editorial Bringing it back 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 frst scientifc 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.

ample return of extraterrestrial This Nature Astronomy issue features is roughly double the size) will allow us to materials from the Moon was quite OSIRIS-REx, a NASA mission that aims perform in-depth comparative planetology, Scommon towards the end of space race. to bring back a sample from near-Earth which will only be strengthened when both In total, the American Apollo programme asteroid Bennu in 2023, after spending samples hit the laboratory. brought a whopping 382 kg of lunar samples a couple of years orbiting the asteroid Small bodies have been enjoying some to Earth. The corresponding Soviet Luna in order to characterize it. OSIRIS-REx special attention in space exploration for programme acquired only ~300 g, but with arrived at Bennu at the end of last year, and quite some time, but the next decade will fully robotic procedures. In contrast, the the relevant papers of this issue cover the exhibit a string of missions from a variety of amount of extraterrestrial material brought Approach and Preliminary Survey phases, actors. JAXA has built a full vision behind back since the end of the Luna 24 mission in between August and December 2018, which its small-bodies programme, as described 1976 sums up to a handful of microparticles are crucial to get a first impression of the by Masaki Fujimoto and Elizabeth Tasker, from the Stardust and Hayabusa missions. asteroid. The Nature Astronomy papers are which transfers the old ‘follow the water’ Now, after 45 years, sample return is coming part of a package of seven papers whose mantra to interplanetary scales. NASA will back in force, with a wider scope and publication has been coordinated with launch a series of spacecraft targeting some selection of target types. Nature, Nature Geoscience and Nature interesting main-belt asteroids, Jupiter Why is sample return so important? Communications. This allocation allows each Trojans, near-Earth objects and — if the After all, sample-return missions are more paper of a complex mission like OSIRIS-REx CAESAR mission is selected this summer — technically challenging and risk-prone than to be presented in the journal most-suited to an ambitious sample return from a comet. standard spacecraft procedures. One reason maximize community relevance. At the same China is also planning a sample return from is technological: we need to master sample time, the unity of the package is preserved a comet or asteroid. In contrast, ESA does return if we want to explore the Solar System by gathering all of the papers in an online not seem to have capitalized on its success with crewed expeditions. But there is also a collection that also includes commissioned with the Rosetta mission in the near-term. purely scientific one. As Rosario Brunetto pieces to provide context and perspective. Such interest should actually not come and Cateline Lantz describe in their And these first results already deliver as a surprise. As Richard Binzel writes in a Comment, sample return is essential to close a series of surprises, together with Comment, small-body missions can provide the virtuous cycle that links remote sensing, valuable confirmations of ground-based answers to important scientific questions in situ exploration and laboratory analyses observations. Intriguingly, the top-shape of with relatively limited budgets. The pristine together in order to characterize a body the asteroid with indications of an internal surface and interior of small bodies without from the global- to the micro-scale. collapse, as well as the diversity of surficial those processes that alter planet-sized bodies In this sample-return revival, the Moon albedos and textures despite the rather provide scientists with a window to the past is back in the spotlight as old and new space uniform composition, point at a more through which they can reconstruct the powers are pushing to visit our satellite complex history than expected for such history of the Solar System at different epochs again. NASA has big plans that involve the bodies. The mission planners must have (and distances, now that we have started to assembling of a base in lunar orbit, the Lunar rejoiced at the fact that hydrated minerals observe trans-Neptunian objects from close

Orbital Platform-Gateway, which would are widespread across Bennu’s surface rather by, with the flyby of MU69 by New Horizons). allow easier back-and-forth from the lunar than being localized, but the dominance At the same time, in situ resource utilization surface. Also, on 26 March 2019 the White of boulders instead of the expected fine of asteroids will surely play some role in the House directed NASA to move crewed Moon regolith would not have pleased them, as it future exploration of the Solar System. landing up to 2024. Russia has revived its will complicate the sample acquisition. These lofty objectives cannot be Luna programme, which will include sample Bennu is not the only near-Earth asteroid achieved without international cooperation. return in the second half of the 2020s. And currently hosting a spacecraft: the JAXA The OSIRIS-REx and Hayabusa2 teams China will build on its success streak after mission Hayabusa2 is orbiting asteroid demonstrate it clearly: as similar missions, the recent landing of Chang’E 4 on the Ryugu with the plan of bringing back a they could have tried to outpace each other, Moon’s far side with a sample return planned sample to Earth by 2020 (Hayabusa2 will whereas instead they are in close contact for next year with the Chang’E 5 spacecraft. return a sample more quickly than OSIRIS- and they will exchange part of the samples But the attention now seems focused on REx, but it won’t reconnoitre its asteroid they will gather. We hope that this approach more ambitious targets, such as Mars. The at the same level of detail). Hayabusa2 has will extend to other initiatives, which will recent US budget request for NASA in 2020 already accomplished several impressive need to walk the thin line between global specifically includes an entry for a future milestones, as described by Hikaru Yabuta’s advancement of humanity and national — or Mars sample-return mission, with the first Comment, including the first successful even private — interest. ❐ step of the programme happening with the touchdown to acquire the sample. Having Mars 2020 rover. However, the area where two spacecraft around two similar but sample return is really flourishing is the distinct targets (both Ryugu and Bennu Published online: 5 April 2019 smaller bodies of the Solar System. are carbonaceous asteroids and the former https://doi.org/10.1038/s41550-019-0767-2

Nature Astronomy | VOL 3 | APRIL 2019 | 281 | www.nature.com/natureastronomy 281