JAKARTA – Scientists have recently been puzzled by the fact that the planet Mars has been rotating mysteriously faster.
Recent findings from NASA’s InSight lander show that Mars is now shortening its day length by three-quarters of a millisecond each year as it rotates faster.
For information, the standard day on the planet, or the so-called “sol”, is 24 hours 37 minutes.
However, measurements of the length of the day using fractions of a millisecond accuracy have revealed that Mars’ rotational speed increases by a minuscule amount.
Launch Spacealthough scientists are not 100% sure what causes this phenomenon, they say that it is most likely related to the redistribution of the mass of Mars.
The redistribution, they say, impacts the planet’s rotation like an ice skater pulling on her arm to spin faster.
In addition, this redistribution may also be caused by the accumulation of ice on Mars’ polar caps, or by the surface itself slowly recovering under the weight of large glaciers that existed at equatorial latitudes during the world’s most recent ice age, which ended approx. 400,000 years ago.
To get these very precise measurements of Mars’ rotation rate, the study scientists used radio waves.
“This is a historic experiment,” Sebastien Le Maistre, a planetary scientist at the Royal Observatory of Belgium and lead author of a new paper on the findings, said in a statement.
“We have spent a great deal of time and energy preparing for the experiment and anticipating this discovery,” he added.
A powerful radio signal is blasted toward Mars by NASA’s Deep Space Network, which consists of three worldwide radio antennas used to communicate with interplanetary missions.
The radio signal is then received by InSight’s RISE (Rotation and Interior Structure Experiment) instrument and reflected back to Earth.
Mars’ spin adds a Doppler shift to these reflected radio waves.
Doppler shift is the same effect that causes emergency vehicle sirens to rise in pitch as they approach a listener before dropping again as they move away.
Similarly, when InSight is in the rotating hemisphere of Mars into view, the radio signal it emits is Doppler shifted to a higher frequency.
And when InSight is in a rotating hemisphere out of sight, the signal is Doppler shifted to a shorter frequency.
This Doppler shift is completely dependent on the rate of rotation, and exploiting it to measure the length of a planet’s day–to a fraction of a millisecond–is no easy task.
“What we are looking for is a variation of only a few tens of centimeters over a Martian year [687 hari Bumi],” said Le Maistre, who is also the RISE principal investigator.
“It will take a very long time and a lot of data to collect before we can even see this variation,” he added.
The experiment used data from InSight’s first 900 days on Mars, and concluded that Mars’ rotation was accelerating by 0.76 milliseconds per year – the most accurate measurement of Mars’ rotation period ever made.
These results were published in June in the journal Nature.
Sumber: Space
2023-08-21 18:31:41
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