The interior of Mars has been simulated for the first time
The interior of Mars has been simulated for the first time and it could tell us what the Red Planet is made of and how it was formed.
Seismic tremors are giving up the Red Planet’s darkest secrets, say scientists.
The regular quakes hold the key to uncovering the mystery of our most habitable neighbour’s formation.
Now their velocity has been measured on Earth using data from the InSight lander.
The Nasa probe has detected hundreds of significant events since touching down in 2018.
Seismic data reveals how the underground rock of a planet is layered – as well as its origins.
Lead author Dr Keisuke Nishida, a planetary scientist at the University of Tokyo, said: ‘The exploration of the deep interiors of Earth, Mars and other planets is one of the great frontiers of science.
‘It is fascinating partly because of the daunting scales involved, but also because of how we investigate them safely from the surface of the Earth.’
The core of Mars is thought to mostly comprise iron with some possible lighter elements such as sulphur.
His team’s experiments on iron-sulphur alloys will be compared with observations made by Insight and other Martian space probes in the near future.
The results will either confirm existing theories about the planet’s composition or call into question the story of its origin.
Mars is between 35 million and 250 million miles away depending on where Earth is relative to the sun.
Donald Trump wants the first manned mission by 2033 but getting there will be extremely difficult and dangerous.
Dr Nishida said: ‘It is sometimes more sensible to investigate the Red Planet through simulations than to send an expensive probe or, one day, people.’
Given how inaccessible the Earth’s core is, direct observations of Mars’ will likely have to wait some time.
But seismic waves are like enormously powerful sound waves. They can travel through a planet and offer a glimpse inside.
Dr Nishida said: ‘However, even with the seismic data there was an important missing piece of information without which the data could not be interpreted.
‘We needed to know the seismic properties of the iron-sulphur alloy thought to make up the core of Mars.’
His researchers calculated the speed of primary, or P, waves, the fastest type of seismic wave, in molten iron-sulphur alloys. The other, known as sheer, or S, waves arrive slower.
Dr Nishida explained: ‘Due to technical hurdles, it took more than three years before we could collect the ultrasonic data we needed, so I am very pleased we now have it.
‘The sample is extremely small, which might surprise some people given the huge scale of the planet we are effectively simulating.
‘But microscale high-pressure experiments help exploration of macroscale structures and long time-scale evolutionary histories of planets.”
A molten iron-sulphur alloy just above its melting point of 1,500 degrees Celsius and subject to 13 gigapascals of pressure has a P-Wave velocity of 4,680 metres a second.
This is over 13 times faster than the speed of sound – which is 343 metres a second.
The researchers used a device called a KMAP (Kawai-type multianvil press) – designed to produce extremely high pressures in a very small space.
They used powerful laser beams at two radiation facilities in japan where extreme conditions inside planets can be recreated.
This enabled them to image the samples in order to then work out the P-wave values.
Dr Nishida added: ‘Taking our results, researchers reading Martian seismic data will now be able to tell whether the core is primarily iron-sulphur alloy or not.
‘If it isn’t, that will tell us something of Mars’ origins.
‘For example, if Mars’ core includes silicon and oxygen, it suggests that, like the Earth, Mars suffered a huge impact event as it formed.
‘So, what is Mars made of and how was it formed? I think we are about to find out.’
InSight is equipped with seismometers that detect ‘Marsquakes’. They are not big – only 3 to 4 on the magnitude scale if you were standing directly above them.
Their size and frequency is actually not that dissimilar to the UK where a magnitude 4 event will occur roughly every two years.
But they show that far from being dull and dead Mars – like Earth – is an active planet.
Taken together, Insight’s data should reveal the position and nature of all the rock layers below the surface of Mars – from the crust to the core.
It’s information that can then be compared and contrasted with Earth. Both planets formed around the same time – about 4.6 billion years ago.
But they are very different – which has baffled experts for decades. Dr Nishida believes the mystery is about to be solved.
Seismic waves pick up information as they travel through different rocks. It appears as wiggles on a graph.
But many Marsquakes from different directions can piece together a three dimensional image of the inside.
Nasa last sent seismometers to the Red Planet on the Viking landers in the 1970s. But the instruments were positioned on the body of the probes.
All they recorded was the landers’ shaking as the wind whistled by. InSight has placed its seismometers directly in the Martian dirt.
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