Terraforming Venus; Venus-forming Earth

Terraforming Venus would require taking almost all of the CO2 out of its atmosphere, so it becomes breathable, doesn't crush us (currently 90 atm pressure) and cools the planet down. Using our current mechanical carbon scrubber technology may seem simplistic and unimaginative, but the other options that have been discussed feature similar science-fiction-level ideas (crashing outer solar system ice moons into it, locking carbon into the crust down to a kilometer deep, or getting theoretically present hydrogen out of the mantle.)

This is less likely to happen than being able to move moons around the Solar System. Image from reddit.com/r/mapporn.

Let's make many optimistic assumptions:

That we can build self-replicating independent carbon sequestration plants; this minimizes transport costs and covers the planet.

That they can build and fuel themselves from materials available on the surface of Venus.

That they can withstand conditions on Venus (when the longest any machine we've put down has lasted is on the order of an hour.)

Current carbon sequestration plants are the size of a cargo container, and sequester 900 tons of carbon per year. Assume that this is the rate at which they operate on Venus, and that self-replicating carbon sequesterers are 100x bigger than the real, non-self-replicating ones we have.

Assuming near 100% working replicas, and a one-year self-replication cycle, it would take 40 years to cover the entire surface of Venus with these - after which they would take 2000 years to clean the atmosphere of CO2. (This would still leave a nitrogen atmosphere several times higher pressure than Earth's.)


Venus is not the best candidate for terraforming or habitation, and humans will not settle its surface for thousands of years at least. We should concentrate on terraforming planets in our solar system, building self-replicating technologies, and having humans in isolation from Earth in case of some sort of collapse (most easily, on the Moon.)


On the other hand, here on Earth, just to keep even with carbon emissions at the 2017 level, we would need 40 million of the scrubbers we currently have. That means no matter where you went on Earth, there would be one within less than two and a half miles of you.

We do have machines that are Venus-forming Earth, by making more CO2. They aren't self-replicating, but they seem to have a relationship with one species (unclear if parasitic or symbiotic) and in places they cover the surface just the same.

First Interstellar Asteroid? It's Interstellar, But Not the First We've Seen

Information here and here. Based on the velocity and path, this asteroid originated from outside the solar system. This is a great additional finding, but not actually news! Comet Wild-2 was the subject of the Stardust sample return mission, and analysis showed more than a few interesting things: that it contained the amino acid glycine, and that the nitrogen isotope ratio showed that the object likedly originated from a different solar system.

A point of interest here is that since the solar system's origin, there must have been multiple close passes by other stars - close enough that our respect Oort clouds would mix at the margins, and material would be exchanged between star systems. We have now verified this logical inference visually, and through direct chemical evidence.

Previous post about alien evolution, Life's Origins at Four Billion Years Ago; Implications For Our Future

Organics on Ceres Are From Ceres (not from other impacting bodies)

The organic material on Ceres, while intriguing, appears to be native, rather than delivered from other impactors. So says data from the Southwest Research Institute at the 2017 Astronomical Society meeting. The possibility of simple organic replicators on low-gravity bodies in the solar system ("space viruses", to be dramatic) an interesting one, and is one form (or one part) of the pan-spermia hypothesis that's been considered for over a century, going back at least to Arrhenius. (Space viruses might also be the only evidence we would ever see of alien life or even an alien singularity.) What this tells us is that the large majority of material on Ceres, and presumably on most large old asteroids, is native to those bodies since the dawn of the solar system.

What the findings mean for the "space virus" hypothesis is that we can be more confident that Ceres is not crawling with foreign space viruses - although if there is a replicator that can use the typical organics on large asteroids as building materials, that's not what you would usually see. That is to say, when an organism gets infected by a virus, the organism isn't infiltrated with foreign matter, but rather with a tiny bit of foreign matter that then rearranges the atoms in the organism into copies of itself.

What If We Assume We're Surrounded by a Galactic Civilization, and We're Missing It?

Overcoming Bias covers two papers on SETI; importantly, the papers distinguish between the search for artifacts (like Dyson spheres) and the search for communication. There are problems with searching for communication, among them: do we know what medium they'd use, can we understand them, and should we expect the beacons to be on all the time, or just intercept them briefly, like the WOW signal? The search for artifacts can be divided into looking for massive engineering undertakings of far away civilizations that are solar system- or galaxy-wide, and looking for them right here in the solar system where you're reading this. The latter is not a frequently considered approach, but that's why I'm excited for Dawn to finally make it to Ceres; there are specific reasons to think low-gravity bodies with water and organics would be the places to look for evidence of extrasolar technology. (But until there's a probe that lands and gets good chemistry we won't have evidence.)

Yet, we've found no clear evidence as yet. Add to that the argument that if there is any chance different than zero for any species to develop interstellar travel, the galaxy is very likely to already be full - that is to say, if space-traveling life is anywhere, it should be everywhere, because it would be vanishingly unlikely for us to be the first. And we don't see such life everywhere. At this point we can't conclude that no one is out there, but we can be more certain that no one is everywhere out there. Maybe we're looking for the wrong things, but as we look further and include more types of phenomena, the more we find nothing, the more we should assume we're alone or nearly alone as a technology using intelligence.

Hanson's concern is about the great filter. As it seems the evolution of life seems more and more likely in many places, the great silence we observe means that something is stopping all these living things from leaving their homeworlds, and by some arguments that something is more likely to be in humanity's future than our past. One candidate is that intelligence is an evolutionary dead end which causes species to wipe themselves out, which was exactly Fermi's original fear - that intelligence creates a superpredator that not only exterminates its prey but itself. An interesting bit of trivia: we are currently living through a mass extinction at least as bad as the K/T event, and maybe the worst so far on Earth, and we're causing it.

The other question to ask is this: which of the following two propositions is more likely to be true?

1) That life evolves very frequently, and intelligence relatively frequently, but only very few (or no) species make it to the point of interstellar expansion, so that we don't see a galaxy chock full of waste heat from their engineering projects (i.e. that life is anywhere but NOT everywhere);

OR

2) That they are everywhere out there, but we still don't know what we're looking for.

It may be instructive to work backwards. Start with the assumption that we are surrounded by massive (roughly galaxy-spanning) civilizations, as the papers envision them. We've been looking right at them since the first time a human paid attention to the night sky - how could we differentiate them from background? The uncontacted people in the Amazon are surrounded by nation states, and yet for a half century they've been growing up with the sound of planes in the sky, and they haven't inferred the rest of the world.

What are the things we already see that could be evidence? Dark matter is an intriguing candidate just because we understand it so poorly. The absence of obvious life could itself be a hint, i.e. still-extant species are hiding from or destroyed by others.

This is certainly a less depressing alternative than intelligence being an evolutionarily unstable strategy, which of course has nothing to do with its being true. I increasingly suspect that life in the universe is mostly space viroids that when seeded in a large, warm medium, incidentally produce replicators like life on Earth, that is then stuck there, because either it can't travel in space, or it gets smart enough to travel in space and therefore to kill itself.

A Moore's Law Argument for Panspermia

From Sharov and Gordon's paper Life Before Earth at arXiv. The implication is clear from the figure - that life has followed a logarithmic complexity trajectory, which is cooler to refer to in terms of Moore's law, but that at 4.5 GA ago (the formation of Earth from the stellar accretion disc) the complexity is not 0. Their figure crosses that line at a complexity of about 10^4.5, meaning a 30,000 bp genome. For reference, the smallest chemical replicators in nature are viroids (RNA that reproduces in plants), mostly around 2,000 bases, although hepatitis D is a virus essentially parasitic on other viruses with a similar genome size. The smallest replicators with independent metabolism are the Mycoplasma (a medically important genus discovered by Leonard Hayflick), generally under a million bp. Your genome is about 3 billion base pairs.

The first question we should ask here is what we even mean when we say "genome size", and why we care (which the authors do somewhat address). There is a difference between absolute number of base pairs in each cell, non-repetitive DNA (information), and functional complexity. If you want to talk about plain old absolute number of base pairs by mass in the cell, then plants win that one hands down, because they sometimes have many many copies of each chromosome - 20 or more. Modern corn has 6. Fine then; you want to talk about non-repetitive DNA, i.e. the Kolmogorov complexity of genomes? If you want to make a compressed file of a genome, some organisms have long stretches of repeats that can be compressed by saying "[repeat] x a million"; I don't think that complexity is what we're talking about either. (For the record, humans have more non-coding repeat DNA than coding DNA. Coding is about 3% of our genome, and just the most common type of repeat, the Alu element, is 5%.) Even taking that into consideration, yes, vertebrates have bigger non-repeating genomes than most other organisms, but among the vertebrates, non-repeating genome size and behavioral complexity do not correlate. Unless you're willing to concede that fish are smarter than you, because they have bigger non-repeating genomes. (I'm not willing to concede that.)

I think what we're really talking about here is functional complexity - the phenotype that the DNA produces in extension - and the best approximation of this is the number of genes. The authors of this paper refer to functional non-redundant genome, and even then - are you ready? - by this measure, protozoans win. Yes, amoebas and giardia. The kicker is that Trichomonas, which causes an STD, holds the record for the most genes of any organism yet sequenced. (I debated including a picture of its effects but I decided against it. You're welcome.) So it's time to retire your vertebrate chauvinism, or at least find another justification for it, because you're not that complex. For more on this, see the C-value paradox.*


All hail Trichomonas, our genomic superior. This is the one that infects humans; another one in the same genus infected T. rex.

That said, functional non-redundant genome size may still not be a totally awful indicator of genome complexity over geological epochs, but there are still further issues worth pointing out: they assume a constant trend and argue for it based on several other provincial (terrestrial) examples of complexity. We can't really assume that an algorithmic approach to processor speed and scientific publication rates give us the correct start date, and therefore so does the origin of all life, especially when the chemical substrate must have been different early on (see the RNA World hypothesis). They also get a little greedy reducing things to big picture neat-o ideas; for example, the Singularity makes an appearance. I think it's worth pointing out that we're still working out the troublesome details of the origin of replicator chemistry under early-Earth conditions and there are some fairly good answers now, but if replicators predate the Earth that begs the question of under what conditions did they appear. I've made the argument repeatedly that replicators could spread on comets and asteroids but it's much less likely that they originated there. Too cold, too dry, boiling point of solvents too high under low pressure atmosphere.

Of course it's an interesting paper (link here) but that doesn't mean it's correct. If it is correct, it means the evolution of life elsewhere is even more certain than it was before, which makes the Great Filter all the more daunting.


*My own take on the the C-value puzzle is that it's actually not that puzzling, unless of course you assume behavioral complexity must mean genomic complexity. For one thing, those protozoans have very complex life cycles, and have managed to preserve a lot of the behavior of eukaryotes that their single-celled prokaryotic comrades never had; the vast majority of our own cells are coddled in a vast bureaucracy that protects them from the outside world, and even if they screw up and die or reproduce out of control, there are a trillion more of them and an immune system to kill them just in case. There is also very little pressure on multicellular eukaryotes not to let their genomes accumulate a lot of junk, much of which is likely to be non-coding repeat elements. The amount of extra energy it takes your cells to reproduce their Alu elements today is far, far less than the amount of energy it takes you to scratch your head, and you aren't starving because of that either.

Bayesian Astrobiology: Probability of Life on Titan Increasing

Meteorological anomalies parallel the predictions that were made for one possible solution for Titanian biochemistry.

The discovery of life on Titan would be much more exciting than the discovery of life on Mars. The idea has been floated that life on Mars and life on Earth could actually have a common ancestor, seeded on meteor fragments blasted into orbit off each other's crusts during the Eoarchaean when bombardment was much more frequent. If there's life on Mars and that's what it turns out to be, wouldn't that be boring? Sure, we'd get a couple new enzymes out of the deal, a few new twists in biochemistry, but nothing cutting deeply at the problem of life elsewhere in the universe, not much more than would finding a weird cyanophyte in Antarctica's Dry Valleys. Any replicator we find on Titan is much less likely to share a common ancestor with cells on Earth, not just because of the distance involved, but because the chemistry would have to be fundamentally different. If you want to reason inductively you want to generalize based on data from sources as diverse as possible. Life on Titan would teach us much more about chemistry, about early evolution, and about the probability of finding life elsewhere in the universe besides in our backyards.

The Epidemiology of Cancerous von Neumann Comets, Part II

Original post here. The following belief is probably one of my weirdest ones but I'm confident in it and would like to test it. Still it's unlikely that we'll have evidence for or against in my own lifetime. Consequently I went to Longbets.org to post my prediction but learned only at the end that there's a fifty dollar publishing fee. No deal.

So here's what I was going to enter.

SUMMARY: By the time we have surveyed the surfaces of 1% of asteroids and comets in the Solar System, we will have found definitive evidence of extrasolar replicators, von Neumann probes or otherwise.

SUPPORTING ARGUMENTS: The argument has been made by Tipler that the absence of von Neumann probes is in fact much more damning to the prospect of extrasolar life than the absence of signals as observed by Fermi. That we, in the infancy of space exploration, have as yet an absence of evidence of von Neumann probes is certainly not evidence of absence; this is rather like a Roman orator having claimed that there are definitely no continents besides Europe, Africa and Asia. In fact there are good reasons why the Earth's surface would not be a good place for space-traveling replicators, the economics of gravity wells among them. Using the self-indication assumption and the explosion of our knowledge about nearby planetary systems, it is becoming increasingly unreasonable to suppose that there are no other replicators (planet-bound or otherwise). This means that if space-borne replicators are possible, they are probable, and we should look for evidence associated with comets and asteroids. I make this prediction contingent on exploration because I'm not nearly as confident about when that will happen. I do appreciate that 1% is still a massive number of bodies, so I don't realistically expect this to occur within the next two centuries.

[Added later: Japan is about to test solar sail technology which is one passive way that replicators could diffuse. The design is engineered to get to Venus, on the way accelerating to 100 m/s over six months, which translates to a Sun-to-Alpha Centauri crossing in a little over five millennia, a reasonable scale even for biological diffusion on Earth.]