Several parallel discussions inspire me to write this post partly in the hope that you will chime in.

The chance of life elsewhere in the universe just went to near zero. Or did it?

I was just hanging around minding my own business the other day when someone said to me, “you know, every single one of the five thousand or so exoplanet holding stars found to date have the gas giants in the inner, Goldilocks zone, and the smaller Earth-like planets are too far out to have life. So, the chance of life on other planets is way lower. Zero, basically.”

So, that was depressing.

Then, I went to the opening of the Bell Museum, and watched the planetarium show. After the show, I asked one of the people running the show, a somewhat snotty graduate student from the U, about this news. He got even snottier and told me that was ridiculous, that there are plenty of systems with Earth-like planets in the Goldilocks zone. I asked him how many. Plenty. I asked him if the number was double digit percentage or single digit percentage. He said may be single, but that was enough. I told him I had heard zero, which is not many. He said that was wrong.

Just a few minutes later, on visiting the rest of the newly opened museum, the penny dropped.

It turns out one of the major faculty members at the U in astronomy is one of the planet hunters, and a huge portion of the overall universe level exhibitry in the museum is devoted to showing this one guy’s work and talking about exoplanets and stuff. That must have been his student. Clearly, I had stepped in a pile of something.

My question is, a pile of what, exactly? Is there really recent research that suggests that the Earth’s solar system is unique among a sample of 5,000 or so? Or not? Or what?

The origin of life vs evolution

A long time ago, maybe 20 years now, some evolution-believing but sympathetic to religion people decided to say that the origin of life is not really in the purview of biology, and therefore should not be addressed in textbooks, high school courses, etc. You can think whatever you want about the origin of life, but it has nothing to do with evolution.

I’ve written about this. See:

“We can know nothing about the origin of life”
Is the origin of life different from evolution?

More recently, I find myself repeatedly being dragged into Twitter arguments between people saying that the origin of life is separate from evolution, vs. not.

The reason to say that they are separate is to allow religious people to have their god of the gaps, in this case, the ultimate gap. The pre-life gap.

The conception involves a very serious misconception about what the word “evolution” or the term “evolutionary biology” refer to. Most people misunderstand this.

I’ll give you an example. I was at a conference many years ago at the original Bell (not the one that just opened) and a well meaning but not well informed science teacher said to a room full of science teachers, “Evolution is simple. It is simple to teach. All evolution is…” then he proceeded to lay out the three Necessary and Sufficient conditions for Natural Selection.

Unfortunately, that is not what evolution is, and even more dramatically, it is not what evolutionary biology is about.

Evolution is the change over time in organisms, no matter how that happens.

Evolution is the idea of common ancestry and differentiation of lineages form common ancestors.

Evolution is increase of diversification over time, speciation, and extinction.

So that is three or four, maybe five things, depending on how you count them, that evolution is, and none of them need involve natural selection.

Oh, and natural selection is also part of evolution.

The point is this: If you think evolution is only this one thing, and define it very narrowly, then it is easy to figure that the origin of life is not part of evolution. But evolutionary biology is really the study of life in general, and all of it, in the context of evolutionary theory, and evolutionary theory involves everything from how molecules selectively interact (in primordial soup and in cells and other places) to how genes mutate, to how populations randomly drift genetically apart, or interact genetically, to how coeval lineages of organisms affect each other’s evolution (co-evolution), to how life and non life interact, to how natural selection creatively shapes life.

Evolution and evolutionary biology are two terms that refer to a thing and the study of a thing that is whopping big and complicated and wonderful and amazing and confusing and only barley understood.

To say that the origin of this thing is somehow separate is idiotic.

But to underscore the stupidity of this idea further, allow yourself to consider the following idea as possibly true.

Life evolved more than once.

Even more amazing an idea, and a very interesting hypothesis that we hope one day to test:

Under certain conditions, which are not uncommon in the universe, life almost inevitably arises, just as under certain conditions, a crystal is likely to form, rain is likely to fall, or a fire is likely to ignite. Life, in other words, happens.

If that is true, then the multiple origins of many life systems is clearly of no small interest to evolutionary biologists, and is very much part of “evolution.”

Which brings me to my third thought.

Life evolved independently on Mars, Earth’s Moon, Earth, and who knows where else. Or not.

There is a study just out published in Astrobiology, by Dirk Schulze-Makuch, that addresses part of this. I’ve asked for a copy of the paper, and if I get it, I’ll tell you about it. Without the paper, all I have is the breathless press release, and I’m not going to report on that.

But I can tell you that the basic idea seems to be that there is vague isotopic evidence of past life on the Earth’s Moon, and reconstructions of the Moon’s history suggest that at some point after its formation, and another time later when it was very volcanic, there would have been pools of water, an atmosphere, and some degree of protection from radiation, so life could have been there.

I’m of the belief that life is not that hard to get started. Why do I think that? Because it isn’t that hard to maintain it. Bacteria, especially, survive and do well under a wide range of conditions. A very simple virus can exploit cellular machinery pretty easily. Even though conditions on the early Earth were probably pretty tough, bacteria seem to have arisen early and held on — or perhaps re-started? — for a very long time. This is little more than a gut feeling, but it seems to me that life starting up isn’t that unlikely of an event, given the right conditions.

The reason we don’t see life originating again and again on our planet now may be because the startup does poorly in aerobic conditions. It may be because any molecules that start to form up in a way that leads to life are inevitably tasty food for existing life. Hell, there may be life almost starting up all the time in some places, and then being guzzled up by bacteria of some sort. And there are people looking for that sort of thing so maybe we’ll find that eventually.

Here’s my question on this. Which is harder to see happening, harder to believe, harder to accept, given what we know, and what we like to guess, about life?

1) Life started once, say, on Mars, and that’s it. Just that one time. Life found later on the Moon or on Earth came from Mars by a large rock hitting life-bearing mars, spreading rocks across the inner solar system, and some of those rocks eventually landed on the Moon and Earth, burning to a crisp in the atmosphere but somehow the bacteria on the rocks survive.

or

2) Life starts up easily and did so on Mars, the Moon, and Earth. For the first two, conditions for life were transient and have ended. For the Earth, conditions for life are a bit longer lived, and will end later.

Yes, yes, this all assumes there was life on Mars or the Moon, and we simply do not know that to be true at this time. This argument only matters if we pretend it was true, or at least possible. So this is speculation.

Europa’s surface is nearly devoid of impact scars and is covered with cracks and other features that together indicate a liquid water layer beneath the ice surface, as well as melting and refreezing of the surface. Unless catastrophic life-unfriendly events are common on Europa, if it does indeed have constant liquid water owing to tidally induced warmth, then there IS life on this moon!

Maybe. If live is the kind of thing that evolves wherever certain conditions are present, then there is a pretty good chance that there is life there. Or at least, the chances of life on Europa in the past or present are good enough that if one is serious about one’s astrobiology, one would want to go there, a feat best accomplished vicariously through the use of probes and robots.

There is a controversy among planetary scientists as to how think the ice on Europa is. Some say that it is very thick, others say that it is either thin or has the capacity to become very thinned out over large period and for considerable periods of time. The thickness vs. thinness of ice on Europa, and the frequency with which water is exposed directly to the atmosphere will impact both the likelihood of life being there and what that life may be up to, as well as any strategy to examine it directly. For instance, a thin layer of ice would allow some interaction between the atmosphere and the liquid below, and certainly, any regular breaks would enhance this. This brings up several issues not only related to methods and approaches to the exploration of Europa, but also, ethics.

What if there is life there? What if, for instance, life is present in the sub-ice sea like so many walleye in a Minnesota lake in January, but exposure of the sea via holes punched in the surface (by meteors, for example) is deadly and causes local extinctions? An Earthling probe would arrive on the surface of the ice, drill a hole through it like a fisherman on a Minnesota lake in January, and as soon as the hole is punched through, mayhem ensues. Or, if the estimate of thickness of the ice is way off, maybe the machine we send will go crashing through the ice. Like a fisherman on a Minnesota lake in late February. If the life is complex and intelligent, perhaps the Earthling probe’s blunder will kill Europa’s leader. Or a school full of beloved Europan children. Or, if we are lucky, the Europan equivalent of Adolph Hitler.

Of course, most likely, life on Europa would not have intelligence. For that matter, it might not even have multicellularity. Or any cellularity. Which is why we want to look … if there is life there, we want to see what the heck it looks like, and learn how it works, and try to figure out how it came to be and how it may have changed over time, and so on and so forth, because a) that would be so freakin’ cool and b) we would learn so much about what life is, simply by adding to our sample of instances of life in our solar system.

If Europan life includes children and philosophers and workers and criminals, it would be highly unethical to do something that did damage to it … them … whatever. But even if Europan life is essentially bacterial, it would be wrong to mess up the ecology of another planet by simply arriving there and mucking around. And there are plans to go there. Therefore perhaps there should be plans to go there in a way to minimize harm, and that take into account the full range of models of how the ice is distributed, how thick it is, and how it changes over time. This is the subject of a recent paper by Richard Greenberg, who is the author of Unmasking Europa: The Search for Life on Jupiter’s Ocean Moon. Greenberg is one of the scientists who thinks the ice surface of Europa is thin and dynamic and that there is significant ocean-atmosphere interaction. That and the nasty big-science politics linked to this debate are covered in his book. I’m sure the paper, which he sent me last week, will spark some controversy.

Here’s the abstract from Greenberg’s paper, published in Astrobiology:

Europa has become a high-priority objective for exploration because it may harbor life. Strategic planning for its exploration has been predicated on an extreme model in which the expected oceanic biosphere lies under a thick ice crust, buried too deep to be reached in the foreseeable future, which would beg the question of whether other active satellites might be more realistic objectives. However, Europa’s ice may in fact be permeable, with very different implications for the possibilities for life and for mission planning. A biosphere may extend up to near the surface, making life far more readily accessible to exploration while at the same time making it vulnerable to contamination. The chances of ?nding life on Europa are substantially improved while the need for planetary protection becomes essential. The new National Research Council planetary protection study will need to go beyond its current mandate if meaningful standards are to be put in place. Key Words: Europa–Planetary protection–Mission planning–Spacecraft–Geology. Astrobiology 11, 183-191.

The long term plan for exploration of Europa involves three phases: First, an orbiter around the moon, then a lander to explore the surface of the ice, and later a rig to drill through what is assumed (by the dominant thick-ice school of thought) to be a few thousand meters of ice and into the ocean below. This model is predicated on the idea that the Europa’s ocean is fully separate from its atmosphere, and that life on that moon would have evolved along some Europan equivalent of Earth’s hydrothermal vents.

One of Greenberg’s complaints about this stems from the mission’s obvious near-impossibility, especially with respect to the deep drilling part. The assumption of thick ice leads to an assumption of great technical difficulty in the mission which in turn leads to the schedule for the mission being extended significantly. At this point, the orbiter, originally scheduled to have been sent there already, will not be in place until nearly 2030. Greenberg claims that since that plan was originally developed in the 1990s our conception of Europa has changed enough that the mission itself needs to change as well. From the paper:

If Europa’s ice is in fact permeable, it would have major implications for mission planning, because organisms or their markers would be readily accessible near the surface. The prospects for discovering extraterrestrial life in the foreseeable future would improve immensely. At the same time, a europan ecosystem would be highly vulnerable to contamination, so planetary protection becomes a critical issue.

Greenberg goes on to describe his updated model of Europa’s surface conditions and the dynamics of the ice surface, and to suggest alternative views of Europa’s possible biosphere. And, of course, he makes the point that if the ice is permeable, the prospects for life there are enhanced significantly.

There is a lot more to the discussion of ethics (and the evolution over time of ethical guidelines in space exploration) that I will not go into here, but it’s all in the paper. Unfortunately, you may have to subscribe to Astrobiology to get it. If you have questions, put them in the comments and perhaps I can persuade Dr. Greenberg to have a look.

Greenberg, R. (2011). Exploration and Protection of Europa’s Biosphere: Implications of Permeable Ice Astrobiology, 11 (2), 183-191 DOI: 10.1089/ast.2011.0608