Little Story of Infinity: Destination Mars

Each month, Gwenhaël W. De Wasseige tells us through her Little Story of Infinity the latest news about the universe and the domain of the infinitely small.
To celebrate the end of the year, let us meet Véronique Dehant. Mathematician and geophysicist, she seeks to understand why the Earth is habitable and Mars is not. Or rather not anymore!
Winner of the five-year prize in exact fundamental sciences of the FNRS, which was awarded to her by His Majesty the King a few weeks ago, the researcher at the Royal Observatory and professor at UCLouvain has acquired international fame for her work. She works on understanding the deep interior of the planets. Let’s set off to discover an exceptional Belgian.
Véronique Dehant and His Majesty the King
Véronique Dehant © FNRS
How do you explore other planets, such as Mars, while keeping your feet on the ground?
Véronique Dehant: With robots! My mathematical mind enables me to analyze data recorded by satellites and instruments aboard landers to understand the evolution of planets. Among other things, I am trying to define whether the nucleus of planets, i.e. their core, is liquid or solid. My research is however indirect, since I answer this question by observing their rotation (note: and not by digging!).
So the interior of the planets will define how they turn on themselves? Did we follow up?
Yes, that's it! A good illustration of this phenomenon is with a raw egg and a hard-boiled egg. Their movement, when rotated, will be different. With practice, you can tell which egg has been cooked. It's the same with the planets! Their rotation and in particular the variations in their orientation - called precession and nutation - are amplified when the nucleus is liquid.
The landers therefore allow you to precisely follow the movement of the planets! But what instrument on landers, especially on NASA's InSight Mars lander, do you use in particular?
The instrument I'm interested in is called a transponder. Developed by NASA, it was placed on InSight. A 70m antenna is used on Earth to send radio waves to the transponder. The instrument on Mars will detect this signal and send it back unchanged. We receive the return signal to Earth and measure the offset, called the Doppler effect, from the original signal. Repeated a large number of times, this operation makes it possible to retrace the movement of the planet and its variations.
This mission was a real success and the results you obtained will soon be published in the prestigious scientific journal Science. Can you tell us a bit about it?
We cannot yet reveal our results but they aim to confirm by this system the results obtained by a complementary approach using a seismometer, that the core of Mars is liquid. We will even give specific details on it! The existence of a liquid core implies that although there is no longer a magnetic field around Mars today, unlike Earth, it could reform in the future. The existence of this magnetic field, and the magnetosphere that it generates, partly conditions the existence of an atmosphere around the planet. Without atmosphere, no liquid water, and without water, no life! This discovery therefore has an important implication on the question of the habitability of the planet Mars.
Your next challenge is called LaRa, for Lander Radio science. This instrument is almost Made-in-Belgium, isn't it?
LaRa is a gem of a transponder, fully funded and created in Belgium. It will be on board the ExoMars mission of ESA, the European space agency, and Roscosmos, the Russian space agency, which will leave in 2022. Until recently, I was in charge of this project and my colleague, Sébastien Le Maistre, took it over. The miniature and super light antenna of this transponder was developed at UCLouvain by Christophe Craeye. The transponder comes from Antwerp space, an Antwerp company specializing in the construction of space telecommunications instruments. A beautiful Belgian story!
Now that we know that the core of Mars is liquid, data from InSight and LaRa will allow us to estimate its density, in iron and light atoms, and to determine if a magnetic field could reform or not!
Is there a future in your field for the young adventurer-reporters of land and space that your journey has dreamed of?
In short: yes! Space has a bright future ahead of it. The 'New Space' revitalizes space science and offers many career prospects for young enthusiasts. We need courageous and inventive people for the next great Martian adventures!
See you in 2022 for the launch of LaRa!

The word of the expert

Véronique Dehant deciphers for us the vision of the lunar ground of "We walked on the moon": Absolutely correct! Men have walked on the Moon! The craters on the Moon as on the planet Mercury or in the southern hemisphere of the planet Mars are numerous because the grounds there are very old. It shows traces of the beginning of the solar system and the entire history of the solar system is written there. There is an important difference, however: samples have already been brought back from the Moon, which has made it possible to date the rocks and even to calibrate the date-number of craters ratio. In the near future, we will bring back samples from the planet Mars and return to the Moon. Besides, when will the first woman on the moon be?
Tintin and the rocket on the Moon
Explorers on the Moon © Hergé/Moulinsart - 2022
Explorers on the Moon © Hergé/Moulinsart - 2022
  • Lander: spacecraft intended to land on the surface of another planet in order to explore it
  • Doppler effect: Offset of the frequency of a wave e.g., light, when the distance between the transmitter and receiver changes over time.
  • New Space : the philosophy arising from the arrival of private companies, such as SpaceX and Blue Origin, in the space adventure.
About the author
Gwenhaël W. De Wasseige is assistant professor at UCLouvain in astroparticle physics. Each month, Gwenhaël will tell us through her Little Story of Infinity the latest news about the universe and the domain of the infinitely small.
Gwenhaël W. De Wasseige
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16/01/2022 22:14 PM
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