mission control Bringing home a piece of our past The Hayabusa2 spacecraft will soon rendezvous with asteroid Ryugu in order to study its composition using remote sensing, a lander, rovers and sample return, explains Elizabeth Tasker.

n 26 February 2018, the Hayabusa2 A firm schedule has to wait until Hayabusa2 spacecraft caught sight of its can clearly observe the structure of Ryugu. Odestination for the first time. The Mobile Asteroid Surface Scout Asteroid Ryugu appeared as no more than (MASCOT) lander was developed by the a bright dot on the image snapped by German Aerospace Centre and French space the onboard telescopic camera, but after agency, CNES — the team behind the Philae three years in space it is great to see you comet lander for the ESA Rosetta mission. are going in the right direction. Meaning The lander will analyse the asteroid’s ‘falcon’ in Japanese, Hayabusa2 is an regolith using an infrared spectrometer, a asteroid sample retrieval mission led by magnetometer, a radiometer and a camera, the Institute of Space and Astronautical while the rovers will explore an innovative Science (ISAS) at the Japan Aerospace method of transportation in a low-gravity Exploration Agency (JAXA). The mission Fig. 1 | An artist’s impression of the environment: rather than drive, the rovers is the successor to Hayabusa, which visited Hayabusa2 spacecraft collecting a sample will ‘hop’ across the surface. MASCOT will asteroid Itokawa in 2005. from asteroid Ryugu. Credit: © JAXA / Akihiro operate for about 15 hours and the rovers for From June 2018 onward, Hayabusa2 will Ikeshita a few days, communicating with the Earth be close enough to Ryugu to begin to resolve via Hayabusa2. the asteroid’s surface features. Then analysis Hayabusa2 is equipped with a set can begin in earnest. One of the first tasks just the solvent to create life, but also the of three cameras, a near-infrared will be to construct a three-dimensional first ingredients. spectrometer for determining mineral model that can be used to select landing sites Hayabusa2 gathers material through a composition, a laser altimeter to measure and to estimate Ryugu’s gravitational field. sampler horn that resembles a long cylinder distance to the surface and a thermal Even though Ryugu is less than 1 km in with a conical end. As the spacecraft touches infrared imager. This suite had a test run diameter, its weak gravity must be carefully down on the asteroid, a bullet will be fired in December 2015, when the spacecraft considered for the spacecraft to descend to into the surface to lift sand, pebbles and flew by the Earth for a gravitational kick the surface safely. fragments of rock into the horn. Should on its journey towards Ryugu. The camera The plan for Hayabusa2 is to gather three this fail for any reason, the mouth of the filters identified regions of plant life on samples from asteroid Ryugu over a period horn is equipped with teeth that will raise Earth while the spectrometer detected the of the subsequent 12 months and return surface material during touchdown. As presence of water. Once at Ryugu, the these to Earth in late 2020: two samples the spacecraft decelerates, this regolith same analysis will be performed to search of the asteroid surface, and a collection will travel up the horn and into the sample for the presence of hydrated minerals of subsurface material exposed during a container. The sample container has three and organic compounds. controlled impact. In addition to sample chambers to store material collected at Hayabusa2 is not the only mission collection, the asteroid will also be explored each landing site on Ryugu. This triple heading to the asteroids. NASA’s OSIRIS- via a suite of remote sensing instruments, touchdown allows the sampling of different REx is en route to collect a sample from a lander and three small rovers. It is an materials that may be present on the asteroid Bennu and will begin its approach ambitious itinerary to tackle an equally asteroid. The third sample collection (Fig. 1) later this year. The two mission teams ambitious science goal: to uncover the will be particularly distinct because this is are working closely together and will original material that initiated life on Earth. when Hayabusa2 will blast a crater on the share samples once the spacecraft return. Ryugu is a C-type asteroid, a class asteroid surface with its Small Carry-on Hayabusa2 is due to return to Earth in of space rock containing carbonaceous Impactor (SCI). By gathering from this 2020, while OSIRIS-REx will arrive three material that is thought to have undergone freshly exposed region, Hayabusa2 will years later. With their arrival, we will minimal alteration since the Solar System have material that has not been subjected to have a sample of our origins to explore first formed. The small celestial body is weathering from the Sun’s radiation. for years to come. ❐ therefore kin to the meteorites that pelted Operations are planned to begin at the the early Earth. This bombardment was asteroid surface in September and October Elizabeth Tasker a likely delivery service for the Earth’s 2018. The current schedule includes the Department of Solar System Science at ISAS/JAXA, oceans, as our proximity to the Sun would release of the lander, one or two of the rovers Tokyo, Japan. have made it too warm to incorporate solid and the first sample collection. The second e-mail: elizabeth.tasker@jaxa.jp ices into the forming planet. Moreover, sample collection is currently planned for primitive organics have been discovered in February 2019 and the third (complete with Published online: 1 June 2018 meteorites that hint at the delivery of not dropping the SCI) will be in April or May. https://doi.org/10.1038/s41550-018-0486-0

502 Nature Astronomy | VOL 2 | JUNE 2018 | 502 | www.nature.com/natureastronomy © 2018 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. © 2018 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.