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Well, we went and killed ourselves off with our stupid wars. But aliens come along, find our marvelous planet and the evidence that we were here and they find some human (and other) embryos in a base on the moon - in a crater near the pole that is never exposed to sunlight, so the whole base is in a deep freeze, in vacuum, not exposed to light.

I theorize that they could remain viable for thousands of years in those conditions. But the aliens eventually find out how we killed ourselves off, which creates a problem for the humans among them.

These humans, of course, result from those embryos, collected by the first ship and kept frozen... and then the aliens managed to artificially gestate them on their own planet. Now the young humans are on the second colony ship, landing on Earth along with a fresh batch of colonists and scientists.

The question is: do I have to stick with a really short interval between our demise and the aliens' arrival for any information about us to survive - or could I postulate significant data storage in that moonbase remaining viable for thousands of years?

In such conditions, could a computer and a data stick, perhaps along with various CDs and such, remain usable? Or should I make it a short interval - they came in response to a CETI and it's only been, say, a hundred years? Some book-type libraries on Earth would remain viable that long given a really good roof, fireproof construction and a dry climate.

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  • $\begingroup$ Was the data intentionally stored to maximize longevity, or was it simply whatever media was on hand at the time? Also, how much data are we talking about? Storing kB for hundreds of thousands of years is easier than storing TB $\endgroup$
    – Cort Ammon
    Dec 21, 2015 at 20:53
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    $\begingroup$ Possible duplicate of worldbuilding.stackexchange.com/questions/3429/… and links therein. $\endgroup$
    – HDE 226868 ♦
    Dec 21, 2015 at 23:55
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    $\begingroup$ Currently with the technology we have available a good estimate of how long an embryo could stay viable is roughly 20 years. That could be improved in the future of course. You wouldn't want it just at the pole, but in a bunker buried deep to shield it from radiation. $\endgroup$
    – AndyD273
    Dec 22, 2015 at 18:54
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    $\begingroup$ Please keep in mind the difference between storing the physical artefact, and the ability to actually interpret it. Compare the Voynich manuscript, which is probably easier for us to decode than our language would be to an alien civilization. This goes many times over for digital data, especially with any kind of modern storage encoding. The Voynich manuscript has been dated to the early 1400s, and remains undeciphered. $\endgroup$
    – user
    Dec 22, 2015 at 19:59
  • $\begingroup$ @MichaelKjörling: Your point is valid but your example is wanting; there's good indication that the manuscript is an indecipherable hoax. A storage medium that requires a minimum of decipherment is indeed paramount -- I use the example of microfilm in my answer. $\endgroup$
    – Wingman4l7
    Dec 22, 2015 at 22:49

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The most durable information storage is having it carved in stone or in clay that then got burned. Our oldest writings are of that form, and they are thousands of years old. The main problem of this data storage is to explain why the information is stored that way. But maybe it was done intentionally by someone who was expecting the end of civilization, but hoped that some humans would survive and learn from that information later. He would have explicitly chosen a medium that can survive a long time.

For more information about long-time information storage, probably the Rosetta project of the Long Now foundation is a good source. They use not stone, but nickel to carve the information in, enabling a high density of information. While the type of information they store is different, the basic idea is the same: Preserve information for a long time.

Actually I'd be more concerned about the embryos: Given that the moon is outside the earth's magnetic field and outside the atmosphere, it is not well shielded against all types of radiation found in space (from solar wind to cosmic rays). Cooling doesn't help against radiation literally kicking your atoms out of the molecules. I'd expect the DNA to be considerably damaged after that time.

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  • $\begingroup$ Today we can print ceramics. Kitchen and bathroom tiles that look like natural marble or granite without repeats. The same technology could be used to print text. If someone were doing this for posterity he'd try to incorporate a universal key. One possible is a detailed description of each element with the same fields for each, arranged as a periodic table. That pattern and the elements themselves are universal. A science based Rosetta stone. $\endgroup$
    – nigel222
    Dec 22, 2015 at 20:33
  • $\begingroup$ How many clay tablets will it take to store 3 billion base pairs? ;) $\endgroup$
    – Wingman4l7
    Dec 22, 2015 at 20:37
  • $\begingroup$ If you are "writing" for a civilisation that will understand data storage: under two thousand, at 300x300 bits (pixels) per square inch of 8 by 11 inch tiles. $\endgroup$
    – nigel222
    Dec 22, 2015 at 22:12
  • $\begingroup$ A modern way of storing data in stone ? $\endgroup$
    – EngelOfChipolata
    Mar 27, 2017 at 9:19
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Data can be stored as strands of DNA. A DNA strand is essentially a linear, binary code, and it has excellent stability over time. There is a helpful Wikipedia article on it. Here is a section from the first paragraph:

It also has the capability for longevity, as long as the DNA is held in cold, dry and dark conditions, as is shown by the study of woolly mammoth DNA from up to 60,000 years ago

If the same set of information is stored in multiple DNA strands, say a thousand, then the aliens who find it could compare the strands to fix any random mismatches. For example, if one strand started with the equivalent of "000", and all the rest of the strand started with "010", then the aliens will know that "010" is correct.

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    $\begingroup$ +1 as any condition that allows the frozen embryos to survive will necessary have to preserve information on DNA anyway. $\endgroup$
    – celtschk
    Dec 22, 2015 at 8:08
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    $\begingroup$ OF COURSE! Why didn't I think of that? $\endgroup$
    – BrettFromLA
    Dec 22, 2015 at 18:43
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A moonbase is actually a very harsh environment to try to store digital data. Strikes from cosmic rays will flip bits and corrupt data. Here on Earth, it's not too much of a problem because our atmosphere shields us from most cosmic rays. Even so:

Studies by IBM in the 1990s suggest that computers typically experience about one cosmic-ray-induced error per 256 megabytes of RAM per month. (Wikipedia)

On the moon, these effects will be much worse. Of course, we can assume that the electronics on the moonbase are rad-hardened, so the majority of cosmic ray strikes won't affect them, but over time everything breaks down. Typical flash memory will only hold data for about 101 weeks (slightly under two years). Even unused HDDs will eventually be erased by thermal cycling (Forbes), although in your scenario they may be spared this by never being in direct sunlight. Over very long time scales I would expect that the magnetic grains in the platters will diffuse and become unreadable, but at very low temperatures this might give you a considerable amount of time, maybe 200 years as a complete guess. We don't really have any information about the chemical stability of HDD platters under low temperature conditions over long timescales. I would be very willing to bet that even under ideal conditions, 1000 years would be a hard upper limit for any digital data.

As others have pointed out, though, by this time it's almost certain you won't be able to find any viable embryos in the base. It's tricky to preserve living tissue without damaging it, especially if there's nobody around to monitor it. I'd say definitely no more than 100 years for this reason, and then only if there are a lot of redundant embryos to allow the DNA to be reconstructed even if many are damaged.

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Paper.

Sometimes the simplest solution is the most compelling. The oldest surviving printed book is about 1150 years old. If we expand our search to all material printed on flexible organic fibers, we can double that easily -- the oldest papyrus is about 2700 years old. Keep in mind that these have had to survive unpredictable storage conditions and the vagaries of human beings, which your storage cache would presumably not be subject to.

Engraved or etched metal would probably be better but decidedly more expensive, time-consuming to write to, and bulkier to store. Some sort of metal-paper hybrid might be good to keep the size & weight comparable -- a metal foil, bonded to flexible fibers. The fiber backing would prevent tearing of the thin foil, and the foil would be more resistant to becoming brittle and crumbling.

Being able to read your media without obsolescence-prone technology is important. Microfilm is an excellent example of future-proof storage technology. While not a viable enough medium itself to serve as a solution for this problem (silver-halide film "can last more than 500 years", but I'd be concerned about radiation exposure, and it requires temperature-controlled storage), all it will ever require to read is a magnifying element of some sort (anything from a fancy collection of electronics to a chunk of clear, shaped crystal) and a bright light. For a real-life case study, the Voyager record is a fascinating & well-known example of attempting to create a media storage object & accompanying instructions for playing it, intended for interpretation by an alien audience.

With all the radiation and generally extreme conditions found in space, I'm pretty concerned about the viability of human embryos at these timescales, so I'm going to take this a step further. Let's treat them as data and store them, too!

Now, it's easy to say that you can just store genomes on paper -- but is it really a workable solution? Assuming we have perfect copies of genomes, they're about 3 billion letters apiece. A very rough experiment (Verdana, 6pt, default margins, "gatc" repeated) gives ~13,000 characters per page => 230,000 pages. A typical box of printer paper is 10 reams (5000 sheets) -- so that's 46 boxes of paper for a single genome. Not great. This could of course be shrunk significantly by using an optimal typeface, minimal margins, double-sided printing, possible shorthand for letter pairs, etc. Still, that's a lot of paper, especially since you presumably want to store many embryos. However, there is a workaround! Only about 0.1% of our genome varies between individuals (ignoring rare variants). Thus, you can store a reference genome, and diffs for individuals. That brings us down to 230 pages per person -- only half a ream, even at my original, highly inefficient & inflated calculation.

To ensure sequence integrity, the genome could be encoded into binary and parity bits (or other error detection/correction techniques) could be applied to the data prior to printing -- but this would come at the cost of obfuscating the inherent readability of a plaintext genome. It'd certainly use a lot less paper, though.

However you encode it, be sure to number the pages! Or at least stripe the ends of them with a marker, punchcard-style.

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