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OSIRIS-REX: Preparing to Collect a Pristine Sample of a Carbonaceous Asteroid Kevin Righter, NASA Johnson Space Center Featured Story | From the Desk of Lori Glaze | Meeting Highlights | News from Space | Spotlight on Education In Memoriam | Milestones | New and Noteworthy | Calendar LUNAR AND PLANETARY INFORMATION BULLETIN January 2020 Issue 159 FEATURED STORY OSIRIS-REX: Preparing to collect a pristine sample of a carbonaceous asteroid Kevin Righter, NASA Johnson Space Center After a nearly two-year journey since planning, and among the bodies most combined with detailed analyses of its launch in September 2016, the likely to collide with Earth in the future. returned samples will allow evaluation of OSIRIS-REx spacecraft arrived at its e mission has ve main goals, which connections between asteroids and mete- target asteroid Bennu in December 2018. are re ected in its name: OSIRIS- orites. ird, the volatile-rich nature of e initial images sent back to Earth REx stands for Origins, Spectral asteroids may o er important resources revealed a rocky surface with unexpected Interpretation, Resource Identi cation, for space exploration, and OSIRIS-REx roughness. e spacecraft is currently and Security-Regolith Explorer. First, will provide a better understanding characterizing the asteroid in preparation as noted, pristine samples will allow of the type and amount of volatiles for sample collection in August 2020. scientists to understand the origin of present on a typical low-albedo aster- organic compounds present in carbo- oid. Fourth, the mission will better e OSIRIS-REx mission was selected naceous asteroids and their potential characterize the variables that control in May 2011 in the third New Frontiers contribution to life on Earth. Second, Bennu’s orbital evolution and, thus, its Program. Pristine carbonaceous asteroid the characterization of spectral features potential for Earth impact. Finally, the material is not part of any collection on Earth; carbonaceous chondrite meteorites are heated upon entering the atmosphere and undergo chemical and mineralogical transformation on Earth. ese Earth e ects hinder the understanding of which organic compounds in meteorites originate from space and which are formed on Earth, and whether any become unstable and disappear after arrival at Earth’s surface. Getting a pristine piece of a carbonaceous asteroid would eliminate this uncertainty and allow scientists to better understand the organic chemistry of the early solar system. is idea led mission planners to choose near-Earth asteroid (101955) Bennu as the mission target. Bennu is accessible, volatile-rich, su ciently large, and su ciently characterized to allow Note from the Fig. 1. Instrument deck schematic for the OSIRIS-REx spacecraft. fundamental navigation and encounter Credit: University of Arizona. 2 Issue 159 January 2020 © Copyright 2020 Lunar and Planetary Insitute FEATURED STORY head of the Touch and Go Sample (materials that have dened open and eled through Earth’s fourth Lagrange Acquisition Mechanism (TAGSAM) closed periods at points throughout point, located 60° ahead in Earth’s has a ring of specially designed collector the mission, exposing and protecting orbit around the Sun. e mission team pads that will sample the upper layer them from environmental conditions) took multiple images in this region of regolith material at the surface. were deployed in the various ATLO with the OCAMS MapCam camera in environments in Denver and Florida. In the hope of identifying Earth-Trojan e mission is a partnership between the addition, materials are archived at JSC asteroids. Although none were discov- University of Arizona, NASA Goddard from various spacecraft and instrument ered, the spacecraft’s camera operated Space Flight Center, and Lockheed components that will have direct or awlessly and demonstrated that it Martin. University of Arizona planetary indirect contact with collected samples. could image objects two magnitudes scientists Michael J. Drake and Dante dimmer than originally expected. Lauretta were the Principal Investigator As ATLO activities shifted from the (PI) and Deputy PI when the mission Denver cleanrooms to Florida, so did e spacecraft used an array of small was selected, and Lauretta serves as the monitoring for contamination, including rocket thrusters to match Bennu’s veloc- current PI. Scientic payloads onboard eorts focused on the payload fairing ity and rendezvous with the asteroid. the spacecraft include the OSIRIS-REx containing the spacecraft. e most After nearly 20 months of instrument Laser Altimeter (OLA), provided by the challenging aspects involved the last checkouts and testing along the way, Canadian Space Agency; the OSIRIS- days before launch, as the fairing (the the OSIRIS-REx spacecraft entered REx ermal Emission Spectrometer nose cone used to protect the spacecraft the approach phase of the mission in (OTES), built by Arizona State against the impact of dynamic pressure August 2018. As the spacecraft closed University; the OSIRIS-REx Visible and aerodynamic heating during launch in on Bennu, surface features began to and InfraRed Spectrometer (OVIRS), through an atmosphere) had to move sharpen, and upon arrival in December built by NASA Goddard; the OSIRIS- through a number of environments on the spacecraft sent back beautiful images REx Camera Suite (OCAMS), built the way to assembly on the launchpad. of the entire asteroid (Fig. 2). One by the University of Arizona; and the is collection of witness plates and remarkable observation is that the shape Regolith X-Ray Imaging Spectrometer materials is being stored and curated model for Bennu derived from previous (REXIS), built by the Massachusetts at JSC in Houston. ese items will be Earth-based observational data was an Institute of Technology (Fig. 1). available indenitely with the purpose excellent match to the actual shape as e returned sample will be stored of allowing evaluation of any possible imaged by the mission. By early 2019, and curated at the NASA Johnson contamination of the collected sample several exciting discoveries had already Space Center ( JSC) in Houston. by the spacecraft hardware or assemblies. been made. First, OVIRS measured an absorption peak near the 2.7-microme- e launch of OSIRIS-REx was carried ter (0.0001-inch) wavelength, which is Construction out with tremendous eciency. e a key signature of OH in minerals and 21-day launch window for OSIRIS- in this case a conrmation that Bennu and Launch REx aorded exibility in the launch has hydrated phyllosilicates, like CM schedule. However, OSIRIS-REx, chondrite meteorites (Fig. 3). Second, under the guidance of United Launch as JAXA’s Hayabusa2 mission found at Building the spacecraft began in 2015 Alliance (ULA) at Cape Canaveral, asteroid Ryugu, the surface of Bennu is with the Assembly, Testing, and Launch lifted o from launch complex 41 at rougher than expected and even con- Operations (ATLO) phase of the mis- only 100 milliseconds into the launch tains very large boulders. Some of the sion. Because one of the mission goals window at 7:08 p.m., September 8, boulders appear to have embedded clasts is to study the organic geochemistry of 2016. is portion of the mission was (Fig. 4). e paucity of ner-grained the collected sample, special attention described in Issue 146 of this publi- material, as observed at other asteroids was given to building and assembling in cation (see suggested reading below). such as Itokawa (by Hayabusa in 2006) a “clean” environment. (In this context, or Eros (by the Near-Earth Asteroid a clean environment refers to one that Rendezvous mission in 1999), was is as free from any kind of biological Activities since puzzling, as were particle ejection events contaminants as humanly possible.) that were observed almost immedi- Mission scientists and curators made a Launch ately upon entering orbit in January considerable eort to acquire data and 2019. Initial assessments indicate that materials that allow a complete under- In February 2017, the spacecraft the shape of Bennu is consistent with standing of the ATLO environments undertook a search for the enigmatic a rubble-pile structure. Many of the as well as the materials composing class of near-Earth objects known as boulders and large rocks exposed at the the spacecraft and its components. Earth-Trojan asteroids. Trojan asteroids surface contain evidence for brecciation, Monitoring of the ATLO environ- are trapped in stable gravity wells, called and the loose material on the surface is ments was focused on both particle and Lagrange points, which precede or diverse with respect to color, reectance, volatile characterization. Witness plates follow a planet. OSIRIS-REx trav- and grain size (Fig. 5). Another import- 3 Issue 159 January 2020 © Copyright 2020 Lunar and Planetary Insitute FEATURED STORY and relative safety (presenting min- imal hazards to the spacecraft). All four sites show the hydration feature that is ubiquitous across Bennu. After a thorough evaluation of all four candidate sites, the mission team selected Nightingale as the site with the greatest amount of sampleable material that is safely accessible. Nightingale is located in a 20-meter (66-foot) crater within a larger crater in the northern hemisphere of Bennu. Its northern location means that it experiences lower temperatures than elsewhere on the asteroid, and the presumably young crater is well preserved. ese charac- teristics support the possibility that the site will allow for a pristine

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