Since going to Mars, one of our closest terrestrial neighbors, is still very far away, Japanese scientists have tried something on our own planet with simulations and found that the iron-sulfur alloys thought to comprise the core of Mars to reveal details about the planet’s seismic properties for the first time.
This information will be compared to observations made by Martian space probes in the near future when Mars missions yield results. Mars is usually 55 million and 400 million kilometers away from the Earth depending on where both the planets are relative to the sun.
Keisuke Nishida, an Assistant Professor from the University of Tokyo’s (Todai) Department of Earth and Planetary Science and his team studied the seismic data and composition which revealed the present state of the red planet, including its past and the possible origin.
“The exploration of the deep interiors of Earth, Mars and other planets is one of the great frontiers of science,” said Nishida. “It’s fascinating partly because of the daunting scales involved, but also because of how we investigate them safely from the surface of the Earth.”
For a long time it has been theorized that the core of Mars probably consists of an iron-sulfur alloy but it will take decades to confirm scientifically. Hence, the Todai team focused on seismic waves, which are akin to enormously powerful sound waves, and can travel through a planet and offer a glimpse inside, albeit with some caveats.
The Missing Middle
“NASA’s Insight probe is already on Mars collecting seismic readings,” said Nishida. “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-sulfur alloy thought to make up the core of Mars.”
Nishida and the team have measured the velocity for P-waves (one of two types of seismic wave, the other being S-waves) in molten iron-sulfur alloys. The study that last for more than three years to collect the ultrasonic data, however, helped to throw some light on the red planet. “A molten iron-sulfur alloy just above its melting point of 1,500 degrees Celsius and subjected to 13 gigapascals of pressure has a P-Wave velocity of 4,680 meters per second; this is over 13 times faster than the speed of sound in air, which is 343 meters per second,” explained researchers.
They used a device called a Kawai-type multianvil press to compress the sample to such pressures, besides X-ray beams from two synchrotron facilities, KEK-PF and SPring-8, to get images of the samples and then calculate the P-wave values.
“Taking our results, researchers reading Martian seismic data will now be able to tell whether the core is primarily iron-sulfur alloy or not,” said Nishida. “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.”