Mars' rotation is speeding up

Mars’ rotation is speeding up

mission to marsmission to mars They not only study the surface of the Red Planet, but also probe its interior as demonstrated by the Mars Lander insightinsight From NASANASAwhich operated for four years before being scrappedenergyenergy In December 2022. In particular, it allowed the French equipment Cess to accumulate. ,Seismic experiments for internal structures,a real seismic scaleseismic scale like its cousins ​​on Earth, allows to extract the characteristics of seismic wavesseismic waves That he could detect many things on the interior of Mars. This is not the first time that Noosphere has deposited seismometers on Mars. Viking missions had done this since the 1970s but it was a much less efficient instrument than SIS.

was also equipped with a tool called Insight Rise and we learn today Via An article published in a famous newspaper Nature Rise’s data analysis killed two birds with one stone. The first is the fact that after looking at data from the first 900 Martian days from InSight, we now know that the planet’s rotation is speeding up by about 4 milliarcseconds per year, which is consistent with shortening. DurationDuration The Martian day digresses by a fraction of a millisecond per year.

A presentation beginning 2018, ahead of the launch of the InSight mission Interior exploration using seismic investigations, geodesy and heat transport , In French: Exploration of the interior by seismic sounding, geodesy and thermal flow). The video explains why planetary scientists want to understand the interior of Mars and why it no longer has a magnetic field. © Keynes

The RISE data also make it possible to establish constraints on the size of the Martian core, a size that is quite comparable to the size deduced from the analysis of the CIS data, and to better understand Head gestureHead gesture of the rotation axis of Mars. The change in nutrition is thought to be related to the fact that the inner core of the Red Planet is likely composed entirely of liquid (unlike Earth) and a Metal AlloysMetal Alloys Of againagain And out, makes sloshing movements. Let’s remember that this word, in its strict sense, refers to the smallest movements of someone liquidliquid Contained in a tank with quick movement and free surface.

Researchers also have some ideas about the origin of the acceleration of Mars’ rotation. Some preliminary thoughts are necessary to better understand NASA’s latest interpretations of InSight’s discoveries.

Gravity, magnetic fields and seismology, investigation of internal geophysicists

We can already specify how SIS had already made it possible to conclude that Mars has a liquid iron core whose radius is between 1,790 km and 1,870 km and which contains light elements as in the case of the Earth’s core. Are. (But since nothing but a fossil crustal magnetic field exists on Mars, that liquid core has no equivalent to Earth’s geodynamo today.)

These conclusions are typically reached by searching for matches with thousands of observations. digital modeldigital model Of layerlayer and the Martian core depends on a number of adjustable parameters, it is somewhat like looking for the exact characteristics of a musical instrument, comparing the sound produced by a whole family of instruments to the sound that is allegedly similar to the We listen without seeing. it is called ResolutionResolution an inverse problem in the jargon of physicistsphysicists mathematician.

we can get better and more detailed information SolidSolid By transferring the techniques used in the case of Earth to the study of Mars. Thus planetary scientists were initially able to rely on the study of the region. GravityGravity about these planets and their rotational motions, and this continues today in conjunction with the study of seismic waves.

change in rotation induced by a change in the distribution of mass

distribution of CaseCase Because of the variation in density inside the planets, the gravitational field is necessarily localized just outside the planets, so that the measurement gravimetrygravimetry Precise movements of orbiting probes on the surface, and above all, crossing the valleys and bulges of equipotential surfaces of the gravitational field generated by them estraceestraceAlready allowed to get ideas about what hides the surfaces of Earth and Mars.

We can also keep in mind what is called tensortensor since the time ofinertiainertia of a planet, which also depends on the distribution of matter and the size of the planet. famous injected the equationthe equation of a solid body in rotation, will determine how the axis of rotation of a planet is subjected to external gravitational forces, or to modify the distribution of matter on occasion, for example EarthquakeEarthquake, will change over time. Thus, the study of the movements of Earth’s rotation axis, which for example manifests as the drift of its geographic poles, also proved valuable for constraining the internal structure of our blue planet.

in the matter of mission insightmission insightThis is the nutrition and precession of the axis of rotation of Mars – which was used thanks to the instrument Rise ,Rotation and Internal Structure Experiment) – which provided constraints on the core of the planet. Researchers believe that the change in rotation and nutrition is also due to this sources saysources say Of glaciersglaciers change the distribution of publicpublicalready melting, and indirectly due to the increase in blocks crustcrust The phenomenon on Mars is largely analogous to what is called isostatic rebound on Earth after the end of the previous snow coversnow cover, As in the case of Earth, the crust is less dense than the mantle and therefore floats like a boat that can be loaded and unloaded.

Ultimately, all these mass movements change the inertial tensor of Mars, causing adjustments as the planet’s rotational position changes. Earth has been doing the same throughout the adventures of its history.

To get a fairly accurate French translation, click on the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Select “French”. ©NASA

planetary scientists already used itDoppler effectDoppler effect to the waves radioradio emitted by a probe in orbit around Mars and picked up by antennas on Earth deep space network (DSN) to remove from NASA VitseVitse This probe also provides information indirectly about the gravitational field of Mars, which is determined by the precise distribution of the mass that makes up Mars. This is explained above by NASA.

but in the article NatureIt is also explained that the researchers used the Doppler effect in the radio waves transmitted by the DSN and sent back to Earth by the antennas. Rotation and Internal Structure Experiment, which is precisely the rise. It was the Doppler effect measurements that made it possible to measure the rotation of Mars continuously or nearly continuously for 900 days and to conclude that it was accelerating.

In fact, this technology had already been used by the mission’s landers vikingviking in the 1970s but advances in technology now allow us to achieve accuracies up to almost 5 times!





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