The small worlds of our solar system help us trace its history and evolution, including comets. (NASA / JPL -Caltech / UMD)
They speak of a time when innumerable meteors and asteroids rained on the planets, burned in the sun, shot down beyond the orbit of Neptune or were bumped into each other and
From distant icy comets to the asteroid that ended the dino's reign Sures, each space rock contains epic clues of events that shaped the solar system as we know it today – including life on Earth. [19659012] Highlights:
> Asteroids, comets, and other small objects in space hold clues as to our origins, but may also be dangerous. > Small worlds have probably delivered the ingredients of life to Earth. > Several NASA missions are either on their way to these small worlds, or in development.
NASA missions studying these "non-planets" help us understand how planets, including the Earth, are formed, how to locate the dangers of incoming objects, and how to think about the future of exploration . They have played a key role in the history of our solar system and reflect the constant evolution of it.
"They may not have giant volcanoes, planetary oceans or dust storms, but small worlds could answer big questions about the origin of our solar system" said Lori Glaze, acting director of the Planetary Science Division at NASA's headquarters in Washington.
NASA has long explored small bodies, beginning with the overflight of the Gaspra asteroid by Galileo in 1991. The first spacecraft to orbit an asteroid, Shoemaker, also Landed successfully on the asteroid Eros in 2000 and took measures that had not been planned originally.
The Deep Impact mission conducted a probe in Comet Tempel 1 in 2005 and prompted scientists to rethink the place of formation of comets. More recent efforts have built on these successes and will continue to teach us about our solar system. Here is a preview of what we can learn:
This representation of the crater of the Ceres ocator in false colors shows differences in the composition of the surface of the Dwarf Planet. (NASA / JPL- Caltech / UCLA / MPS / DLR / IDA)
Constitutive Blocks of the Planets
Our Solar System as We Know it Today we have grains of dust – tiny particles of rock, metal, and ice – swirling around our baby. Most of the material in this disc fell into the newborn star, but some fragments have avoided this fate and have remained glued together to form asteroids, comets and even planets. Many remnants of this process have survived to this day.
The growth of planets from smaller objects is an element of our history that asteroids and comets can help us study.
"Asteroids, comets and other small bodies contain materials dating back to the birth of the solar system. If we want to know where we're from, we need to study these objects, "said Glaze.
Two ancient fossils providing clues to this story are Vesta and Ceres, the largest bodies in the belt. Asteroids between Mars and Jupiter NASA's Dawn spacecraft, which has just completed its mission, either orbits them and definitely shows that they are not part of the "asteroids club."
that many asteroids are collections of loose rubble, the interiors of Vesta and Ceres are superimposed, with the densest material at their cores. (In scientific terms, their interiors are said to be "differentiated".) This indicates that these two bodies were on the verge of becoming planets, but their growth was slowed down: they never had enough material to become as big as the big planets.
But while Vesta is largely dry Ceres is moist and can contain up to 25% water, mainly mineral or ice-bound, with the possibility of underground liquid. The presence of ammonia in Ceres is also interesting because it usually requires temperatures lower than the current location of Ceres.
This indicates that the dwarf planet could have formed beyond Jupiter and migrated there, or at least incorporated materials from far away. . The mystery of the origins of Ceres shows how complex the formation of the planet can be and underlines the complex history of our solar system.
This artist concept describes NASA's Psyche mission probe near the target of the mission, the metal asteroid Psyche. (NASA / JPL-Caltech / Univ./Space Systems Loral / Peter Rubin)
Although we can study indirectly the deep interiors of the pl anetes looking for clues about their origins, As will NASA's InSight mission to Mars, it's impossible to drill into the heart of a large object in space, including the Earth. Nevertheless, a rare object called Psyche can offer the opportunity to explore the core of a planet-like body without digging.
The asteroid psyche appears to be the exposed iron-nickel core of a protoplanet – a small world that formed early in our solar environment. the history of the system, but never reached the planetary size. Like Vesta and Ceres, Psyche has seen her planet trajectory turned upside down. NASA's Psyche mission, launched in 2022, will help tell the story of the formation of a planet by studying this metallic object in detail.
Artist's view of NASA's New Horizons spacecraft meeting the MU69 2014, a Kuiper belt object circling the Sun 1.6 billion kilometers beyond Pluto, the 1st January 2019. (NASA / JHUAPL / SwRI)
Further on, NASA's New Horizons spacecraft is currently en route to a distant object called 2014 MU69, nicknamed U Itima Thule "by the mission. One billion kilometers farther from the Sun than Pluto, MU69 lies in the Kuiper Belt, a region of ice-rich objects beyond the orbit of Neptune. Objects such as MU69 may represent the most primitive, or the most altered material remaining in the solar system.
As the planets revolve around ellipses around the Sun, MU69 and many other objects in the Kuiper Belt have very circular orbits, which seems well not to be displaced from their trajectories of origin in 4.5 billion years. These objects can represent the constituent elements of Pluto and other distant icy worlds like this one. New Horizons will be closest to MU69 on January 1, 2019 – the world's farthest over-flight.
"Ultima Thule is extremely valuable from a scientific point of view to understand the origin of our solar system and its planets," said Alan Stern, research director of New Horizons, based at Southwest Research Institute in Boulder, Colorado. "He is old and virgin, and looks nothing like what we have seen before."
Delivery of Elements of Life
Small worlds are also responsible for seeding the Earth with the ingredients of life. The study of their amount of water proves how they helped create life on Earth.
"The small bodies are the ones who change the game. They participate in the slow and steady evolution of our solar system over time and influence the atmospheres and opportunities of planetary life. Earth is part of this story, "said NASA chief scientist Jim Green.
This" super-resolution "view of the asteroid Bennu was created with the help of eight images obtained by NASA's OSIRIS-REx spacecraft on October 29, 2018, from a distance of approximately 330 miles (330 kilometers). (NASA / Goddard / University of Arizona)
Bennu, the target of the OS NASA, is an example of an asteroid containing the basic elements of life. IRIS-REx Mission (Origins, spectral interpretation, resource identification, security regolith explorer). Bennu can be loaded with carbon and water molecules, necessary for life as we know it.
As a result of the formation of the Earth, and afterward, objects like Bennu rained and delivered these materials to our planet. These objects had no oceans, but rather water molecules bound to minerals. It is thought that 80% of the Earth's water comes from small bodies like Bennu. By studying Bennu, we can better understand the types of objects that allowed a young barren land to flourish fully.
Bennu probably originated from the main asteroid belt between Mars and Jupiter, and would have survived a catastrophic collision. between 800 million and 2 billion years. Scientists believe that a large carbon-rich asteroid has broken down into thousands of pieces and that Bennu is one of the remnants.
Rather than a solid object, Bennu is considered an asteroid "pile of rubble", a loose collection of stuck rocks. OSIRIS-REx, which will arrive in Bennu at the beginning of December 2018 after a journey of 2 billion kilometers (2 billion kilometers), will bring back a sample of this document. intriguing object to the Earth in a sample return capsule in 2023.
The Japanese Hayabusa-2 mission is also interested in an asteroid from the same family who allegedly transported the ingredients of life on Earth. Currently orbiting the Ryugu asteroid, with small mobile devices on the surface, the mission will collect samples and return them in a capsule for badysis by the end of 2020. We will learn a lot by comparing Bennu and Ryugu and understanding the similarities. and the differences between their samples.
Tracers of the Solar System Evolution
Most of the materials that formed our solar system, including the Earth, have not lived to tell the story. He fell into the sun or was ejected beyond the reach of our most powerful telescopes; only a small fraction formed the planets. But there are still renegade remnants of the early days when the body of the planets revolved around an uncertain fate.
The solar system experienced a particularly catastrophic period between 50 and 500 million years after its formation. Jupiter and Saturn, the most mbadive giants in our system, reorganized the objects around them as their gravity interacted with smaller worlds such as asteroids. Uranus and Neptune may have originated closer to the Sun and were expelled while Jupiter and Saturn were moving. Saturn, in fact, might have prevented Jupiter from "eating" certain terrestrial planets, including the Earth, because its gravity thwarted the subsequent movement of Jupiter toward the Sun.
The conceptual image of Lucy's mission on Trojan asteroids. (NASA / SwRI)
Asteroid swarms called the Trojans pourraient aider à régler les détails Les chevaux de Troie comprennent deux groupes de petits corps qui partagent l'orbite de Jupiter autour du Soleil, un groupe devant Jupiter et un autre restant à la traîne. différents matériaux que d'autres, comme l'indiquent leurs couleurs variables.
Certains sont beaucoup plus rouges que d'autres et pourraient provenir de l'orbite de Neptune, tandis que les plus gris se seraient formés beaucoup plus près du Soleil. La théorie principale est que, lorsque Jupiter s'est déplacé il y a bien longtemps, ces objets ont été rbademblés en points de Lagrange – des endroits où la gravité de Jupiter et du Soleil créent des zones de rétention où les astéroïdes peuvent être capturés. Les scientifiques disent que la diversité des Troyens reflète le voyage de Jupiter à son emplacement actuel.
"Ce sont les vestiges de ce qui se pbadait lors du dernier déménagement de Jupiter", a déclaré Hal Levison, chercheur au Southwest Research Institute.
La mission Lucy de la NASA, lancée en octobre 2021, enverra pour la première fois un véhicule spatial aux chevaux de Troie, enquêtant de manière approfondie sur six chevaux de Troie (trois astéroïdes sur chaque essaim). Pour le chercheur principal de la mission, Levison testera les idées sur lesquelles il travaille avec ses collègues depuis des décennies sur la transformation du système solaire par Jupiter. «Ce qui serait vraiment intéressant, c'est ce à quoi nous ne nous attendons pas», a-t-il déclaré.
Processus dans un système solaire en évolution
Après le coucher du soleil, dans de bonnes conditions, vous remarquerez peut-être des rayons de soleil dispersés dans le plan écliptique, la région. du ciel où les planètes orbitent. Ceci est dû au fait que la poussière du soleil laissée par les collisions de petits corps tels que les comètes et les astéroïdes diffuse la lumière du soleil. Les scientifiques appellent ce phénomène «lumière zodiacale», ce qui indique que notre système solaire est toujours actif. La poussière zodiacale autour d'autres étoiles indique qu'elles peuvent également abriter des systèmes planétaires actifs.
Les poussières de petits corps ont joué un rôle important dans notre planète en particulier. Chaque jour, environ 100 tonnes de météorites et de poussières tombent sur la Terre. Certaines proviennent de comètes, dont l’activité a des conséquences directes sur l’évolution de la Terre. À mesure que les comètes s'approchent du Soleil et ressentent sa chaleur, les gaz à l'intérieur de la comète bouillonnent et emportent les matières poussiéreuses de la comète – y compris les ingrédients de la vie. Le vaisseau spatial Stardust de la NASA a survolé Comet 81P / Wild et a découvert que la poussière de comète contient des acides aminés, qui sont des éléments essentiels à la vie.
This view shows Comet 67P/Churyumov-Gerasimenko as seen by the OSIRIS wide-angle camera on ESA’s Rosetta spacecraft on September 29, 2016, when Rosetta was at an altitude of 14 miles (23 kilometers). (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)
Occasional outbursts of gas and dust observed in comets indicate activity on or near their surfaces, such as landslides. The European Space Agency’s Rosetta mission, which completed its exploration of Comet 67P/Churyumov-Gerasimenko in 2016, delivered unprecedented insights about cometary activity.
Among the changes in the comet, the spacecraft observed a mbadive cliff collapse, a large crack get bigger and a boulder move. “We discovered that boulders the size of a large truck could be moved across the comet’s surface a distance as long as one-and-a-half football fields,” Ramy El-Maarry, a member of the U.S. Rosetta science team from the University of Colorado, Boulder, said in 2017.
Comets also influence planetary motion today. As Jupiter continues to fling comets outward, it moves inward ever so slightly because of the gravitational dance with the icy bodies.
Neptune, meanwhile, throws comets inward and in turn gets a tiny outward push. Uranus and Saturn are also moving outward very slowly in this process.
“Right now we’re talking about teeny amounts of motions because there’s not a lot of mbad left,” Levison said.
Fun fact: The spacecraft that has seen the most comets is NASA’s Solar & Heliospheric Observatory (SOHO), most famous for its study of the Sun. SOHO has seen the Sun “eat” thousands of comets, which means that these small worlds were spraying material in the inner part of the solar system on their journey to become the Sun’s dinner.
This image portrays a comet as it approaches the inner solar system. Light from the Sun warms the comet’s core, or nucleus, an object so small it cannot be seen at this scale. (NASA/JPL-Caltech)
Hazards to Earth
Asteroids can still pose an impact hazard to the planets, including our own.
While the Trojans are stuck being Jupiter groupies, Bennu, the target of the OSIRIS-REx mission, is one of the most potentially hazardous asteroids to Earth that is currently known, even though its odds of colliding with Earth are still relatively small; scientists estimate Bennu has a 1?in?2,700 chance of impacting our planet during one of its close approaches to Earth in the late 22nd century.
Right now, scientists can predict Bennu’s path quite precisely through the year 2135, when the asteroid will make one of its close pbades by Earth. Close observations by OSIRIS-REx will get an even tighter handle on Bennu’s journey, and help scientists working on safeguarding our planet against hazardous asteroids to better understand what it would take to deflect one on an impact trajectory.
“We’re developing a lot of technologies for operating with precision around these kinds of bodies, and targeting locations on their surfaces, as well as characterizing their overall physical and chemical properties. You would need this information if you wanted to design an asteroid deflection mission,” said Dante Lauretta, principal investigator for the OSIRIS-REx mission, based at the University of Arizona in Tucson.
Another upcoming mission that will test a technique for defending the planet from naturally occurring impact hazards is NASA’s Double Asteroid Redirection Test (DART) mission, which will attempt to change a small asteroid’s motion. How? Kinetic impact — in other words, collide something with it, but in a more precise and controlled way than nature does it.
DART’s target is Didymos, a binary asteroid composed of two objects orbiting each other. The larger body is about half a mile (800 meters) across, with a small moonlet that is less than one-tenth of a mile (150 meters) wide. An asteroid this size could result in widespread regional damage if one were to impact Earth.
DART will deliberately crash itself into the moonlet to slightly change the small object’s orbital speed.
Telescopes on Earth will then measure this change in speed by observing the new period of time it takes the moonlet to complete an orbit around the main body, which is expected to be a change of less than a fraction of one percent. But even that small of change could be enough to make a predicted impactor miss Earth in some future impact scenario. The spacecraft, being built by the Johns Hopkins University Applied Physics Laboratory, is scheduled for launch in spring-summer 2021.
Didymos and Bennu are just two of the almost 19,000 known near-Earth asteroids. There are over 8,300 known near-Earth asteroids the size of the moonlet of Didymos and larger, but scientists estimate that about 25,000 asteroids in that size range exist in near-Earth space. The space telescope helping scientists discover and understand these kinds of objects, including potential hazards, is called NEOWISE (which stands for Near–Earth Object Wide–field Infrared Survey Explorer).
“For most asteroids, we know little about them except for their orbit and how bright they look. With NEOWISE, we can use the heat emitted from the objects to give us a better badessment of their sizes,” said Amy Mainzer, principal investigator of NEOWISE, based at NASA’s Jet Propulsion Laboratory. “That’s important because asteroid impacts can pack quite a punch, and the amount of energy depends strongly on the size of the object.”
This artist’s concept shows the Wide-field Infrared Survey Explorer, or WISE, spacecraft, in its orbit around Earth. In its NEOWISE mission it finds and characterizes asteroids. (NASA/JPL-Caltech)
Small Worlds as Pit Stops, Resources for Future Exploration
There are no gas stations in space yet, but scientists and engineers are already starting to think about how asteroids could one day serve as refueling stations for spacecraft on the way to farther-flung destinations. These small worlds might also help astronauts restock their supplies. For example, Bennu likely has water bound in clay minerals, which could perhaps one day be harvested for hydrating thirsty space travelers.
“In addition to science, the future will indeed be mining,” Green said. “The materials in space will be used in space for further exploration.”
How did metals get on asteroids? As they formed, asteroids and other small worlds collected heavy elements forged billions of years ago. Iron and nickel found in asteroids were produced by previous generations of stars and incorporated in the formation of our solar system.
These small bodies also contain heavier metals forged in stellar explosions called supernovae. The violent death of a star, which can lead to the creation of a black hole, spreads elements heavier than hydrogen and helium throughout the universe. These include metals like gold, silver and platinum, as well as oxygen, carbon and other elements we need for survival.
Another kind of cataclysm — the collision of supernova remnants called neutron stars — can also create and spread heavy metals. In this way small bodies are also forensic evidence of the explosions or collisions of long-dead stars.
Because of big things, we now have a lot of very small things. And from small things, we get big clues about our past — and possibly resources for our future. Exploring these objects is important, even if they aren’t planets.
They are small worldsafter all.
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Asteroid, Asteroids, Bennu, Ceres, Comet 67P/Churyumov-Gerasimenko, Comet Tempel 1, Comets, Dwarf Planet, earth, Gaspra, Gravity, Jupiter, Kuoper Belt, Mars, NASA, NASA's Dawn Spacecraft, NASA's Deep Impact Spacecraft, NASA's Galileo spacecraft, NASA's InSight mission, NASA's Jet Propulsion Laboratory, NASA's Lucy Mission, NASA's NEOWISE Mission, NASA's New Horizons Spacecraft, NASA's Psyche Mission, National Aeronautics and Space Administration, Near Earth Asteroid, Neptune, Orbit, OSIRIS-REx, Pasadena CA, Planets, Pluto, Saturn, Solar System, Space, Sun, Trojan Asteroids, Ultima Thule, Uranus, Vesta
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