Washington, Aug 8: Scientists have achieved groundbreaking measurements of Mars’ rotation, uncovering the planet’s wobbling caused by the sloshing of its molten metal core. The detailed findings, published in the journal Nature, are based on data collected from NASA’s InSight Mars lander, which operated for four years before depleting its power during its extended mission in December 2022.
The study’s authors utilized InSight’s Rotation and Interior Structure Experiment (RISE), consisting of a radio transponder and antennas, to track the planet’s spin rate. They observed that Mars’ rotation is accelerating at a rate of approximately 4 milliarcseconds per year, leading to a slight shortening of the Martian day by a fraction of a millisecond annually.
The cause of this subtle acceleration is not entirely understood, but scientists have proposed potential factors, such as ice accumulation on the polar caps or post-glacial rebound, where landmasses rise after being covered by ice. The redistribution of a planet’s mass can cause acceleration, akin to an ice skater spinning faster by pulling their arms inwards.
To conduct this historic experiment, scientists worked diligently to eliminate sources of noise in the data, including signal distortion caused by water in Earth’s atmosphere and solar wind interference from particles emitted by the Sun.
Lead author Sebastien Le Maistre, RISE’s principal investigator at the Royal Observatory of Belgium, emphasized the significance of the study and the surprises encountered during the research. He stated, “RISE still has a lot to reveal about Mars.”
Additionally, the RISE data allowed the authors to measure Mars’ wobbling, known as its nutation, resulting from the movement of its liquid core. This measurement provided insights into the size and shape of the core. Based on the RISE data, the core’s radius was estimated to be approximately 1,835 kilometers, while Mars’ overall radius is about 3,390 kilometers, approximately half the size of Earth’s.
Further analysis of the core’s shape indicated that its rotation alone could not account for its observed form. Instead, regions of slightly higher or lower density buried deep within the mantle seem to contribute to the core’s distinctive shape, as noted by Attilio Rivoldini, the paper’s second author from the Royal Observatory of Belgium.
The groundbreaking measurements provided by InSight’s RISE instrument offer significant insights into Mars’ internal dynamics and contribute to a better understanding of the Red Planet’s structure and evolution.
