Scientists at the Australian National University (ANU) have developed a new cost-effective deep-scanning technique that can provide a window into the interiors of planets in Earth’s solar system.
The new approach uses a single instrument on the planet and provided ANU seismologists with an analysis of the Red Planet’s interior, including its core. The dynamo theory suggests that the core generates and maintains a planet’s electromagnetic field, which protects creatures on a planet from cosmic radiation.
Electromagnetic fields are crucial for survival; however, Mars has none, except for relatively small patches of magnetized crust. Therefore, developing an understanding of how and why Mars lost its field is an investment in keeping Earth safe and advancing terraforming efforts on the Red Planet itself.
The researchers hope their approach can be useful for investigations of other planetary bodies and their interiors, including the moon. However, it should be noted that while this study presents a cheaper and more innovative approach to planetary scanning, it is not the first to scan and measure the Martian core. The first research team to prove the existence of the core did so in 2021.
Differences between studies
In an email to The Epoch Times, the study’s lead author, Sheng Wang PhD, said the 2021 team used direct reflections of seismic waves from the core-mantle boundary (CMB) to confirm and measure the core.
Specifically, Wang said, the 2021 research team measured shear wave reflections, or ScS. Shear waves or elastic waves are a form of seismic wave, which propagate through or over the earth and are usually caused by earthquakes. They move through an object’s body, not through the surface, and can only move through solids.
Wang said the 2021 study used different datasets and methods, using seismic wave records in early time windows after the origin of a Marsquake and ScS reflections from local spots of Mars. CMB.
The ANU team measured a range of signals or “echoes” emitted by seismic waves. These echoes gradually change as they reverberate through the interior of the planet, passing through and bouncing off the core. Wang said the ANU study uses recordings much later after the origin of an earthquake and cross-correlation analyzes of late coda cross-correlation, which detect CMB at the scale world.
The data used in both studies was collected by instruments attached to NASA’s InSight lander, which has been collecting information about Martian weather, the planet’s interior and earthquakes since it landed in 2018.
Planetary Interior “Echo” Fingerprint
Using Earth as an example, Wang described the processes that transform “echoes” into a fingerprint of the planet’s interior. Wang said the “echoes” are reverberations of seismic waves inside the Earth, which reverberate because of the Earth’s free surface, core-mantle boundary and other internal structures. He said that all of these causes of reverberation could result in the separation of wave energy or reflection and refractions.
“Therefore, the ‘echoes’ change over time. First, their strength/amplitude decreases as they reverberate due to energy dissipation,” he said.
“Secondly, the whole late coda wavefield that we used will be shaped due to the internal structure of the Earth. The energy distribution, geometry, energy content in different frequency bands, etc. , are shaped.”
“You can imagine that the resulting coda wave field is like a fingerprint from inside the Earth,” Wang said.
In an ANU press release, study co-author Professor Hrvoje Tkalčić of the ANU Research School of Earth Sciences said that in terms of Mars, these signals seem noisy and unnecessary.
However, he noted that there is a similarity between the recorded signals. He said that this similarity stands out as a new signal and reveals the presence of a large Martian nucleus.
“We can determine the distance traveled by these seismic waves to reach the Martian core, but also the speed at which they pass through the interior of Mars,” said Tkalčić.
“These data help us make estimates of the size of Mars’ core.”
Tkalčić noted that the team found the diameter of the Martian core to be around 3620 kilometers (about 2249 miles).
What the waves can say
Wang said the fundamentals of scanning planetary interiors using earth vibrations, as in the ANU’s new approach, are similar to those of X-ray imaging.
“Well, fundamentally speaking, the fundamental of seismic imaging of the interior of the Earth and planets is similar to that of X-ray imaging of the human body that most of us have experienced in hospitals. “, did he declare.
Wang said seismic waves carry great information about planetary interiors when sampled.
“Based on this, we can measure multiple quantities of wave observations (time, amplitude, waveforms) to reverse targeted internal structures,” he said.
Wang said this is the foundation of all seismological investigations of planetary interiors, while in specific uses different types of datasets and methods/ways of processing and analyzing the dataset are noted.
Wang said a specific example is reversing the distance of a reflector/boundary from a receiver, which can be done if the speed/velocity of the wave and the time it takes can be measured .
“This geometry is like an analogue for studies using direct observations of seismic waves,” he said.
“We mentioned this specific analog/example just to help explain what seismic imagery can look like, and many seismic images are not like velocity=distance/time.”
Measure core size
Wang said the team got an estimate of the kernel size and its uncertainty by considering sets of possible interior models.
“In our method, the cross-correlations between sources, physics and mathematics are different from the analog for direct observations of seismic waves, as explained above,” he said.
“In the cross-source cross-correlation framework, we don’t explicitly have this type of geometry of Velocity=Distance/Time.”
“In other words, cross-source correlation is a new method/way of analyzing the late coda, the ‘fingerprint’ of the Earth’s interior and planets, and it works with a single station. “Wang said.
The importance of cost effective solutions
Wang said that due to the high cost, restrictions on the number of instruments available are unlikely to change in the coming decades or even this century.
“We need an approach right now to using just one seismometer to study planetary interiors,” he said.
Tkalčić said the United States and China plan to send seismometers to the Moon, and Australia has ambitions to join future missions. Therefore, he said there is potential for further studies using new and more advanced instruments.
“Although there are many studies of planetary cores, the pictures we have of planetary interiors are still very blurry,” Wang said.
“But with new instruments and methods like ours, we will be able to get sharper images, which will help us answer questions like the size of the nuclei and whether they take on a solid or liquid form.”
“Our method could even be used to analyze Jupiter’s moons and outer solar system planets that are solid,” he said.
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