I would like to make this post a call to arms of sorts to all geobloggers and internet-savvy geologists out there to help with something. This particular page, Wikipedia’s entry on the mantle, is an absolute shambles. Not only are things like the Mohorovičić discontinuity only mentioned in passing without much description:

The top of the mantle is defined by a sudden increase in seismic velocity, which was first noted by Andrija Mohorovičić in 1909; this boundary is now referred to as the “Moho.”

(The page on the Moho is equally as vauge), but the figures, links and some of the references and suggestions in this page are simply stupid. Look at this bit of the extremely brief section on temperature:

Modern observations suggest that the mantle is cold.[15][16][17][18][19]
The mantle of Mars is also cold.[20]
This has very serious implications for those who believe the mantle is convecting hot fluid.

That has a very serious whiff of the EEdiots about it. Especially considering that every single reference given about the “cold mantle” is either in regards to an underlying section of the equatorial Atlantic MOR being colder than expected, or other areas of other MORs or spreading regions being cooler than expected (for the record, references 16 and 17 are the same). Not a single one of those references suggests the mantle is cold. The reason being that the mantle isn’t “cold” (whatever that means anyway, cold compared to what? Very unscientific). Any layperson reading this page would, however, be left with the impression that there’s serious debate regarding whether the mantle can flow at all.

I hereby kindly request that anyone out there with sufficient expertise in the mantle or associated sciences to please help in righting this travesty. I’m not asking for this to be done today, but over the next year we should endevour to pretty much rewrite this entire Wikipedia entry (lest the EEdiots take it upon themselves to do it for us and misinform the public even further). Wikipedia is fickle, however, and the formatting can be difficult to master, so getting a grasp on it now would be advantageous if you intend to contribute.

I’ll be doing some of my own research and clean-ups, but it’d be great if other concerned parties could help out too. After all, we blog about our science because we want to inform the layperson about how cool it is and to advance public awareness. Ensuring the go-to website for basic scientific facts is accurate can only help our cause.

This week’s episode discusses hidden mountains in Antarctica, bacteria living high atop the Andes, panspermia and extraterrestrial life and more.

Participants (links in brackets are Twitter feeds)

Chris - goodSchist (@yorrike)

Chris –  Highly Allochthonous (@allochthonous)

The Gamburtsevs Mountain Range and Antarctica

The BBC News article “‘Ghost peaks’ mapped under ice” is a nice summary of the story. New Scientist article has additional information in the article “Alpine mountain range revealed beneath Antarctic ice.”

And as always, there’s a little more information at Wikipedia on the GamBurtsevs Mountain Range.

Here’s some information about Lake Vostok.

And you can read about the International Polar Year at Wikipedia.

Extremophile Bacteria at the top of the Andes

Have a read of Science Centric’s Article “Earth’s highest known microbial systems fuelled by volcanic gases.”

NASA’s Kepler Mission

There’s the Wikipedia page on Kepler and the NASA’s official Kepler Mission page too. Plus there’s an example of the mass media misinterpretation from the BBC.

And Venetian resurfacing I was talking about is detailed  in this interview with David Grinspoon “Venus (and Earth) Resurfaced in a Single Catastrophic Event?” and in the paper Catastrophic Resurfacing and Episodic Subduction on Venus from Science Direct. This episodic resurfacing is still up for debate, though, and The Imperial College in London has a counter view.

Exbiology, Panspermia and Planetary Geology

Titan is Saturn’s moon with methane oceans.

Europa is the Jovian moon (beware the obelisk).

You can read about the Dawn Mission at NASA’s official site, or there’s the Wikipedia entry.

My article on Ceres, Dawn and (no) Panspermia (containing information on Ceres, 4-Vesta, the HED meteorites and the Murchison meteorite). And the offending article on The Universe Today.

There’s information about the bacteria on the Moon

Dave’s article on resurrected Eocene yeast and the resulting beer.

The Allan Hills 84001 was the one with the bacteria-looking inclusion in it.

Mars had recent running water and there’s Google Mars to have a look at too.

del.icio.us/podclast

We have a del.icio.us account which can be found at http://del.icio.us/podclast. All the web pages and resources we’ve found and used in the discussions on the podclast can be found here. A convenient way to browse per episode is to go to, for example, http://del.icio.us/podclast/episode8 (for this episode).

If you find a link to a topic that you’d like to hear discussed on the podclast, or have a link to a topic that’s already been discussed, you can add links to the podclast page through your own del.icio.us account.

When saving a link, include the tags for:podclast and episodeX (where X is the episode number – for example episode8). You can add more than one episode tag if the link applies to multiple episodes.

Next Episode

We like to have a new episode of the podClast every fortnight, so the next episode will be recorded on Sunday the 22nd of March at 2000 GMT.

Contributing

If you’re keen to hear a specific topic talked about, or would like to join the discussion during the next episode, either leave a comment below or email chris [the at symbol] goodschist.com. You’ll probably also do well reading the details on joining the podclast. If you don’t have the time to join us but would like to contribute a 3-5 minute audio clip to the show simply record it, make sure it’s an mp3, and send it to the address above.

Credit

The intro and exit music was Roots Fi Cool by Burning Babylon.

Text Addresses

The post that accompanies this podcast can be found at http://www.goodschist.com/2009/03/12/the-podclast-episode-8/ or http://is.gd/n2PW and an archive of all  podClasts can be found at http://www.goodschist.com/category/podclast/

Another important part of the Dawn mission will be swinging passed 1 Ceres (Ceres for short), the largest body in the asteroid belt, but the smallest identified dwarf planet in the solar system. There’s strong evidence Ceres contains a lot of water. The implications of water on an extraterrestrial body need not be repeated here, I’ll assume you’ve jumped to the same hope that some in the astroblogosphere have: life! The source of the panspermia that seeded the Earth!

This brings me to one of my major annoyances with the subject of panspermia. Don’t get me wrong, I think the idea is fascinating, and the prospect of interplantary geographical isolation and it’s evolutionary prospects makes me giddy. But the mere prospect of Earth being seeded from a source within the solar system just seems plainly ridiculous, and frankly, verging on the fantastical. Let me explain.

The Murchinson meteorite is a carbonaceous chondrite which landed near the town of Murchison in Victoria, Australia on the of 28th of September 1969. Murchison and its associated CM-class of meteorites are incredibly important because in addition to the normal treasure trove of mineralogical gems (some of which are literally gems) you’d expect from a carbonaceous chondrite, Murchison contains something very unusual: amino acids. The particular amino acids are not a form of contamination from Earth – the living systems on Earth which produce amino acids have a heavy preference for “left-handed” molecules (see the article Meteorites Made Life Left Handed), while the acids from Murchison have a left-hand/right-hand ratio of ~55/45 t0 60/40 (and that slight difference may have pushed life here to be left handed, see the aforementioned article for details). It’s therefore reasonable to assume that no living system has gotten in there and biased the handedness of the molecules present (at least, that’s extremely unlikely).

Murchison, being a carbonaceous chondrite, is from a parent body (we’re not sure which), which was not big enough to melt and differentiate. This implies that the amino acids we find in Murchison were formed either in space, or in a very, very low gravity situation. Therefore, amino acids, the building blocks of DNA, could very well form in space, away from any biological systems, and then rain down on planets during the formation of a solar system. So the building blocks of DNA can form in space without life and rocks containing these chemicals are still raining down, to this very day on Earth.

Why then do we require a hypothesis that Earth was seeded by already-formed life from somewhere else? This is the exact same infinite-regress problem one arrives at when debating the existence of a god – if the creator created everything, who created the creator? What is wrong with the concept that life formed, originally, on Earth, from the basic ingredients? Earth had the conditions right – liquid water, and therefore a warm environment, a protective magnetic field, a thick atmosphere (but no too thick), also protective from the nasty radiation of space, and a good, steady, consistent orbit. Ceres too may have had similar conditions 4.55 billion years ago, and it too would have had amino acid-laden meteorites raining down on it prior to and during the late heavy bombardment. If you’re willing to accept that life formed on Ceres, Mars, Venus or any other body from the same raw ingredients the Earth was receiving, but that life  THEN had to be transported to Earth, why not cut out the middle-planet and concede that life probably formed on Earth?

The hunt for extraterrestrial life will continue, and will remain exciting. Should I be privileged enough to see its discovery in my lifetime, I will have witnessed one of, if not the most important scientific discoveries ever. What I object to is needless scientific hypotheses gaining traction in the public mind when there’s absolutely no evidence to support them. Yes, panspermia is an incredible idea, and yes, exerts wildly pontificating about its mechanisms and implications is important, but in my opinion it is far more important to study and concentrate on the origins of life from those basic, and it would seem abundant, ingredients, and once proven, continue to unravel more mysteries of the mysteries of the solar system and beyond.

In short, to answer Universe Today’s article title of “Life on Ceres: Could the Dwarf Planet be the Root of Panspermia?” No, probably not. And what’s wrong with the idea of life starting here?

(note: if you’re reading this in an RSS reader, you’ll probably be missing out on the artwork I did for this post. Make sure you click through to get the full visual experience)

Venus

A world of beauty, or a galactic volcano in sediment’s clothing? Only Hypocentre of Hypo-thesis can distil the ancient doom of the Cambrian on Venus!

Something catastrophic may (or may not*) have happened during the Cambrian on Venus.

Maria Brumm of Green Gabbro gives cibophobics another reason to fear cakes, as she compares a plum clafoutis to Venetian impact craters in What Planet is my Clafoutis From?

Like so many moments of culinary inspiration, this plum clafoutis is nothing like what I was thinking of prior to actually wandering into the kitchen to make dinner.

Earth

The Earth. A pale blue dot suspended in a sunbeam. The target of jealous and tyrannical alien invaders. And impacts! Geology Happens relays the shocking facts about Impacts from Space!

I am cheating somewhat since my post is about a phenomenon that happens here on earth as well as in space. That is the idea of impact craters.

Tuff Cookie from Magma Cum Laude tells of impactors too in Rocks in from space. Could this be the first wave of yet another alien invasion?

Anyway, spending so much time at the museum – around the meteorites, among other things – was one of the reasons I became a geologist.

Mars

The constant, unending invasions from Mars during the 1900s should have been horrifying enough, but now SamStag from cryology and co. makes us quiver in fear at the prospect of Rockglaciers from Mars !!! Will the red menace ever be defeated!?

From all planets and minor objects of the solar system, most similarities to features of periglacial regions on Earth can be found on the red neighbour – Mars.

And if the thought of glacial processes on Mars didn’t send shivers down your spine, Brian from Clastic Detritus informs us of Fluvial Deposits on Mars! Walk for your lives!

High-resolution mapping of planet surfaces (including Earth) from orbiting spacecraft is revealing the beauty and complexity of erosional and depositional landforms.

The Asteroid Belt

The inner Solar System could have bore five terrestrial planets. The smoldering remains of planet 4.5 are what make up the asteroid belt, where material unchanged since the dawn of the Solar System remains. Though there’s no perceived threat of alien attack from the asteroid belt, who can really be sure? Silver Fox of Looking for Detachment discusses Mining the Asteroid Belt, in what can only be described as a preemptive attack to deprive potential invaders of potential resources. Potentially.

But first off, mining in space – in the asteroid belt or anywhere else – is not likely to happen anytime soon, IMO. Numerous people, however, have been looking into it, perhaps at least as long as we have been actively exploring space, beginning with our 1960′s race to the moon.

Jupiter

The gaseous bully of the Solar System offers up intrigue for the bravest of volcanologists. And Dave Schumacher of Geology News gives us the terrifying details of Extraterrestrial Volcanism on Io! Will the space bound geo horrors never cease!?

What is all the lava that erupts on Io composed of? Scientists do not know for certain the composition of the lava, but based on spectrometer data, Io’s surface is covered with a mix of hot, basaltic or ultramafic silicates and a sulfur dioxide frost.

Saturn

The unfolding story of Titan should surely serve as a warning! Peter Polito over at Geology News regales us with tales of Titan Channels: What we know four and half years later.

One of the most fascinating things about the surface of Titan is that five years ago we knew nothing about it.  But with the arrival of Cassini and Huygens that has all changed.

Lockwood of Outside The Interzone also contemplates the channels of Titan and low temperature freeze-ray geology, as well as details of the moons of Enceladus, Europa and Miranda in A Fine Piece of Ice:

We knew there was a chance a chance of methane/ethane preciptation, we knew there was a chance of liquids on Titan. But the idea that dendritic drainage might form at 178 below zero Celsius never crossed my mind.

Pluto

Disregarded as a fully qualified planet, could the menace of an atmosphere make Pluto a body of geological interest? Yes! And Chris from Pools and Riffles heralds in the new threat of the Geology of Pluto.

The hardest thing about studying the geology of Pluto is the distance. Pluto is at a minimum 4.28 billion km from earth. A little to far for a rock hammer. At that distance, even satellites have problems.

The Entire Solar System

Cosmochemists (as I could claim to be), like the big picture. The REALLY big picture. Chuck at Lounge of the Lab Lemming tells us of the radioactive horrors that endured when the solar system was dragged kicking and screaming into the galaxy, in Isotope Park.

When’s the last time your non-geological friends told you their 6 year old loves ⁶⁰Fe?

The Entire Universe

MJC Rocks of Geotripper contemplates scarring the children of today with thought of the universe-sized scorpions and bears, but not as part of some sort of dome, in Done with Domes.

The ancients thought of the cosmos this way, and they made stories to go with the random arrangements of stars that formed bears and hunters and scorpions.

And speaking of space in its entirety:

You have read it. You cannot unread it. Stay tuned for more exciting geological tales in next month’s Accretionary Wedge. Your very survival could depend on it!

For those wondering, no I didn’t manage to get my thesis in on time. I’ve got a 4 week extension, though, so it’s not far off.

In the title comic book cover, illustrations of the Earth split in twain, the characters floating in space, and the terrifying martian are from various covers of the comic book series Mystery in Space and © DC Comics.

Just a reminder that posts for the Accretionary Wedge #13 are due this Thursday (or Friday), your time (25th or 26th of September). Check out the original post for submission details and get those little space themed articles rolling on in!

You may also want to check out the upcoming and previous hosts of the Accretionary Wedge here.

It’s my turn again to host the geoblogosphere’s blog carnival, The Accretionary Wedge. This month for the Wedges thirteenth edition the theme, as chosen by me, is:

Geology in Space (pronounced Geologeeeeee in Spaaaaaaaace).

Geology doesn’t just happen here on Earth, it’s happening everywhere there’s a small amount of silicates being drawn together by gravity. This month, give yourself a few hours, pick a body within the solar system, and tell the world about the geology that goes on there. You could talk about yardangs on Mars, the extreme tectonics of Venus, the enormous equaitorial ridge on Saturn’s moon Iapetus, what the HED meteorites tell us about 4 Vesta, or anything else that may tickle your geological interest.

The Earth is so huge and varied geologically, just think about what else is going on, on the other 7 planets and thousands of other bodies in the solar system.

I’ll be handing my MSc thesis (which deals with the formation of the solar system) in on the 25th of September, so that’s the date for everyone to get their submissions to me on the weird and wonderful things that have happened since. Either email me (chris (-then the usual symbol-) goodshist.com), or post a link in the comment thread of this post.

Happy writing!

Chondrites & Carbonaceous Chondrites

Figure 1. A slice of the NWA 2364 CV3 carbonaceous chondrite, with a white CAI visible in the top left. The CAI is ~5 mm across the longest axis. This is one of the CAIs I used for my MSc research. Click to enlarge.

Chondrites are ancient stoney meteorites and direct remnants of the processes that formed the solar system. Broadly ultramafic in composition, they contain mostly iron, magnesium, silicon and oxygen (Scott & Krot, 2004). They were originally named due to the high concentrations of chondrules, mm-sized spherical droplets of silicate glass with minor metal and sulphide contents. There are plenty of chondrules visible in Fig. 1, they’re the red/brown/black circles that make up a large portion of the meteorite slice. The important thing about chondrites is they have not experienced the alteration you’d expect where they part of a planet with sufficient mass to begin differentiating. That is, forming a crust-mantle-core configuration like the terrestrial planets.

The chondrite above is what’s known as a carbonaceous chondrite. The name carbonaceous chondrite is a bit misleading, as this class of meteorite are not universally rich in carbon. The defining property of these carbonaceous chondrites is that they contain concentrations of refractory lithophile elements, such as the Rare Earth Elements (REE), that are equal to or exceed that of the Ivuna-like sub class. That equal to part means that Ivuna is also classified as a carbonaceous chondrite.

Ivuna and Ivuna-Like Chondrites.

Table 1: Data on the types of carbonaceous chondrites. Adapted from Scott & Krot (2004) with additional data from Greenwood et al. (2004). Click to enlarge.

Ivuna was a witnessed “fall” which landed in Tanzania in 1938 as a single 705 g stone. As it was the first meteorite of its type classified, the Ivuna-like group (CI) is named after it.

The Ivuna group is comprised of the Ivuna, Orgueil, Alais, Tonk and Revelstoke meteorites, making up a total of ~3% of discovered carbonaceous chondrites (Table 1). Whether this is indicative of the true proportion of meteorites or not, is up for debate. Ivuna is reasonably fragile, and if a sample makes it through the atmosphere, it faces the prospect of erosion, due to the Earth’s helpful weather systems. The proportions of all samples shown in Table 1, therefore, could be indicative of the proportions of the particular types of meteorites, or simply indicative of the likeliness of each type to survive passage through the atmosphere and/or erosion before being discovered.

Ivuna has very low refractory inclusion (RI) and chondrule concentrations relative to other carbonaceous chondrites. Refractory inclusions include Calcium-Aluminium Inclusions (CAIs) and Ameboid Olivine Aggregates (AOAs).

Why a Sample with Solar Composition is Useful

The sun makes up a total of 99.8 % of the Solar System’s mass, a lion’s share of the material that constituted the original solar system. It’s therefore perfectly reasonable to assume the Sun is representative of the original composition of the gaseous pre-solar nebular the planets, plutoids, moons, meteorites and you and I formed from. And though you can make pretty good measurements of solar composition using spectral analysis, there’s nothing better than having a nice big chunk you can chip a little of into a mass spectrometer. This has the distinct advantage of allowing geochemists to determine the isotopic, in addition to elemental, composition.

Isotopes are important because the cloud the solar system formed from, was generated by a supernova or supernovae, generating huge quantities of stable and radioactive isotopes. Many people in the western world will have direct experience with some of these radioactive isotopes – Uranium and Thorium are the elements on which all nuclear power technology is built. So switching on a light in places is almost directly extracting power from a supernova.

Magnesium, for example, has 3 stable isotopes: 24Mg, 25Mg and 26Mg. The latter of those isotopes, in addition to being a stable isotope produced in supernovae events, also happens to be the daughter product, or the left over material, following the radioactive decay of the short-lived isotope 27Aluminium. 27Al has a half-life of ~700 KYr and when it decays, it produces heat, and lots of it. Knowing how much heat the pre-solar nebula cloud was producing, in addition to the heat-input from the young T-Tauri Sun, is important in understanding how refractory inclusions like CAIs, chondrites, planetesimals and eventually planets, formed. So Having a hand sample of the material that started it all, lacking the more volatile elements such as Hydrogen and Helium, of course, let’s us build a model for where and when things formed in the Solar System.

Figure 2: Generalised Rare Earth Element proportions in refractory inclusions, normalised to the bulk concentrations in Ivuna. Adapted from Taylor (2001). Click to enlarge.

Fig. 2 is a good example of the CI bulk composition being used as a standard. It shows generalised plots one should expect from the Rare Earth Elements (REE) in refractory inclusions, such as the CAI in Fig. 1.

Why Ivuna is so Important

Ivuna is important because it is a sample of the bulk Solar System. Unlike CV (Vigarano-like), CK (Karoonda-like) or CM (Murchison-like) chondrites, which are all enriched in refractory elements, Ivuna is pristine insofar as bulk concentrations go. Containing a bulk composition in close proximity to that of the Sun lets you measure just how enriched those aforementioned meteorites are, in direct comparison to the solar system.

CV3 chondrites, for example, contain a large number of refractory inclusions (Table 1), named so because of their enrichment in refractory elements. Those being elements which very high melting and boiling points. That means the highest condensing temperatures too – making them the first elements to condense out of a hot nebulous cloud. Due to the presence of those inclusions, CV3 chondrites are enriched, in bulk, in the refractory elements relative to Ivuna, and therefore the solar system. Knowing this lets you make the assessment that CV3s, or at least the refractory inclusions contained within, formed in conditions that were much hotter than those in which CIs formed. And since this is the early, hot solar system we’re talking about, that means they formed earlier (this is also confirmed by the elevated level of 26Mg, also in relation to those in Ivuna, and good old-fashioned absolute Pb-Pb dating).

The comparisons don’t stop with meteorites, though. CI concentrations are the values many geochemical systems are normalised to (that’s when you divide the value you have in your sample, by the value measured in the standard), allowing for a comparison with the solar system. Any deviation away from the bulk solar system composition denotes a chemical process has taken place, and can tell a story of heat, pressure or aqueous alteration.

Using the most modern equipment, the new samples available from the Natural History Museum purchase will better refine the standard measurement values we have. This will, in turn, allow for higher precision geochemical comparisons and potentially allow us to refine or rethink our models as to how the solar system formed and why the planets, like Earth, got to be the way they are.

References

Greenwood, R., Franchi, I. A., Kearsley, A. T., & Alard, O. (2004). The relationship between CK and CV chondrites: A single parent body source? Lunar and Planetary Science, XXXV.

Scott, E. R. D., & Krot, A. N. (2004). Chondrites and their Components. In A. Davis (Ed.) Treatise on Geochemistry, vol. 1: Meteorites, Comets and Planets, chap. 1.07, (pp. 143–200). Elsevier Ltd.

Taylor, S. R. (2001). Solar System Evolution A New Perspective. Cambridge University Press, 2 ed.

Episode 5 of the podClast is ready for download. You can grab the mp3 here (19.1 Mb, 33:18), or subscribe through iTunes here.

Today’s show discusses The Mars Phoenix Lander,

Participants

Chris – goodSchist

Jess – Magma Cum Laude

Show Notes

Notes on taming volcanoes with limestone and dolomite

There’s images from the Phoenix showing grains from the Martian surface.

Big Earthquakes Spark Jolts Worldwide? We had a discussion about that.

Ice quakes are a topic you may like to read about.

I managed to digress into talking about the ANDRILL project.

There’s the Geotimes article and the AAPG article about geoblogging. And Chris has a list of all the active geobloggers over at Highly Allacthonous. There’s also Aiden’s post about it all.

And here’s the link to the call for posts for the Accretionary Wedge #10.

Jess was right with her first guess, it was Tambora that caused the year without a summer (not Krakatoa). And the artist we couldn’t remember the name of was James M. W. Turner

del.icio.us/podclast

We have a del.icio.us account which can be found at http://del.icio.us/podclast. All the web pages and resources we’ve found and used in the discussions on the podclast can be found here. A conveniant way to browse per episode is to go to, for example, http://del.icio.us/podclast/episode5 (for this episode).

If you find a link to a topic that you’d like to hear discussed on the podclast, or have a link to a topic that’s already been discussed, you can add links to the podclast page through your own del.icio.us account.

When saving a link, include the tags for:podclast and episodeX (where X is the episode number – for example episode5). You can add more than one episode tag if the link applies to multiple episodes.

Next Episode

We like to have a new episode of the podClast every fortnight, so the next episode will be recorded on Saturday the 21st of June at 2300 GMT.

Contributing

If you’re keen to hear a specific topic talked about, or would like to join the discussion during the next episode (we’d really like a few more voices in there), either leave a comment below or email chris [the at symbol] goodschist.com. You’ll probably also do well reading the details on joining the podclast. If you don’t have the time to join us but would like to contribute a 3-5 minute audio clip to the show simply record it, make sure it’s an mp3, and send it to the address above [I'll add more thorough instructions at a later date]

Credit

The intro and exit music was Roots Fi Cool by Burning Babylon.

The splash image on the homepage is a section of the painting “The Fighting Téméraire tugged to her last Berth to be broken up” by J. M. W. Turner and the album art is from NASA.

Today’s show is a little different from normal. We had a lot of problems getting Skype running properly, due to network problems. The audio was just too choppy to record and broadcast. Instead Dave Schumacher and I put together a clip each detailing two of the topics we were planning on covering. So today you’ll hear about the Sichuan province earthquake in China the Phoenix Mars Lander, which is due to land in 9 hours at the time of posting.

Participants

Chris – goodSchist

Dave – Geology News

Show Notes

Photos of the Sichuan earthquake can be found on Dave’s blog, Geology News.

The British Geological survey identified the risk of such a large earthquake happening again just months beofre it occurred.

And an eighty (!!) year old man has just been pulled from rubble, 266 hours (11 days) after the earthquake struck.

There’s the overview for the mission of the Mars Phoenix Lander. (Wikipedia has details too).

You can watch the landing and mission progress at NASA TV here. It’s in a few hours, so act quickly!

If you miss that, there’s a neat guided tour of the simulated landing.

And finally, the video entitled 7 minutes of terror is a dramatic overview of what will be a dramatic landing.

del.icio.us/podclast

We have a del.icio.us account which can be found at http://del.icio.us/podclast. All the web pages and resources we’ve found and used in the discussions on the podclast can be found here. A conveniant way to browse per episode is to go to, for example, http://del.icio.us/podclast/episode4 (for this episode).

If you find a link to a topic that you’d like to hear discussed on the podclast, or have a link to a topic that’s already been discussed, you can add links to the podclast page through your own del.icio.us account.

When saving a link, include the tags for:podclast and episodeX (where X is the episode number – for example episode3). You can add more than one episode tag if the link applies to multiple episodes.

(I haven’t added the links for today’s show yet, I’ll do this in the next couple of days).

Next Episode

We like to have a new episode of the podClast every fortnight, so the next episode will be recorded on Saturday the 7th of June at 2300 GMT.

Contributing

If you’re keen to hear a specific topic talked about, or would like to join the discussion during the next episode (we’d really like a few more voices in there), either leave a comment below or email podclast [the at symbol] podclast.com. You’ll probably also do well reading the details on joining the podclast.

Credit

The intro and exit music was Roots Fi Cool by Burning Babylon.

The splash image on the homepage and the album art is from NASA.

On this Pangea Day, as a geologist, or simply as a geologically minded person, or even someone mildly interested in deep time (and passing by YouTube’s event), I proposed you post an image showing where on or about Pangea the bedrock that currently underlies you was sitting. More precisely, where would you be living now if Pangea hadn’t broken up.

Here’s my submission (Mid to late Triassic about 220 million years ago):

My bedrock was almost as far south as you could get, while still having land to stand on.

Where was your bedrock? There’s a fantastic resource for paleogeography at Dr. Ron Blakey’s (of Northern Arizona University) Global Paleogeography project page. Here’s a quick link to the rectangular paleogeography maps – but be sure to take a good look at the other resources there (including the regional paleo maps).