From August to early December, OSIRIS-REx spacecraft directed three of its scientific instruments to Bennu and began to make the first observation of the mission on the asteroid. During this period, the spacecraft traveled the last 2.2 million kilometers of its outbound journey to arrive at a location 19 kilometers from Bennu on December 3. The science derived from these initial observations confirms that many of Bennu's mission ground observations have revealed several new surprises.
Members of the mission team, led by the University of Arizona, presented the results at the Annual Meeting of the American Geophysical Union or AGU in Washington on December 10th.
In the main discovery of the mission's scientific research, data from two spacecraft spectrometers, the OSIRIS-REx Visual and Infrared Spectrometer (OVIRS) and the OSIRIS-REx (OTES) Thermal Emission Spectrometer reveal the presence of molecules related to hydrogen atoms, known as & quot; hydroxyl & quot ;. The team suspects that these hydroxyl groups exist throughout the asteroid in water-bearing clay minerals, which means that at some point the rock material interacts with water. While Benou himself is too small to host liquid water, the finding indicates that over time, Bennu's body is a liquid, a much larger asteroid.
"This discovery can provide an important link between what we think has happened in space with asteroids like Bennu and what we see in the meteorites that scientists are researching in the lab," said Ellen Howell, senior research fellow at Lunar and Planetary Laboratory) and a member of the Mission Spectrum Analytical Group. "It is very exciting to see these hydrated minerals distributed on the surface of Benou because they suggest that they are an integral part of Benou's composition and not just spray on the surface with a striking feature."
"The presence of hydrated minerals through the asteroid confirms that Bennu, a remnant of the formation of the solar system, is an excellent model for the OSIRIS-REx mission to study the composition of primitive volatile and organic substances," said Amy Simon, OVIRS Deputy Instructor in the NASA Goddard Space Flight Center.
In addition, data from the OSIRIS-REx Camera Suite (OCAMS) confirms Bennu's ground-based radar observations and confirms that the original model, developed in 2013 by OSIRIS-REX's chief scientific team, Michael Nolan, now based in LPL, the actual form of the asteroid. Bennu's diameter, rotation speed, inclination, and overall shape are represented almost exactly as intended.
Soon after the asteroid later called Benou was discovered in 1999, the Nolan group used the Arechido Observatory in Puerto Rico to collect clues about its size, shape and rotation by diverting radar waves from it during one of its close approaches to the Earth, the distance between the Earth and the Moon.
"Radar observations do not give us any information about the colors or brightness of the object, so it's really interesting to see the asteroid near OSIRIS-REx's eyes," Nolan said. "As we get more details, we find where craters and stones are and we were very pleasantly surprised that almost every little boom we saw in our radar image really is there."
The mission team uses this Bennu model to design the OSIRIS-REx mission. The accuracy of the model means that the mission, the spacecraft and the planned observations have been appropriately designed for the tasks ahead of Bennu.
One deviation from the pattern of the intended shape is the size of the big stone at the southern pole of Benou. The ground pattern model calculates this stone at least 33 meters high. Preliminary calculations from the OCAMS observations show that the stone is closer to a height of 50 meters, with a width of about 55 meters.
As expected, the initial assessment of the regio of Benau shows that the surface of Bennu is a mixture of many rocky, stony-rich areas and several relatively smooth regions that have no stones. However, the amount of surface stones is higher than expected. The team will make further observations in closer ranges to better assess where Bennu can be sampled for later return to Earth.
"Our initial data shows that the team has chosen the right asteroid as the OSIRIS-REx mission target," said Dante Lauretta, chief researcher of OSIRIS-REx and professor of planetary science and space chemistry at LPL, "so far, we have not found any insurmountable problems. . "The spacecraft is robust and the scientific instruments work better than it is required." It is now time for our adventure to begin. "
"What has once been science fiction is now a reality," said the president of the AR Robbins. "Our work in Bennu brings us closer to the possibility that asteroids can provide astronauts for future missions in the solar system with fuel, such as fuel and water."
The mission is currently conducting a preliminary survey of the asteroid floating on the spacecraft, passing through the north pole of Benou, the equator, and the south pole on ranges about 7 km to better determine the mass of the asteroid. This study also provides the first opportunity for the OSIRIS-REx (OLA) laser altimeter, a tool contributed by the Canadian Space Agency to make observations now that the spacecraft is near Bennu. The first orbital insertion of the spacecraft is scheduled for December 31, and OSIRIS-REx will remain in orbit until mid-February 2019 when the mission goes into the next phase of the study. During this first orbital phase, the spacecraft will orbit the asteroid in the 1.4 km radius to the center of Bennu by placing two new records for the smallest body ever orbited by a spacecraft and the closest orbit of a planetary body any spacecraft.