Forty thousand light years away sits a planet that consists almost entirely of diamond. Recently, scientists used gold and lasers to investigate what the immense pressure of the planet would do to the diamond at its core

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Forty thousand light years away sits a planet that consists almost entirely 

of diamond. Recently, scientists used gold and lasers to investigate what 

the immense pressure of the planet would do to the diamond at its core.

In this lesson you will investigate the following:

•  What is pressure?

•  How do we measure pressure?

•  What is the role of pressure in the formation of rocks?

•  How are diamonds formed?

•  Can we create an analogue to model the effects of pressure on rocks?

Welcome to the high-pressure, sparkling world of planetary science!

This is a print version of an interactive online lesson. 

To sign up for the real thing or for curriculum details 

about the lesson go to

Earth and Space Sciences

Pressure: How to make a 

diamond planet

Introduction: Pressure

Diamond is one of the hardest things we know. It is so hard that when scientists want to test what happens to materials under

high pressure they usually crush them between two diamonds. But what if you want to crush diamonds?

Scientists recently set a world record in high-pressure experimentation, creating enough pressure to very briefly – 25 billionths of a

second briefly – squeeze a sliver of diamond to a quarter of its original size. It required five terapascals' pressure – roughly

equivalent to 40,000 Asian elephants standing on your toe!

The scientists created the pressure by placing the diamond in a small gold cylinder and then aiming 176 powerful lasers at the

cylinder. The energy from the lasers vaporised the gold, turning it from solid to gas in an instant. This explosion pressed in on the

diamond from all directions, putting it under immense pressure. 

Pressures at this scale might be used in nuclear fusion reactors of the future and could also lead to discoveries of exotic new

materials. But there's another more surprising link to this research, to do with diamonds in particular. Forty thousand light years

away is a planet that scientists believe consists almost entirely of diamond. But can it be diamond to the core, or do the crushing

pressures inside the planet force the carbon (which diamond is made out of) into some other form? 

It is possible that in the centre of the "diamond planet" high pressures create materials at present unknown to us, much as the

intense pressures and temperatures inside Earth create new minerals from existing rocks. 

Read the full Cosmos magazine article 



Question 1

Paint a picture: The introduction uses an analogy of 40,000 Asian elephants on your toe to try and convey the immensity of five

terapascals' pressure. Such analogies are often important in the communication of scientific ideas, as they help people relate to

things well outside their experience. Create another two examples of this immense pressure, that could have been used instead.

Gather: Pressure

Pressure is force applied to a given surface area. You can increase pressure by increasing the force or by decreasing the area.


1. Pressing into the palm of your hand with your finger; and

2. Pressing into the palm of your hand with the same force, but pushing a pin.

Big difference, isn't there? The force is the same but with the pin it is concentrated into a much smaller area, so there's a much

greater pressure.

The standard unit of pressure is the pascal (Pa). 

One pascal isn't much – a sheet of A4 paper on your open hand puts about five pascals' pressure on the hand. You can barely

notice it. So you'll often see pressures given in kilopascals (kPa) or other large units. 

The air pressure at sea level is 101.3 kPa

. We don't really notice it because our bodies are at the same pressure, pushing back

against the air so we are not crushed.

But it's not the same when we go underwater. Even diving to the bottom of a pool you can feel the extra pressure on your ears.


Measuring pressure

Question 1

Research: To avoid having to write enormously large or small numbers scientists add prefixes to the units they use to measure


Perform an internet search to find a list of unit prefixes to help fill in the table below. 

Hint: You will not be able to write superscript numbers (e.g. the 3 in 10 ) so write it like this instead: 10^3.




Magnitude (size)




It takes 2 ______seconds for a plant to trap a photon of

sunlight for photosynthesis



A virus is about 100  ______metres across


Merino wool can be as fine as 15 µm diameter




Take 10 millilitres of the medicine daily



A marathon is 42.2 ______metres long


She bought a 20 megapixel camera


A 200 GB broadband plan



The highest pressure achieved experimentally is 5 _Pa

Question 2

Investigate: Give two more examples using unit prefixes from the table.

At the Earth's surface the air pressure is caused by the weight of the air above. Air molecules all the way to the top of the

atmosphere are pulled down by Earth's gravity.

In the ground the pressure is higher. Not only is there the weight of the air above pressing down, but the weight of the rock and soil

above as well. The deeper you go the greater the weight of material above and the greater the pressure. 

Did you know?

In rock the pressure increases about a hundred kilopascals (roughly one atmosphere) every four metres you go down, while in

water you have to go down ten metres for the same pressure increase.

What's the pressure inside the Earth?

Question 3

Order: Type each of the six pressures below into the appropriate rectangle in the sketchpad. Take into account the altitude or depth

of the rectangle and the type of material above it.

30 kPa   |   101 kPa   |   104 kPa   |   400 kPa   |   850 kPa   |   25,000 kPa 

As well as the high pressure it's also hot underground – over 500 ºC 20 km down. The intense temperatures and pressures can

change the chemical constitution of rocks. Rocks changed this way are called metamorphic rocks. They form part of the rock cycle. 

The rock cycle

Image credit: Kate Patterson / Medipics and prose.

Question 4

Match: Fill in the table with processes from the list below. The processes (one or more) act to change one material into another in

the rock cycle. 

weathering   |   compaction   |   melting   |   high pressure   |   deposition   |   cementation   |   transport   |   burial

Start material

Process 1

Process 2

Process 3

Process 4

End material

  Igneous rock




  Sedimentary rock

  Sedimentary rock

high temperature

  Metamorphic rock

  Metamorphic rock


Metamorphic rocks


Question 5

Define: Define these three important terms:



Metamorphic rock

Contact metamorphism

Regional metamorphism

Before continuing, watch 

this ABC Catalyst video

Question 6

Classify: In the table below write the metamorphic rock next to its unmetamorphosed parent. 

Unmetamorphosed rock

Metamorphosed rock




Question 7

Communicate: Create a diagram, flowchart, table, mind map or other graphic organiser to show how metamorphism fits in the

rock cycle.  

You can use any of the tools below or upload files or photos of handwritten work.

Process: Pressure

In the experiment described in the Cosmos article a diamond was compressed to a quarter of its original size. That's particularly

impressive because diamonds are one of the hardest materials known. 

Diamonds are hard because of their molecular structure. They are made out of pure carbon, the same as graphite (the "lead"

in pencils), and coal is mostly carbon as well (70–90%).

Each carbon atom can bond to four other atoms. In graphite, though, the atoms bond with just three others, forming sheets one

atom thick. The sheets are able to slide away easily, which explains why pencils leave a trace as you draw across paper.

In coal the atoms are jumbled up with no regular pattern. Diamonds are at the opposite extreme. In them, each atom links to four

other atoms, forming a very strong, rigid, three-dimensional lattice – a crystal. It is this structure that makes diamonds so hard, able

to withstand high pressures.

Diamonds, graphite & coal

Image credit: Kate Patterson / Medipics and prose.

Question 1

Link: In graphite each carbon atom bonds with three other atoms, forming a flat sheet. Draw lines to show the bonds between the

atoms in the sketchpad. You should get a regular hexagonal pattern.

The bonds to atoms just outside the picture have been put in for you.

Question 2

Link: In diamonds each carbon atom bonds with four other atoms, forming a rigid three-dimensional crystal. This structure is

difficult to show in two dimensions, so for this question show just the bonds from one carbon atom to four others. 

Hint: You should be able to recognise the shape you create from the diamond structure diagram above. 

It may seem surprising, but just like other gems, diamonds are part of the rock cycle. They are created from graphite under

conditions of extremely high pressure and temperature.

Making diamonds


Question 3

Recall: Use the video to fill in the blanks in the table below, summarising the process of diamond formation.

Note: Prof. Haggerty gives the pressure that diamonds are formed in kilobars. One bar is equal to 100 kPa.

Prompt for the video


Diamonds were discovered in South Africa in the ___________ century.

They are formed deep within the Earth in an area called the ______________.

The mantle of the Earth is between its crust and its _______________________ .

Diamonds are made from the element ________________ , whose molecular structure is changed by

_______________ and ____________________.

This new structure is described as a _________________-like structure.

Diamonds form at a temperature and pressure of __________________and _______________ respectively.

_________________ is the volcanic rock that transports diamonds to the surface of the Earth.

The Earth is made up mostly of oxygen, iron, silicon and magnesium – carbon is less than 1%. So the Earth is not even a carbon

planet let alone a diamond plant. 

In contrast, scientists believe they have identified a few planets outside the solar system that have high proportions of carbon. One

of them is called PSR J1719-1438 b. Scientists estimate it could be 80% carbon.

Diamond planets


Cosmos challenge

Question 4

The pressure inside planets is due to gravity acting on all the matter that the planet is made up of, with all the parts attracted to

each other. The strength of the attraction is due to the amount of matter – the mass – and how close the different parts are to one


PSR J1719-1438 b is smaller in volume than Jupiter, but has the same mass.

Do you think the pressures at the centres of these two planets are different, or the same? If different, which one do you think has

the higher pressure? Explain your reasoning.

Question 5

In Jules Verne's Journey to the Centre of the Earth a group of

travellers descends into a volcano and finds, underground, vast

lands and oceans with prehistoric animals and humans. Of

course, the story is fictional and we're pretty sure that there's

nothing like that down there.

Imagine you are in a new exploratory mission to descend to the

very centre of the Earth in a futuristic submersible that can

"melt" it's way through solid rock. 

Tell the story of your journey and the adventures you might

have. What will happen to the temperature and pressure

outside as you descend? What sorts of materials will you go

through and what might you see through the porthole? Will

gravity change?

Apply: Pressure

Modelling the effects of pressure in metamorphic rock formation

Image credit: Kate Patterson / Medipics and prose.

Shale is a sedimentary rock that, under heat and pressure, metamorphoses into slate. With further heat and pressure the slate

turns into phyllite, even more, into schist, and with more again schist turns into gneiss (pronounced "nice"). With any more heat and

pressure the rock turns into magma.

Shale can contain a range of minerals, all of which go through the same processes and may each respond in different ways. One

such mineral is mica – often present as small, light-coloured, shiny flakes distributed through the shale. Sometimes you see seams

of mica in rocks at the beach.

An analogue is something that has properties similar to another type of thing, and which might be able to be used to model or

represent the other thing. We are going to produce an analogue for the metamorphic process of turning shale to schist.

Model the effects of pressure on shale as it metamorphoses by crunching up and applying increasing pressure to aluminium foil. 

Small flat areas in the crunched up foil can be thought of as representing crystals of mica.

4 pieces of aluminium foil approximately 30 cm x 30 cm

1 magnifying glass or hand lens

Rolling pin or similar

Hammer or mallet

Hard work bench able to withstand hammering

Safety glasses




If possible, samples of shale, slate, phyllite and schist for comparison

1. Take one sheet of the foil and form it into a loose ball. Do not press strongly.

a. Examine the ball closely with the magnifying glass. Notice little flat areas aligned in different directions.

b. Sketch a small area of the surface to show several of the flat areas.

c. Annotate your sketch to describe the features you see (useful words: edgescurvesanglesvalleysgapsflat areas)

d. Try to measure the sizes of the flat areas. Record your observations.

e. If you have a camera, take a close-up photo of the ball's surface.

f. Compare your observations with the shale sample if you have one. Record your observations.

2. As before, form the second piece of foil into a loose ball then squash it with your hand.

a. Examine the foil carefully – make the same observations as previously.

b. Compare to a piece of slate if you have one. Record your observations.

3. With the third piece of foil follow the instructions for the previous two steps, then firmly squash it again using the rolling pin.

a. Examine the foil carefully – make the same observations as previously.

b. Compare to a piece of phyllite if you have one. Record your observations.

4. With the fourth piece of foil follow the instructions for the previous three steps, then hammer it until it is as flat as you can

make it. Wear safety glasses for this step – pieces of foil may break off (which itself simulates what can happen in the process

of schist forming).

a. Examine the foil carefully – make the same observations as previously.

b. Compare to a piece of phyllite if you have one. Record your observations.


Question 1

Use your choice of the widgets below to present your data. Upload photos of your sketches and any photos you took of the foil


Hint: You can upload images into the Sketchpad and then annotate them if you like.



Question 2

Summarise the main changes you saw as the pressure was increased on the foil.

Question 3

What happened to the small flat areas in the foil that you observed in the first part of the experiment, as the pressure increased? 

It was suggested above that these areas could model mica crystals in shale. Do you think it is a good analogue? 

Question 4

Overall, compare the changes you documented in the foil to the changes in the rocks. If you did not have rock samples, use the

pictures above.

Question 5

Assess how good an analogue this experiment is for the process of rock metamorphosis.

In what ways is it a good analogue? In what ways a poor analogue? Suggest ways in which the experiment could be made to model

metamorphosis more accurately.


Question 6

Summarise the points you made in the discussion section above to provide a conclusion to the experiment. The conclusion must

directly address the aim of the experiment. 

Career: Pressure

Jordan Theseira grew up in Kuala Lumpur, the sunny capital city of Malaysia, surrounded by bustling roads and

skyscrapers. It's a far cry from the dry, desolate mining areas of Western Australia where, working in a laboratory, he spends his

days now.

Like many high school students, Jordan didn't know what he

wanted to be when he left school. He was good at calculus,

which derives its name from the Latin term for “pebble”, but he

doesn’t study calculus now – he studies rocks of a totally

different kind. 

At university Jordan decided he wanted to pursue a career in

Earth sciences. His time studying geology at university taught

him many interesting things about the Earth. He was fascinated

by everything -- from how its landscapes were formed to how so

many rocks and minerals ended up in its crust.

“There are still many questions about the Earth that I

find intriguing,” says Jordan, “for example, what makes some

rocks harder than others? And why does gold only occur in

certain rocks?”

Answering these questions is a big part of Jordan's job as an

extractive metallurgist. He works long hours analysing rock

samples, trying to figure out how to best extract valuable ores

and minerals from them. In order to do this it is crucial to

understand the origins of each type of rock, he says. It's hard

work and the lab can get dusty and noisy, but the satisfaction he

gets from unlocking the secrets of the planet makes

it worthwhile to him.

When he isn’t making a mess “rocking out” in the lab, Jordan

likes keeping his body and brain busy. He enjoys staying fit,

watching documentaries, and tackling minor science projects of

his own.

Question 1

Imagine: ​You are a metallurgist like Jordan, living and working in the gold mining town of Kambalda, near Kalgoorlie in WA. What do

you think are the benefits of living in a small community like this, where everyone either works in the mines or provides goods and

services to the mine workers? List five benefits and describe why you would find these attractive to you.

Cosmos Lessons team

Lesson authors: 

Kathryn Grainger and James Driscoll

Profile author:

 Yi-Di Ng


Jim Rountree and Bill Condie

Art directors: 

Robyn Adderly and Anton Banulski

​Education director:

 Daniel Pikler

Image credits: 

Kate Patterson / Medipics and prose, iStock,

Marian Kemensky / Political

Video credits: 

National Geographic, NrNingaMittens, Michael

Sammartano and YouTube.

Document Outline

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