(image: Smithsonian Museum)

How things have changed!

Way back when, I started this blog off with an entry that suggested you should never bring up the subject of meteorites in polite, social conversation for fear of being thought of as, well, a bit boring, or perhaps worse! But that was back in the days before the so-called “Brian Cox effect”. As a result of the popularity of the astronomy programmes presented by the charismatic Professor Brian Cox, all matters “space” are now seen as cool and trendy. So, for example, astronomy clubs, such as the Derby and District Astronomical Society, have seen at least a doubling of their membership. In addition, science subjects have become much more popular at A-level. Space enthusiasts no longer need to seek refuge in the kitchen at parties (unless they want to of course).  This positive trend is set to continue with three consecutive nights of Stargazing Live starting on Tuesday 8^th January at 8pm on BBC2.

BBC2′s Stargazing Live hosts Professor Brian Cox (left) and Dara Ó Briain (right).

So people are now interested in space and want to know how meteorites fit into the bigger picture? Well, up to a point.

The problem is that even among some scientists the field of meteorite research is sometimes seen as being highly specialised, or worse still, a bit of a backwater. Nothing could be further from the truth. In reality, much of what we know about the origin and early evolution of our Solar System comes from the detailed laboratory study of meteorites.

Perhaps these misconceptions about meteorites arise in part from the random way these space rocks arrive on Earth. After all, how could such rocky debris, that plunges through the atmosphere so fast that it creates a spectacular fireball and sonic booms, be left in any sort of state to provide meaningful scientific information once it hits the ground?

Fireball of the Pasamonte meteorite as seen early in the morning on 24th March 1933. This famous image was taken by a ranch foreman who just happened to have a loaded camera beside him while he was eating his breakfast! The twisted trail is sometimes taken to indicate that the meteroid spiralled during flight. However, it is more likely that it was caused by camera shake.

In fact, despite the pyrotechnics that often accompany the arrival of a meteorite, the material that makes it to the ground is in a near-pristine state. Here’s why:

Meteoroids (the name given to space rocks before they land) enter the atmosphere at velocities in excess 11.2 km per second, the Earth’s escape velocity.  If the meteoroid has a retrograde orbit, that is opposite in direction to the motion of the Earth around the Sun, it can arrive with a relative velocity as high as 70 km per second. That means it would take less than 10 seconds to travel from Edinburgh to London, compared to 7 hours 25 minutes by car (as estimated by the AA). The enormous speeds at which meteoroids enter the atmosphere results in extremely intense frictional heating due to collisions with the surrounding air molecules. This causes their outer surface to melt and partially vaporise.

Bolide (a large meteor), seen over the Flinders Ranges, in the South Australian desert on 24th April 2011. The object broke up during flight into about a dozen fragments, each with an individual dust trail. The bolide was observed for about seven second. (image: wikipedia)

Now here’s the neat bit!

As soon as the outside of the meteoroid melts the molten liquid is swept off the back of the speeding object taking all the heat with it. It’s nature’s own heat shield! As a result, the material that reaches the Earth’s surface has a cold interior, with the last remaining melt on the outside solidifying to form a thin (usually about 1 mm thick), black, glassy layer, known as fusion crust.

Small fragment of the Tissint Martian meteorite, partially covered in black, shiny, fusion crust (field of view ~ 2cm) (image: Andy Tindle)

So, while meteoroids take a huge battering when they enter the Earth’s atmosphere and often break-up  into a shower of fragments, the material that is eventually recovered (it can now be officially called a meteorite) is close to pristine and provides science with a treasure trove that has been used to unravel the secrets of the Solar System.

TEN THINGS YOU NEED TO KNOW ABOUT METEORITES

Here are just some of the amazing discoveries that have been made as a result of the detailed study of meteorites:

1. The precise age of the Solar System

 When scientists confidentially state that our Solar System formed 4,567 million years ago (give or take a million years) this age is based exclusively on precise laboratory dating of objects known as calcium aluminium-rich inclusions (CAIs for short). CAIs were the first solid objects to form from the cloud of gas and dust from which the Solar System formed. CAIs are found in an important class of meteorites known as carbonaceous chondrites.

The large (~ 1cm long), pale, irregularly-shaped object on the left-hand side of the image is a calcium aluminium-rich inclusion (CAI) in the Allende carbonaceous chondrite. (image: Andy Tindle)

2. Meteorites contain grains that predate the Solar System

One of the most astonishing breakthroughs in the study of meteorites was the recognition that they contain mineral grains that originated in stars that predated the formation of our Solar System. Approximately 20 different types of so-called “presolar” grains are now recognised and these provide a unique record of the processes that take place in a wide range of different types of stars.

Presolar silicon carbide (SiC) grain isolated from a carbonaceous chondrite meteorite. Most presolar SiC grains are thought to have formed in asymptotic giant branching stars. (image: Larry Nittler)

3. Meteorites tell us how the Solar System formed

Meteorites contain evidence that certain short-lived radionuclides (⁴¹Ca, ³⁶Cl, ⁵³Mn, ²⁶Al and ⁶⁰Fe) were “live” in the early Solar System. The abundance of these isotopes means that they must have been synthesised just before the formation of the Solar System. The most likely explanation is that they were formed when a nearby massive star exploded to produce a supernova. The shock wave from this explosion would have initiated the gravitational collapse of the surrounding gas and dust to produce new stars, including our own.

4. Meteorites tell us about conditions in the early Solar System

The study of meteorites allows us to construct a detailed picture of how the Solar System evolved. Recent dating studies have demonstrated that small planets formed much more rapidly than was previously thought and from these evolved the larger rocky planets, including Earth. The results of these studies may have implications for the evolution of planetary systems around other stars.

5. Samples from Mars

While the NASA Curiosity rover is doing some fantastic science on Mars, one thing it cannot do is return a sample from the red planet for detailed study in the laboratory. However, thanks to a group of meteorites known as SNCs we already have a large number of samples from Mars. The total number of official Martian meteorites currently stands at 113 (source: Meteoritical Bulletin), of which 5 were witnessed “falls”. The most recent arrival from the red planet was the Tissint meteorite which fell in Morocco in 2011.

The NASA Curiosity rover is doing amazing things on Mars. Unfortunately, one thing it isn’t going to do is bring back samples. Fortunately, we already have samples from Mars in the form of Martian meteorites.

6. Samples from the Moon

In addition to the 382 kg of Moon rock returned by the NASA Apollo program and  0.32 kg returned by the Soviet Luna missions, we also have 165 official lunar meteorites with a combined mass of 63.6 kg (source: Meteoritical Bulletin). The Apollo and Luna samples were collected from a relatively restricted region of the Moon’s near side, whereas lunar meteorites are believed to be derived from much more diverse areas, including the Moon’s far side. While lunar meteorites are significantly less pristine than the samples returned by the Apollo and Luna missions, they do provide a very important complimentary suite of samples.

7. Samples from asteroids, including 4 Vesta

The majority of meteorites are believed to be fragments derived from asteroids that lie between the obits of Mars and Jupiter, in what is generally termed the Asteroid Belt. These meteorites are extremely varied in both their physical characteristics and chemical composition and are thought to be samples of at least 80 asteroids.  One asteroid from which we have a particularly large number of samples is 4 Vesta, with a total of 1158 officially recognised specimens of which 61 are witnessed falls. The group of meteorites that are believed to originate on Vesta are known as the HEDs (howardites, euctites and diogenites). One of the major scientific reasons for sending the NASA Dawn spacecraft to visit 4 Vesta was the wealth of information about the asteroid that had been obtained through the study of the HED meteorites.

Composite view of asteroid 4 Vesta, as imaged by the NASA Dawn spacecraft. The wealth of knowledge gained about Vesta through the study of the HED meteorites was a major factor in the decision to send a spacecraft to study this important asteroid, the second largest, by mass, in the asteroid belt.

8. Meteorites brought water and other volatiles to the Earth

The Earth formed in the inner part of the Solar System and would have been essentially “dry” until the very final stages of its growth. Water and other volatile components were delivered to the Earth by late-stage impacts of disrupted icy bodies from beyond the “snow line”. Thus, meteorite impacts were an essential prerequisite for the evolution of life on Earth. It has also been suggested that the complex organic molecules found in some meteorites and interplanetary dust particles provided the “prebiotic” ingredients for life.

9. Meteorites brought gold to the Earth!

The Earth is a “differentiated” body, consisting of an inner core of metal, surrounded by a rocky mantle and crust. During its formation the Earth grew by absorbing smaller asteroids and mini-planets. As this new material was incorporated, almost all of the “metal” loving elements in these small bodies, including gold and platinum, would have gone into the growing core. This should have left the overlying mantle essentially devoid of these elements. In fact the present day Earth’s mantle has higher concentrations of these elements than predicted by experiments. The relative abundance of such metal-loving elements in the mantle indicates that they were added at the end of Earth formation as a “late veneer”. Primitive meteorites are the most likely source of this veneer.  So, almost all the world’s available gold was transported here by meteorites. Of course there is plenty of gold in the core, you just need a very good shovel!

Almost all of the world’s available gold was transported to Earth by meteorites as a “late veneer”.

10. Meteorites are the best models we have for the bulk composition of the Earth

Unlike the Earth, a small group of meteorites known as CI chondrites have retained a primitive composition that is close to that of the Sun. This group contains only 9 known examples, but provides the best chemical reference material with which to test models for the formation and evolution of the Earth.

I could go on! But I think you will agree that meteorites provide a wealth of important information about the origin of our Solar System and even how life evolved on Earth.

It always makes for a great movie. The lonely scientist in his white coat, working alone in his lab late into the night. There he is, mixing crazy coloured chemicals as part of an insane quest to find some sort of secret elixir. Like Alec Guinness in The Man in the White Suit, or Spencer Tracy in Dr Jekyll and Mr Hyde success is pyrrhic at best. Yes, the lonely nutty professor remains a powerful cliché for how science works.

Of course reality is generally a little different. Splendid isolation is not usually a recipe for scientific success. Most researchers work as part of a well-organised group that meets regularly to share new results and discuss recent important developments. Our group here at the Open University is no exception. With the impressive title of: the Cosmochemistry Research Group (CRG), we meet up every Tuesday for a round-up of what everyone has been doing over the past week and to listen to a short seminar presentation by one of the group members. To be successful such meetings need to be properly organised. Over the past few years Dr Natalie Starkey has done an exceptional job of keeping things focussed and on track. She has recently handed on this role to Dr Romain Tartese. Longstanding readers of this blog will be pleased to know that cake remains an essential ingredient of CRG weekly meetings. As always, the chocolate brownies are particularly good.

Well, OK! this is not really a picture of a cake from one of our weekly CRG meetings, but one prepared by Margaret Tindle for the Moon Rocks ibook celebration. But you get the idea!

But while regular weekly meetings are a vital part of keeping research group members in touch with each other, it is also important to find out what’s going on in the wider scientific world. A vibrant programme of visiting speakers is an essential part of the mix. Thanks to the hard work and organisational skills of Dr Susanne Schwenzer we have been benefiting from a series of fascinating talks covering a wide range of planetary science topics. Take the last two weeks as an example. Dr Bill Bottke (Southwest Research Institute) presented a talk examining the Late Heavy Bombardment on the Earth and Moon and Professor Jamie Gilmour (University of Manchester) discussed aspects of the development and analytical application of the RELAX and RIMSKI noble gas mass spectrometers. We also had a talk about the potential for life on Mars given by NASA scientist Professor Everett Gibson, and Professor Alex Halliday (University of Oxford) gave a presentation on the delivery of volatiles to Earth both before and after the Giant Impact.

Good science communication involves using a wide range of new media. On his recent visit to the Open University Prof. Everett Gibson of NASA (left) takes a look at the new Moon Rocks ibook – the first ibook published by the Open University and now available as a free downlaod on the Apple Bookstore. In the picture with Everett are Prof. Peter Scott – Head of the Knowledge Media Institute (centre) and Dr. Andy Tindle (right), co-author of the new ibook. 

Then there are more organised scientific meetings. These range from large international gatherings, such as the annual Lunar and Planetary Science Conference in Houston, Texas, to smaller-scale more focussed events. A nice recent example of the latter was held in London on November 9^th by the Royal Astronomical Society and highlighted how new lunar research was changing our views on the early evolution of the Solar System. An important theme of this meeting was the possibility that, as a result of impact processes, terrestrial samples may have been ejected from the early Earth and then landed on the Moon. Of course identifying terrestrial meteorites within the lunar regolith will be extremely challenging.

Apollo 12 astronaut Alan Bean holding a sample of lunar soil. The picture was taken by Commander Charles “Pete” Conrad, who can be seen in the reflection in Bean’s visor. One of the soil samples collected during the Apollo 12 mission contained a small meteorite sample called Bench Crater. It was the first meteorite to be discovered on a solar system body other than the Earth. The lunar soil may also contain meteorites from the Earth, although none have so far been identified.

So is that all there is to it? Lots of very enthusiastic scientists having lots of meetings! All a bit self-indulgent you might think. And of course it would be, if that was the end of the story. Happily it isn’t.

So let’s move on. It’s a cold damp Saturday afternoon in early November. A group of twelve enthusiastic members of the Derby and District Astronomical Society head down to the Open University for an afternoon visit. We kick things off with a talk about meteorites and early solar system evolution. It’s looking good, no one falls asleep. Then there’s a chance for people to handle some real meteorite specimens and later observe meteorites under the microscope.  We finish with a Cook’s tour of the various bits of kit we use to study the oxygen isotope composition of extraterrestrial materials (laser fluorination line, NanoSIMS). That’s all great. But the fun bit is done over coffee and biscuits. Here are a really enthusiastic group of people asking questions and showing real interest in the subject. They come at things from a different angle. They find it all fun (well most of it!) and ask challenging and thought-provoking questions. This sort of activity is given the jargon name “Outreach”, but that doesn’t really cover it. It’s all about dialogue and discussion.

One of the Derby astronomers told me that they now have more than double the number of people at their regular meetings as a result of the “Cox Effect”. Communication it seems is at the heart of keeping science fresh and relevant.

Members of the Derby and District Astronomical Society studying meteorites in thin section. (image: Graham Ensor)

(image: NASA)

Spot the difference! Glenelg in Scotland and on Mars

Our close planetary neighbours, the Moon and Mars, have been receiving a bit more coverage in the media lately. Well, OK, perhaps it’s not been an all-out deluge of publicity. Not really the journalistic equivalent of a feeding frenzy, I agree. But nonetheless, the news outlets seem to have been paying a bit more attention to matters extraterrestrial of late.

The Mars Curiosity Rover has been providing a fairly steady stream of internet news, as its various systems have been checked out and scientific operations gradually get underway. However, as always, the problem for news organisations covering robotic missions is the lack of a clear human-interest angle. As we all know, what primarily drives the 24 hour news agenda are people-related stories, be they natural disasters, political scandals, celebrity gossip, crime or the effects of the present economic crisis. I am afraid a rover on Mars comes a long way down the news pecking order.

Mars twinning celebrations in Glenelg, Scotland. (image: The Oban Times)

Interestingly, if you take the same ingredients:  a Mars rover, NASA scientists etc. and then add something new, like a bunch of partying Scottish highlanders, you  get into a whole different territory. So it was that driving back home last Friday I heard a report on the BBC Radio 4 “PM” programme about the world’s first extraterrestrial twinning event. This was the news that Glenelg in northwest Scotland (population 300) was holding a special twinning ceremony to mark the arrival of NASA’s Curiosity rover at “Glenelg” on Mars (population: yet to be determined). The space shuttle astronaut Bonnie Dunbar attended the ceremony and gave a talk, as did  Professor John Brown, the Astronomer Royal for Scotland.  Doug McCuiston, director of NASA’s Mars Exploration Program, attended the festivities via a live video link and answered questions from local villagers assembled in a marquee that had been specially erected for the occasion.

A little earlier in the month, Mars-related research was the focus of numerous internet articles. This was in response to our paper in Science Express presenting new results for the Tissint meteorite. Most internet contributions, particularly from mainstream news organisations, provided a reasonable summary of the research findings. These included: The New York Times, New Scientist, The Guardian, Sky and Telescope. But other reports went way off tangent; a notable example being Time magazine’s online piece entitled: “Could Martian Bacteria have seeded Earth?”. Fascinating stuff, but absolutely nothing to do with research reported in Science Express.

New research published in Nature and Science Express provides additional support for the giant impact model of lunar formation. (image: NASA)

The Moon displaced Mars towards the end of last week, as news organisations focussed on a group of papers reporting new research results related to the giant impact hypothesis. A study in Nature by Paniello, Day and Moynier showed that lunar magmatic rocks are enriched in the heavy isotopes of zinc and suggested that their data is consistent with a giant impact origin for the Earth and Moon. Since a range of earlier isotopic studies had called into question the giant impact model these were important results and were deservedly given significant online coverage. A News and Views article discussing the research in Nature by Tim Elliott began with the perfect opening sentence: “Like the perfect Martini, the Moon has a reputation for being dry”. Who said writing about science has to be dull!

A new giant impact model for the formation of the Earth-Moon system by Robin Canup has been published in Science Express. Shown is an off-center, low-velocity collision of two protoplanets containing 45 percent and 55 percent of the Earth’s mass. Color scales with particle temperature in kelvin, with blue-to-red indicating temperatures from 2,000 K to in excess of 6,440 K. After the initial impact, the protoplanets re-collide, merge and form a rapidly spinning Earth-mass planet surrounded by an iron-poor protolunar disk containing about 3 lunar masses. The composition of the disk and the final planet’s mantle differ by less than 1 percent. (image and caption: Southwest Research Institute)

Meanwhile, Nature’s competitor journal, Science, had arguably an even bigger scoop on its hands with the publication of two papers that effectively re-energize the giant impact model for the formation of the Earth-Moon system.  Earlier versions of this model considered the present angular momentum of the system to be a primary constraint. However, the results of such simulations were not consistent with the measured geochemical composition of the Moon. In their Science Express article, Matija Ćuk and Sarah Stewart demonstrate that the initial angular momentum of the Earth-Moon system could have been significantly higher than at present and was reduced through an orbital resonance between the Sun and Moon. Ćuk and Stewart suggest that without this constraint a range of impact scenarios are compatible with the observed geochemical composition of the Earth and Moon. In a paper in the same issue of Science Express, Robin Canup builds on the work of Ćuk and Stewart to present a model for the formation of the Earth and Moon via an impact between two planets of roughly equal mass. The results presented in these two papers are highly significant and will have a major influence on future research into the formation and early evolution of the Earth and Moon. It is therefore not surprising that they have already received wide attention on the internet and blogosphere.

Professor Monica Grady discussed meteorites and Mars with Professor Jim al-Khalili on the BBC Radio 4 programme: The Life Scientific. (image: BBC)

Perhaps a little flippantly, I started out by suggesting that science news lacks a human interest angle. But of course science only happens through the drive and determination of the scientists who carry it out. But with an emphasis on objectivity and evidence-based reasoning, science itself generally downplays this human dimension.   However, it’s nice to know that scientists are human too.  That’s why the Radio 4 series: The Life Scientific, presented by Professor Jim al-Khalili, is such a refreshing change. Each programme in the  series consists of an interview with a well-known scientist and focuses particularly on what has influenced and motivated them during their academic careers. Last week’s episode featured our own Professor Monica Grady discussing a range of topics that are close to her heart. The programme explored her fascination with the study of meteorites and what they can tell us about other planetary bodies, particularly Mars. Not unexpectedly she was enthusiastic about the new results coming from the Curiosity Rover, but pointed out that the loss of ESA’s  Beagle 2 lander had been extremely disappointing. In response to the question about the likelihood of finding life on Mars Monica couldn’t resist the imortal line: “It’s life, Jim, but not as we know it”.  Science is an important activity, but clearly it’s also important to retain your sense of humour, especially when things go pear-shaped, as they inevitably do from time to time.

Cartoon that appeared in the Salzburger Nachricten. Translation by Marcus Hanke.

]]> http://www.open.ac.uk/blogs/meteorite/?feed=rss2&p=1937 3 http://www.open.ac.uk/blogs/meteorite/?p=1925 http://www.open.ac.uk/blogs/meteorite/?p=1925#comments Mon, 15 Oct 2012 16:11:32 +0000 Richard Greenwood http://www.open.ac.uk/blogs/meteorite/?p=1925 The Earth is depleted in xenon. A new model suggests that it’s all due to a mineral called perovskite. To find out more visit my research blog.

The results of an international study, published today in Science, has found traces of material from both the surface and atmosphere of Mars in the Tissint Martian meteorite. The research team, which was led by Professor Hasnaa Chennaoui Aoudjehane from the Hassan II University, Morocco, included four members of the Open University’s Physical Science Department.

The meteorite fell to Earth in a fireball on 18th of July 2011 near Tissint, a Moroccan town along the Algerian border. As it is only the fifth witnessed fall of a Martian meteorite to have been recovered, the rock has provided a unique opportunity for researchers to expand their understanding of Mars. Previous Martian meteorites have suffered varying degrees of terrestrial contamination. In contrast, the Tissint meteorite is so fresh that it has been possible to detect evidence of components from both the Martian surface and atmosphere. The features observed in Tissint are broadly compatible with previous observations made by spacecraft sent to Mars by NASA and ESA.

A small fragment of Tissint (width ~ 2 cm). The black glassy material on the left corner is called fusion crust and formed during heating in the Earth’s atmosphere as the stone arrived from space. The dark material in the centre of the stone formed during an impact event on Mars, probably when the rock was ejected from the surface of the red planet into space about 700,000 years ago. It is these dark areas which contain traces of the Martian surface and atmosphere. (image: Andy Tindle)

The meteorite is a type of Martian volcanic rock known as a shergottite and contains abundant glass produced by impact processes on Mars. When this glass formed it trapped not only a sample of the Martian atmosphere, but also traces of soil-like material. The composition of the trapped atmosphere is very close in composition to that detected by the NASA Viking landers in the 1970s and so unambiguously demonstrates that the meteorite is from Mars. The glass also displays relatively high levels of sulphur and fluorine which, together with its distinct trace element signature, indicates that it contains material from the Martian surface.

A further important finding of the study is that Tissint has a similar cosmic ray exposure age to a number of other Martian meteorites, including the important sample EETA79001, collected in Antarctica. It would seem that all these meteorites were ejected into space by a single impact event that took place on Mars around 700,000 years ago.

The research on Tissint undertaken at the Open University involved detailed carbon, nitrogen and oxygen isotope measurements that not only authenticated its Martian origin, but were able to decipher the various atmospheric and soil components it contains.

Professor Monica Grady, head of the Open University’s Physical Sciences Department and one of the scientists who worked on Tissint says: “Tissint is an extremely important sample that has provided us with very fresh material from the surface of Mars that we can study in the laboratory. The recognition of Martian weathering products in Tissint will provide important constraints for the interpretation and evaluation of data currently being collected on Mars by the NASA Curiosity rover.”

]]> http://www.open.ac.uk/blogs/meteorite/?feed=rss2&p=1855 2 http://www.open.ac.uk/blogs/meteorite/?p=1694 http://www.open.ac.uk/blogs/meteorite/?p=1694#comments Thu, 27 Sep 2012 22:37:23 +0000 Richard Greenwood http://www.open.ac.uk/blogs/meteorite/?p=1694 Continue reading →]]>

The Mars Science Laboratory (MSL) team celebrate the safe arrival of Curiosity on Mars. (image: NASA/ Bill Ingalls)

Last Friday I went to a really fascinating talk by Dr Carlton Allen, the Astromaterials Curator at the NASA Johnson Space Centre, Houston, Texas. Dr Allen is in charge of all the extraterrestrial samples collected by NASA, including those returned from the Moon during the Apollo program, all the meteorites collected in Antarctica by ANSMET, cosmic dust particles collected in the stratosphere by modified U2 aircraft and the samples returned by the Genesis and Stardust spacecrafts. Of course he doesn’t  do all the work himself, he leads a team of about thirty dedicated scientists and technicians. So, if you are involved in laboratory-based studies of samples from space, Dr. Allen is a pretty good guy to know.

Computer generated oblique view of Gale Crater from the north showing the Curiosity landing ellipse. Aeolis Mons (Mount Sharp) dominates the central region of the crater. (image: NASA)

But while the curation of extraterrestrial samples is an important topic, that wasn’t what Dr. Allen had come to talk about. In fact the subject of his presentation was the geology of Gale Crater, the 154 km wide structure on Mars which is currently being studied by the Curiosity rover.  With an estimated total cost of about 2.5 billion dollars, you can be sure that NASA put a lot of thought into the choice of landing site for the Mars Science Laboratory (MSL) mission. Curiosity touched down on August 6^th (EDT) 2012 without a hitch using the unique “sky crane” landing system. Once it was clear that the so called “seven minutes of terror” had come to a happy conclusion, the anxious scientists and engineers at mission control were seen to erupt into a spontaneous show of unconstrained celebration. Well who can blame them?

Curiosity touching down on Mars (artist’s impression). Instead of the air bag system used on previous missions, Curiosity was deposited on the Martian surface using a “sky crane“. (image:NASA)

So what is special about Gale crater? Dr Allen explained. It is located just south of the Martian equator, close to the boundary between the southern highlands and northern plains. At the centre of the structure is a spectacular mountain “Mount Sharp” (also known as Aeolis Mons) that rises 5.5 kilometres (18,000 feet) above the crater floor. Orbital observations indicated that Mount Sharp was composed of a number of distinct packages of layered sedimentary rocks. The mountain also displays a prominent erosional unconformity. The rocks that form Mount Sharp appear to be the eroded remnants of sediments that once completely filled the crater. Mineralogical evidence suggests that the sediments on the lower slopes of the mountain were laid down in a water-rich environment, whereas further up the slope they were deposited under much dryer conditions.  A critical part of Curiosity’s mission is to investigate this transition from wet to dry sedimentation.

The location of Gale Crater shown in relation to the landing sites of previous Mars’ missions. Gale Crater sits close to the boundary between the southern uplands and northern plains of Mars. (image: NASA)

Dr. Allen started his talk by emphasising the science goals of the MSL mission. It is a mission designed to investigate a site that shows clear evidence of past aqueous processes and so the research is directed at looking at whether conditions in the past were ever suitable for life. He made it clear that Curiosity is not in the business of looking for evidence of either past or present life on Mars. The MSL website is quite clear on this point: ”MSL is not a life detection mission and is not designed to detect extant vital processes that would betray present-day microbial metabolism. Nor does it have the ability to image microorganisms or their fossil equivalents”.  All of which sounds a bit disappointing.

Layered sedimentary rocks at the base of Mount Sharp. (image: NASA)

I asked Dr Allen after his talk whether in private scientists on the mission weren’t secretly hoping to detect evidence of past life on Mars. “Like imaging a trilobite?” he joked.  It was clear from his presentation, and the MSL website, that this is a mission driven by science and not in the business of setting unrealistic and ultimately self-defeating goals. And yet the rover carries an astonishingly powerful payload of scientific instruments. And the MSL website does nuance things a bit by stating: “MSL does have, however, the capability to detect complex organic molecules in rocks and soils. If present, these might be of biological origin, but could also reflect the influx of carbonaceous meteorites. More indirectly, MSL will have the analytical capability to probe other less unique biosignatures, specifically, the isotopic composition of inorganic and organic carbon in rocks and soils, particular elemental and mineralogical concentrations and abundances, and the attributes of unusual rock textures.” So, while they are not directly looking for the signs of past or present life on Mars, if it pops up they won’t ignore it.

Slopes of Mount Sharp showing that strata at the base of the mountain are relatively flat-lying, whereas higher up they have a steeper inclination. The junction between the two sets of strata (picked out by white dots) appears to be a sharp erosional surface, known as an “unconformity”. Curiosity will be investigating how these differing rock units were formed. (image: NASA)

But for me the most astonishing aspect of Dr Allen’s presentation was the clarity of the images that Curiosity has already taken at Gale Crater. The views were simply breathtaking. This should be no surprise because Curiosity is equipped with a total of seventeen cameras. So while the objectives of MSL may be predominantly scientific, it is already clear that Curiosity is going to bring Mars to life, at least visually, if nothing else. But will Curiosity uncover real evidence for life on Mars? It might not be a mission objective, but it remains a possibility.

The robotic arm of Curiosity examines its first sample (22nd September). (image: NASA)

Curiosity at Gale Crater, an artist’s impression. (image: NASA)

(image: The Beach Resident)

As mentioned in a previous post, we have been busy in the oxygen isotope lab installing some new kit. It hasn’t all gone entirely to plan. You can read the full story on my research blog.

Professor Colin Pillinger and “the meteorite from Lake House” now on display to the general public at the Salisbury and South Wiltshire Museum. (image: Andy Tindle)

Last Tuesday, a small group from the Open University headed down to the Salisbury and South Wiltshire Museum for a rather special event. A unique British meteorite was finally going on display to the general public and we had been invited to the media launch. So what was all the fuss about? Well, “the meteorite from Lake House” has an extraordinary tale to tell. We still don’t know all the details, but here is the story so far:

The Open University’s Lake House Extraterrestrials outside the Salisbury and South Wiltshire Museum (from left to right: Diane Johnson, Judith Pillinger, Colin Pillinger, Richard Greenwood, Dave Revell, Liz Sugden and John Watson. (image: Andy Tindle)

For as long as anyone could remember, a large rusty bolder sat close to the front door of Lake House, an impressive Elizabethan mansion located in  the village of Lake near Salisbury. It was a long held tradition that the rock was a meteorite, but no one could be certain. Then, in the early 1990s, the owners of the house contacted scientists at the Natural History Museum in London, who were able to confirm that the rock really was a meteorite. It was subsequently transferred to a storage facility, where it languished until a few years ago, when Professor Colin Pillinger decided to investigate things further.

The Lake House Elizabethan mansion, Lake near Salisbury. The meteorite can be seen clearly on the steps of the mansion in a 1908 Country Life photograph of Lake House (image: English Heritage/John Rendle)

The reason Professor Pillinger wanted to take another look at the specimen was because its composition matched that of Danebury, a small meteorite found by archaeologists during the excavation of an iron-age settlement. The Danebury Hill fort is only a relatively short distance from Lake House, so perhaps there was a chance that the two objects were the products of a single event, in which a large meteroid broke up during atmospheric entry producing a strewn field comprising many meteorite fragments ?

The Danebury meteorite (top left) weighs only about 30 grams and was found at the bottom of a grain storage pit by archaeologists  excavating the Danebury iron-age hill fort in Hampshire (bottom right). (images: Andy Tindle/English Heritage)

Dating of Danebury indicates that it fell only a few thousand years ago, whereas “the meteorite from Lake House” arrived on Earth much earlier and gave a “weathering age of approximately 10,000 years before present. So, the two space rocks must have fallen during two distinct events.

But questions still remained. How did the meteorite get to Lake House and how come the owners seemed to know that the rusty, weathered bolder was a meteorite? One theory was that, at some time in the recent past, it had been imported from abroad. Professor Pillinger and his wife Judith undertook a study of historical records and investigated the background of previous owners of the Lake House estate. They uncovered photographic evidence showing that the meteorite had been located on the doorstep of Lake House for at least 80 years. The possibility that it had been imported from the “colonies” in the early twentieth century looked increasingly unlikely. In fact, oxygen isotope evidence demonstrates that the meteorite had been weathered in a cold climate. It was also covered in fragments of the local chalk country rock. There now seems little doubt that the specimen is a genuine British “find” and may have been transported to the Salisbury area by glaciers, in a similar way to that proposed for the rocks used to construct nearby Stonehenge.

But who had found the meteorite and put it on the doorstep of Lake House? Professor Pillinger’s research suggests that one possibility is that it was dug up by Edward Duke. He was a previous owner of Lake House and an antiquarian who excavated burial mounds in the local area.

Edward Duke (1779-1852) (inset) inherited the Lake House estate in 1805 and devoted his leisure to the study of antiquities, including nearby stonehenge. (image: wikipedia)

Weighing in at just over 90 kg, “the meteorite from Lake House” is by far and away Britain’s largest meteorite. Only a relatively short distance from Lake House, the Salisbury and South Wiltshire Museum makes an ideal home for the meteorite. The Museum has a fine collection of local archaeological artefacts, particularly appropriate in view of the possibility that the meteorite may once have been used in the construction of an Iron Age burial mound.

Professor Pillinger introducing the new meteorite display.  The event was widely covered by both the national (Guardian, BBC, Daily Mail) and local press and even made it to the blogosphere. (image Diane Johnson)

To celebrate the opening of the meteorite display, the Museum has organised a two week programme of activities aimed at school students, in which they will also have the opportunity to study other meteorites and Apollo lunar samples supplied by the Science and Technology Facilities Council (STFC). As part of the Museum’s programme, Professor Colin Pillinger gave a special talk, in which he presented details of the mystery that surrounds the identification and recovery of “the meteorite from Lake House”. Professor Pillinger’s Royal Society talk on the same subject is still available on the web.

The Salisbury and South Wiltshire Museum are putting on various schools workshops using the  STFC extraterrestrial materials collection (displayed on the table). Dr Andy Tindle of the Open University is seen here demonstrating the benefits of the Virtual Microscope to the Museum’s Learning and Access Officer, Ruth Butler. (image: John Watson)

And so, “the meteorite from Lake House” seems to have finally come to the end of its long journey.  Starting in the asteroid belt, it reached Earth at least 10,000 years ago, landing in a frozen, unknown northern wasteland. It was then transported south by a glacier, deposited on Salisbury Plain and probably used to build a tomb by Iron Age man. It was then dug up by a gentleman archaeologist and, for perhaps a century or so, rested near the doorstep of the Lake House mansion. In the early 1990s, it was transported to the Natural History Museum, London, and eventually consigned to a storage warehouse. After all that, it is comforting to know that the meteorite is now on open display at the Salisbury and South Wiltshire Museum, where hopefully it will help to inspire and excite visitors for many years to come.