The study analysed data from the first 900 Martian days of InSight’s mission to identify fluctuations in the planet’s rotation.

The rotation of Mars is exhibiting an unusual acceleration each year, resulting in a slight reduction in the length of a Martian day, data from NASA revealed.

The study, recently published in the journal Nature, revealed that Mars is experiencing an acceleration in its axial rotation of around four milliarcseconds annually.

This leads to a gradual reduction in the length of a Martian day by a small fraction of a millisecond each year, NASA’s InSight Mars lander suggested.

Researchers, including those affiliated with NASA’s Jet Propulsion Laboratory in California, are uncertain about the exact cause behind the gradual increase in the rotation speed of Mars.

However, they have formulated some hypotheses around the topic.

“I’ve been involved in efforts to get a geophysical station like InSight onto Mars for a long time, and results like this make all those decades of work worth it,” study co-author Bruce Banerdt noted.

The study involved scientists conducting the most accurate measurements ever of Mars’ rotation, while also identifying the planet’s wobbling motion caused by the movement of its molten metal core.

The research speculates that elements like the accumulation of ice on Mars’ polar caps or the phenomenon of post-glacial rebound, where landmasses elevate after being submerged under ice, might be responsible for this acceleration in the planet’s rotation.

NASA draws a parallel between this alteration in rotation speed and the analogy of an ice skater adjusting their spin by extending or retracting their arms.

The study analysed data from the first 900 Martian days of InSight’s mission to identify fluctuations in the planet’s rotation.

In the research, scientists employed Nasa’s Deep Space Network situated on Earth along with InSight’s equipment, which consists of a radio transponder and antennas collectively referred to as RISE.

The process involved transmitting a radio signal from Earth to the lander through the Deep Space Network, which RISE would then reflect back to Earth.

By examining the altered signal, researchers would search for minute alterations in frequency induced by the Doppler shift phenomenon, similar to the change in pitch of an ambulance siren as it approaches and moves away.

Through measuring this shift, they were able to ascertain the rotational speed of the planet.

“What we’re looking for are variations that are just a few tens of centimetres over the course of a Martian year. It takes a very long time and a lot of data to accumulate before we can even see these variations,” said study lead author Sebastien Le Maistre from the Royal Observatory of Belgium.

“We have spent a lot of time and energy preparing for the experiment and anticipating these discoveries. But despite this, we were still surprised along the way – and it’s not over, since RISE still has a lot to reveal about Mars,” said Dr Le Maistre, as quoted by reports.