Mars in Motion: The Red Planet's Mysterious Accelerating Spin
In a cosmic ballet, Mars, our neighboring Red Planet, is subtly quickening its spin with each passing year, and scientists are on a quest to understand why. According to a paper published in the journal Nature, data from NASA's InSight mission reveals that Mars's rotation is accelerating at a rate of 4 milliarcseconds per year. This means that a Martian day is gradually becoming shorter by fractions of a millisecond annually.
A Detailed Portrait of Planetary Spin
InSight, which collected over four years of data before its power depletion in December 2022, employed a novel technique. By bouncing radio waves into space and assessing their return time to Mars's surface, InSight painted a detailed portrait of the planet’s spin. This meticulous method allowed the mission to detect even the most subtle changes in Mars's rotation over its first 900 days on the planet.
Unraveling the Causes
The cause of this acceleration remains a tantalizing mystery. Scientists speculate that one possibility could be the accumulation of ice at Mars's poles, subtly altering the distribution of its mass. Another hypothesis points to a phenomenon known as post-glacial rebound, where landmasses rise after being buried under ice for millennia. In either scenario, these gradual shifts might have been sufficient to subtly alter Mars's rotation over vast spans of time.
Insights into Mars’s Core
In addition to tracking the planet's spin, InSight’s data offered an unprecedented glimpse into Mars’s core. Researchers found that Mars’s core, with a radius of about 1,150 miles (1,850 kilometers), is not uniform. It has regions of varying density, causing its molten material to "slosh" as Mars spins. This intriguing behavior, the study suggests, could be another possible reason for the Red Planet's accelerated spin.
"It's a historic experiment," said Sebastien Le Maistre, a planetary scientist at the Royal Observatory of Belgium and lead author of the study. "We were still surprised along the way," he added, highlighting the unexpected nature of these groundbreaking discoveries.