The solar system was formed about 4.5 billion years ago. Numerous asteroids orbiting the center of the solar system like debris are witnesses to the early formation of the solar system. Most of them are carbon-rich C-type asteroids. Over the course of billions of years, the C-type asteroid sat little changed, as “time capsules” preserved ancient material. Ryugu, the target of Japan’s Hayabusa 2 probe, is one of them.
“Dragon II” in the flying “Dragon Palace”, released three inspectors, the asteroid “Dragon Palace” of the “su-yan photo”, the photo of the loose rubble seems to be the results of the study – “Dragon Palace” almost entirely composed of porous loose matter early evidence. Photo: JAXA.jp
Our reporter, Tang Wei
Recently, the infrared image data sent back by Osprey II has been published in the journal Nature, revealing that the Dragon Palace is almost entirely made up of porous loose material. Scientists speculate that the fragile porous structure of the C-type asteroid, represented by the Dragon Palace, may be similar to that of a star, which formed in the original solar nebula and accumulated into planets in numerous collisions.
So far, however, we have not fully understood the early formation of the solar system, and many of the theories are based on model data that have not been confirmed by actual observations. Now, on its way back with a sample of the Dragon Palace, scientists hope to find the answer.
Type C asteroid sings solar system ‘childhood’
The Type C asteroid is a kind of carbon-containing asteroid and the most abundant and primitive asteroid type in the solar system. They account for about 75% of the total number of known asteroids, account for a higher proportion in the solar system’s main asteroid belt, and penetrate deep into the outer edge of the main belt.
“Because of its small size and low degree of progresssinceping since its inception, type C asteroids still retain the physical conditions of most primitive asteroid periods, such as envelope casings, porosity, and granularity distribution. Therefore, their existence provides clues to the understanding of the origin and evolution of the solar system. Ping Jinsong, a researcher at the National Observatory of the Chinese Academy of Sciences, said.
In the clear night sky, it’s hard to catch the C-shaped asteroid. Because of their high porosity and extremely low albedo, they are darker in the night sky than other types of asteroids, requiring small optical telescopes to be visible. Astronomical observations show that in addition to being free of hydrogen, helium and volatiles, the chemical composition of such asteroids is almost identical to that of the original solar nebula, and that they also contain hydrated minerals.
Overall, the spectrum of a Type C asteroid is very similar to a carbon-grain meteorite. It is generally believed that the carbon pellet meteorites that landed on the Earth’s surface are likely to have originated from a Type C asteroid. It is inferred that the composition of the solar nebula that forms the solar system is also preserved in carbon-grain meteorites.
“The gas and dust that make up the solar system may have been involved in the birth of earlier and second-generation stars before. Ping Jinsong points out that scientists have found changes in the special isotope composition of many elements in carbon-magdemeteorites for decades. This change in composition cannot be explained by the inner processes of the solar system. For the solar system, this change in isotope composition may have been inherent in the formation of the solar system.
Scientists have long hoped to explore the C-type asteroid to understand the birth of the solar system’s planetary system and the evolution of early planets. Before Osprey II detected the Dragon Palace, NASA targeted another Type C asteroid numbered 253 Mathilde.
A probe also revealed loose structures on its surface and explained that it may have been a loose substance from a meteor impact.
In fact, there are various hypotheses about the process of the birth of planets in the solar system. Ping Jinsong introduced, one of the widely accepted hypothesis that many planets in the solar system are formed in the “solar nebula”, the solar nebula is the solar formation process of the remaining gas and dust formation of disk-shaped clouds.
The solar nebula is home to a large amount of fine particulate matter such as silicate dust and ice. By agsycars, these particles form tiny objects of block yin in diameter of one to ten kilometers. They then collided with each other to form larger, porous piles of loose rubble, about a few kilometers in diameter to tens of kilometers in diameter, becoming the first planetary or microplanets in the solar system.
These stars are clusters that are loosely bound by multiple polymerization sags of interstellar particles, which gradually increase their size through further collisions. In the inner planetary region, within four days of the sun, the easily volatile water and methane molecules are difficult to gather in the region of the inner planet, which is largely formed by high melting point material. These substances are so scarce in the universe that Earth-like planets do not grow too much.
The study suggests that there were 50 to 100 planetary embryos in the solar system after the end of the planetary formation era. These planetary embryos have undergone considerable changes since their formation. Collisions between them continue. Without collision aggregation between stars, huge planetary individuals cannot be formed.
“Dragon Palace” hides clues to solve the problem
The Dragon Palace is a C-type near-Earth asteroid with a distance of 0.96 and 1.42 times the average distance between the sun and the sun, respectively. “Ostrich II” through near-infrared spectroscopy observationconfirmed that most of the spectrum of “Dragon Palace” has no characteristics, and CM type of carbon globular meteorite is very close.
CM type of carbon globulus meteorite, containing a high percentage of water and organic compounds. The presence of volatile, organic compounds and water indicates that they were formed without experiencing a certain degree of heating. As a result, most of its mineral composition remains primitive in physicochemical states, recording the evolution of early solar nebulae, as well as the evolution of their parent stars.
In April last year, The Osprey II fired a 2 kg copper shell at the Dragon Palace, hitting the surface of the Dragon Palace, blowing up gravel and rocks, and even moving a 5-meter-wide boulder, forming an artificial impact crater with an outer edge larger than 10 meters in diameter and 2 to 3 meters deep.
Looking at the formation of the new crater, the researchers found that the surface of the Dragon Palace was not very strong, it was more like a pile of gravel with many gaps than a solid rock. The main purpose of the experiment, which targeted the Dragon Palace, was to collect raw samples containing material below the asteroid’s surface after impact.
Infrared imaging leads to new discoveries
Infrared imaging analysis of “Dragon Palace” is similar to spectral analysis of prospecting. Through the observation of near-infrared spectrometer, the continuous spectrum of small celestial minerals and rock surfacecans can be obtained, and the particle size, porosity, boulder abundance and roughness of the surface matter can be understood.
The thermal infrared imager on board the Osprey 2 took a global thermal image around the Dragon Palace. Analysis of infrared images shows that the surface rock body of the “Dragon Palace” has a similar temperature to the substance that surrounds it, and its thermal inertia is low. The researchers believe this low heat inertia suggests that the “Dragon Palace” surface rock mass is more porous than a typical carbon-grained meteorite, indicating that it is covered with porous gravel material with a diameter of more than 10 cm. Close infrared detection also confirmed the presence of these porous gravels.
At the same time, the remote sensing thermal imaging observations of the Dragon Palace also show its possible formation history, that is, it is a pile of gravel formed by the impact fragments of the parent object, its micropore is about 30% to 50%, and experienced a low degree of solidification. Some dense boulders that exist on the surface may originate in the innermost solid area or may be exosome.
In Ping Jinsong’s view, the fragile porous structure of the C-type asteroid represented by the Dragon Palace may be similar to the primitive star, and the inner ice may sublimate during the evolution, resulting in a porous and unstable structure. The surface of the “Dragon Palace” is an uneven layer of sand, but also probably because in the course of operation encountered a large number of impact, resulting in the impact of ice melting, and thus lost moisture.
It is planned that Osprey II will fly through The Earth by the end of 2020 and send the rock samples it has collected to the Woomera Desert in southern Australia. Scientists are looking forward to this precious gift that it is about to bring back.