Space scientists have discovered the planet Mars is spinning faster.
Researchers have been able to make the most precise measurements ever of the Red Planet’s rotation – thanks to a lander that sadly lost power.
For the first time, they have detected how the planet “wobbles” due to the “sloshing” of its molten metal core.
The findings, detailed in a recent Nature paper, rely on data from NASA’s InSight Mars lander, which operated for four years before running out of power during its extended mission in December 2022.
Dust on InSight’s solar panels caused it to lose power, but data recorded by its instruments is still leading to new science.
To track the planet’s spin rate, the study’s authors relied on one of InSight’s instruments: a radio transponder and antennas collectively called the Rotation and Interior Structure Experiment, or RISE.
They found the planet’s rotation is accelerating by about 4 milliarcseconds per year² – corresponding to a shortening of the length of the Martian day by a fraction of a millisecond per year.
NASA explain: “It’s a subtle acceleration, and scientists aren’t entirely sure of the cause.
But they have a few ideas, including ice accumulating on the polar caps or post-glacial rebound, where landmasses rise after being buried by ice.
“The shift in a planet’s mass can cause it to accelerate a bit like an ice skater spinning with their arms stretched out, then pulling their arms in.”
“It’s really cool to be able to get this latest measurement – and so precisely,” said InSight’s principal investigator, Bruce Banerdt of NASA’s Jet Propulsion Laboratory in Southern California.
“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.”
RISE is part of a long tradition of Mars landers using radio waves for science, including the twin Viking landers in the 1970s and the Pathfinder lander in the late ’90s.
But none of those missions had the advantage of InSight’s advanced radio technology and upgrades to the antennas within NASA’s Deep Space Network on Earth.
Together, these enhancements provided data about five times more accurate than what was available for the Viking landers.
In the case of InSight, scientists would beam a radio signal to the lander using the Deep Space Network.
RISE would then reflect the signal back.
When scientists received the reflected signal, they would look for tiny changes in frequency caused by the Doppler shift (the same effect that causes an ambulance siren to change pitch as it gets closer and farther away).
Measuring the shift enabled researchers to determine how fast the planet rotates.
“What we’re looking for are variations that are just a few tens of centimeters over the course of a Martian year,” said the paper’s lead author and RISE’s principal investigator, Sebastien Le Maistre at the Royal Observatory of Belgium.
“It takes a very long time and a lot of data to accumulate before we can even see these variations.”
The paper examined data from InSight’s first 900 Martian days – enough time to look for such variations.
Scientists had their work cut out for them to eliminate sources of noise: Water slows radio signals, so moisture in the Earth’s atmosphere can distort the signal coming back from Mars.
So can the solar wind, the electrons and protons flung into deep space from the Sun.
“It’s a historic experiment,” said Le Maistre. “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.”
On 20 December 2022, NASA announced that the InSight lander had lost communications with Earth on 15 December 2022, with the end of the mission being declared on 21 December 2022.
Produced in association with SWNS Talker