Thursday, August 18, 2016

Reflections on the Bizarre Behavior of a Science Fiction Nerdkid

Recently I was contemplating the many ways in which I was a weird kid. Here are but two, both of them grimace-inducing as I ponder them today.

When I was in sixth grade, I was obsessed with the show V. (Partly because I was obsessed with Jane Badler but who can blame me.) As you may recall, the aliens in this show were the Visitors, reptiles who disguised their appearance from humans with fake human-looking skin. (Fortunately for the show's producers, this also had the effect of minimizing special effects and makeup budgets.) However, this "skin" could be torn off revealing the scaly hide underneath - and often was in fact torn off, inevitably to dramatic effect. My obsession with the show around age 11 was such that I actually starting telling other kids I was a Visitor. Of course, this made me every bit as popular as you might expect. One day, a helpful classmate demanded to test my claim by saying "it won't hurt if I pinch your skin then." I don't recall ever thinking I was actually a Visitor, but also recall thinking I'd be damned if I was going to be forced to admit that I wasn't. Seeing no way out, I allowed a very very painful pinch and twist of the hand which felt like it would break the skin but did not; after which I announced that I had special skin that couldn't be torn off. However, perhaps wary of additional tests, I shortly decided I was sick of playing this game (had it been weeks? months? oh boy) and one day I started telling other kids I wasn't a Visitor. When they gleefully claimed victory over my ruse, I also insisted that I had never said that, which made me even more popular.

Perhaps more disturbing in retrospect was the time at about age 13 when my own made-up science fiction universe actually confused me about reality a little bit. I had invented bad guy aliens, the Ptranians, a race of bipedal reptiloid rats, 7-8 feet tall. (Because that would be cool.) They hailed from a harsh moon of a gas giant orbiting the star Algedi. One day I found myself wondering what the Algedi system was actually like, and found myself unable to imagine that there were no Ptranians there in reality. This unpleasant experience scared me and I stopped making up aliens for a while. The reader will be pleased to know that today I can clearly imagine there are no Ptranians at Algedi, but of course the space lemmings at Epsilon Eridani are real.

Friday, August 12, 2016

There's a 1-in-3 Chance of Life on Europa

Based on the new paper reconstructing the most recent common ancestor of life on Earth - and its environment - there's a 1-in-3 chance of a similar organism living under Europa's ice right now.

We can now be much more certain that life on Earth originated in deep sea volcanoes, which makes the prospect of life in Europa's oceans much more exciting. Life had already appeared by at latest 500 million years after the formation of the planet. If we assume mediocrity (ie that by 500 million years into it, there was a 50% chance of LUCA having developed) then that gives us a 0.14% chance of life evolving per million years. Assuming that the chance of life evolving is directly proportional to the surface area of the ocean floor (rather than the volume, because it was around volcanoes), and that Europa has volcanoes, that means a 0.00854% chance of life evolving on (or in) Europa per million years. After 4.5 billion years, this gives us 1 in 3 odds of a LUCA-like organism living under that ice right now.

If we hold all else equal, but instead assume that the likelihood of life evolving is proportional to volume, then the chance of life on Europa today is essentially 100%.

Of course this holding "all else" equal is a bit of an assumption. I didn't try to account for the different chemical composition of Europa's oceans (which we don't know yet), the volcanic activity (which we also don't know yet), and reaction kinetics based on water temperature (which we also don't know, and is a real wild card since tidal heating is a big deal when you're orbiting Jupiter.)

Besides the obvious excitement about the possibility of ocean-floor life on Europa, this also means that life evolved WITHOUT sunlight, DURING the Late Heavy Bombardment. You need water with stuff in it, but not sunlight, and if space rocks keep crashing into it, that's fine. If you're covered with ice and kilometers of water, even better.

When are we getting probes there?