Big News and space trash
Big news last week was also that NASA had upgraded it’s Deep Space Network and sent commands 11+ billion miles to Voyager 2. Of the events in the last week Voyager 2 will probably hold more space in history books in the long run. It was one of our first grand tours of the Solar System and one of 5 objects flung into Interstellar space. The engineering to leave the Solar System alone was immense, but the fact that we are still talking to it is another.
Each of the 5 probes we have sent into interstellar space have a limited lifespan. They operate far enough out that solar panels aren’t an option. Instead they use radioisotope thermoelectric generators (RTGs). The RTG uses a decaying radioactive substance, like plutonium-238 to generate heat. With a high difference in temperature between the radioactive fuel and space, special thermal junctions will provide a usable current as they conduct the heat to space. Voyager I & II will essentially die in 2025 when they run out of Hydrazine for thrust and the RTG’s power dwindles below useful levels. Even though half of the radioactive fuel will still be present in 2050.
Once the probes loose their ability to talk with Earth they are essentially discard technology. Slightly radioactive for many centuries to come and just coasting on a path for hundreds of millennia. While they will essentially be space trash at that point, they still hold one more mission. Each of the first 4 had messages in case they were found by an alien species. The last one, New Horizons did not include anything similar, but sent some mementos along.
Message in a bottle
So the first 4 become messages in a bottle. That’s kind of cool even if the chances are near 0 that they will be found by anything intelligent (we do not know the ability of any potential finder to detect or retrieve these small probes, but it is more likely the stuff of movie scripts than an event).
If one of them is found the information on them becomes an exercise in anticryptography immediately. Hopefully the forethought put into making them was done well and the information was properly extended in time and space. In these 4 cases we have 2 different approaches with widely varying information.
This plaque was the first attempt for the Pioneer 10 & 11 craft. As you can see in Figure 1 it was a small plate of gold anodized aluminum weighing in at 120g (4.2 oz). The whole plate was cut in inches (I prefer to use metric where the choice was not made before hand). Measuring 9"x6"x.0.05" it was engraved 0.015" deep. This license plate like object was mounted on the antenna support struts hoping it would reduce erosion from interstellar dust.
That last part and the overall thickness got me thinking, how long would these plates survive in a meaningful way? The engraving is roughly a quarter of the thickness in depth. That aluminum is fairly hard and the gold should make it less reactive and roughly the same strength as the struts it is mounted to. Looking at the mounting I think the plastic mounting straps are going to go first, and I wouldn’t be surprised if they already have.
If an intelligence does find the plaque what will they see? There was an assumption that the top left corner is the starting point. You have to choose a point to start and unless we use some rotational positioning any corner is as good as any other.
In that upper left corner is a set of symbols that is trying to represent the transition of the hydrogen electron from one energy level to another. Hydrogen is the most abundant element and any intelligence running across the plaque will have an excellent understanding of it. A good choice of natural process and it does provide references to time, frequencies, and distance. In this case setting the binary ‘1’ to mean 21cm for the wavelength of the emitted light. The measurement is not a far leap, but the binary 1 scribbled below the line is a bit of a leap.
The next is a star burst like object that represents our solar system in the center and the relative distances to 14 pulsars and the galactic center. The lines are made with binary 1 marks and dashes to represent each pulsar’s period in multiples of the hydrogen emission frequency described above. If someone figures out a few parts they may be able to back out the others from basic scientific understanding. Pulsars are obvious observations and the period will be easy to measure and figure out the decay. If a reader figures out these are pulsars and the binary frequency (still the biggest leap) they can tell our position and the general era that the plaque was made in.
The Solar System is depicted on the bottom with an arrow and cute little Pioneer showing it’s path past the planets. The Sun is the largest of course. Each planet has the same binary notation under it that denotes the relative distance from the Sun (measured in tenth’s of Mercury’s orbit).
Saturn’s rings are shown. This ended up being a bad idea. A few years after the launch of the craft rings were discovered around the other gas giants. They may be a common feature for all we know. Top it off, the rings would not be visible unless the viewer was inside the Solar System. If they were the prominence of Saturn’s rings might help, but relative size would be better.
Finally on the side we have a rough sketch of the craft with a man and woman. The sketch does provide a rough average height for our species compared to the dish of the craft. There are also hash marks for the woman’s height and the binary notation for 8, which works out to 168 cm if multiplied by the wavelength from the hydrogen transition.
There isn’t a lot of information for the viewer to go on from these sketches. They would know our height and that we are bipedal with 2 arms. Everything else is kind of artistic license in my view. There was a lot of controversy over them being naked and parts were “erased” for modesty, but in the end stick figures might have been as useful until actual contact.
A few years later the Voyager missions were poised to make a grand tour of the outer Solar System and leave at a very high rate of speed. There was some extra time and a bunch of ideas were thrown in over a simple plaque. Almost too many.
The creators threw in a stylus and diagram of how it can be used with the cover. The same binary as Pioneer was used with the same hydrogen reference in the bottom right. The pulsar relative location map is in the lower left. The stylus record diagram also tries to represent the revolution speed in a binary multiple of hydrogen emissions. The speed was 16 2/3 RPM.
If the holder of the record understands that much they will get almost an hour of sound and other data. Greetings in 55 languages, music, nature sounds, etc. There are also instructions on how to translate some of the sounds into images. Those images included people doing all manner of things, places around Earth and some features of biology and and geology. I’m not sure what another species would think or get out of any of it, but let’s consider it a preservation of our planet and it makes more sense.
This time the records were not only plated in gold, but a special cover was made for it and that would help preserve the record for a long time to come. So long that an ultra pure sample of Uranium-238 with a half life of roughly 4.5 billion years was included. This allows the discoverer to estimate how old the item is from the radioactive decay and may be the one concept that is easy to believe is understood far into the future.
Why call it trash?
There was meme going around a few months ago about our first contact with aliens would be a complaint to stop throwing our obsolete tech and doodled porn out in space. It was funny and had somewhat of a point.
Different parts of the attempts ranged from good ideas to feel good actions of the 70’s. There are some notes about the recording of brain waves of Ann Druyan while she thought different things being included. I’m hard pressed to understand what a listener might think this is let alone what it would mean to them.
Really the information that is common to both the plaque and the record are the key items and the only ones that I would give a passing grade in anticryptography to. Brain waves and sounds of humans are a hard leap. The receiver may not consume sound and images the same way we do. Knowing where it came from via the pulsars if it is found a billion years from now would be a huge archaeological find. The decay of the Uranium or the drift of the pulsars would also give that rough time of launch.
I don’t think the creators of these messages were expecting to reach out and communicate with alien civilizations. They were adding meaning to the object in the near 0 probability that it happened, but more importantly they were sending a message to the people of Earth in the 1970s. We have to start thinking about ourselves in a larger context of countries and single life times. I don’t know if they achieved that goal as I don’t remember the 70s well enough to compare things with today. The overall attempt though was worth the money spent (the price of a luxury car) as a thought exercise and public relations tool that has lasted for decades on the planet of origin.