Deep planetary scan confirms Martian core

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An illustration of the Martian interior. Credit: Dr Sheng Wang and Professor Hrvoje Tkalcic/ANU

A new method for scanning the deep interiors of planets in our solar system to confirm whether they have a core at the heart of their existence has been developed by seismologists from the Australian National University (UNA).

Operating similarly to an ultrasound using sound waves to generate images of a patient’s body, the scanning method requires only a single seismometer on a planet’s surface to operate. It can also be used to confirm the size of a planet’s core. The research was published Oct. 27 in the journal natural astronomy.

Using the ANU model to digitize the entire " data-gt-translate-attributes="[{" attribute="">March‘ Inside, researchers have confirmed that the Red Planet has a large core at its center – a theory first confirmed by a team of scientists in 2021.

Study co-author Professor Hrvoje Tkalcic of ANU said that based on data collected using the ANU technique, researchers determined that the Martian core, which is smaller than Earth’s, is about 3,620 kilometers (2,250 miles) in diameter.

“Our research presents an innovative method using a single instrument to scan the interior of any planet in a way that has never been done before,” he said.

Confirming the existence of a planetary core, which researchers call the “engine room” of all planets, can help scientists learn more about a planet’s past and evolution. It can also help scientists determine when in a planet’s history a magnetic field formed and ceased to exist.

The core plays an active role in maintaining the magnetic field of a planet. In the case of Mars, this could help explain why, unlike Earth, the Red Planet no longer has a magnetic field – something that’s essential to sustaining all life.

“Modeling suggests that the Martian core is liquid and although it is composed mainly of iron and nickel, it could also contain traces of lighter elements such as hydrogen and sulfur. These elements can alter the ability core to transport heat,” said lead author Dr Sheng Wang, also from ANU.

“A magnetic field is important because it protects us from cosmic radiation, which is why life on Earth is possible.”

Using a single seismometer on the surface of Mars, the ANU team measured specific types of seismic waves. Seismic waves, which have been triggered by earthquakes, emit a spectrum of signals, or “echoes”, that change over time as they reverberate throughout the Martian interior.

These seismic waves pass through and bounce off the Martian core.

Professor Tkalcic said researchers are interested in “late” and “weaker” signals that can survive hours after being emitted by earthquakes, meteoroid impacts and other sources.

“Although these late signals appear to be noisy and unnecessary, the similarity between these faint signals recorded at various locations on Mars manifests as a new signal that reveals the presence of a large nucleus in the heart of the Red Planet,” said Professor Tkalcic.

“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. These data help us make estimates about the size of the core of Mars. »

According to the researchers, their method of using a single seismometer to confirm the presence of a planetary core is also a “cost-effective solution”.

“There is only one seismic station on Mars. There were four on the Moon in the 1970s. The situation of having a limited number of instruments is unlikely to change in the coming decades or even this century due to the high cost,” Dr. Wang.

“We need an approach right now to using just one seismometer to study planetary interiors.”

The researchers hope that this new technique developed by the ANU involving a single seismometer could be used to help scientists learn more about our other planetary neighbors, including the moon.

“The United States and China plan to send seismometers to the Moon, and Australia also has ambitions to participate in future missions, so there is potential for further studies using newer, more sophisticated instruments. “, Professor Tkalcic said.

Dr Wang said: “Although there are many studies of planetary cores, the pictures we have of planetary interiors are still very blurry. But with new instruments and methods like ours, we will be able to obtain sharper images that will help us answer questions such as the size of the nuclei and whether they take on a solid or liquid form.

“Our method could even be used to analyze Jupiter the moons and planets of the outer solar system which are solid.

To carry out their research, the ANU scientists used data collected from a seismometer attached to NASA’s InSight landerwhich collects information about march tremors, Martian Weatherand the inside the planet since land on mars in 2018.

Reference: “Scanning for planetary cores with single-receiver intersource correlations” by Sheng Wang and Hrvoje Tkalcic, October 27, 2022, natural astronomy.
DOI: 10.1038/s41550-022-01796-8

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