NASA’s InSight Mars lander will lose power in December 2022 due to solar panel dust, but the data it has obtained on Mars for four years is still Scientists continue to provide new discoveries. A study published this week in the journal Nature, using data from the InSight lander, has made the most precise measurement ever of Mars’ rotation rate and detected, for the first time, a spin due to the “wobble” of its molten metal core. The planets wobble.
The InSight lander carries a variety of instruments, one of which is RISE, which is used to measure the rotation rate of Mars. It consists of a radio transceiver and antenna that can receive and reflect radio signals from NASA’s Deep Space Network (DSN) on Earth. By analyzing the signal’s Doppler effect (the change in signal frequency with distance), scientists can determine the speed and direction of the planet’s rotation.
The researchers found that the speed of Mars’ rotation accelerated by about 4 milliarcseconds per year, equivalent to a reduction of a few tenths of a millisecond per year in the Martian day, or the length of a day on Mars. It’s a tiny acceleration, and scientists aren’t entirely sure why, but they speculate it may have something to do with the buildup of polar ice caps, where changes in the planet’s mass cause it to spin faster like an ice skater.
RISE data is also used to measure the sway of Mars due to core liquefaction (called nutation), which allows scientists to determine the size of the Martian core: According to RISE data, the radius of the Martian core is about 1140 miles (about 1835 kilometer). The researchers also compared this figure to two previous measurements taken by the InSight lander’s seismometer, and taking the three measurements together, they estimated the radius of the Martian core to be between 1,112 and 1,150 miles (1,790 and 1,850 kilometers). Mars itself has a radius of 2,106 miles (3,390 kilometers), about half that of Earth.
