Mars is reducing the length of its days due to spinning faster and faster

Mars is reducing the length of its days due to its accelerating rate of rotation, according to data obtained by NASA's InSight lander before the end of its mission last December..

In addition, the scientists in charge of said laboratory that is located on the surface of the Red Planet have made more precise measurements of the rotation of Mars, detecting for the first time that the planet wobbles due to the “splash” of its molten metal core..

To track the rate of spin of the planet, the study authors have relied on a radio transponder and antennas collectively called the Rotation and Interior Structure Experiment, or RISE.. They found that the planet's rotation is accelerating by about 4 milliarcseconds per year, which corresponds to a reduction in the length of the Martian day by a fraction of a millisecond per year.

It's a subtle acceleration, and scientists aren't entirely sure what's causing it.. But they have some insights, including the buildup of ice on polar caps or post-glacial rebound, where landmasses rise after being buried by ice.. The change in a planet's mass can cause it to speed up a bit like an ice skater spinning with its arms outstretched and then retracting them, NASA explains.

The study authors have also used the RISE data to measure the wobble of Mars, called its nutation, due to splashing around in its liquid core.. The measurement allows scientists to determine the size of the nucleus: according to the RISE data, the nucleus has a radius of approximately 1,835 kilometers.

The authors then compared that figure to two previous measurements of the core derived from the spacecraft's seismometer.. Specifically, they looked at how seismic waves traveled through the planet's interior, either reflecting off the core or passing through it unimpeded.

Taking into account the three measurements, they estimate that the radius of the nucleus is between 1,790 and 1,850 kilometers. Mars as a whole has a radius of 3,390 kilometers, about half the size of Earth.