'We've never seen...' — Marsquakes reveal 4.5-billion-year-old structures embedded in the red planet

Mars is hiding pieces of planets that formed in the early solar system, perfectly preserved for billions of years. A study has found that deep inside the red planet are several mysterious blobs which belong to ancient "protoplanets" that failed to grab a place in our system. The revelation was made when they were going through Marsquake data collected by NASA's InSight lander. It monitored tremors beneath the Martian surface from 2018 until 2022 until it went off due to a dust storm. As they saw vibrations under the Martian surface, they came across dense lumps that were different from the surrounding material. They are approximately four kilometres in size and were discovered at various depths within Mars' mantle. The temperatures here can reach a whopping 1,500 degrees Celsius, yet the blobs had held together.

Study lead author Constantinos Charalambous, a planetary scientist at Imperial College London, said in a NASA statement, "We've never seen the inside of a planet in such fine detail and clarity before." It is a "mantle studded with ancient fragments." Further analysis of the size and depth of the structures showed that they crashed into Mars nearly 4.5 billion years ago, around the time our solar system was being born. These rocks are likely bodies that could have gone on to become fully formed planets had they not been disturbed by the chaotic cosmic occurrences that were going on at the time.

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These blobs were uncovered purely by accident. The researchers were actually studying Marsquakes when they noticed that some signals took longer to pass through parts of the mantle than others. They traced the path of these signals and came across regions that were denser than the surrounding rock. This meant that they did not originate there but were intruders that forcefully made their way in. This discovery also proves that the interiors of Mars are not active. On Earth, tectonic movement causes earthquakes. But on Mars, no subduction occurs, meaning the mantle stays in its place. Because no melting happens inside Mars, these blobs have survived for billions of years. Charalambous says, if something like this ever existed on Earth, they would have been erased.

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How do Marsquakes occur?

If Mars has no tectonic plates and no similar activity, then how do quakes occur? This is largely because of landslides, cracking rocks or meteoroid impacts that regularly happen on Mars. InSight had gathered data on Marsquakes, and scientists used it to identify a giant underground ocean last year.