The most accurate spin measurement of Mars has just been obtained from internal recordings, and the findings are a perplexing surprise.
The data from the now-retired InSight lander show that Mars’ rotation is speeding up by about 4 milliarcseconds annually. A fraction of a millisecond each Martian year, which is a very little amount, is lost from the length of a Mars day, although the cause is not immediately clear.
However, the discovery might help us comprehend Mars and its earlier evolution. Long-term patterns, like material building up at the polar ice caps, and internal dynamics are the leading forerunning explanations explaining the acceleration.
Planetary geophysicist Bruce Banerdt of NASA’s Jet Propulsion Laboratory said, “It’s really cool to be able to get this latest measurement – and so precisely.” “I’ve spent decades working to get a geophysical station like InSight onto Mars, and results like this make it all worthwhile,” the author said.
InSight was decommissioned in December 2022 after running out of power, but the data it collected during its four years of operation has given scientists a lot to think about. The rover’s studies of the Martian interior have completely changed our understanding of the planet in its brief four years of operation. Not only did its seismic records show Mars’ internal structure, but also the make-up of its liquid core and continuous geodynamic activity.
Despite how useful such measurements have been, the data used in the latest study came from radio transmissions between NASA’s Deep Space Network on Earth and InSight’s Rotation and Interior Structure Experiment, or RISE, instruments instead of seismic recordings.
As Earth and Mars moved and turned, signals were reflected back and forth between them, enabling researchers to look for minute changes in radio wave frequency that would allow them to precisely calculate Mars’ rotation.
The researchers discovered the small acceleration using 900 Martian days of Insight communications with Earth. This probably has something to do with the redistribution of Mars’ mass. The opposite is happening here on Earth, where long-term patterns indicate that the planet’s rotation is slowing down as a result of the Moon’s braking force, which pulls on the seas to redistribute Earth’s mass.
Since Mars lacks oceans, something else must be happening. In order to identify the most likely reason for the acceleration, scientists will need to conduct a more thorough examination.
By providing measurements of a wobble known as nutation induced by fluid moving around, the RISE data also allowed the researchers to improve measurements of the Martian core.
The core of Mars is estimated to be between 1,780 and 1,830 kilometers (1,137 miles) in radius, which is fairly enormous and is more than half the planetary radius of 3,390 kilometers. These measurements came from seismic data. A core density of 6.2 to 6.3 grams per cubic centimeter was likewise predicted by seismic analysis.
The RISE data, which provides a core radius of 1,835 kilometers and a core density of 5.9 to 6.3 grams per cubic centimeter, is in perfect accord with these observations. The planet’s nutation, however, indicates that this density may not be uniformly dispersed; further investigation will be required to look into density differences in the core.
Astronomer Sebastien Le Maistre of the Royal Observatory of Belgium describes the experiment as “historic.”
“We have put a lot of time and effort into planning the experiment and looking forward to these findings. Despite this, we were nonetheless taken aback along the road, and RISE still has a lot of Mars-related revelations to make.
The research has been published in Nature.
