Newly recorded data of the interior of Mars has provided the most precise measurement to date of the planet’s rotation. Surprisingly, the data from the retired InSight lander has shown that Mars’ rotation is accelerating at a rate of approximately 4 milliarcseconds per year. While this acceleration may seem minuscule, shortening the length of a Mars day by only a fraction of a millisecond every Martian year, the reason behind it remains a mystery. Nevertheless, this finding has the potential to deepen our understanding of Mars and its past evolution. Leading hypotheses explaining the acceleration include long-term trends such as the accumulation of material at the polar ice caps and interior dynamics.
The Importance of the Findings
The discovery of Mars’ accelerating rotation holds significant implications for our understanding of the red planet’s history. With the precise measurements obtained from InSight’s observations, planetary geophysicists are now equipped with invaluable data to study Mars’ interior structure, composition of its liquid core, and ongoing geodynamic activity. These seismic recordings have revolutionized our understanding of Mars in just four years of operation.
Despite its recent retirement in December 2022 due to power depletion, InSight has provided scientists with a wealth of data to analyze. The focus of this particular study was not seismic recordings but radio communications between InSight’s Rotation and Interior Structure Experiment (RISE) instruments and NASA’s Deep Space Network on Earth. By analyzing the radio waves’ frequency variations, scientists were able to precisely measure Mars’ rotation. The data from 900 Martian days of InSight communications with Earth revealed the tiny acceleration, likely attributed to the redistribution of Mars’ mass.
The slowing rotation of Earth, caused by the Moon’s gravitational pull on the oceans, stands in contrast to Mars’ accelerating rotation. This discrepancy is likely due to the absence of oceans on Mars. Further analysis is necessary to determine the exact cause of the rotation acceleration on Mars.
Additionally, the RISE data provided an opportunity to refine measurements of the Martian core. Specifically, it allowed scientists to observe a wobble called nutation, which indicates fluid movement within the core. Seismic data previously suggested a core radius of 1,780 to 1,830 kilometers and a density of 6.2 to 6.3 grams per cubic centimeter. The data from RISE aligned excellently with these measurements, revealing a core radius of 1,835 kilometers and a density of 5.9 to 6.3 grams per cubic centimeter. However, the observed nutation suggests that the density within the core is not evenly distributed. Further analysis is required to investigate these density variations.
Astronomer Sebastien Le Maistre at the Royal Observatory of Belgium describes this experiment as historic. The time and effort invested in preparing and conducting the experiment have paid off with surprising discoveries. The RISE data still holds untapped potential in unraveling more secrets about Mars, ensuring that our exploration and understanding of the red planet continue to evolve.
The recently recorded data from the InSight lander has provided us with a surprising revelation – Mars’ rotation is accelerating. This finding, although perplexing, offers a fresh perspective on the planet’s past evolution. Through meticulous analysis of the data, scientists have refined their measurements of the Martian core and gained a deeper understanding of its composition and structure. As we await further investigations into the cause of this rotation acceleration, one thing is certain: the exploration of Mars is an ongoing journey filled with unexpected twists and turns.