DNA has a 521-year half-life (2012)
nature.com
nature.com
However, in temperature below zero at -5 degrees Celsius for example, half life of DNA is actually 10,000 years or more. https://en.m.wikipedia.org/wiki/Ancient_DNA
Still, this would also only allow 200 years of freezing before more than 1% of bonds would have been broken.
The third and probably most viable option is to wake up the crew every 200 years to repair accumulated DNA damage.
Also, a small percentage of the crew would probably be awake at all times for repairs etc., so the crew could rotate every 200 years.
>>> log(0.99, (1/2)**(1/10000))
144.99569695122509[1] It may be a bit worse in the long run, since if many bonds break, the higher order DNA structure gets damaged and that may change the rate of decay experienced by individual bonds (?).
If indeed 1% break after 15 years, then 10% (ignoring compounding) break after 150 years, and 50% after 750 years. That doesn’t square with a half life of 10,000.
https://www.researchgate.net/post/How-long-can-fresh-frozen-...
http://www.projectrho.com/public_html/rocket/enginelist3.php
But even if you ignore that limit, at that kind of speed you also need to account for your outer hull undergoing significant damage as each stray intergalactic hydrogen you hit has a kinetic energy of 34.75 TeV in your frame of reference, and while this will create a large supply of antimatter, it will do so in a way significantly less helpful to your goal than the fact we can transmute lead into gold by using the former as a radiation shield in a nuclear reactor is useful to someone who wants to get rich quick.
Bonus fact: this energy level is higher than the LHC, so you may have some extra weird mass-modification effects besides relativity as the front of your spaceship is now a Higgs Boson torch.
(1) we don't really know the threshold yet to be beyond repair I think. It may be 1% but may be 20%.
(2) as others noted, it's 15 years for 0.1% damage using your math.
(3) your timeline directly contradicts the article doesn't it, which suggests keeping people in ideal conditions would have a DNA half life of millions of years.
(4) it's not a given that you need to wake people up to repair DNA. Maybe you just need to bring them to 1 degree Celsius or something. Or maybe nanobots can work on you while completely frozen. I think we are quite far from knowing right now.
So yes, for long term travel DNA repair will be important but how it actually works I think we know little about.
If the ship requires human crews to conduct regular repairs, then the ship probably won't last long enough to get where it is going. A ship that is going to last for 10,000 years will need to be built like an Egyptian pyramid, solid enough to last forever and be functional despite millennia of erosion. Putting someone on that pyramid to conduct repairs might sound good, but after 10,000 years those repairs would become just another source of erosion. The activities of that one person would wear down any system with which they interact.
As long as it can support crops, oxygen generation, etc the passengers just proceed to live a “normal” life for the next couple generations until they arrive in orbit around a brand new star.
The hardest part would be maintaining culture to still identify with the purpose of the mission after there’s no one of the original passengers left over
Anyone got a back-of-the-envelope calculation for what size asteroid we'd need for this?
A planet. You're describing a planet. And we're doing a pretty terrible job keeping this planet we're traveling on sustainable for human habitation.
Add a gas giant or two (or 4) to protect it against incoming space debris and help stabilize orbits.
Add some neighboring rocks to also help with that + give them extra material to use once they arrive.
Implant ideas of leaving the rock and coming from a place of great power into the colony’s generational memory.
Include some infrastructure to aid them.
Even the worst outcomes predicted by climate change models leave some inhabitable regions right? Definitely not sustainable for current population levels though...
Then you only need a crew of X people at any given time to keep the ship operational. Some generations would be born and die during the trip (kinda depressing, but I like to think I would be happy in that scenario)
If you don't like the idea of having a machine as your mother, you could also do IVF with the women that are alive and well and constitute ~50% of the crew keeping the ship operational
Half-life of atoms as in "radioactive decay" (weak, strong and EM force) cannot really be modified by perservations methods. Here [0] a precise answer.
The decay-time of bio-molecular strucutres/bonds (containing information like DNA) can be modified in many ways very easily: low temperatures, exclusion of oxygen (amber) ... I guess "half-life" of DNA is just some fast and crude laboratory proxy for chemical "stability" in a specific setting.
[0] https://www.wtamu.edu/~cbaird/sq/mobile/2015/04/27/can-the-d...
I assume seed cells probably aren’t dividing, but I guess maybe they could be using energy and slowly reproducing? And apparently bacterial spores can basically freeze themselves in time for thousands of years and wake themselves up once conditions are favorable.
[1] https://www.newscientist.com/article/dn14125-jesus-era-seed-...
Presumably the half-life of these proteins is shorter than free DNA but their presence will still change the overall half-life.
Environmental conditions are another factor. The inside of a seed could have a more controlled pH, temperature, humidity when compared to the surrounding environment. That would also change the effective half-life.
To reach cryptobiosis involves packing the interior of cells with materials and reducing metabolism tremendously (I suspect there is still some tiny residual activity, barely measureable), and probably also some repair enzymes for the inevitable strand breaks.
If the DNA molecule is immobilized in a solid, either by freezing or by extreme drying, the half-life will be much longer.
That half-life was for bird bones preserved at 13.1 Celsius degrees.
Even in this paper it was mentioned that at minus 5 Celsius degrees some information from the DNA should remain even after 1 million years.
Unfortunately, there are very few, if any, places on Earth where ancient DNA would have the chance to be preserved for a long time either by freezing or by extreme drying.
The paper that started this thread was not about the decomposition of the individual nucleotides, which might be preserved even from dinosaurs, but about the speed of the fragmentation of the DNA molecule, which causes a continuous loss of information until the fragments are so short that no useful information remains.
I certainly hope that we will find cases of extremely lucky preservation of long DNA fragments that are more ancient than what was found until today.
Until now, the oldest DNA that was preserved well enough to allow sequencing of significant parts of it had an age of up to a few tens of thousands of years, e.g. from mammoths, woolly rhinoceroses, cave bears, cave lions, Neanderthal humans etc.
Science progresses. What's possible in the future can't be predicted today. Let's start with what we can do in 2022 which we couldn't imagine in 1922.
* Of course, we can sequence DNA now (and we know it exists).
* We can also trace back sequences of DNA by when they were created (from splits in evolutionary trees) and extrapolate portions of old DNA of organisms long gone.
* We can probably use machine learning to predict portions of DNA.
Now, let's imagine 2122.
* Will we be able to make inferences from partially-degraded DNA? Perhaps.
* Will we be able to make inferences from the structure about the organism about the corresponding DNA? Perhaps.
* Will our ability to combine inferences grow? Perhaps.
Overall, one thing I've learned is to not predict what's /im/possible. Eventually, engineering finds a way to do some truly counter-intuitive things (and conversely, can't solve problems we'd think would be solved by now; where's my rocket car?)...
The first thing that comes to mind is the fictional society from the planet Krypton. They stored data in crystals, likely artificially created diamond material. I suspect we could do this today without consideration for cost.
I was really just asking.
Either way there must be advantages in multiple backups: - DNA - Digital sequence - Crystals - Stone etching
Even with different decay rates they won't all decay in the same way. We can diff multiple records and reproduce a probable original.
(I think - I'm not expert in digital storage or the mechanics of DNA)
But it seems better to just make a dark dry cold repository and store DNA in a matrix that lasts for a long time.
https://www.genome.gov/genetics-glossary/Shotgun-Sequencing
You cannot unfortunately do this for dinosaur DNA. The longest human chromosome has 250M basepairs.
With a half life of ~500 years it only takes about 14K years for the chromosome to break down into individual nucleotides. 2^(14000/500) is roughly 170M
I would expect if you could find ancient (1Mya) tardigrades preserved as tuns, they could probably be extracted and sequenced.
1. A DNA molecule is billions of pairs long. What does half-life measure? When does a DNA molecule count as destroyed? When one pair breaks, when 10% of the pairs break, when 99.9% of them break?
2. Even if pairs break, so what? When we sequence DNA from various organisms, we start by breaking the strands in small pieces anyway.
3. Even if this half-life had any meaning, it would not be a constant number. Half-life is a constant number for radioactive decay. For other things, it's just a somewhat helpful concept. How long do onions keep until they spoil? Maybe they have a half-life of one week. But, the storage conditions make a huge difference. If you put a lot of onions in a plastic bag, and leave them in a hot, humid and unventilated place, they'll spoil much faster than if you keep them well separated, in a dry and cool place. The same with DNA. In fact DNA's half life is probably days, not hundreds of years. In exceptional conditions, some animal or human remains get exposed to some conditions that make them "fossilize". So, if the 521 year half-life has any meaning, it's a conditional expectation given some exceptional situations. But then some situations are more exceptional than others. The 521 years (ha, just think of it, not 500, but 521! ) is already millions of times longer than the normal decay time of animal tissues. What is to say there are no more exceptional conditions under which the DNA half-life won't be 5 million years?
4. And even if 521 was an exact number, for every type of animal tissue, for all places in the world, that still does not mean we can't reconstitute the DNA's of the dinosaurs. Dinosaurs had both ancestors and successors. The successors are the birds, the ancestors lead to crocodiles, and maybe other animals as well. They have common ancestors with lots of other animals, or more precisely, with all animals. DNA is information. Information propagates. Science comes up all the times with better and better methods to retrieve information. Just look at how your iPhone is able to take a picture at night now, versus 10 years ago. Sure, part of that quality leap is the sensor, but a huge part is the Machine Learning algorithms used for denoising. In other words, for information retrieval.
Your claim half-life doesn't apply is incorrect. All atoms undergo radioactive decay, so half life applies as precisely to all matter as is does to uranium.
Are you sure about that?
Ultimately quantum tunneling will get them all. There is no known mechanism to prevent it.
So if the essence of a thing breaks down, and the model for it is exponential decay, then it has a half life.
Thus DNA has a half life, just as the paper in Nature, one of the premier scientific publications in the world, demonstrates.
My explanation was to point out that even if you don't like the definition in the article, that there are other valid ways to define half-life for atoms and complex molecules.
> By comparing the specimens' ages and degrees of DNA degradation, the researchers calculated that DNA has a half-life of 521 years. That means that after 521 years, half of the bonds between nucleotides in the backbone of a sample would have broken; after another 521 years half of the remaining bonds would have gone; and so on.
Even if the term “half life” isn’t really appropriate here, it’s clear enough (and explained well enough) in the article. This isn’t a published scientific paper, this is an article likely meant for a more general audience, so, jeez, cut it some slack.
The article itself is ok, and the researchers had good intentions. The problem is the idea took a life of its own. It almost became a meme. I heard this article many times quoted on HN. And the idea itself is definitely wrong, and needs to be debunked.
If the 521-year half-life were remotely true, we couldn't hope to ever sequence something older than 100 or 1000 half lives (i.e. half a million years). Well, we did that just the year after (this article was published in 2012, we sequenced a 500k year old fossil in 2013) We also sequenced a one million year fossil in 2021 [1])