Changing the Pace

By Thomas

I don`t know why exactly – maybe it is for no reason at all, maybe because it is “winter” here in Australia, or maybe because I came across the video below a few weeks back – but these days I found myself quite often thinking back to the half-year of my life in 2009 that I spent in the beautiful city of Bergen in Norway.


I was there due to the European exchange program “Erasmus” to study for one semester. So yes, classical exchange semester right there. No worries, I`m not going to bore you to death (I hope) with an account of my activities there.

While these memories are very dear to me, I know that they`ll – at best – will be of medium interest to you.

So I will not tell you about the awesome time I had with the group of people working at the local student club (Klubb Fantoft).

I will not tell you about the time when one of my best friends visited me and we ended up in an Irish bar on St. Patrick’s Day (where else?) and we had much too much Guinness.

I will also not tell you about my trip to Trondheim, a city with a wonderful city centre of old wooden houses in the shadow of an impressive cathedral.

I will not … well you get the point. I will not write about specific things that happened to me while I was there.

What I want to write about is what (for me) turned out to have the biggest impact in the long-term:

It all starts with a “negative” side of this exchange semester.1 At least something I considered negative months before I even got to Bergen. I had enrolled for the exchange while I was still in my undergraduate studies of chemistry. But by the time it came down to finalising the details, I had slightly changed course and was enrolled in a master’s program about mineralogy and material science. This program was set on the border between inorganic chemistry and geology. As the University of Bergen had both, a chemistry and a geology department, I did not expect big problems to find some courses to take.

Well, I was wrong. The advanced chemistry courses would have provided a rich source, if I would still have been enrolled in a chemistry program. The advanced geology courses required a geology background that I lacked. In the end I settled for an undergraduate course in Oceanography2, and graduate courses in Microscopy3 as well as Isotope Geochemistry4.

And there was another problem that I realized relatively late:

The new semester in Norway started with the new year, while the old semester in Germany was still running into February. This meant I couldn`t take most of the exams for the old semester and I would be back too late to catch up with the new semester at home. So that was how the situation looked for me before I even went to Bergen:

I would effectively lose two semesters at home and wouldn`t be able to compensate much of this time with the courses I could do abroad.

And that was the best thing that could have happened to me.


Bergen in winter at day

Why? Because it forced me to change pace. Until this point I thought this to be a bad thing. My CV was a neat sequence from school to military service to undergraduate degree without any unnecessary interruptions or prolongations.5 And stupid as I was, I thought I had to finish my master’s degree in two years while quenching an exchange semester in between, else … yes, what was I thinking would happen?

In retrospect it`s hard to say what really kept up this (mostly self-imposed) pressure: It was something along the lines of being intellectually not worthy of a graduate degree if you can`t finish it in the pre-set time6 and the stupid assumption not to be able to get a job or into a PhD program if you don`t finish all your studies exactly in time.

But the details that I worried about are actual not that important, it is more the general direction: I worried (too much) about the Undiscovered Country!7 And there are only so much things that we can know and influence about it. Accepting that there are a lot of things ahead that we can`t control takes a lot of your shoulders and sharpens the view on the things you can actually do something about.

Okay, I start to sound like a walking fortune cookie. The point I try to make is, even though something might be common (fortune cookie) “wisdom”, it might need an event that forces us out of our comfort zone, to get this “wisdom” really into our heads. And better we learn life’s lessons from small stumbling blocks than when the shit really hits the fan.8


Bergen in winter at night

And of course, these lessons will not completely change who we are!

I still worry about the future. I still feel imposter syndrome from time to time. I worry about getting my PhD done. At the moment I worry a lot about a paper I`m writing on.

It is not about having no fears about the future. It is about finding something to balance them out with. And for me these six months in Bergen are one very good counterbalance at hand – casted as a concentrate into the memory of a single evening:

2nd of January 2009 – Just a few hours after arriving in Bergen: I decide to walk to the city centre. The city is lit with thousands and thousands of window lights, reflected from the all-covering snow – filling the whole valley with a golden shine. The landscape was forged by the irresistable force of the ice ages long ago, while the city – that huddles between the mountains – seems a fragile construct from human hand, merely existing for the blink of an eye. And while I stump through the snow, time slows down. If feels like it`s not me who`s changing the pace, but the world around me.9

Of course this memory is massively pimped and distorted by my subconsciousness. But it is a place in my heart10 I can retreat to. A place that reminds me that the future might be an undiscovered country – but that the only thing we need, to forge ahead through whatever awaits us, is the willingness to change our pace from time to time.


1 Negative side of an exchange semester – yep, first world problem coming your way.

2 Visiting a renowned Marine Science University, it seemed a nice field to have a glimpse at.

3 The only one really fitting with my master program, and even though mainly taught in Norwegian (which I don`t speak), one of the best courses I`ve ever had – might have had something to do with the fact it was mainly a practical course, and you`re looking at beautiful minerals all the time.

4 Which I barely passed. Considering that`s one of the main things I do now in my PhD project … well, irony.

5 All hail to the neoliberal dogma of the perfect human resource!

6 I guess that qualifies as imposter syndrome.

7 For those of you who haven`t seen or don`t remember Star Trek VI: … the Future!

8 Ever since I first heard this saying, I tried to find a way to put it in a post.

9 Seriously, if you ever have the possibility to go to Bergen in winter, do it. It`s the most “magical” place I know of. Well maybe rivaled by Lisbon’s Baixa (city center) in a warm summer night at four in the morning …

10 Well, my brain …

Betting on climate change will not get you money

By Tanja

Over the course of the past few weeks I have been reading quite a lot about climate all over the news. El Nino and La Nina events have been mentioned on a few occasions. I was always fascinated by these events, even as a kid, when I hadn’t the slightest clue as to what they were (but they do sound cool right?). Later on, as education slowly crept on me, I learned exactly what they were and how they impact the world.

But did I really understand how they ACTUALLY IMPACT the world?

Of course not!

I was born, raised and gained my masters-level education in Croatia, a country that doesn’t directly feel the impacts of either. My Oceanography and Dynamic-Meteorology teachers have put quite an effort to demonstrate the devastating and/or benevolent impacts of El Nino and La Nina events – depending on the part of the world. I had to derive some fearsome equations and was awarded with pictures of drought or floods all over the world, of people moving countries etc. For me personally, this probably meant that the price of some imported fish or seed was going up.

Right now, I live and study in Australia. And it seems, that an El Nino event will come crashing down on my head (and many other heads). And it will finally manifest itself to me in all its power. Probably some prices will go up too.

El Nino is a part of a natural cycle known as El Nino Southern Oscillation (ENSO) that manifests itself in prolonged periods of warming (El Nino) or cooling (La Nina) over the central and eastern Pacific Ocean.

In neutral mode we have the trade winds blowing from east to west across the Pacific, pushing warmer surface waters towards the western Pacific and causing convection in that area. The Central Pacific is kept relatively cool. The thermocline is deeper in the west than in the east. This means, that the ocean temperature gradient is not very steep in the west, which in turn means the water is warmer there.

During the El Nino conditions the trade winds are weakened or even reversed which allows this body of warm water to float further east and cause convection elsewhere. This also levels out the thermocline a bit. Now – without further ado – this means drought in Australia. It means rain and possible floods in Kiribati and Peru.


Neutral and El Nino Systems over the Pacific Ocean
Source: Australian Bureau of Meteorology

To me this means – seriously, even warmer summers? And a drought? In a country where water is already an expensive commodity?

Wonderful. I am affected now. Probably some prices will go up to!

Since this is a natural cycle it might prompt some people, like say …

… the government …

…. to deny climate changes. And the current prime minister here is adamant in trying to convince this nation that there is no such thing as man induced climate change.

Now let’s take a look at Australia’s Bureau of Meteorology brief explanation as to what might cause the El Nino conditions:

“An El Niño occurs when sea surface temperatures in the central and eastern tropical Pacific Ocean become substantially warmer than average, and this causes a shift in atmospheric circulation.”

Brilliant, I have established something similar above. So we have a natural occurring phenomenon here, but it is interesting to see that this phenomenon has gained a substantial power over the last few decades (see for example here, Pages 8 and 9). Now I won’t go into proving and showing that some aspects of climate change are man induced, others have done so, repeatedly (as in – many times). But on the low chance of Tony Abbot reading this – yes, climate changes have occurred naturally during the geological past of this planet. But not on the scale we are observing now. Climate change may not be something new on the face of this planet, but we – humans – are empowering it. Making it bigger, faster, stronger. The upcoming El Nino may be another record-breaking one, because the ocean is just a tad warmer, thanks to us. And it is affecting me and millions of other people directly.

And just to top it off, a scientist is offering a 10000$ reward to anyone who can use scientific methods to prove that man-made climate change is NOT real.

Tony Abbot should jump on that boat. He should actually hope that this boat wouldn’t be turned back too. I think proving something like that would be an ultimate win-win situation – someone would get the reward AND go down in history. While everyone else would be able to happily exhale in relief, knowing that it is not us messing up this planet, it is completely natural. We could happily live our lives, knowing that there really is NOTHING we can do to prevent this. And just imagine what the 10000$ would do to the budget! Probably some prices would go down too.

Looking up to find what’s beneath our feet

By Eleanor

Everyone loves a good asteroid impact… although preferably not on the Earth today anywhere near human civilisation. You’ve heard it all before – big explosion (Figure 1), shock waves, nuclear winter, mass extinctions, dying dinosaurs. Death and destruction, as Thomas mentioned about a few weeks ago.


Figure 1: Artist depiction of a big asteroid hitting Earth.
Source: Wikimedia

But have you ever wondered what happens to the rocks? Probably not, right? It sounds kind of dull. Who cares about the rocks? Dinosaurs are way cooler!

Perhaps that’s true for some… but the rocks are interesting too. Looking at rocks that have experienced an impact can actually tell us very fundamental information about our planet.

I’m not talking about impacts like the one that killed the dinosaurs… in these cases, the asteroid (and some Earth rock too) gets completely vaporised because of the massive energy of the collision. Let’s head out to the asteroid belt, which is between Mars and Jupiter. There are millions of asteroids here, and although they are pretty spaced out (no pun intended) sometimes they do collide (Figure 2).

When that happens, you get a lot of debris thrown out (the very low gravity on these small objects means that this stuff doesn’t fall back onto the surface), and a shock wave will pass through the rock that survives. The shock wave causes a short period of intense pressure and temperature, which can have a pretty strong effect on the rock.


Figure 2: Artist depiction of two colliding rocky bodies.
Source: Wikimedia

Smaller impacts might cause deformation in the minerals, like parallel sets of fractures in olivine grains (olivine is a common mineral in asteroids). Bigger impacts can cause parts of the rock to melt.

If you melt a rock, you make lava, and if you cool the lava down very fast, you make glass (think obsidian, which is a volcanic glass found on Earth). This is because the atoms don’t have time to rearrange themselves into the ordered crystal structures of minerals. If you cool down the lava a bit more slowly, there is time for a few crystals to form (think basalt, which can sometimes have small crystals of olivine surrounded by glass).

In asteroids, you often form melt veins – thin slivers of molten rock that are surrounded by solid minerals. The veins form because shock waves travel through each mineral differently, leading to localised spikes in pressure and temperature which creates pockets and veins of melt. These melt veins will cool down pretty quickly if the surrounding rock is cold, so they turn into veins of glass with small minerals that have crystallised, like the black vein in the meteorite in Figure 3.


Figure 3: Meteorite Sahara 99898 with a black shock vein.
Source: Meteorites Australia

Sometimes, the melt can cool down before the peak shock pressure has dissipated. When this happens, the minerals that crystallise from the melt as it cools can be quite different minerals to those found in the rest of the rock. To accommodate the high-pressure conditions, these minerals have much denser, more compact structures. Olivine, for example, takes on a different structure under high-pressure conditions, and we call that mineral ‘ringwoodite’.

Okay, so why do we care about minerals that form under high pressure?

We live on the surface of the Earth under the pressure of the atmosphere. If you went out to space without a space suit, you would explode, because there is not enough pressure to hold you together. If someone dropped a boulder on you, you would be squished, because the pressure is too much for you to withstand. (Incidentally, you being squished is analogous to olivine turning to ringwoodite. ‘Squished-you’, is favoured at high pressure, because it’s more compact than ‘Non-squished-you’; same goes for ringwoodite and olivine.)

Obviously the Earth is very big, and so the pressures deep in the Earth are huge. Imagine being underneath hundreds or thousands of kilometres of rock. MASSIVE pressure. (You would be very squished.) What are the rocks like down there? We can only guess, because they are much too deep for us to get at, usually.

There are lots of ways to guess. We can make predictions based on looking at the way earthquakes travel through deep interior of the Earth. We can also do high pressure and temperature experiments. But there is really nothing like a natural sample.

Meteorites, which are fragments of asteroids that have fallen to Earth, provide one kind of natural sample. These rocks have experienced shock pressures equivalent to being thousands of kilometres under the surface of the Earth, and when minerals crystallise out of melt at high pressure, we can get a tantalising glimpse at the minerals that exist deep within our planet.

Ringwoodite, the high-pressure version of olivine, was predicted way back in the 1960’s, and expected to be a very common mantle mineral. The first natural ringwoodite was found in a shock vein of the Tenham meteorite (Figure 4), which fell over Australia in 1879 (Binns et al., 1969). And this year, real terrestrial ringwoodite was found as a little inclusion in a diamond from Brazil. Magma carried this diamond from >660 km depth, all the way up to the Earth’s surface (Pearson et al., 2014). Finding samples of rock that come from this deep is rare.


Figure 4: Tenham meteorite with glass veins.

Even deeper than this, in the lower part of the Earth’s mantle, another high-pressure mineral is thought to exist – and it’s probably the most common mineral on Earth. We’ve called this one ‘silicate-perovskite’ up until last month, when it was seen for the first time in the wild. This mineral, now known as ‘bridgmanite’, was also found in the Tenham meteorite’s shock melt veins.

So it seems that impact events are not only interesting because of death and destruction… rather, looking towards impacts in outer space is one way to study what is deep beneath our feet.


Binns, R.A., Davis, R.J., Reed, S., 1969. Ringwoodite, natural (Mg, Fe)2SiO4 spinel in the Tenham meteorite. Nature 221, 943–944.

Pearson, D.G., Brenker, F.E., Nestola, F., McNeill, J., Nasdala, L., Hutchison, M.T., Matveev, S., Mather, K., Silversmit, G., Schmitz, S., Vekemans, B., Vincze, L., 2014. Hydrous mantle transition zone indicated by ringwoodite included within diamond. Nature 507, 221–224.


The revolution may not be televised – but it can be blogged!

By Tanja

So you may have heard talks about the Earth Physics group within the RSES. You may not know this, but you do know some of them! They allegedly show up at morning teas and student lunches. Also various on and off campus gatherings. Some of them are quite loud, or so I was told1.

You may also have heard talks about this group being unsocial – this is a lie. I infiltrated this group about a year and a half ago and people are far from unsocial. They are lovely, witty, hilarious, social, warm and fuzzy and more than anything PhD students – just like you lot – and they in fact do love to party!

You may have also heard talks about Fluid Dynamics group. This is a group within the Earth Physics group. Everything I just said about the Earth Physics group applies to this small group too – basic tautology and Venn diagrams taught us this. But I have to admit here and now, that it is – unfortunately – very true, that we don’t see much of them. I don’t know why this is. I tend to believe that some horrible Mexican-like standoff went down – way-back in the days that separated this group from the rest. It’s not unlikely in the academia.


Artist rendition of a standoff

It may have been some water-level rise dispute, office space, or a maniac running around with an axe2. I don’t know – but what I do know is that from my limited contact with some of the people within this group, I can almost guarantee that they are amazing!

This is why I decided to go around all the prejudice and smugness and invite this group to our Cake Friday morning tea. I was told they would be there. They weren’t. Well, with the exception of one person who confirmed to me that the invitation DID spread out through the group (thank you my ambassador of goodwill – you know who you are and I appreciate your effort).

I found out later from the ambassador of goodwill that this group has their regular meetings at this particular time when the rest of us are stuffing cakes down our pie holes. Rumor has it they asked to have this moved to a different time. This is positive, eh?!

The revolution has started everyone! We will reunite once again – sooner or later. I am not giving up on this. I was called names for trying – I was accused of wanting more friends. I was told that the universe might explode because of something so improbable … probably happening. Well bring it on universe! Call me a friend if you want! In spite of all of this I have negotiated peace talks with the Fluid Dynamics group and we have successfully moved on. Some bribery in form of cake may or may not have been involved (people talk). Fluid Dynamics group is very welcome to gatherings, teas, lunches and whatnot. I am looking forward to see them there soonish. I’m inviting all of you to join me in this crusade and make them feel so welcome that we can all quickly forget that any separation ever happened.

Stay tuned!


1 The people, not the gatherings. Oh well, actually…

2 This apparently happened

ArtUp your Science

By Thomas

A few weeks back I wrote about the “epicness” and literary quality that is hidden behind the technical terms in which scientific ideas (i.e. hypotheses or theories) are presented.

A picture is worth a thousand words“, so a good way to present your scientific idea to the community are figures. Of course, figures in scientific papers (e.g. data plots, model visualisations, maps) are subject to the same modus of presentation as a scientific text:

Anxious to be accurate, clear and as plain1 as possible.

I often come across figures in papers, which not only tell their part of the story very well, but also look like they were done by a professional designer.

Up to and through my master thesis I always used a combination of Excel and relative simple graphic programs to create my figures. Consequently, they often looked like I let my 5-year-old self do the job.

To be able to create better looking figures in the future I started using Adobe Illustrator a while back. To get a feeling for the program and to learn the basic tools2, I decided to create a map of the Apollo 16 landing site, from which most of my samples are coming from.

Using images taken by the Lunar Reconnaissance Orbiter Camera at different times of the day and a Traverse Map of the Apollo 16 mission I created Figure 1. I marked different craters (red), added the traverse of the astronauts during the mission (orange) and marked the sample locations of the samples I`m working on with different colored dots.

Apollo 16 Area_v1-02

Figure 1: Apollo 16 Landing Site.
Red Areas: Craters; Orange Lines: Apollo 16 Travers Paths; Colored Dots: Sample Locations

Not very impressive, but a start. The nice thing with Illustrator is, that you can save every detail separately and change their appearance later. So I hope, when I learn to handle to program better, I can go back and improve the figure more and more.

But now to the fun part: As I mentioned, the program is new to me. So I started browsing through the menu and play around with the different options. And there are a lot of options – probably more aiming at people doing professional graphic design.

Nevertheless, I started applying different filters, graphic features etc. to the various layers of my figure. The result (Figure 2) can`t probably count anymore as a geological map of any sort, but looks quite “arty”.

Apollo 16 Area_ArtedUp-02-02

Figure 2: ArtedUp Version of Figure 1.

I guess a lot of you have some nice Illustrator files lying around. So if you want to let your creative site out for a walk, dig up some files and Art’em’Up!

If you are pleased with the result, feel free to send them to, and we will display them here.


1 That doesn`t mean scientific figures can`t be detailed. They just eradicate every unnecessary detail.

2 Thanks for the introduction, Paula!

A Brief History of the Moon

By Thomas

Most of my posts here on the blog are related to the Moon, which stems from the fact that my PhD project is on lunar samples. I therefore could devote a big deal of my time in the last two years to read about, what a lot of people, much smarter than me, found out about the Moon.

That means, when I write about some new and/or interesting piece of research about the Moon, I do that on the rag rug of information, that I have mentally stitched together in my head. I try to provide the necessary information, why the topic I`m writing about is “new” or “interesting” (and I hope I succeed at least from time to time).

One of the most vital pieces of information normally needed, is the time or respectively the timeframe of the topic in question. A while ago, I came across the Video “Evolution of the Moon” from NASA that provides a nice summary of key events in lunar history. I think it can provide a nice Guideline through Lunar History, and allow you to place the topics I`m writing about in a broader context.

Source: NASA

The video starts after the formation of the Moon through the Giant Impact of a planet called Theia, about 4.5 Billion years ago. At that time the Moon was likely covered in a Magma Ocean. When this Magma Ocean cooled the Crust of the Moon formed on top.

The oldest feature we can identify on the Crust is the South Pole-Aitken basin, formed by a big impactor slamming into the Young Lunar Crust on the southern farside, that might have even had big effects on the nearside of the Moon. The video states that the impact happened “~4.3 billion years ago”.

You can mentally format the “~” in a bold font and underline it – twice.

The age of this basin could be 4.4 billion years or 4.0 billion years for all we know. It`s actual age could tell us a lot about the next important time frame:

The “Basin Formation/Heavy Bombardment” somewhere between ~4.1-3.8 billion years ago.

This “Late Heavy Bombardment”1 might have been caused by impactors that were the leftovers of the planet formation in the Early Solar System, which randomly hit the Moon over a long timeframe of a few hundred million years.

Or they swept in a wave (or several waves) through the Inner Solar System, caused by migration of the Big Planets in the Outer Solar System. In this case the impactors would hit in a much shorter timeframe (million to tens of million of years), the so-called “Lunar Cataclysm”.

The impacts of the Late Heavy Bombardment formed large basins, that subsequently were flooded by lava, rising up from the still hot Interior of the Moon. The result of this “Mare Volcanism” are the dark areas we still see on the Moons surface today.

Over the next 3.8 billion years the Moon was (and still is) constantly bombarded by meteorites, forming numerous smaller craters. The youngest ones can be identified by the rays that extend from them. These rays are formed from ejected material. The ray systems of older craters were destroyed through the following bombardment.

Of course, the events were not as distinct as in the video. Small Meteorites bombarded the Moon from the Beginning, but they had a minor effect during the time of the big impacts. Volcanism occured as soon as the Crust had formed. The video shows the dominant force acting at the timeframe in question – and it does a very good job at that.

1 “Late” because it happened after the formation of the Lunar Crust.

The Teeny-Tiny Trace of a Giant Impact

By Thomas

The Moon formed in a Giant Impact of a planet called Theia with Earth (Figure 1). You can find a nice simulation of this event at the end of this post or watch the orginal here. In a post a few weeks back I mentioned that there are some problems with the details of this theory and that I would write about that soon.

The Giant Impact

Figure 1: The Giant Impact
Source: National Geographic

As a paper published last week in Science [1] is exactly about that topic, I thought it is time to follow up on this promise. The mentioned paper shows that technology has developed far enough to allow science to tackle the problems lurking within the Giant Impact Theory. Responses in the media (e.g. here, or for german speakers here) about the paper seem to focus on the fact that the paper supports/confirms the Giant Impact Theory.

Yes, the results are in agreement with the theory and therefor support/confirm it!

But to focus on this, implies that the main question we are facing, when it comes to the Moons origin, is:

Was there a giant impact?

Of course one is allowed to ask this question. However, in science this question is only taken seriously if you`ll offer an alternative hypothesis, that works equally well or better in hindsight of the known facts. When it comes to the origin of the Moon, all other origin hypotheses have already been discarded for various reasons and to my knowledge there are no rival hypotheses to the giant impact left.1 The Giant Impact is a fact, and was one before this paper!2

The question is not: Did it happen?

The question is: How did it happen?

The Giant Impact Theory came a long way since it was first proposed in 1975 [2]. It solved a lot of problems regarding chemical similarities and differences between Earth and Moon. But in recent years it got stuck in a bottleneck.

What had happened?

Measurements of the elements oxygen, chromium, titanium, tungsten and silicon had shown that the ratios between the isotopes of those elements were the same in the Earth and the Moon. [3]

Why was that a problem?

Those ratios are fundamentally different in other rocky bodies in our solar system like the asteroids and – more important – Mars. Therefor it is likely that Theia and the Proto-Earth (the Earth before the Giant Impact) differed in these isotopic signatures as well. If that was the case, the standard model of the Giant Impact would predict that those ratios would be different in the Earth and the Moon (Figure 2).


Figure 2: Different Models of the Giant Impact.
Source: Science

Different changes in the model were proposed to achieve the similarity in isotopic ratios, but all of them require very special conditions, such as a fast spinning Proto-Earth or Theia being the same size as Earth (Figure 2) or complex processes following the impact [3-5].

Or maybe Theia didn`t had a similar isotopic signature to the Proto-Earth? For that line of thinking we would have to revise what we assume about the distribution of isotopic signatures in the solar system. That would be a great and enlightening thing to do, but would require samples from a rocky planet other than Mars – preferentially our twin planet Venus. [3]

So what`s the great news?

Actually, the great news are small – very small. That best describes the differences between the isotopic signatures of Earth and Moon rocks which now were uncovered.

But didn`t I said above that there were no such differences?

Indeed, but I should have added “within error”. The error is used to describe the area of uncertainty around a measured result. For example, I know I`m 185 cm tall. But I have never measured that very accurately, so it could easily be that I`m actually 1 cm taller or smaller. The 1 cm is the error on the measurement of my height. If I now meet a person who has measured his or her height (equally lax) to be 185 cm, we would have to conclude that we are equally tall (within error), even though he or she might be 186 cm and I only 184 cm. How can we find out? We have to measure more precise, let’s say with a mm-scaled tape.

In a nutshell, that is what the new study did – measured more precise. They found that when you compare 1 million oxygen atoms on Earth to 1 million oxygen atoms on the Moon, you`ll find that 123 of those atoms are different isotopes4.

This means a great relief, for some reasons:

a.) It means there is a difference in those isotopic signatures and we don`t have to invoke very special conditions5 for the Giant Impact.

b.) It promises that we`ll find similar differences in the other isotope systems apart from oxygen.6

c.) When we know how the Earth and the Moon differ, we can infer more on the nature of Theia, the Proto-Earth and the details of the impact.7

And that is much more, than just to confirm that there was a Giant Impact!


A simulation showing the Giant Impact.
Source: Nature

1 That doesn`t mean someone might come up with a new one in the future.

2 Imagine the media would title every article about new advances in evolutionary biology with “Evolution Confirmed!” – Technically true, but still missing the point.

3 If we`re including the error: 9-15

4 Don`t worry about the isotopes. It basically is like two boxes filled with 1 million red and blue balls, where one box has 12 more of the blue balls. Even finding that out, would be hard. Now imagine that on an atomic scale, where you can`t “see” the atoms and where the difference between the balls is the equivalent of blue and very-slightly-darker blue.

5 Special conditions are often a sign that there`s something wrong with your theory.

6 Oxygen isotopes were the first to indicate the similarity-problem [6], it`s good that they make up by showing a way out.

7 In the presented paper, the authors speculate on the basis of their data, that Theia might have had a enstatite chondrite composition, which is material we find in the asteroid belt. But we have to see what the future (and other isotopic systems) will bring.


1. Herwartz, D., et al., Identification of the giant impactor Theia in lunar rocks. Science, 2014. 344(6188): p. 1146-1150.
2. Hartman, W.K. and R.D. Davis, Satellite-Sized Planetesimals and Lunar Origin. Icarus, 1975. 24: p. 504-515.
3. Canup, R., Lunar conspiracies. Nature, Vol. 504, 2013(7478): p. 27.
4. Elkins-Tanton, L.T., Planetary science: Occam’s origin of the Moon. Nature Geoscience, 2013. 6(12): p. 996-998 (2013).
5. Clery, D., Impact Theory Gets Whacked. Science, 2013. 342(6155): p. 183-185.
6. Wiechert, U., et al., Oxygen isotopes and the moon-forming giant impact. Science, 2001. 294(5541): p. 345-348.