Archive for the ‘Astrobiology’ category

Carnival of Space 152

May 2, 2010

Welcome to The Martian Chronicles and the 152nd edition of the Carnival of Space! As always, we’ve got a great bunch of space-related posts from across the blogosphere, ranging from life on Mars to the age of the universe to Science Ninjas!

I’ll get things started with a pair of posts from right here at The Martian Chronicles. A couple weeks ago I went on a cool geology field trip in the El Paso/Carlsbad area along with a whole bunch of other martian and terrestrial geologists. Among other things, we learned that printed Mars panoramas make good raincoats, that graduate students are ideal for menial labor like counting hundreds of thousands of layers of rock, and that ancient reefs have a surprising amount to teach us about stratigraphy on Mars. Check out my summaries of Day 1 and Day 2 of the field trip! Day three is coming soon, with lots of pretty pictures of Carlsbad Caverns!

Speaking of rocks and Mars, Paul Scott Anderson at Planetaria has a post about another Mars meteorite that might have evidence of life! He includes a few very nice electron microscope images of the meteorite for your consideration. Personally, I’m not convinced, but I’m also not an expert on this corner of Mars science. Take a look for yourself!

Ian O’Neill at Discovery News also has been thinking about martian microbes, and whether germs from Earth might have hitched a ride on our rovers, set up camp on Mars and wiped out the locals. It would sure be disappointing if we discover life on Mars only to learn that someone at JPL forgot to wash their hands! Of course, there are also those who think we should stop bothering with all this planetary protection business and deliberately seed Mars with Earth life. What do you think?

While we’re on the topic of our potentially infectious little rovers, Stuart Atkinson has some beautiful pictures from the Opportunity rover. Oppy is slowly making her way across the Meridiani Plains, and has a tantalizing view of the distant hills that are her ultimate destination. As Stu says, “The far horizon is calling…

But this is the Carnival of Space, not the Carnival of Rocks and Bugs and Rovers, so let’s get on to the more “spacey” stuff! I’m a big fan of stuff, and so is Steve Nerlich at Cheap Astronomy! This week they have a great podcast about “stuff” in space and the surprisingly limited number of shapes in which it can be found.

A radar "image" of an asteroid and its two tiny moons. Credit: NASA / JPL / GSSR / Emily Lakdawalla

While we’re on the topic of stuff and its various shapes, I should point out that radar is a great way to find out the shape of stuff in space like asteroids. If you’ve ever seen one of the “images” of an asteroid taken by a telescope like Arecibo and wondered how a radar antenna can be used to take a picture, then wonder no longer! Just take a look at Emily Lakdawalla’s post about radar imaging and all your questions will be answered.

If radar images are not your cup of tea, then maybe you’d prefer to learn about an old-school optical telescope: the Radcliffe 1.9 meter telescope. Markus shares the joy of handling the massive old wrought iron telescope in this post at Supernova Condensate.

Not a fan of old school ‘scopes? Well, perhaps I can interest you in some futuristic¬† Hypertelescopes? Next Big Future also has some cool posts about even more far-out ideas like Dyson Swarms and Dyson bubbles and “statites” – structures that hover above a star by balancing its gravitational force with its radiation pressure.

We’re a long way from that level of engineering, but solar sail technologies are getting more advanced. Centauri Dreams has a post about the Japanese IKAROS mission: an interplanetary solar sail that also uses its sail as a solar panel to generate electricity! I hadn’t heard of this mission, but it sounds really cool!

Whether you’re talking about star-enveloping Dyson spheres or relatively simpler missions, you have to wonder what drives exploration, particularly since big steps forward like the Apollo program come so rarely. Well, 21st Century waves talks about the idea that what we’re really dealing with is a chaotic system in this post on how complexity drives exploration.

Of course, sometimes it’s just the brilliance of one person that makes the difference, and lights the path forward, and Robert Goddard is a great example. Over at Music of the Spheres, there’s a great post about Goddard that takes a look as some of his earliest thoughts on space and also some of his inventions, which are now available online thanks to Google Patents.

Weird Sciences contributed three posts this week: First up, some thoughts on why Stephen Hawking is wrong about aliens and the threat they pose. Also, some thoughts on the implications of self-replicating machines. And third, visualizing the fourth spatial dimension.

Speaking of weird, what does Weird Warp have for us this week? Why it’s a nice, informative (and actually not very weird!) post all about the ins and outs of comets, everyone’s favorite icy visitors to the inner solar system.

While we’re back on the subject of “things that are in the inner solar system”, let’s take a look at Astroblogger Ian Musgrave’s post about how to use the moon to find stuff in the night sky. Ian even provides some scripts for the free programs Celestia and Stellarium!

Once you have rounded up your friends and family and taken them on a tour of the night sky using the moon as your guide, you’re bound to start getting pelted with questions. Luckily, “We are all in the gutter” has started a new “how do we know” feature. Their first post in the series is an answer to the question: “How do we know how old the universe is?” Do you have other “how do we know”-type questions? Contact the “We are all in the gutter” folks and get your answer!

Our penultimate post is from Steinn Sigurdsson, who reports on the unfortunate incident of the Nuclear Compton Telescope: a balloon-borne telescope that crashed in Australia during an attempted launch earlier this week. Condolences for those on the telescope team; it’s painful to watch so much work fall apart at its culmination.

And finally, on a (much) lighter note, what you’ve all been waiting for. Toothpaste ingredients! Which of course, logically, lead us to discover Amanda Bauer’s secret alter ego: the Science Ninja. This post makes me wish that a) all products had ingredient lists like the one on that toothpaste, and b) that I, too, was a science ninja.

Update: one late addition to the carnival! Nancy Atkinson at Universe Today is working on a series of posts entitled “13 Things that Saved Apollo 13“. The main article has link to the rest of the articles. Very interesting stuff!

Update 2: One more latebreaking addition! Out of the Cradle has a nice review of the book “The Big Splat, or How the Moon Came to Be”.

Phew! Well, that does it for this week’s Carnival of Space! It’s been a wild ride, as always. Thanks again to Fraser for letting me host, and thanks to all the space bloggers who contributed!


TED Talk: Why we need to go back to Mars

March 25, 2010

I recently started subscribing to the TED talk RSS feed, and I really love coming home every day after work and listening to smart people talk about cool ideas. If you aren’t familiar with TED, you should be. Most of the talks are fantastic and very thought-provoking. So you can imagine I was excited when I saw that today’s talk was about Mars!

The talk was given by Joel Levine, the principal investigator for the proposed ARES mission, which is a rocket-powered airplane that would fly for a couple of hours on Mars and study the atmosphere, surface and subsurface.

He starts off with an overview of Mars exploration history, describing the Mariner flyby in 1965, followed by images from the Viking orbiters and landers. He says that the Viking landers returned the first images ever from the surface of another planet, but that’s actually not true! That achievement actually belongs to Venera 9, which, astoundingly, returned photographs from the surface of Venus in 1975! Everyone forgets poor Venus.

Levine goes on to talk about some of the stunning topographic features on Mars, highlighting Olympus Mons, Valles Marineris and the Hellas basin as the largest volcano, canyon and impact crater in the solar system, respectively. If you really want to be pedantic, Olympus Mons is the tallest volcano, not the largest, but it’s not really a big deal because Mars also has the largest one (Alba Patera). But what really made me pause for a moment was that Hellas is not the biggest crater in the solar system: the South Pole Aitken Basin on the moon has a diameter of 2500 km, 400 km larger than Hellas!

He continues and talks about the mysterious crustal magnetism on Mars and the fact that all of the water on present-day Mars is in the form of ice, and all of this is fine, but then a slide comes up which Levine claims shows “recent” photos from the Mars rovers with evidence of very fast-flowing water on the Martian surface. The only problem is, the images on the slide are all orbital images! I can’t say for sure but I think they are from the MOC camera, which stopped functioning in 2006, three years before this talk was given. Yes, the images show features that could be due to ancient flowing water, but they are certainly not from the rovers, and they’re not very recent either.

I got even more suspicious when Levine showed this picture of a crater filled with ice and claimed that it was taken a few weeks ago and had not yet been publicly released. The only problem is, I remember seeing that picture years ago. A quick web search reveals that it was released in a 2005 press release. Levine also misspeaks and says that the crater is filled with liquid water, but immediately corrects himself so I’ll let that slide. I’m baffled by his claim that it is a never-before-seen image though.

Credit: ESA/DLR/FU Berlin (G. Neukum); Image released: 2005

Shortly after the icy crater image, Levine makes a very strong claim that Mars once had oceans. He doesn’t equivocate at all, he states this as a fact. I find this to be very misleading. Yes, there are some hypotheses about a northern ocean on Mars, but the evidence just is not there to make such a definitive claim, and to pretend that it is gives people an incorrect impression about the Mars community’s consensus.

Even worse, later on in the talk, he claims that the northern lowlands are smooth because they were protected from impacts by an ocean. This is patently false. Oceans are not an effective protection against impacts and if you think about it, you’ll see why. The average ocean depth on earth is 2.3 miles. For comparison, the object that killed the dinosaurs was at least 6 miles in diameter and was traveling at tens of miles per second. It went through the ocean like it wasn’t even there.

Also, there is evidence for craters in the northern plains. They have been buried but they still are just barely visible in elevation data. Of course, an ocean would be one way to bury a huge expanse of the surface, but if the ocean isn’t thick enough to block impacts, then the burial must not be very old, and all evidence points to the water on Mars being a very ancient phenomenon.

Ok, oceans aside, Levine goes on to talk about the recent detections of methane on Mars. He summarizes the results well enough, but draws a misleading parallel with the earth. He says that 99.9% of Earth’s atmospheric methane is biogenic, which may well be true. But that doesn’t mean that life is the only possible source of methane on Mars! I don’t know the exact numbers involved but it would have been much more informative if he had compared the estimated amount of methane on Mars to the estimated amount from abiotic sources on the earth.

The second half of the talk focuses on the ARES Mars airplane mission. I have actually visited the lab in Langley that works on this concept and seen the models of the plane. It is undeniably really cool, but I am not convinced it is the best way to explore Mars. The problem with an airplane is that you need active control to keep it from crashing. Of course the technology exists to fly planes automatically, but to do so on Mars could be difficult. And even assuming that you can get the plane to fly automatically, it would only last for a couple of hours at most. It would collect some fantastic atmospheric and magnetic field data, and some very nice images and video, but it would only be able to cover a few hundred kilometers.

I think if you want to fly something on Mars it should be a balloon. The thin atmosphere is not ideal for a balloon, but they have the advantage that they fly without any active control: they’re lighter than air! It would be a slower ride, for sure, but it could last much longer than an airplane, and the winds could carry the balloon long distances.

In case you couldn’t tell, I was disappointed in this talk. For most people, it will be very enjoyable and they will probably learn something about Mars and about a cool proposed future mission, but the talk also had a lot of misinformation in it. Some was very minor and innocent, but the certainty with which the ocean hypothesis and the biogenic origin of methane were presented struck me as misleading.

I am all in favor of getting people excited about exploring Mars, but we should not give them the wrong impressions about the current state of knowledge. There’s plenty to get excited about without distorting the truth, whether it is intentional or not. That’s why I decided to write this blog entry. Is some of it pedantic? Yes. But I wanted to set the record straight so that maybe a few people get a more accurate picture of the red planet.

LPSC 2010 – Day 4: Mars Oceans, Titan Lakes, Astrobiology and Asteroids

March 6, 2010

Thursday started off with a couple of talks about the possibility of oceans on Mars. The first one, given by Gaetano DiAchille looked at possible locations of deltas all over Mars to try to figure out the water level of a past ocean. Deltas form when a river hits a standing body of water and drops its sediment, so they are a reliable marker of the water level. DiAchille found that “open deltas” – that is, deltas that do not end in a closed basin like a crater, all appear at the same elevation. This might mean that they all fed into a large northern ocean.

A map of valley network density on Mars and the possible extent of a northern ocean.

In the second talk, Wei Luo described his work mapping where all of the valley networks on Mars are and found that the northern limit of the networks fits with elevations that had previously been considered as possible ocean shorelines. The valley networks also matched with locations that atmospheric models predict would get the most precipitation.

Neither of these studies is conclusive evidence for a northern ocean on Mars, but they are interesting and they suggest that the “ocean hypothesis” is becoming popular again after years of little interest.

Later that day I saw a talk by Nick Warner describing the possible thermokarst lakes that he discovered in Ares Vallis on Mars. I wrote an article on Universe Today about this discovery when it was first announced a couple months ago.

I ducked out of the Mars talks to go see a talk by my friend Debra Hurwitz about a lava channel in a crater in Elysium Planitia. The channel was formed when lava breached the rim of the crater, flowed down the inner wall and ponded in the bottom. She calculated that the lava probably flowed at about 17-35 meters per second and that 6,000 cubic meters per second flowed down the channel for about 15 days. She also found that the channel could have been eroded mechanically without the need for the lava to actually melt the underlying rock very much.

A sketch of the lava channel filling the crater in Elysium Planitia.

After that, I headed over to the Titan session to hear a talk by Ralph Lorenz about waves on Titan lakes. Most of what we know about the surface of Titan, including the presence of liquid hydrocarbon lakes, is based on radar images from Cassini that measure roughness. The lakes show up as perfectly smooth (and therefore dark) surfaces, which is weird because radar images of lakes on earth usually have slight roughness due to waves. On Titan the gravity is lower, so you would expect bigger waves. It’s possible the lack of waves is due to the viscosity of the lakes, which might be increased by bigger “tar-like” molecules dissolved in the thinner ethane and methane, but it might also be due to a lack of wind. The Cassini mission will be watching as the seasons at Titan change to see if the wind changes and kicks up any waves.

A (suggestively colored) radar map of lakes on Titan.

I did a lot of session hopping on Thursday! The next stop was the astrobiology session. Oleg Abramov presented some results of his investigation of what intense impacts might have done to early life on the earth or Mars. He found that even during the Late Heavy Bombardment, the crust is not sterilized by the impacts, and in fact it might be more habitable for early life because impacts deliver organic molecules and cause widespread hydrothermal activity!

The talks I was really interested in were two talks on the magnetite crystals discovered in the famous ALH84001 meteorite. I posted a while back about a new paper that claims these crystals are evidence of life on Mars, and these two talks were focused on the claim. The first talk, by Allan Treiman gave some good background on the debate over whether ALH84001 preserves evidence of life and then addressed some of the new claims about the magnetite crystals. He said that most of the attributes of biological magnetite crystals, such as their size, lack of flaws, and precise crystal structure were not observed in the ALH84001 crystals. The big question is why the crystals are so pure. Allan argued that you can get pure crystals just from the heating of iron carbonate, which is found in the meteorite.

The following talk was by Kathy Thomas-Kleptra, whose paper Treiman was responding to. She showed that Treiman had probably made an error in calculating the breakdown temperature for iron carbonate. She also pointed out that the crystals are found in carbonates without much iron and that there is no graphite observed, but it is also a byproduct of heating the carbonates.

I don’t know enough about petrology and geochemistry to know who is right here, and I was very disappointed that both Kathy and Allan used up all of their time talking, so there was no chance at all for questions! I wasn’t the only one. When the moderator said that there was not time for questions and that they had to get on with the next session, most of the room groaned and protested. But alas, the talks pressed onward.

Biogenic magnetite crystals inside a bacterium one Earth.

I zipped back over to the Titan talks in time to catch the end of one pointing to features that they claimed were “deltas” in one of the lakes. I was very skeptical of this because the quality of the radar images is so low. What they avtuall observe is a dark branching channel that ends at a peninsula in one of the lakes. That’s not evidence for a delta in my book. This talk made me realize how spoiled I am with HiRISE, CTX, MOC and other high-resolution data on Mars!

Finally, I stopped by the asteroid session for two talks. The first was by Dan Scheeres and he talked about the role that tiny forces might play in holding asteroids together. He showed that Van Der Waals forces, normally ignored for all but the tiniest particles, actually might be important in holding particles together in asteroids. He made the analogy to powders like flour or cocoa powder on earth. These can clump together and when they are stressed the form fractures even though they are made of loos grains. The same thing might happen on a much bigger scale with the gravel and boulders in low-gravity asteroids!

It's possible that the fractures in objects like Phobos are more like the cracks you see in flour than like cracks in a solid, fractured rock.

The last talk I caught on Thursday was by my friend Seth Jacobson, who showed some simulations of asteroids that spin so fast they break apart. He showed that the ratio of sizes between the two bodies make a big difference in how the binary asteroid evolves. In some cases, the secondary asteroid even swings so close to the primary that it splats apart and forms a short-lived three-body system!

How to Cook Primordial Soup, with Julia Child

February 1, 2010

(Courtesy of Amanda Bauer’s blog, astropixie)

How to cure the Avatar Blues

January 12, 2010

I was innocently browsing through my twitter list yesterday when I came across this article on CNN. The gist of it is that many people are experiencing depression after watching Avatar because the fictional world depicted is so beautiful and amazing that life back here on earth seems drab and boring.

Many people have responded to this story with shock and derision, and this definitely hints at some pre-existing issues for the folks who are feeling suicidal after watching a sci-fi film, but it also concerns me for another reason. It suggests a troubling lack of knowledge about the real world.

One person quoted in the article said: “When I woke up this morning after watching Avatar for the first time yesterday, the world seemed … gray. It was like my whole life, everything I’ve done and worked for, lost its meaning. It just seems so … meaningless. I still don’t really see any reason to keep … doing things at all. I live in a dying world.”

This really bothers me, because despite all the nasty things that humans have done to the world, it is a far cry from a dying world! (And if our world really is “dying” then shouldn’t we be out there trying to save it rather than despairing?) I can tell you this: studying other planets makes you realize that Earth is a paradise. And believe it or not, many of the “creative” flora and fauna in Avatar are based directly on living things here on Earth, past or present.

Remember those glowing spiral “plants” that Jake taps, causing them to curl up into their stem in the blink of an eye? They’re real! They exist in miniature in coral reefs around the world as “christmas tree worms”.

Jake Sully walks in awe through a glade of giant christmas tree worms.

Actual christmas tree worms in Bonaire.

What about those glowing mushrooms that he plays like drums? Yeah we’ve got those. Again, much smaller, but similar.

Glowing mushrooms really exist too!

And of course the seeds of the Tree of Life are obviously based on real-world jellyfish. James Cameron is a guy who knows all about the weird living things on our planet. Heck, have you seen his documentary “Aliens of the Deep”? It’s pretty obvious where he got some of his inspiration for the creatures in Avatar!

A deep-sea jellyfish from Cameron's "Aliens of the Deep".

Ok, but what about the sweet dragon-like creatures that they ride? I think people would notice if we had those flying around, taking out our helicopters and planes! Well no, they don’t exist now, but go back to the mesozoic and there are plenty of flying creatures, including this one which was taller than a giraffe when on the ground:

And how about good old Quetzalcoatlus, with a 30 foot wingspan?

Quetzalcoatlus had a wingspan comparable to some airplanes. The silhouette should look familiar to anyone who has seen Avatar...

So that’s the biology, but what about the moon itself? What about the floating mountains? The spectacular rock formations? Well, habitable moons probably do exist, and there are astronomers searching for them right now. Floating mountains would be rather difficult, but superconductors do, in fact, allow things to levitate. Take a look at Joe Shoer’s post about Avatar’s floating mountains if you don’t believe me. And the rock formations? Well, Earth doesn’t have arches of rock following magnetic field lines like iron filings, but we do have some pretty spectacular stuff, like caves full of giant crystals:

Spectacular crystal formations? Yeah, we've got that.

My point is this: yeah, it’s a shame that Pandora isn’t real. I was sad too when the movie ended and the credits rolled. But the world we live in is just as amazing. You won’t get rid of the Pandora blues just by watching Avatar endlessly, or running out and getting the Avatar video game. But much of what was in the movie was based on real things here on Earth. Many of the photos I’ve shown here are relatively recent discoveries. There is plenty of wonder to go around and plenty more to discover. And if you get tired of Earth, there are other planets in our solar system. Tired of those? Check out exoplanets. Still not enough? Head into the realm of astrophysics and you’ll never get bored. And for those longing to live like the Na’vi there are options too. Anthropologists regularly study native cultures and learn their ways. Or you could become an archaeologist and learn about past cultures by studying their artifacts.

Still not enough? Well, then instead of living in someone else’s fictional world, why not make your own? Become a science fiction or fantasy writer and see if you can do better than James Cameron. Who knows, maybe someday people will see your world and long to go there too.

Avatar’s vivid world should not be a source of depression, it should be a motivation to seek out (or create) the beautiful and the interesting and the fragile in our own world, to study and learn from it, and to preserve it so future generations can experience the wonder as well.

Avatar Review

December 21, 2009

Avatar was spectacular. I always worry when a movie gets as much hype as Avatar did that in the end it will not live up to expectations, but Avatar delivers. It is probably the most beautiful movie I’ve ever seen and one of the best sci-fi movies in recent memory. And even better, it is not a sequel or a remake or based on a comic book or novel. It is genuinely original, an unfortunate rarity these days.

The story follows the crippled marine Jake Sully (Sam Worthington) as he arrives on the tropical moon Pandora as part of a human mining operation. The indigenous people, the Na’vi, are not too happy that the humans are bulldozing their forest paradise, and the humans aren’t too happy that the Na’vi live atop the richest ore deposit around. Jake was brought in because he is the genetic match to his dead twin brother’s avatar: a lab-grown Na’vi body that can be remotely inhabited and mind-controlled by a human operator.

His mission is to learn about the Na’vi and convince them to move away from the ore deposit, but the more he learns the more he realizes that his species may not be the good guys.

If the story sounds familiar, it is. Dances with Wolves, Shogun, and many other stories follow the same pattern, with a main character “going native” and switching loyalties as they learn about a supposedly backward culture. It’s an extremely effective story, and I’m a sucker for it every time. So yes, Avatar is Dances with Wolves in space, with strong overtones of Fern Gully and Star Wars. But frankly, that’s fine with me. I like those movies. And despite its similarities to other stories, Avatar manages to shine. Or should I say, bioluminesce?

I’m referring, of course, to the glowing plants and animals of Pandora. Avatar succeeds because Pandora is one of the most well-crafted, beautiful and immersive fictional worlds I’ve ever seen. The plants and animals are bizarre and unusual, but plausible. Much of the vegetation is based on sea creatures on Earth, giving it an alien but familiar feel. The animals have six limbs instead of four, but they move so convincingly the extra legs make perfect sense.

And then of course, there are the Na’vi. The motion-capture technology used to turn human actors into ten-foot-tall blue aliens is perfect. Every facial expression and subtle movement is captured, making the Na’vi feel completely real and convincing. Done poorly, the Na’vi could have fallen squarely in the uncanny valley, either creeping people out or making them laugh. Cameron has managed to jump over that valley, and his blue aliens are in many ways more real than the human actors in the movie. Their language is completely convincing too, and it’s no wonder since it was designed from scratch by a professional linguist.

Believe it or not, this is CGI.

Of course, I have to say a little bit about the science of the movie, because that’s what I do. For the most part, this is a science fiction movie where the science is behind the scenes, and I think that was a wise move. We are never lectured about how exactly the avatars work because that’s not important. We learn precisely what is needed for the story and no more.

I already mentioned the alien life forms, and these are excellently imagined and always convincing. One minor nitpick is that the Na’vi have four limbs, just like humans, but all the other large creatures on Pandora have six limbs. I understand the need to make them familiar enough for the audience to sympathize, but it would make more sense biologically for them to have the same body plan as the other creatures in their world.

As far as the moon Pandora goes, we aren’t shown much. It orbits a jupiter-like gas giant, and has a thick atmosphere that humans can’t breathe. This atmosphere is a perfect example of the attention to detail in Avatar. When Jake arrives on Pandora and the door to the shuttle opens, there is a brief shimmer in the air as the breathable gas inside the ship mixes with the moon’s atmosphere. Anyone who has mixed a gin and tonic or swam in an estuary where salt water and fresh water mix is familiar with this shimmer as fluids of slightly different densities mix.

The issue of day-length is not mentioned, but it seems to be similar to an earth-day. This would mean an orbit likely too close to the planet to be stable, but this is a very minor detail.

The most obvious bad science in Avatar are the floating mountains. Don’t get me wrong, these are awesome! The movie wisely doesn’t try to explain in too much detail, but it is implied that powerful magnetic fields are involved. It’s obvious that this part of the movie is fantasy, but I just have to say, I wish they didn’t call the area with the high magnetic fields the “flux vortex”. It made me flinch every time. I loved the rock formations that followed the magnetic field lines though. Implausible to have such strong fields, but very cool. I will add that powerful magnetic fields would be quite handy for a moon close to a gas giant, handily deflecting the powerful radiation that would otherwise strip away the atmosphere and damage life on the surface.

Bottom line, Avatar was fantastic. Yes the story was familiar, and yes some of the dialog was cheesy, but none of that matters because Avatar is a chance to visit Pandora. The acting is good, but the real star of this movie is the world. It is gorgeous and exotic but the attention to detail and the unprecedentedly effective use of 3D technology makes it feel utterly real. Avatar is nearly two and a half hours long, but at the end, as the credits rolled, I was sad that it was over. I wanted to go back and walk the bioluminescent footpaths of an alien forest one more time. I wanted to fly between floating mountains again. And yes, I wanted to be blue.

Go watch it. You will too.

AGU 2009: Day 3 – Astrobiology and Society

December 20, 2009

Wednesday was full of particularly interesting stuff: in between the Venus and moon talks there was also the Sagan lecture and an afternoon session about astrobiology and its implications in society.

The Sagan lecture was given by Tori Hoehler, a scientist at NASA Ames. He discussed the fundamental thermodynamics behind life, and showed that even if alien life relies on completely different molecules, there are basic requirements, such as the availability of free energy, that should be universal because they are rooted in the way the universe works. To paraphrase, he said: Life must evade the decay into equilibrium by reproducing extremely low probability results. There is a lot of thermodynamics behind this, but everyone has common sense experience with it. The world tends toward entropy unless energy is applied. Just take a look at the nearest college dorm room.

The DNA molecule is an incredibly complicated "aperiodic crystal" that is highly unlikely to form spontaneously. Energy is needed to make unlikely things like DNA assembly happen.

Hoehler used real world examples showing that living systems, be they simple bacteria colonies or all the complex cells involved in a human being, tend to grow until they are using all of the free energy available. There is a certain minimum amount of energy required to add a new piece (such as a cell) to the system, so the system can’t grow unless that amount of energy is available.

Tori concluded with a quote from Carl Woese: “Organisms are resilient patterns in a turbulent flow.” Hoehler argued that when thinking about biosignatures, we need to look at the fundamental requirements of any life. Regardless of its specific chemistry: energy use is the ultimate biosignature.

Later in the afternoon on Wednesday there was a really thought-provoking section about the societal implications of astrobiology. One of the first talks that I saw in the session was by David Koch, discussing the Kepler telescope. Kepler is a mission designed to stare at a single large patch of the sky for years, monitoring the brightness of hundreds of thousands of stars. Why? Well, occasionally a star will have planets that orbit in just the right configuration so that they “transit” – pass between their star and Kepler’s detector – blocking out a tiny fraction of the star’s light. Kepler was specifically designed so that it will be able to detect even the tiny dip in starlight caused by an earth-sized planet passing in front of a sun-like star. Koch showed an example of Kepler data, as compared with ground-based data of a star with a known transiting giant planet. The ground-based data was very noisy because of the turbulent atmosphere, but the Kepler data was so good that it looked like a solid line rather than a series of data points. The Kepler data was good enough that you could see the change in brightness as the planet went through phases like the moon. Koch also showed a tantalizing signal from a binary system that may have a planet orbiting both stars, much like everyone’s favorite binary-orbiting plant, Tatooine.

Sunset on a world orbiting binary stars. However, the planet detected by Kepler is likely a gas giant, not a rocky world like Tatooine. Image copyright Lucasfilm Ltd.

Next, Jacob Haqq-Misra, author of the new book “Planetary Messenger”, talked about how life and climate are intertwined. One example of this was the early climate, when the only life was methane-producing bateria. Methane is a powerful greenhouse gas, and so the global climate would warm rapidly with a world full of methane-making critters, but methane also undergoes chemical reactions when exposed to UV light and forms a thick haze. Just take a look at present-day Titan for proof of this! The haze would eventually get thick enough to cool the planet’s surface, balancing out the warming due to methane and preventing the planet from overheating.

Of course, then along came oxygen-producing life, which destroyed the methane and organic haze and poisoned most ofther forms of life, relegating them to dark anaerobic places like the stomachs of cows. Haqq-Misra also pointed out that the modern climate is pretty unusual: we have ice caps. Models suggest that Earth typically is quite warm, with no ice caps even at the poles, or it enters a “snowball” phase, where everything freezes up and ice extends down to the equator. In either case, live persists, and it may be the action of life that nudges the Earth out of these extremes. Haqq-Misra’s bottom line was that life is extremely resilient and can have a powerful effect on climate. Modern-day climate change could have serious consequences for humans, but life in general will adapt in the long run. “We’re not saving the world, but ourselves,” he said. It’s not quite that simple, since many species other than humans are threatened by climate change, but his basic point still is valid.

The Earth likely oscillates between a “snowball” and “hothouse” climate, with life-driven cycles, particularly the CO2 cycle, playing a major role.

The last few talks in the session strayed from science into social science and philosophy. Linda Billings spoke about the relationship between astrobiology and culture. She pointed out that astrobiology has gained credibility from large agencies like the National Research Council, and has always been popular with the public, but that the public and scientific perception is somewhat different. The public tends to assume ET life is common and like us, while science focuses more on extremophiles and the origin of life. One thing that I wish she had addressed a bit more was whether the public perception of ET life is necessarily a bad thing. Yes, there are powerful misconceptions to work against, but the public’s interest in astrobiology makes it a perfect “entry point” into all sorts of science!

The last few talks in the session considered the interplay between astrobiology and religion. Richard Randolph, presenting for Ted Peters who couldn’t make it, showed the results of a survey asking the question “Could the confirmation of another civilization in the universe cause a religious crisis?” The findings were not that surprising: Religious people did not think it would cause them to lose their faith, but were somewhat more likely to think that other people might lose faith. Non-religious people were almost all sure that such a discovery would cause religious people to have a crisis of faith. I would like to see the results of the survey if the word “crisis” was removed from the questions. I suspect more people would be willing to admit that discovering ET would make them think hard about their religion, but that they wouldn’t consider that a “crisis” of faith.

Next, Connie Bertka talked about astrobiology and evolution. She said that we really can’t avoid discussing science versus religion because, to paraphrase, “nature and creation are no longer purely in the theological domain”. Thus, she said that astrobiologists should encourage dialog with religious people. I think it’s a fine line to walk. We don’t want to give people like creationists legitimacy by engaging them on equal ground, but we equally can’t just avoid the interface between religion and science.

Finally, Richard Randolph discusses the Christian ethical implications of astrobiology. He asked two primary questions: What ethical obligations would Christians owe non-intelligent extraterrestrial life? and Is there a Christian obligation to spread life in the universe?

Based on his reading of Genesis, Randolph extended the common interpretation of humans as “stewards” or “god’s authority on earth” to extraterrestrial life. I was disappointed that he so obviously avoided talking about the elephant in the room for this issue though. Sure, the bible gives us stewardship over extra-terrstrial microbes. He even said that predation, in moderation, is “acceptable” just as it is for life here on earth. That’s all well and good. But what happens when we find aliens who are as smart or smarter than us? Does the bible give us stewardship over them? Permission for “predation in moderation”? Why would a creator make mere humans stewards over equally intelligent or possibly much more advanced species?

Ok, we are stewards over alien microbes, but what if we meet these guys?

As for the obligation to extend life in the universe, Randolph said that, since the bible repeated describes creation of life as “good” then by extension, spreading that life elsewhere qould also be good. Thus he said that there was “qualified affirmation” of the assertion that we are obliged to extend life elsewhere. Again he dodged a big question: do we extend terrestrial life at the expense of possible more primitive extra-terrestrial life? (a.k.a. when is it morally justified to terraform Mars?) What if spreading terrestrial life is at the expense of more advanced ET life?

It was refreshing to have these more philosophical talks after so much science. I may not have agreed with much of what Randolph said, but it definitely made me think, and it was a good reminder that science does not operate in a cultural vacuum.

Life on Mars?!

December 1, 2009

On August 6, 1996 NASA announced that scientists at the Johnson Space Center had found evidence for life on Mars, and everybody went crazy.

Yesterday, NASA announced two new papers by the same scientists at the Johnson Space Center claiming that they have found strong evidence of life on Mars. For the most part, there hasn’t been much of a reaction. No presidential press conferences, and only a few headlines. What gives?

Well, I suspect it is partially due to the fact that one of the papers is very long and esoteric, but even more this might be a case of “the boy who cried wolf”. This is the same research group saying, on the face of it, essentially the same thing more than a decade later. Still, these are respected scientists, and the fact that they are standing by their claim after all this time means they must be pretty confident. That’s why I decided to take a look at the two papers in question.

The first paper is a 47 page beast entitled “Origins of magnetite nanocrystals in Martian meteorite ALH84001“. And really, that’s what it is about. Biology only makes a few brief cameo appearances; for the most part this paper meticulously describes the study of the magnetite crystals in the famous ALH84001 meteorite. The significant thing about this paper is that they suggest that the magnetites could not have formed by alteration of the materials in the meteorite.

Magnetite crystals (highlighted in pink) can be formed by some types of bacteria on Earth. Source: NASA

Back in 1996, magnetite crystals were proposed as evidence of martian microbes because some types of terrestrial bacteria form perfect, pure magnetite crystals in their guts. However, other scientists proposed hypotheses by which the magnetites could form when carbonate minerals in the meteorite were heated. This latest paper disagrees with that idea, pointing out that the magnetites in the meteorite have a completely pure composition, but the carbonate, from which they are supposed to have formed, has other elements in it that don’t appear in the crystals. The authors argue that since the crystals don’t show those contaminants, they must not have formed from the carbonates. Here is their conclusion:

We suggest that the majority of ALH84001 magnetites has an allochthonous origin and was added to the carbonate system from an outside source. This origin does not exclude the possibility that a fraction is consistent with formation by biogenic processes, as proposed in previous studies.

There you have it! It is possible that a fraction of the magnetite crystals are not inconsistent with life on Mars!

Ok, so that’s not exactly a resounding “yes”. I think the authors were being very conservative in this paper. In a companion paper entitled Life on Mars: New Evidence from Martian Meteorites, they show their feelings a little more. They give a concise and fairly readable summary of their original hypothesis and the subsequent alternatives that people have proposed and which in turn have been addressed. They also provide an easy-to-understand pdf slideshow summarizing their findings.¬† At this point, people seem to agree that the carbonates in the martian meteorites formed on Mars, as did the few organic molecules detected in them. With the magnetite paper, the authors consider the various hypotheses about creating magnetite by heating to be disproved, leaving an organic origin as the best explanation.

They point out that on earth, pure magnetite crystals with the specific shape and properties of the ones found in ALH84001 would be considered definite biomarkers:

The unique properties of these magnetites (elongated along the c-axis, single domain grain size, extremely pure Fe oxide, tightly sorted grain size distribution) remains a suite of properties absolutely unique to magnetotactic magnetites on Earth.

The “Life on Mars” paper also shows lots of examples of electron microscope images of “biomorphs” in multiple Mars meteorites. Biomorphs are like mini-fossils. Some of them might be actual preserved remnants of single-celled organisms, while others are pits and textures formed by long-gone bacteria colonies. Picture them as the microscopic equivalent of finding fossil dinosaur tracks. They also make the case that the observed biomorphs show influence on the shapes of the minerals of the meteorite, suggesting that they formed long ago on Mars rather than more recently on Earth.

Biomorphs from Storrs Lake, Bahamas and the Yamato 000593 mars meteorite from Antarctica. Source: NASA / McKay et al., 2009

I’ll admit, a lot of their biomorphs look like bacteria, and they show examples of biomorphs from Earth that look quite similar.¬† But many of their examples don’t look like much to me. Granted, that may be due to an untrained eye and overactive skepticism.

Biomorphs from two Mars meteorites (top and right) and a terrestrial basalt (bottom left). NASA/McKay et al., 2009

From the McKay et al. paper: "Closeup view of a Nakhla biomorph partially embedded in an iddingsite matrix. Clearly, these two phases were formed at the same time; their texture shows the influence of the biomorph form on the shape of the iddingsite. We interpret this biomorph as the remains of a Martian microbe."

So, what does it all mean? Is this evidence for life on Mars? I give it a definitive “maybe”. It’s clear that the debate is far from over, and I expect to see some interesting rebuttal papers in the next few years. There’s a fine line to walk here. If this really is evidence of life on Mars, we should be shouting it from the rooftops! But it is so easy to trick ourselves into seeing what we want to see that we have to be cautious. Carl Sagan summed this up nicely: “Extraordinary claims require extraordinary evidence.” Right now I think the evidence is not extraordinary, but it may be getting there.

ResearchBlogging.org
Thomas-Keprta, K., Clemett, S., McKay, D., Gibson, E., & Wentworth, S. (2009). Origins of magnetite nanocrystals in Martian meteorite ALH84001 Geochimica et Cosmochimica Acta, 73 (21), 6631-6677 DOI: 10.1016/j.gca.2009.05.064

David S. McKay, Kathie L. Thomas-Keprta, Simon J. Clemett, Everett K. Gibson, Jr., Lauren Spencer, & Susan J. Wentworth (2009). Life on Mars: New Evidence from Martian Meteorites Instruments and Methods for Astrobiology and Planetary Missions XII http://www.nasa.gov/centers/johnson/pdf/403089main_7441-1.pdf


How Habitable is the Earth?

November 4, 2009

491px-Habitable_zone-en_svg

Charlie Stross has an interesting post on his blog that asks the question “How habitable is the Earth?” He goes on to conclude, through a great discussion of the evolution of our planet, that the fraction of time that the earth has been habitable to humans is a tiny sliver of the time the Earth has been around, and that furthermore, much of the earth is not habitable for humans because it is water or ice or mountains. If much of our planet, even now, is not habitable, he argues, what hope is there of finding other habitable worlds out there in space?

It’s an interesting discussion, but I find it somewhat misleading. It makes the rather large assumption that for a world to be considered habitable, a human would have to be able to survive for 24 hours, naked, on the surface. Ok, that’s one definition of habitable. But if you are postulating that these humans are capable of interstellar travel, it seems like you might make allowances for the use of clothing and the ability to build shelter. After all, we’ve known about those ones for a while. You could go even further and suggest that these humans might be able to alter the air they breathe, either through individual gas masks, or on a planetary scale. We used CO2 scrubbers on the Apollo missions to make the air breathable, maybe that would work on a planet with otherwise unbreathable air?

I think he’s fundamentally right in terms of human habitability: the likelihood of a planet being perfectly attuned to humans is extremely low. We evolved to live on Earth and nowhere else. We are going to have to make some adjustments to ourselves or our environment to live anywhere else.

The problem is that he then extrapolates and suggests that this might explain the Fermi paradox (aka. if there are so many stars and planets out there, why haven’t we heard from any little green men?). But that is completely off-base! He is essentially saying that, because humans evolved to live on Earth and nowhere else, it is unlikely for anything else to be living out there because there are likely few earth-like places. That does not follow. There could be aliens out there that are completely happy on their planets that would be instantly lethal to us. And it’s entirely possible that if they set foot on Earth they would find it a very hostile and uninhabitable environment (and not just because of the terrified earthlings).

Anyway, it’s an interesting article. Go take a look.

And speaking of interesting articles, have you gone and voted for my MSL: Mars Action Hero article over at scientificblogging? I’m one of the finalists for their science writing competition, so take a look and vote for me if you like it. To see the other entries, click here. Feel free to vote for as many as you like, and remember you can vote daily until the 23rd!

 

Disney’s “Mars and Beyond”

September 12, 2009

I just stumbled across this awesome Disney cartoon from 1957 over at the Tor.com blog. It’s worth watching just for the various bizarre aliens, but is also surprisingly informative about the history of astronomy, the origin of earth and life, and our fascination with life on Mars. Also note how they call galaxies “island universes”.


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