Space missions are studying certain asteroids considered to be witnesses to the formation of the solar system, according to our partner The Conversation.
Asteroid exploration missions present particular technical challenges, but also very attractive for those who participate in them.
This analysis was conducted by Aurélie Moussi-Soffys, Hayabusa2-MASCOT project manager at the National Center for Space Studies (CNES).
Asteroids, these bits of planets orbiting in the solar system, have fascinated and frightened us since the dawn of time.
Although probably at the origin of the disappearance of the dinosaurs, they are especially essential witnesses of the formation of the solar system.
They hold great secrets about the genesis of our planet and the appearance of life.
The exploration of asteroids is very recent: for a very long time, the only information we could glean came from the infinitesimal quantity of matter arriving on earth via meteorites.
Missions intended to probe these small celestial bodies are now in the scientific news.
The objectives of these explorations are many, but they present special technical challenges that make them attractive to those who participate.
Asteroids, what?
Let's start with a small portrait of this very special family.
Asteroids are small, inert celestial bodies that orbit the sun.
They are mainly composed of rocks and metals.
Close to comets, the latter are distinguished by the significant presence of ice and a characteristic tail.
The majority of asteroids are located in the main asteroid belt, between Mars and Jupiter.
A few “dissident” asteroids cross Earth's orbit, hence their name of near-Earth planet.
Another small population of asteroids named after the heroes of the Trojan War, the Trojan asteroids, call Jupiter's orbit home.
Finally, the last population evolves beyond the orbit of Neptune, within what is called the Kuiper belt.
The first asteroid (Ceres) was discovered by mistake at the beginning of the 19th century.
Initially named "small planets", many asteroids were discovered over the next two centuries, thanks to telescope observations from Earth.
However, asteroids are of little interest to international exploration missions: apart from rare exceptions, it was not until the end of the 1990s that missions were dedicated to them.
It is moreover rather opportunistic and short overflights during a trip to other objects: the Rosetta probe spinning towards the comet Churuymov-Gerasimenko thus flew over two asteroids.
Understanding the formation of the solar system
Recently, space missions have been specially defined to study certain asteroids.
They primarily target carbonaceous asteroids of the primordial type, considered to be witnesses to the formation of the solar system… but also to the beginnings of life on Earth, which the asteroids could have seeded.
Thus, the Japanese missions Hayabusa then Hayabusa 2 are particularly interested in the origins of water and life on Earth.
The asteroid Ryugu was thus probed in order to bring back to Earth (end of 2020) samples of carbonaceous and hydrated matter, for the first time in history.
Extensive analyzes carried out in many international laboratories will soon unlock some of the secrets of the formation of the solar system.
The American Osiris-Rex mission twinned with Hayabusa2 is a similar sample collection mission on a carbonaceous asteroid.
The two missions and the international scientific community also work in close collaboration and the challenges encountered are tackled together.
This objective of understanding the formation of the solar system is also shared by the American Lucy mission, launched on October 16, 2021 and now on its way to the Trojan asteroids for a mission of more than 10 years.
It is planned to study 6 asteroids (including a double), in order to confirm or amend the
Nice model
theory .
This scenario describing the formation and evolution of the Solar System explains in particular the late massive bombardment of the Moon as well as the formation of the Kuiper belt by a major reorganization of the Solar System, and in particular the displacement of the giant planets.
Planetary defense missions
If we consider that mining activities for rare materials on asteroids are currently utopian and ethically questionable, there remains another major interest in the study of asteroids: planetary defence.
For several years, space agencies have been working on solutions to consider if, in the future, a near-Earth asteroid becomes a risk for the Earth.
Humans have the means not to become the next dinosaurs and we are far from an
Armageddon
scenario .
Indeed, it is now possible to predict the orbits of the most dangerous asteroids.
In the event of a proven risk, the space agencies will have the time to study the best technical solutions without kamikaze human intervention.
It should be remembered that the risk on the scale of a life is almost negligible, it is above all a question of anticipating and improving physical models in order to be ready in case of need.
The DART probe was launched by NASA on November 24.
After an observation phase, it will voluntarily crash into the surface of the small asteroid Dimorphos in orbit around the asteroid Didymos at the end of September 2022. The objective of this mission is to assess the modification of the orbit of the asteroid caused by this impact, in order to improve and dimension possible future missions of deflection of objects by kinetic impactor.
This American mission is part of a larger program involving Europe and France.
Indeed, the European Space Agency's (ESA) HERA partner mission will be launched in 2024. Its purpose will be to study Didymos and Dimorphos from every angle after the DART impact, in order to complete the measurements that will be taken from Earth before, during and after impact.
The technical challenges of asteroid exploration
Asteroids present an ongoing technical challenge for the teams preparing them.
It is these challenges as well as the valuable information they can bring us that make the salt of this particular exploration.
Their low gravity is a valuable ally, as it allows samples of extraterrestrial matter to be collected and brought back to Earth without running into the thorny problem of extracting gravity from the body being visited.
A feat that we are still far from being able to achieve with samples from planets: for example, no sample has been brought back from Mars, researchers having to content themselves with analyzes carried out on site by robots less powerful than those available in laboratories. terrestrial.
However, with this low-severity advantage comes many challenges.
Indeed, this makes it impossible to actually place yourself in orbit to observe the celestial body.
It is therefore necessary to provide for many sometimes complex and fuel-intensive maneuvers during the approach, observation and remote mapping phases.
Similarly, it is very difficult to land on the surface and stay anchored there.
The landing is then very complicated to prepare, especially since the landing site is selected late because the target asteroid is by definition poorly known (shape and gravity, aspect of the surface, composition, density, etc.).
It is therefore impossible to plan operations in detail and it is often a question of making assumptions and determining the probabilities of action… taking into account the unforeseen events which do not fail to arise.
Another characteristic of these missions to very distant destinations is a very long preparation and cruising time.
Thus, the Lucy satellite will take more than 6 years to reach the Trojan asteroids and the Hayabusa2 mission has set off again for a 10-year journey before reaching the asteroid selected for the extension of its mission.
This requires the involvement of the ground teams over the long term, which presents a considerable human challenge.
Fortunately, this cruise is often used to finish developing the software on board the satellite, the tools on Earth necessary for operations at destination and to train the teams.
Finally, the object's great distance from the Earth increases the signal's travel time (often greater than half an hour) and requires the use of communication relays.
Interactions with Terres are then reduced, and decisions in the event of unforeseen events must be made quickly and with little data, as was the case for the Franco-German lander MASCOT on the surface of Ryugu in October 2018.
Our "ASTEROIDS" file
The element of the unexpected, mystery and risk inherent in these asteroid exploration operations is often part of the deep motivations of the technical and scientific community involved.
The numerous advantages, both scientific and technical, of these small objects, left out of the formation of the solar system, are at the origin of the current enthusiasm for these space missions which, despite everything, remain inexpensive.
The very rapid development of technologies now makes it possible to envisage even more distant missions, opening up new prospects for the exploration of asteroids and even comets.
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This analysis was written by Aurélie Moussi-Soffys, Hayabusa2-MASCOT project manager at the National Center for Space Studies (CNES).
The original article was published on
The Conversation website
.
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