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Australian National University scientists discover more about the makeup of the Earth

Nick Whigham, September 21, 2017 7:24PM News Corp Australia

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Australian scientists believe they have come up with a new way to tell what's inside Earth. Picture: NASA media_cameraAustralian scientists believe they have come up with a new way to tell what's inside Earth. Picture: NASA

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It might come as a surprise to you, but there’s actually a lot we don’t know about the Earth’s composition*.

This also shocked Dr Charles Lineweaver, a planetary scientist at Australian National University in Canberra, who assumed scientists had a better knowledge of what made up our planet.

“We, too, were surprised that we didn’t know this better than we did,” he said.

Our deepest drilling can only scratch the surface of the planet so scientists use magnetic fields and seismic waves* to measure the density* and movement of the various materials deep below our feet.

We know, for example, that the core of the Earth is mostly iron and that more than 90 per cent of the planet’s mass is made up of iron, oxygen, silicon and magnesium.

But the finer details about the internal makeup of Earth aren’t understood.

Researchers from the Canberra-based university Dr Lineweaver, Haiyang Wang and Professor Trevor Ireland believe they have come up with “a new and improved elemental composition of Earth”.

Cut-away diagram showing the Earth's core. Picture: Getty Images media_cameraCut-away diagram showing the Earth’s core. Picture: Getty Images

The motivation for the project was to better understand the makeup of planets both within and outside our solar system, to know which ones could be habitable*.

“Basically we’re astrophysicists. We’re starting to find exoplanets* all over the universe and we know that they’re rocky and wet and many of them are going to be very Earth-like and we want to know more about these things.”

Astronomers have been estimating the composition of stars in the galaxy for about 100 years, Dr Lineweaver said.

NASA artist rendering of satellite orbiting the globe. Picture: AFP media_cameraNASA artist rendering of satellite orbiting the globe. Picture: AFP

“We said; wait a minute, if we know the composition of the star, that probably tells you a lot about the composition of the rocky planets that we strongly believe are in orbit around almost every star.”

To test this theory they looked at the composition of the Sun and the Earth to better understand the process that took place 4.6 billion years ago that formed the early Sun, Earth and other planets.

But when they set about “making the best comparison ever of the Sun and the Earth” by looking at all the data and literature on the elemental composition they realised there were huge gaps in the knowledge.

“We were very disappointed and said we’re going to have to do this ourselves,” he said.

That was about a year ago and their efforts have now been published in the international journal Icarus.

The new model produced by the research suggests Earth contains significantly more of several scientific elements that can be found on the periodic table including sodium, potassium, chlorine, zinc, strontium, fluorine, gallium, rubidium, niobium, gadolinium, tantalum, helium, argon, and krypton than previously believed.

The Milky Way. Picture: Martin George media_cameraThe Milky Way. Picture: Martin George

It also points to the fact that the abundances of magnesium, tin, bromine, boron, cadmium, and beryllium within our planet seem to be significantly lower than previously thought.

Co-researcher Prof Trevor Ireland from the ANU Research School of Earth Sciences said planetary scientists would find many uses for this new composition record.

For Dr Lineweaver, the next step is to use the type of analysis used in the paper to investigate the composition of the planets around Alpha Centauri, the closest star system to our own.

Alpha Centauri is about 4.37 light-years away and is thought to host some potentially Earth-like planets.

The big question, said Dr Lineweaver, is: “How will they be different from Earth and what does that mean for their habitability*?”

GLOSSARY

  • composition: make-up
  • seismic waves: elastic waves produced by earthquakes
  • density: how compact it is
  • habitable: able to be lived in
  • exoplanets: planets orbiting stars outside the solar system
  • habitability: how easily it can be lived in

LISTEN TO TODAY’S STORY

CLASSROOM ACTIVITIES
 1. Earth’s composition
Draw a table with two columns.
In one column list the things scientists knew before conducting this research and, in the other, list the new knowledge they discovered.

Extension
Why do you think scientists are trying to find other planets that are habitable? What could be the benefits of having access to other planets that are habitable like Earth?

Time: allow 30 minutes to complete this activity
Curriculum links: English, Science

2. Earth’s elements
Use a Periodic Table to help complete the following task.
You can find one online if you don’t have one at school to access.

Make a list of the elements that the article says can be found in the Earth.
Find the symbol for each one.

Extension
From this list choose one element that you have heard of before and one you haven’t.
Find out three facts about each of these elements.

Time: allow 30 minutes to complete this activity
Curriculum links: English, Science

VCOP ACTIVITY
VCOP Everything
Create a tally of the VCOP included in this article.
Draw four columns with the headings vocabulary, connectives, openers and punctuation.

Highlight the VCOP in the article and then tally how much of each has been used.

Extension:
Create a graph displaying the data you have discovered. What VCOP is used throughout the article?

Time: allow 15 minutes to complete this activity
Curriculum links: English, Big Write, VCOP

EXTRA READING 

CANBERRA TO CAPTURE CASSINI’S FINAL TRIP

HURRICANE HARVEY HITS US

NASA’S COOL SUPERVOLCANO PLAN

MAN, WE’RE IN HOT WATER

SLICE OF MOON HIDES IN OUR SHADOW


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