InSight: the first scientific results on Mars



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After 200 days in the Martian soil, the InSight module (for "Exploration of the interior using seismic investigations, geodesy and heat transport") reveals its first unpublished analyzes of the magnetic field, variations in surface temperature, atmosphere and seismic waves red planet, on the occasion of the conference at the Sorbonne (Paris, 5and arrondissement) on June 18, 2019. Science and Future participated.

" story [d’InSight] It's beautiful because it's a feat."

The project was launched in 2011, but the sketches were drafted 30 years ago, when Philippe Lognonné, now the scientific manager of the SIS instrument, finished his thesis in 1889 (interview here). . " story [d’InSight] It's beautiful because it's a feat. It must be remembered that in the forty missions launched to the red planet since the beginning of the conquest of space, more than half failed"Recalled the Minister of Research and Innovation, Frédérique Vidal, in the Grand amphitheater of the Sorbonne. " Previous attempts to operate a seismograph on Mars (Viking modules 1 and 2 in the 1970s) were in vain. Therefore, it is the first time that the world brings us here today and gives the measure of what men are capable of satisfying a desire, that of understanding, knowing and knowing.".

From the week of June 24, 2019, teams from the Institute of Physics of the Paris Globe (IPGP) will file on-line (every three months), in open access, Seismological and meteorological data collected between January and March 2019. New exploration missions will be launched in the next few years, such as March 2020 and Exomars 2020, whose aim is to bring Mars back to Earth in search of life sign (exobiology ). " Numerous and future exploration programs of the 21st century show that the space epic is in full swing"Enthusiastic the minister." Research and space exploration is a powerful engine of technological innovation, because space is an extreme laboratory where the smallest error is fatal.

Why explore Mars at all?

" The goal of Insight is identical to what man had set for Earth, that is, to define the structure and internal composition of Mars."Says William Bruce Banerdt, head of the Insight mission at NASA's space research laboratory, which has to go back to 4.5 billion years, the date of the genesis of our solar system.which has a solid surface like that of Earth) is formed by the accumulation of meteoric material. As it grows, the inside begins to heat up and then melt. After a while, the planet becomes structured « how putmagic Of a crust, mantle and core, with distinct mineralogies. This evolution, called differentiation, is a particularly complex process that researchers have not yet mastered well. The InSight project was therefore sent to Mars to better understand global training by studying the "remnant" witnesses to the process.

The internal structures of the Earth, the Moon and Mars (proportions on the same scale). Credit: Nasa / JPL.

A complete geophysical station was deployed to sweep the inner layers of Mars into its atmosphere. The four instruments on board are the French SEIS seismograph, the German heat flow sensor HP3, the sensor of variations of the axis of rotation of the planet by the radio waves RISE, and the Spanish meteorological station APSS.

Presentation of the measuring instruments of the InSight module. Credit: NASA.

A thermal probe in the Martian soil

Since February 28, 2019, the HP instrument3 is blocked to only 30 cm in the Martian soil, whereas it was planned that it sinks until 5 m of depth: We are trying to find a way to unlock the probe"When the drilling can be resumed, the probe will heat the earth several times at different depth scales so that the sensor measures the rate of diffusion of heat at a given depth. let us deduce how quickly the temperature increases to the nucleus"Although at the time only a thermal surface study was carried out, an interesting observation was noted: When one of the Mars moons passes between the Sun and Mars, the probe recognized an instantaneous drop in surface temperature", Add Insight Mission Manager to JPL.

MARITIME MOONS. Mars has two moons (or natural satellites) called Deimos and Phobos. His existence was predicted by Kepler at age 17and century, then each discovered by the American astronomer Asaph Hall, respectively, on August 12 and 18, 1877.

Rotation and magnetic field of Mars

" Thanks to four antennas arranged in the world (note: California, Spain, Australia and Ireland) which receive the radio signals sent from Mars, located 200 million kilometers from Earth, we get to know where the InSight is with a precision of 10 cm"Says William Bruce Banerdt. This incredible precision enables them toincarefully follow the movement of the North Pole, then by extension that of the planet. " With just the measurement of the speed of rotation of the pole, we can deduce the composition of the nucleus, because the movement of a planet is determined by its internal structure."However, we will not receive the response soon: "The experiment requires between one and two years of measurements", Adds the scientist.

Until recently, the magnetic field of Mars (the action of a force coming from a magnet, here a planet) was measured using satellites in orbit. Now, with InSight, you can measure it on the Martian surface: " It was found that the magnetic field was 10 times more intense at the surface than when measured at altitude"Said William Bruce Banerdt, who is the author of the study," It will help to understand how the magnetic field is generated in the nucleus and especially in the crust of Mars, so the variation of this field will provide crucial indications in both composition and temperature of the Martian crust, as well as the core, especially through electrical conductivity (the ability of a material to allow the passage of electric current).

Earthquakes

The idea of ​​building a tool that knows in what direction an earthquake is being propagated was first formulated by the ingenious Chinese scientist Zhang Heng in 132, which he called the "sismoscope." The first seismograph, capable of recording the passage of seismic waves, was developed by the Italian Nicola Zupo in the late eighteenth century. Thus, the first recording of the velocity of the seismic wave could be done on April 17, 1889 in Potsdam (Germany).

Earthquakes. Earthquakes (or earthquakes) are generated by internal forces causing a rock break. They spread on the surface and on the layers as waves. Seismology is the science that studies these waves through a seismometer (or geophones), a device that measures the propagation velocity of seismic waves in the soil.

These seismic waves are essential for understanding the internal structure of rocky bodies, such as telluric planets or natural satellites. In fact, its propagation speed depends on the material covered and, in general, increases with depth, once the cross material becomes stiffer. That is why scientists decided to deposit a seismograph on the moon 50 years ago and on Mars since November 26, 2018 thanks to Lander Insight. As early as April, the seismic seismograph SEIS captured earthquakes and there were about fifteen days, including a deep (magnitude 3) 20 km deep on May 24, 2019. " Martian seismology has become a new scientific discipline"Said Jean-Yves Le Gall, President of CNES, opening the conference.

Photo of one of the seismographs on the Moon, taken during the Apollo 16 mission. Credit: NASA.

Measurements of Martian earthquakes will provide valuable clues to researchers about the planet's internal structure and activity. This instrument can detect minimum variations, comparable to those induced by a hair on the surface of a table », says Philippe Lognonné. When the thermal thermal shield (WTS) was deposited in SIX on February 6, the quest for "Mars tremors" could begin. The stability of this dome is such that it made it possible to render insignificant the sign of the cracks of the ground, because it was " of the order of displacement in a hydrogen atom. The SIX is therefore extraordinarily sensitive thanks to this precaution, enabling the capture of distant earthquakes, thousands of miles away.".

Diagram describing the two types of waves created by an earthquake and propagating in the mantle. © IPGP / David Ducros.

To study an earthquake, the SIX must recover the signal from the waves that are emitted and that deform the surface. By measuring the speed of propagation of these waves, the team can know the speed of these waves and how far the earthquake occurred. In addition, it is possible to deduce the nature of the fracture by analyzing how the signal is absorbed by the planet. Unfortunately, seismic activity on Mars is described as " quite calm "(No earthquake between February and March.) That is why, as explained by the French research professor at the Paris Diderot University, we used "dust devils" to trigger a seismic signal, just as the astronauts were asked to jump on the moon to create one. The depression at the center of these small vortices of the atmosphere (whose action resembles that of a vacuum cleaner) is sufficient to create a seismic disturbance"The advantage is that some may be as heavy as an elephant, but must pass close to or above the seismograph.

The black trail corresponds to the movement of a devil in dust on Mars, photographed by Mars Global Surveyor. Credit: NASA / JPL.

The first to be recorded was April 23. It has been concluded that an earthquake on Mars lasts about ten minutes (on the moon one hour and on Earth five minutes). The biggest tremor detected was on May 5 (SOL 173, 173and the day that InSight is on Mars) of magnitude 3, because that is what allowed the compression waves (called P waves) to diffuse deep into the mantle, in addition to the crust. Researchers are comparing the fifteen recorded earthquakes to understand how the spread changes in depth. " We hope to detect more intense so that the waves can ricochet in the nucleus (at least of magnitude 4)".

MAGNITUDE. In seismology, magnitude makes it possible to quantify the energy released by an earthquake. A moment scale of magnitudes allows you to tell the level of danger of an earthquake. A magnitude below 3 is not felt and from the bumps can cause more or less serious damage. The magnitude 9 devastates an area of ​​1,000 km to the round.

A meteorological station for the Mars atmosphere

The role of the APSS station is to understand the dynamics of the Martian atmosphere through pressure, temperature and wind sensors. First of all, the atmosphere of Mars is much finer than that of Earth: " The difference in pressure between the bottom and top of the Saint-Jacques tower (54 meters) corresponds roughly to the atmospheric mass of Mars, because according to Blaise Pascal, a pressure variation is equivalent to a variation of atmospheric mass"InSight co-investigator Aymeric Spiga says InSight reported that there were significant pressure variations on Mars because when we arrived in the spring, ice CO2 sublime surface until it disappears completely to become gas. The pressure then increases mechanically", Explains the researcher of the dynamic meteorology laboratory (LMD, Sorbonne University).

A very surprising first observation about the climate of Mars was observed recently. " We mistakenly thought that in the image of the Earth, knowing that InSight had landed near the equator, we would not see the baroclinic fronts of the Martian sky. (Ed .: Bad weather on Mars is incarnated through very strong winds that raise dust and create atmospheric depressions, that is, disturbances that resemble clouds). On the other hand, InSight's location presents an advantageous and unprecedented statistic in terms of the frequency of passage of "dust mishaps" (a dozen per day) compared to other sites of Martian exploration. " The big puzzle is that we do not know what holds the dust that is suspended in the atmosphere of Mars".

Weather forecast InSight. Credit: NASA.

If you happen to make a short stay on Mars in a few decades, InSight will reassure the anxious of time: Mars weather reports are available for free on your phone at NASA's Web site, giving weather forecasts for a week. Although InSight regularly returns photographs (currently 2,345 photos), these photos are not studied because the goal " it is not geology but geophysics (note: study of the physical properties of the planet), "recalls Mr. Banerdt.

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