Did you know that diamonds could be one of the most common rocks in the universe? While carrying out literature research for this series, I experienced amazement after amazement about where one can find these shiny stones…
We will discover in this episode that diamonds from space hide in interstellar dust, in asteroids and in… the walls of a German town. You will see, the latter is so amazing that it has defined where I will most probably spend my next travel holidays!
1/ Where did we find diamonds in our sky up to now?
In the two first episodes we realized that stars like our sun might well end their life as being a huge planet-sized diamond floating in the sky. We realized this by understanding which conditions are required for diamonds to form and remain stable. (episode 1, episode 2)
Then, in the 3rd episode, we swam inside the liquid diamond ocean of Neptune, admiring huge diamond icebergs floating at its surface, while protecting ourselves from the diamond rains. The second part of this episode looked at the thermodynamic data that allowed us to realize that this romantic sci-fi landscape was probably real. Liquid diamond oceans do exist in our own solar system!
After this, we resumed our search for diamonds in the sky by visiting carbon planets, where we admired oily tar-like oceans from on a beach made of diamond sand, while in the background, an active volcano was spitting out diamond crystals.
Following this incredible expedition, we looked at the scientific literature to figure out if these hypothetical planets could actually exist. We realized that in the current state of our knowledge, they probably do, even though they may be rare (1 carbon planet for 10 stars). Still, their number should increase with the age of the universe and carbon planets might even become the most common planet type in the far future. (episode 2, episode 3)
So are we done? Have we listed all the diamonds in the sky?
As you will see in this paper, we definitely have not. Are you ready for the ride?
2/ Diamonds could be the most common mineral in the universe.
We have seen in a Part 2 that diamonds are made entirely of carbon atoms that arrange themselves in an offset sp3 configuration.
In addition, in Part 3 episode 2, we learned that diamonds form at high pressure high temperature, and then are metastable when the conditions return to normal (i.e. the carbon atoms can remain in a diamond form for millions or even billions of years) .
Keep these two facts in mind…and now let’s look at what are the most common elements in our galaxy.
Yes, Carbon is the 4th most common element in our galaxy. Sample 1 Kg of matter from an interstellar clouds floating around in our galaxy, and about 5 grams of it consist of carbon atoms.
Carbon is a stable element. This means that Carbon does not decay naturally into another element. So carbon atoms can be floating around for billions of years, without being disturbed, until one day something happens to them. And in our universe, when something happens, it is often cataclysmic, like the shock wave of a supernova, the birth of a star, the coalescence of black holes etc.
All these events involve in one way or another that our lonely carbon atoms may condensate into grains of graphite, and be subjected (simultaneously or later) to high temperatures and high pressures… Thus, it is possible that, under such conditions, a significant fraction of the carbon atoms in the universe take on a diamond structure. That could mean that our random kilogram of matter contains amounts of diamonds that could be counted in grams!
3/ Interstellar dust is more glamorous than it appears…
We have seen that carbon and oxygen are the most common heavy elements formed in stars. These heavier elements can condensate into microscopic grains and be insufflated into the vacuum of space by either the stellar winds of their dying star or the shock waves of supernovas.
An article by Anders et al. suggested for example that microscopic diamonds are formed in the atmosphere of red giants and are dispersed in space when the star goes supernova. These diamonds are really tiny: millions of them could fit in the volume of a pin head. Thus with time, space between stars gets enriched with these nano-diamonds.
Consequently the gas clouds of hydrogen and helium from which new stars are born get also enriched with heavier elements, including significant amount of nanodiamonds.
We have discussed in a previous article that just after the birth of a star, the accretion disc of dust and gas that forms around it condensates into grains. With time, these grains aggregate with each other to form rocks, asteroids, planetesimals and finally planets.
If the original dust cloud was enriched with nanodiamonds, the resulting massive objects formed out of it would also contain nanodiamonds.
But that’s not all…
4/ The hidden diamonds encrusted in asteroids
The formation of planets is a very violent process that goes through a tremendous amount of very energetic collisions between aggregates. For example asteroids or planetesimal can collide and explode into smaller parts, re-aggregate again by gravity, collide again etc…
With time, bigger and bigger bodies are formed. It is the aggregation process that wins leading finally to the formation of planets (a planet is defined by a spherical body that has ‘cleaned up ‘ its orbital path).
A fascinating example of collision is the Theia hypothesis: in the early days of our own solar system (between 20 to 100 million years after the birth of the sun), The Earth was nearly formed when it crossed the path of another planet in formation called Theia. The collision must have been really cataclysmic! The Earth became a gigantic ball of overheated magma around which the fragments left of Theia went into orbit and formed rings. In time, the particles coalesced into what is now known as the Moon.
Each of these collision led to very high pressure and temperature conditions, ideal conditions for carbon to take on a diamond structure. Even today, there can still be some epic collisions that occur in the asteroid belt. At the impact points, diamonds form. Asteroids of our solar system, especially carbonated ones, most probably contain diamonds in large quantities. Many of those we have had a chance to analyse the composition do.
What is also quite fascinating is that the geological study of these diamonds is like a window on the origins of our solar system. For example, in a paper published in Geochimica et Cosmochimica Acta, Masaaki et al. observed that a meteorite that fell in on Earth in 2008 had diamonds much larger than expected. This suggests that these could not originate either from interstellar dust, or from standard asteroid collisions, but were actually formed inside a planet that existed in the violent early days of our solar system and that has been pulverized since. The corresponding meteorite would be a remnant of this hypothetical planet!
But wait… there’s more… and this time closer to home… much closer… I might even go there for a week holiday next summer…
5/ Nordlingen, the town built with diamonds
If I told you that there is a whole town made of diamonds, you would think that writing this series got me bonkers, right? Well no, I have not lost my mind yet ;-), such a city exists.
Nordlingen, in Germany, is located on the exact spot where a meteorite hit the Earth about 15 million years ago. The impact left a 26 km wide crater that early settlers took for the mouth of a long-extinct volcano. It is only in the middle of the 20th century that geologist realized that the crater did not match that of a volcano. Further observations of the local geology revealed that the crater was that of a 1 km meteor that collided with Earth at 26 m/s.
The violence of the impact led to the right conditions for the transformation of the carbon within the meteor into tiny diamonds not more than 0.2mm wide. These diamonds are now encrusted in the local rock, named suevite, which was used by the early settlers to build the city.
I read that when wandering in the old part of the city center on a sunny day, the walls, the pavements and the stairs illuminate with flashes of light. This shimmering originates from diamonds embedded in the materials used to build them. It was estimated that there are 72000 tons of diamonds encrusted in the buildings and walkways of Nordlingen. Amazing isn’t it?
I was looking for a nice place to visit this summer, not too far away, yet exotic enough. I think I found my next holiday destination, and it's a city made of diamonds.
References and to dig deeper
- "Unique large diamonds in a ureilite from Almahata Sitta 2008 TC3 asteroid" (Masaaki et al., 2015). (link)
- "The diamonds that came from space" (Michael Marshall). (link)
- "The German town encrusted with Diamonds" (Matthew Vickery). (link)
- "Interstellar grains in meteorites" (Brewer et al., 2016). (link)
- "The carbon-to-oxygen ratio in stars with planets" (Ulrich Ott, 1993). (link)
- "Interstellar grains in meteorites : Diamond and silicon carbode" (Anders et al., 1989). (link)
- "Diamonds in the Sky" (Peter Tyson). (link)
- "Tiny diamonds in space as clue to evolution of stars" (John Noble Wilford). (link)
- "Diamonds Beneath the Popigai Crater" (Hobart M. King). (link)
- https://en.wikipedia.org/wiki/Giant-impact_hypothesis#Theia
- https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements
Image Credits:
- The post's thumbnail background is a an artistic view by NASA/JPL-Caltech (link)
- The white dwarf with a gas giant in the foreground is by NASA/JPL-Caltech (link)
- The picture of the diamond ocean with the iceberg and the diamond rain was put together by
using a picture found on wikimedia common and authored "Visit Greenland from Nuuk" (link)
- The theoretical phase diagram for carbon was found on wikimedia commons (link)
- The diamond structure is public domain and was created by Ben Mills (link)
- The crab nebulae picture is by NASA, ESA, J. Hester and A. Loll (link).
- Theia collision by NASA/JPL-CAltech (link)
- Global view of Nordlingen By Wolkenkratzer (link)
- Microscopy picture of nanodiamonds By D. Mukherjee (link)
- The accretion disc showing rock formation is by wilyD (link)
- Asteroid collision by NASA/JPL-Caltech (link)
- Pictures not mentionned in this list originate from Pixabay
- All text and illustration added on pictures are by
- Illustrations by
Diamonds in the sky series - Previous episodes:
- Part 1: The story of how our sun will become a massive diamond floating in the sky.
- Part 2: Clathrate Stars
- Part 3: Diamond Oceans (Episode 1/2)
- Part 3: Diamond Oceans (Episode 2/2)
- Part 4: Carbon planets (Episode 1/3)
- Part 4: Carbon planets (Episode 2/3)
- Part 4: Carbon planets (Episode 3/3)
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My life revolves around music production, teaching sciences, and discovery through travel.
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