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David Darling's Newsletter #15


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October 3, 2003


Contents

1. Meanderings
2. Life on Mars
3. Bookends



1. Meanderings

A belated greetings, everyone. The Yahoo Groups site has been down for a bit, so, for the benefit of those who receive it that way, I was holding off with the newsletter until the glitch was resolved. This last week has seen the first blast of wintery air arrive in Minnesota, with temperatures dipping well below freezing at night and the leaves rapidly changing to a delightful mixture of reds, oranges, golds, and browns. It would be perfect except for the thought that we'll soon be running our annual five-month-long Pluto simulation!

With a great deal of help from my son-in-law, Murray Etherington, I've now set up a new version of my website hosted by Globat which will allow for a lot more expansion, traffic, and nifty facilities. As I write, the domain name www.daviddarling.info is in the process of being transferred to this new location. This means that if you've been accessing my site via www.daviddarling.info, instead of the more cumbersome www.angelfire.com/on2/daviddarling, you'll automatically go to the new version when the switchover takes effect. I'll still be maintaining the old angelfire-based site for a couple of months to allow for a smooth transfer of traffic, but if you have a bookmark that points to the old URL or to any of the pages within the angelfire site, I suggest you update this to point to the new address. Let me know if you run into any problems or if seems like I'm talking Greek.

At first glance, when you go to the new site, you'll notice nothing different. But if you look more closely in the menu items at the top of the front page (and on every other page of the site), you'll see that a new item has appeared: "bulletin board". This is something that people have been asking that I set up for quite a while. It's a multithread forum hosted by PHP and is a great way to get involved in a discussion or argument on any topic related to the site – astronomy, life in the universe, spaceflight, faster-than-light travel, time machines, cosmology, teleportation, the nature of consciousness, my books, you name it. In fact, you can literally name it by setting up your own thread and starting a new dialog. These things tend to be organic by nature, so I've no idea how it will develop. I'm putting up a few topics to get started, but you can take it anywhere you like. It'll make the site a lot more interactive and fun. Don't be shy – please plunge in and have your say. I'm hoping especially that newsletter subscibers will get involved so that I can learn more about you and your interests. Please drop me a line if you run into any broken links or other anomalies – there are bound to be a few. You can also check out a couple of pictures I took on our summer trip to England by going to the "me" page on the new site and following the link from there. (Apologies to Mike B. from Australia who asked that I visit the Green Slate Company in Honister Pass, just for him. I didn't make it this time – my wife refuses to travel by road on Honister or Hardnott and Wrynose Pass after an unfortunate encounter with a sheep some years ago. But I'll get there next time!)

In the last issue of the newsletter I rambled on about time travel (past newsletters are also available on the new site, by the way), and asked if anyone could remember who wrote the old classic science fiction tale in which a time traveler goes back to the age of the dinosaurs, inadvertently steps on a bug, and because of that, alters the future course of the world. Thanks to Larry Klaes and Daniel Handlin for supplying the missing data: the bug was a butterfly, the story was "A Sound of Thunder," it was first published in 1952 in R is for Rocket, and the author was none other than Ray Bradbury.

And so to this issue's topic. Even as we speak, four spacecraft are converging on the planet Mars to try to pry away some more of its intriguing secrets. They're the European Mars Express, carrying the Beagle 2 lander, the twin NASA Mars Exploration Rovers, and Japan's Nozomi orbiter. What will they find when they arrive? Most importantly, will they uncover evidence of life?



2. Life on Mars

The question of Martian biology goes back centuries, but first became a hot topic in the last quarter of the nineteenth century, when Schiaparelli and others, most notably Percival Lowell, thought they'd seen water channels or even canals on the surface of the fourth planet. Lowell's obsession with advanced Martian intelligence and a civilization that had built a complex irrigation system to carry meltwater from the polar caps to the arid regions of the planet fired the popular imagination. And I don't think that fascination with a dying extraterrestrial civilization on our cosmic doorstep has ever really gone away. Here's my illustrated encyclopedia page on the canals saga. It's a story that, while, unfortunately, long discredited by observational evidence, is too compelling and exciting to relinquish its place in the romance of the Solar System. We badly want it to be true that there was a companion technological race on the Red Planet, and so we still seek signs for it in space probe imagery at the edge of resolution just as Lowell strained to see what he wanted to see in the faint, small disk of Mars imaged by the 24-inch Clark refractor at his purpose-built observatory at Flagstaff.

Now, don't get me wrong. I'm not averse to people poring over photos of Mars sent back by Mars Global Surveyor and, more recently, by Mars Odyssey, in the hope of seeing ruined monuments, cities, and even extant life. I regularly receive requests to look at shots, processed or otherwise, that purport to show Martian pyramids, "glass tubes," colossal sand worms (a la Dune), and so forth. I never pour scorn on these pictures or their senders. (In fact, any "anomalists" are cordially invited to present and defend their case on the new bulletin board!) As soon as a scientist refuses to look at any data with a fresh eye and mind, he may as well pack up his bags and leave town. But I'll always, without fail, apply Occam's Razor. That is, faced with an unknown or indeterminate phenomenon, I'll always go for the most mundane explanation – the one that calls for the least spectacular and number of explanations. Lowell thought he saw hundreds of networked straight lines and took them to be canals. He was wrong: they were an optical illusion. Armchair theorists today argue that they can see geometric shapes, alignments, forests of banyan-like trees, megalithic humanoid faces, etc – evidence of advanced life. I hope they're right. I strongly suspect they're wrong. I know that Mars has a long history of kidding people into thinking that it harbors visible traces of life, animal and vegetable. That isn't Mars' fault. It's ours, because we (me included) so desperately want to find those traces. It's a very human failing that when we want to believe in something badly enough, our minds work hard to invent or suitably interpret the data needed to shore up that belief.

Well, our outward-bound probes aren't going on a hunt for lost Martian cities or technological remains. But one of them at least, Beagle 2, is going to be sniffing the air and sampling the soil of the Red Planet to see if there are any signatures of microbial life. If it finds a minute dash of methane in the atmosphere, for example, that would be very suggestive (though not proof) of methanogenic bacterial action. If Beagle detects traces of organic material in the soil, collected by a miniature "mole," that too will point the finger in the direction of life. Remember, there are still many unanswered questions about the results sent back by the twin Viking probes.

So what are the chances for Martian biology? The good news is that, in its early stages, Mars was a lot more like the Earth than it is now. It was certainly warmer and had liquid water on its surface in the form of run-off channels, lakes, and possibly extensive seas. It would have been much more geologically and tectonically active, and possibly had hydrothermal vents of the type that, on Earth, are on the list of "genesis sites" – locations where life may first have emerged and developed. In fact, as I argue in my book Life Everywhere, it might be more puzzling if we find no evidence of any Martian biology at all, past or present. If Mars never acquired life, what was it about Earth that was so special? What did we have, four billion years ago or thereabouts, that Mars didn't. I'd personally put the odds of past Mars life at better than 75% because of the similar conditions.

What about life on Mars today? That's a lot more problematic. Mars today isn't too friendly, at least on or just below the surface, to the kind of life we know. It's bone dry, very cold for the most part, and, worst of all, is strafed continually by high-energy solar radiation. Harsh solar UV, cosmic rays, and the like, have surely sterilized the soil at ground level and down to at an indeterminate depth. There's a very good chance that the surface regolith is rich in highly oxidizing compounds, such as superoxides, that would be devastating to terrestrial biology. These powerful oxidants may very well (but not conclusively) explain the anomalous Viking lander results. They may also frustrate Beagle 2's attempts to find biological matter. But set against these negatives is the possibly that if life had emerged on Mars in the remote past it might have gradually adapted to the current harsh regime (we have some bacteria on Earth, such as Deinococcus radiodurans, that are incredibly resistant to high doses of radiation) and/or retreated to a more clement environment deeper underground. Getting at deep subterranean (or "subareolian") life, tens of millions of miles from Earth, might be a bit tricky, calling for advanced penetrator probes or even a human-crewed drilling rig. But I suspect that several hundred meters, or even a kilometer or more, down is where we have our best chance of encountering living Martians.

Our search for life, at least within the Solar System, is first and foremost a search for liquid water. Good old H-Two-O is a sine qua non of life as we know it. We can speculate about life based on a different solvent, such as ammonia or hydrochloric acid. But we really haven't a clue how it would work biochemically and we certainly wouldn't know what biomarkers to look for. (We have a hard enough time searching for small traces of Earth-like life!) The fact is that we know of at least one form of life that depends critically on the availability of water in its liquid form and we know that water has some extraordinary properties that make it hard to replace in a biological context. So, it makes sense to look for water first and then ask if there might be life nearby. That's why astrobiologists are so excited about Jupiter's moon Europa, because there are strong signs that it has a sub-ice watery ocean. Mars is harder to read on this point. Its atmospheric pressure is extremely low – around 7 milllibars, on average, which is less than one-hundredth the surface pressure on Earth. Water just vaporizes – essentially boils – away very quickly under these conditions. So you really can't hope to find watery pools lying around Mars today. On top of this, of course, it's pretty cold in most places on Mars, most of the time. Pick a time and location on Mars at random and the chances are it would make Antarctica seem balmy. And yet we know Mars has lots of water ice. Most of its poles and much of its rocks seem to be rich in the stuff. So, if there are mechanisms to temporarily melt this ice, you could have liquid water on or just beneath the surface for brief periods. If you go to the front page of my website you can find an image that seems to show dark stains that have appeared on extensive regions of the Martian surface quite suddenly, over a period of a year or so. We don't know what these stains are or what has caused them. One theory is that they represent water melted by tectonic activity. Another theory, put forward by NASA's Chris McKay, is that they may be due to the spread of bacterial colonies during a short spell when moisture becomes available. McKay, incidentally, has also suggested that plenty of free oxygen may have been available on Mars in its early stages, opening up the possibility that not only life, but possibly advanced life could have evolved there between 3.5 and 4 billion years ago. So, the door is slightly ajar to you anomalists!

And then there are those Martian meteorites. Do they really contain evidence of life as some researchers claim? It gets down to the origin of certain magnetite crystals in meteorites such as ALH84001. The pro-life claim is that exactly the same kind of crystals are produced biologically – and only biologically – on Earth; so, given that they almost certainly came from Mars, they were probably laid down by magnetotactic bacteria on the fourth planet. Well, maybe. But it's pretty thin evidence when stacked up against such a momentous issue: the question of the existence of life beyond Earth. Maybe there are ways to produce these crystal chains by purely chemical means that we don't know about. Maybe they're contaminants (though this seems unlikely). We're not going to settle the problem of Martian life, once and for all, to everyone's satisfaction, through rocks that have been blasted our way, have spent millions of years floating around in space, and have lain around on Earth for thousands more years. We need pristine material from the Red Planet itself: we need to find life, or its remains, in situ. Perhaps that's what Beagle and the other space hounds currently bound for Mars will do.



3. Bookends

Where can you find the latest, greatest guide to the astronomical world, complete with more than 3,000 cross-referenced entries and 230 illustrations (including 8 pages of color photos)? What is the most up-to-date encyclopedia of this astonishing cosmos in which we live? Why, The Universal Book of Astronomy, of course! More on this newest book of mine, about to be published by Wiley and a companion to last year's Complete Book of Spaceflight, on my website, at Amazon.com, and Barnes&Noble.com. Buy your copy now, while stocks last!


Until next time,
Best wishes,
David Darling