It turned out that the lid of the tank was stuck with a lump of soil and did not close. The decision made was to reduce as much as possible various operations and store the material as quickly as possible. In addition, two facilities that were essential for taking the soil samples and which were no longer essential were disconnected from the spacecraft. These actions made it possible to close the lid of the tank
land clearing
The close-up photographs of this asteroid showed for the first time an atmosphereless body whose surface is cracked due to heat differences. Soil cracking usually occurs due to temperature differences between day and night. These heat differences create mechanical pressures that continue throughout the day and cause the soil to crumble over time. Bennu's day is 4.5 hours. It is not difficult to guess that the heat exchange is very fast. During the day the temperature reaches 400 degrees Kelvin and at night it drops to 200 degrees Kelvin. The rate of heat weathering means that the rocks change their shape quickly and they can crumble. The quality of the photographs helped a lot in the analysis of the photographs that led to this conclusion. The OSSIRIS RE spacecraft(X) the asteroid at a height of 600 meters and the resolution of the photographs was 1 cm per pixel (1).
The types of rocks
Two types of rocks were distinguished on the ground. One type dark rocks, weak and porous and light rocks stronger and less porous. These rocks can probably be crushed by hand. The light rocks contain carbonate materials. This fact raises the possibility that carbonate minerals penetrated the pore spaces and hardened the rocks.
The place from where they intend to take soil samples was named Nightngale. This place is considered young in geological time terms and the specimen is actually young. In a spectroscopic test, the color shades in visible light. This may be indicative of the many materials from which Bennu's parent star was made. Bennu's spectroscopic tests showed that the material streaks are redder than the one in the photographs. Other factors that contribute to weathering, besides heat weathering, are cosmic radiation and the solar wind (2).
Rocks from the asteroid Vesta
On Bennu, large rocks measuring 1.5 meters to 3.5 meters each were found. These rocks are very bright. There are some among them whose brightness is 10 times greater than their surroundings. Spectroscopic analysis of this luminosity showed that they contain a large amount of the mineral pyroxene similar to that found on the asteroid Vesta and a group of asteroids called the vestoids, a group of rock masses that were ejected from Vesta by the impact of other asteroids that hit it. These rocks of Bennu are most likely of Vesta origin (3).
water
Near the Nightngale crater, thin and bright channels (veins) were found. Similar to them are found in carbonate chondrite meteorites that hit the earth. It was found that these rocks were previously in contact with water in the parent body from which this asteroid was torn off. In the mother's body the flow of water continued for miles. This phenomenon appears to have occurred and may still occur today in other chondritic asteroids (4). The flow of water can only occur within the asteroid body
internal structure
Measuring the asteroid's gravity allows investigation of its internal structure. It turned out that the internal density in its center is lower than its average. Sounds very strange. The bulge on the equator also has a low density. This phenomenon corresponds to the movement of material from the interior to the equator in recent times. referring to geological time terms (5).
Movement of rock particles
Another interesting phenomenon is the movement of particles from the surface into space. From the way in which these particles are flown into space and from the shape of this trajectory, it will be possible to learn about the weak gravitational field of the asteroid. The size of these particles is 7 millimeters. Some of them return to the ground and some of them fly back into space like ricochets. Other particles enter the orbit of the asteroid, circle it up to 16 times and return to the ground. There are also particles that are released by gravity and move through space. There is no explanation for this phenomenon (6). Their movement speed is 11.2 km/h. Heat and solar radiation contribute to this movement(7).
Mapping the asteroid
The asteroid was mapped using 2155 photographs as the spacecraft orbited it. Its distance from the ground ranges from 3.52 to 4.64 km. The mapping work was completed in February 2020 (8).
Taking the soil samples
According to the central work plan regarding the soil sampling, the spacecraft will touch the surface for only 5 seconds. During this time compressed nitrogen will be sent to the ground. The impact of the gas will blow up the soil samples that will be collected in appropriate containers. The amount of fuel allocated for this is for 3 attempts. The first sampling is planned for 20.10.2020. If this attempt is not successful, the spacecraft is returned back to orbit around the asteroid until mid-2021 and then descends to the ground again to perform the soil sampling and from there returned to Earth. Landing date 24.9.2023/9/14.4. Before the soil sampling, two repetitions were performed. This is in order to test its systems and try to anticipate unexpected events. Do not forget that this is the first event of its kind (11.8). One repetition was on XNUMX and the other on XNUMX.
After the spacecraft took the soil samples, it rose above the surface and there was a leakage of samples from the tank. It turned out that the spacecraft collected 400 grams of material instead of the planned 60 grams. It turned out that the lid of the tank was stuck with a lump of soil and did not close. The decision made was to reduce as much as possible various operations and store the material as quickly as possible (10). In addition, two facilities that were essential for taking the soil samples and which were no longer essential were disconnected from the spacecraft. These actions made it possible to close the lid of the tank (11).
More of the topic in Hayadan:
- The Osiris Rex spacecraft successfully touched down on asteroid Benu in an attempt to obtain a sample
- Asteroid Bennu - interim summary before Osiris Rex collects a sample from it and returns it to DHA
- The Osiris-Rex spacecraft passed near Earth on its way to collect a sample from a nearby asteroid
Sources
1. "OSIRIS- Rex finds heat, cold fracturing rocks on asteroid Bennu" 10.6.2020
https://www.spacedaily.com/reports/Osiris_Rex_Heat_Cold_Fracturing _Rocks_ Asteroid_Bennu_999.html
2. Brittany Enos- "NASA's OSIRIS- Rex unlocks more secrets from asteroid Bennu" 9.10.2020
3. "OSIRIS -Rex finds possible pieces of Vesta On Bennu" 22.9.2020
https://www.spacedaily.com/reports/Osiris_Rex_Finds_Possible_Pieces_Of_Vesta_On_Bennu_999.html
4. Neil V. Patelarchive – Asteroid Bennu may have been home to ancient water flows” 8.10.2020
https://www.spacedaily.com/reports/Asteroid_Bennu_May_Have_been_Home_To_Ancient_Water_Flows_999.html
5. "Planetary astronomer co-authors studies of asteroid as member of NASA's Osiris-Rex mission" 9.10.2020
6. "Why is asteroid Bennu ejecting particles into space" 10.9.2020
https://www.spacedaily.com/reports/Why_Is_Asteroid_Bennu_Ejecting_particles_Into_Space_999.html
7. "How small particles could reshape Bennu and other asteroids" 10.9.2020
8. "Mapping the solar system from the moon to Bennu" 16.7.2020
http://www.spacedaily.com/reports/Mapping_The_Solar_System_From_The_Moon_To_Bennu_999.html
9. Brittany Enos - "OSIRIS-Rex ready for touch down on asteroid Bennu for sample collection" 21.5.2020
10. "NASA works to head off losing too much OSIRIS-Rex asteroid dust" 23.10.2020
11. "OSIRIS- Rex in the middle of the sample stowage" 29.10.2020
https://www.spacedaily.com/reports/osiris_rex_in_the_middle_of_the_sample_stowage_999.html
