The red planet spins faster than before. Scientists discovered it thanks to the now finished InSight mission to Mars. However, no one has yet been able to explain this astonishing acceleration.
The Earth is not the only one spinning faster. New data straight from Mars indicates that this neighboring planet is spinning faster and faster. This acceleration of its rotational movement nevertheless remains unexplained. The discovery, reported by NASA on August 7, 2023, is the subject of a study published in the journal Nature.
It was thanks to the InSight mission, which ended in December 2022, that the scientists were able to reach their conclusion. Before shutting down on Mars, the lander sent data to ” make the most precise measurements ever made of the rotation of Mars “, according to NASA.
Mars is spinning faster, but we don’t know why
While rotating on itself, the red planet “oscillates”, say the authors. They measured that the acceleration of the planet’s rotation is about 4 milliseconds of arc per year. It is extremely subtle: concretely, the Martian day shortens by a fraction of a millisecond per year. But, how to explain it? This is where the researchers are without a firm answer. The hypothesis put forward remains rather elusive. This ” could be the result of a long-term trend in the internal dynamics of Mars or in its atmosphere and ice sheets “, consider the authors in their study.
The follow-up of the rotation of Mars was carried out using one of the instruments of InSight, RISE (for “Rotation and Interior Structure Experiment”, translatable into “rotation and interior structure experiment”). It was a radio science experiment to determine the size and composition of Mars’ core by measuring the oscillation of the planet’s north pole.
Every day, RISE made it possible to monitor the position of the InSight lander to within a few centimeters. From Earth, the Deep Space Network (DSN) sent a signal, which the RISE instrument reflected.
The Doppler Effect is a change in the perceived frequency, when the source of the waves is in motion relative to the observer.
By receiving the signal returned by InSight, scientists could look for tiny changes in frequency caused by what is called the Doppler effect. The offset thus measured made it possible to estimate, during the first 900 days of InSight on Mars, the speed at which the planet rotates.
It now remains to understand where this unexplained acceleration comes from. This could certainly help to learn more about the evolution of our neighbor in the solar system. ” Knowledge of the interior structure and atmosphere of Mars is key to understanding how the planet formed and evolved “, recall the authors of the study.
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