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The OSIRIS-REx spacecraft has begun reconnoitring near-Earth asteroid Bennu. The first results unveil a global composition dominated by hydrated minerals, a diverse surface with an abundance of boulders and a shape indicative of continuous surficial change throughout its history.
NASA’s spacecraft OSIRIS-REx is planning to bring back a sample from a near-Earth asteroid in 2023, and it has just delivered its first scientific results. It is only one of the projects from various space agencies that will put small bodies and sample return into the spotlight in the upcoming decade.
In 1951, three separate research groups established radio astronomy as a contender to the dominance of optical astronomy. Using the interstellar 21-cm line, they provided a method to look deeper into our own Galaxy and back in time to the birth of all galaxies.
Using a pair of modest telescopes, Arimatsu et al. have observed an occultation event that purports to have been caused by a kilometre-sized Kuiper belt object (KBO). KBOs of this order of magnitude in size have not been detected before, but are likely to represent the most populous size of object in the Kuiper belt.
The initial abundance of 26Al in a planetary system determines the surface environment of its solid planets. High levels of 26Al will dehydrate planetesimals and produce water-poor worlds similar to the terrestrial planets in our Solar System; sub-solar levels of 26Al will preferentially generate ocean planets.
Using precise distances to more than 1,300 classical Cepheids, Chen et al. have traced the warp of the Milky Way’s stellar disk to beyond 20 kpc. The Galaxy’s warp likely arose due to the torques exerted by its massive inner disk.
The iodine–xenon record in meteorites can be used to probe late-time processes within the Solar System, during the dissipation of its debris disk. Most primitive meteorites were processed and heated by impacts during this ~50 Myr period, rather than by the decay of 26Al.
Signatures of phyllosilicate-like hydrated minerals are widespread on Bennu’s surface, indicating significant aqueous alteration. The lack of spatial variations in the spectra down to the scale of ~100 m indicates both a relatively uniform particle size distribution and a lack of compositional segregation, possibly due to surficial redistribution processes.
Bennu’s surface presents evidence of a variety of particle sizes, from fine regolith to metre-sized boulders. Its moderate thermal inertia suggests that the boulders are very porous or blanketed by thin dust. Bennu’s boulders exhibit high albedo variations, indicating different origins and/or ages.
Bennu’s surface has experienced continuous changes, mostly induced by its accelerating spin rate, which could have resulted in a collapse of its interior in the past. This scenario is also supported by the heterogeneity of Bennu’s internal mass distribution.
The OSIRIS-REx mission has reached its target, asteroid Bennu, and is engaging in reconnaissance and early science observations in preparation for sample collection. Principal investigator team Heather Enos and Dante Lauretta provide an overview.