Discussion and news about the modern effort to understand the nature of life on Earth, finding planets around other stars, and the search for life elsewhere in the universe

Sunday, March 28, 2010

Chance of a snowball

As the weather in New York oscillates between the warmth of spring and the bitter cold of a winter we'd all hoped was gone, I've been reminded of some of the peculiarities of a 'habitable' planet. Over the past few months I've tagged along with some interesting work on terrestrial planet climates. Recently we put out a couple of papers that discuss in some detail how the orbital arrangement of a world can alter climate and climate variation (Dressing et al., Spiegel et al.). The interesting thing about Earth-type planets in our models - rocky worlds with surface water and atmospheres - is that they have a tendency to go snowball. Going snowball isn't some odd mental state, it's when a planet drops below the freezing point of water from pole to pole. The Earth may have done this itself, about 700 million years ago, since there's evidence of glaciers near the equator during that time. Because frozen surface water reflects more radiation and keeps things cool then once you're snowballed you tend to stay that way. On the Earth it may have been geophysics that got us unfrozen, over millions of years more greenhouse gases got dumped into the atmosphere from volcanic activity until things heated up again. On different planets, where their orbits get strongly perturbed by other objects in the system - increasing and decreasing in ellipticity - this kind of thing may happen on a regular basis, but it's the orbital swings that push and pull a world in and out of a frozen state. I think it's fascinating, not least because if we eventually spot planets like this they may present a conundrum - either caught in the act of freezing up or thawing out. In this case we'll have to consider their orbital circumstances very carefully in order to know whether or not they are merely experiencing a bad case of seasonal adjustment....

Thursday, March 25, 2010

Methane eaters

The ways in which organisms make a living is constantly throwing up surprises. In Nature this week there is a paper by Ettwig et al. that describes something truly unexpected. Many microbial organisms make use of methane, in fact there had been 3 recognized routes for methane metabolism - which involve either producing or 'eating' methane. Methane, as we all know from playing with matches and bunsen burners, is chock full of chemical energy.  Of the eating variety of organisms, then either molecular oxygen is used to oxidize methane, or in the absence of oxygen a less efficient oxidation takes place (also seemingly requiring a symbiotic relationship between different microbes).

The rather amazing discovery by Ettwig and collaborators is of an organism Methylomirabilis oxyfera - a bacterium that actually makes its own oxygen in-situ in order to then oxidize methane the more efficient way. In effect this organism generates its own internal supply of oxygen, like a little submarine, neatly sidestepping the need for an oxygen rich atmosphere.

As these authors recognize, this had implications that go far beyond the terrestrial sludge that such microbes live in. The Earth's atmosphere only became oxygen rich after a couple billion years, so there could have been a real advantage in being able to forage methane independently. Methane is also present, if not abundant, in many environments in our solar system, and it's a great energy source for life - but to make the most of it life needs oxygen kicking around. By circumventing the need for environmental oxygen then M. oxyfera seems to have found the solution - make it yourself. Yet again, what we find on Earth suggests that life is very, very good at eking out a living, and that there is less and less reason to think of non-terrestrial environments as hostile for organisms.

Wednesday, March 24, 2010

The search for life....

Various colleagues have been muttering about the Fermi Paradox in recent days. I'm not sure what's brought this on, but it made me think a little more about the problem of finding life in the universe in general. Fermi's puzzler was of course to ask that if intelligent live exists in the universe then why hasn't it already shown up on our doorstep ? There are many pro and counter discussions.

I thought I'd pose a simpler question. Let's imagine that we were in possession of a master list of all star systems in the visible universe (estimated to total about 10-to-the-power-of-22), and that each system had a 1 or 0 assigned to it to indicate whether life existed in that system or not. Sounds great, somehow we've just been handed the answer to whether or not we're alone in the universe, right ? Well, the hurdle is the size of the list. This is about 11.25 million Petabytes (and a Petabyte is a million Gigabytes). How long would it take to search this list to find all the 1's - assuming there were any ?

Ten years ago the answer would have reasonably accurately been 'forever', but today we have some pretty impressive global computing power. Google, for example, processes about 24 petabytes a day at the last count. So it would take all the computing might of Google about 140 years to search our list of stars. What's so very interesting about this is that it's not a crazy number - sure it's a long time, but computing power continues to grow, and this is using just Google, add in governments, telecoms, and you could bring this down to a couple of decades.

The problem of course is where to get that list from.....

Windless Blight

It seems appropriate to start off with a post about life in a most unexpected place. Last week this item hit the news; a NASA/JPL funded project has been drilling an 8 inch hole through the West Antarctic ice shelf in order to drop cameras down and see - for the first time - what's going on underneath about 600 feet of the ancient Ross Ice Shelf. They did this at a location with was has to be one of the least promising names - Windless Blight.
Lo and behold, as the cameras went down a Lyssianasid amphipod - that most of us would say looked like the kind of shrimp we happily gobble down - swam into view, and curiously investigated the cable. Although the Antarctic ocean has plenty of life, this is a somewhat different environment, obviously it's cold, there's no sunlight under 600 feet of ice, and a relatively big and complex creature like this (about 3 inches across) has to eat something..

This probably means that as they explore further they will find a lot of stuff going on down there. As we try to understand life on Earth we keep finding that it is very good at filling every available niche, the next challenge is to use this knowledge to help us figure out where else life may be lurking - whether within our solar system or beyond.

Welcome to life, unbounded

So here it is, life. Oozing, crawling, walking, swimming, flying. It's all around us, and part of us as much as we are part of it. Where did it all come from, and why is it the way it is ?

Obviously these are big questions, ones that have bothered humans for a very long time and continue to do so. We live at a particularly interesting time - science and technology have allowed us to construct a remarkable picture of not just the nature of life, but the fundamentals of how our universe works. It's certainly an incomplete picture, but it's pretty amazing nonetheless. We also stand poised to find out whether there are other planets at all like the Earth out there in our galaxy, and whether or not there are signs of life on some of them.

This blog is all about this science, the technology that enables it, the incredible discoveries being made, and also - importantly - the ideas and hypotheses that are produced. Life may indeed be unbounded, and we should be sure that our imaginations are too.

Check back in for all this and more !