Luna 5 in May 1965 lost control after a gyro failure and it impacted the moon at high speed as did Luna 7 on October 198 1965. Luna 8 had attitude control problems if it managed to fire its retro rockets for a whole 9 seconds before it lost control again and that resulted in a slower impact velocity compared to the others. It was designed to land and bounce but not at that speed.

05:40 the Luna 9. That would be the first soft landing. While NASA was trying to figure out how to soft land spacecraft with humans using things like landing legs, the Soviet design was focused entirely on being first. The spacecraft decelerated and until it was about 5 m above the surface, and then it ejected its lander inside an airbag that bounced around a bit before coming to a stop, unfolding, and then taking the first pictures from the surface of the moon, which were transmitted in a standard radio fact format.

06:07 And that enabled the British scientist at Jawro Bank to decode and release the images before the Soviet Union. But if you were hoping for impacts, the landing system dumped some rocket stages about 500 meters above the surface. And those no doubt made some satisfying bangs when they hit the surface, or they would if it wasn't a vacuum. Now, the US Surveyor program soon followed, and the Surveyor 1 achieved a soft landing in Oiana's Pressarium in June of 1966.

06:34 And this was unusual for the first flight of his spacecraft to be so successful. JPL engineers themselves had estimated only a 15% chance of success. It also used proper landing gear. Again, this spacecraft would have dumped spent solid rocket motors into the moon at high speed and no doubt made small craters. There were a total of seven surveyors, five of which soft landed.

06:58 Surveyor 2 had an engine failure that caused it to spin, making it impossible for it to hold attitude during its retro rocket fire. that impacted the moon without slowing down at all. Surveyor 4 stopped sending signals during its retrof minutes before the engine was supposed to shut down. Most likely the rocket motor exploded, followed by the spacecraft smashing into the moon at high speed.

07:20 And then we get to July 1969, and everyone that knows spaceflight knows that that date is important for lunar exploration. But fewer people know that at the same time as Apollo 11 was heading for its planned soft landing in the Sea of Tranquility, the Soviet Luna 15 was also going for a soft landing with a sample return. While Apollo 11 was at still on the surface, Luna 15 began its descent, but a few minutes later, contact was lost.

07:45 It's likely that spacecraft hit terrain at high speed, which was incompatible with continued operation of the spacecraft. The impact site has never been found. Now, while the Apollo program was all about the soft landing of the astronauts, the early missions did include lunar seismometers, which were looking for moonquakes. And the NASA scientists clearly decided the moon was far too quiet and introduced some calibrated events.

08:10 Beginning with Apollo 12, NASA deliberately crashed the spent uh Saturn 5 upper stages, roughly 14 tons each, into the moon. The impacts were timed and located to the seismometers left by the astronauts could record and analyze them with more detail. These were the best calibrated seismic sources ever used in another world. The velocities were about 2.5 to 2.6 km/s.

08:33 The masses and the impact locations were known from tracking. The signals after analysis revealed a highly scattering high Q lunar crust that rings like a bell for long periods. Very different from Earth. Wave velocities for the upper crust were measured directly. later reanalysis of the entire Apollo seismic network, including those artificial events.

08:56 They would constrain the existence and size of a small solid inner core and a fluid outer core on the moon. The craters from the Saturn 5 stages were about 30 to 40 m across. They've all been imaged by the Lunar Reconnaissance Orbiter, and in fact, the Apollo 16 site was the last one to be found because they lost contact with that stage before impact.

09:17 Without these known energy artificial impacts, the Apollo seismic data would have been far harder to interpret and so these impacts remain foundational for lunar interior models. Now, other chunks of Apollo hardware would have hit the moon over the years. The descent module from Apollo 10 was ejected in low lunar orbit and would have eventually crashed.

09:37 The ascent modules from many missions also hit the moon. Most of these were actually planned and timed for seismic events as well, so they contributed to the data. Also, the subsatellites deployed also would have eventually decayed and hit the surface. Now, over in the Soviet Union, the Soviet sample return landers continued to fly. Luna 16 would land in September 1970, finally returning samples of the moon to Soviet scientists.

10:03 Well, uh, in addition to the samples that Neil Armstrong had personally gifted Soviet scientists in May 1970, Luna 17 would deliver the Luna 1 rover. Luna 18 was supposed to be a sample return lander, but it crashed in September 1971. Luna 20 was the second successful sample return mission. Luna 21 also record deployed a Luna cord rover in 73. Uh Luna 23 landed softly and then fell over making return impossible.

10:30 And Luna 24 in 1976 would re land and return more samples to the Soviet Union. And this would be the last Soviet mission to the moon. The moon was now old news at this point and we stopped sending missions there. Sometimes spacecraft would make a flyby of the moon as part of some gravity assist, but there weren't any orbiters until Japan's heighten mission in 1990.

10:54 This had a problem with its initial injection and ended up kind of short of lunar altitude. It needed to use some extra propellant to get to the vicinity of the moon, but it wasn't planned to go into orbit around the moon. It did have a small child spacecraft named Hagar Romo which was released during lunar flyby and this had propulsion that was supposed to place it into lunar orbit but they lost contact with that and it's not clear that this ever happened.

11:17 However, there was an American astronamicist named Edel Bruno, and he'd been looking at new uh low energy trajectories to go to and from the moon. And he wrote the team a letter saying, "Hey, I actually have a trajectory that will get you to the moon." And so they used his trajectory that would eventually put the heightened spacecraft into a loose orbit around the moon.

11:35 And later on, they would actually impact the spacecraft and onto the moon, making Japan the third country to fly by, orbit, and impact the moon. with one mission. NASA would return to the moon in 1998 with Lunar Prospector, which was the orbiter designed to build a composition and gravitational map of the moon. It did this over a year, and its final act was to intentionally crash into a shadowed region of the Shoemaker Crater.

11:59 Telescopes on Earth observed the plume generated by this, hoping to see the signature of water, but no positive detections were made. It's also worth mentioning that Shoemaker Crater was named by or named for Gene Shoemaker, a geologist who' specialized in impact cratering and he died in a car crash the year before the mission launched. The spacecraft carried a small amount of cremated remains.

12:21 So even after he died, Gene Shoemaker was involved in making a new crater inside Shoemaker Crater. In 2003, Europe's smart mission would orbit the moon. And after operating for a few years, it was again intentionally crashed into the moon in 2006 with groundbased telescopes observing the dust cloud. The elongated ejector pattern matched laboratory predictions for a grazing impact.

12:44 The event gave useful data on impact flash energetics, ejector dynamics, and the observability of small artificial impacts from the ground. And so now we see the renition of interest in the moon. In 2007, Japan's Kagula mission, which is also known as Seline, was the largest spacecraft to orbit the moon since the Apollo era. It brought an HDTV camera, which produced many exceptional videos of orbiting over the lunar surface.

13:12 Again, the moon is a hard place to maintain orbit, and it would eventually crash on the moon in June 2009. China got involved with the Changa 1 mission, which launched in 2007, and it also orbited the moon for before being disposed in an impact in 2009. And in 2008, India would join the party with Chandryan 1 orbiting the moon. But it also carried a sub spacecraft which is a lunar impactor.

13:36 This would event intentionally crash on the lunar surface near Shackleton Crater again hoping that this impact would stir up something to help them see evidence of water. But that experiment was inconclusive. But some other onboard instruments did detect the signatures of hydroxal molecules, which was a strong indicator of the existence of water on the moon.

13:56 And so with all these small missions, NASA had a big plan. The Lunar Reconnaissance Orbiter and Elcross launched together. LRO has been returning highresolution imagery of the moon for over 15 years. But LCROSS had a shorter mission. It remained attached to the Centaur upper stage, swung around the moon, and carefully placed the Centaur into an impact trajectory inside a shadowed region near the poles.

14:17 The Elcross spacecraft separated and ended up a few minutes behind the Centaur. And it would get a close-up view of the impact and plume and directly sample the plume as it passed through it on the way to impact. It definitively proved the existence of water inside the shaded regions of the lunar poles. See, smashing things into the moon really does work.

14:39 Since then there have been multiple successful landers like the Changa series and some unplanned lunar impactors like Barashit, Chandrion 2, Hakuto and Luna 25. Some landers reached the surface slow enough to survive but weren't able to remain upright making some of the experiments useless. And the rocket which launched both Hakuto R and Fireflyy's Blue Ghost to the moon left its upper stage in an orbit that eventually brought it back to impact the moon.

15:07 And that's what happened this week. It wasn't planned. It if it was, we can think of better places to have put it. The impact point was on the far side of the moon, but near enough to the limb that the plume would rise above the surface. There were many amateur astronomers doing live streams on the internet, and I checked a few of them, and they all showed a perfectly exposed lunar limb, which meant that the plume would be far too faint to show in these images.

15:32 The plume would have to rise kilometers above the surface to be seen, making it thin and faint. Telescopes would have to overexpose the moon without having all that excess light bleed too much into this adjacent pixels and mask the plume. A few telescopes have detected the plume by the signature spectral lines of sodium and lithium and others have masked off the moon to make the plume visible.

15:56 Korea's Denuri spacecraft has already orbited over the impact site and imaged a new crater. Lunar Reconnaissance Orbiter and Chandryan's 2 orbiter will soon make their own passes. And the moon was fine. There were some ridiculous stories about the environment of the root moon being ruined by this rogue rocket stage, which is clearly not the case. It's not nearly close to the energy released by the big Apollo stages or the Elcross stage, which was designed to orbit and impact at very high speeds.

16:25 But if the US or China get their moon bases going, there will need to be more care taken in the future of what we do with spent stages. The moon is big, but without an atmosphere to slow things down, the debris from an impact can travel a long way. And when you get close, the debris risk from an impact exceeds the background meteorite risk by a large amount.

16:44 So, I don't think we'll be seeing many more intentional high-speed lunar impacts. But we all know the risk of rapid unintentional lunar encounter will always rule. I'm Scott Manley. Fly safe.