Summer is currently in full swing and I’m looking forward to taking a relaxing break during August so that I’m fully prepared for what promises to be an incredibly busy and exciting fall. All eyes are going to be on asteroids this autumn, with a host of momentous events that help showcase the importance of our solar system’s smaller bodies. Each of our small-body-focused missions help us uncover more about the diversity of asteroid populations and their role in the story of solar system formation and evolution, as well as providing key data for improving planetary defense endeavors.
First up, we’re eagerly anticipating the return of the OSIRIS-REx sample capsule on September 24. The capsule will land at the Utah Test and Training Range (UTTR) at 10:55 EDT, with an estimated 250 grams (±100 grams) of pristine material that was collected from asteroid Bennu back in 2020. It will then be retrieved by helicopter and taken to a temporary clean room at UTTR for an initial examination. The following day (September 25), the capsule and its contents will be flown to NASA’s Johnson Space Center (JSC) — to a brand-new clean-room facility that has been built to house the OSIRIS-REx collection. Once the samples are safely at JSC, the curation and mission teams will get to work on their careful preliminary examination activities. All aspects of the return, curation, and preliminary examination plan have been meticulously practiced by various teams over the last several months, and a recent rehearsal held in July gives a good idea of what the return itself will look like.
The delivery of the OSIRIS-REx samples will be the first time NASA has brought extraterrestrial materials to Earth since Stardust’s delivery of comet and interstellar particles in 2006. I’m proud to see this event being commemorated by the release of a new USPS postage stamp and I’m glad that the world will be able to share the excitement of the sample return, and the mission as a whole, through a variety of media and public events — including a live feed of the landing on September 24.
We plan to have information about the sample haul to “reveal” publicly on October 11. With a target of six months after sample return, materials from the OSIRIS-REx sample collection are expected to become available (like other NASA-curated extraterrestrial sample collections) for scientists to study. I know the planetary science community is extremely eager to get their hands on these samples, and I cannot wait to see how analyses of Bennu’s rocks and dust will give us new glimpses into the period of planetary formation that took place 4.5 billion years ago and the history of the main asteroid belt.
The return of the OSIRIS-REx sample capsule, however, is by no means the end for the spacecraft. We are delighted that the spacecraft and its payload remain healthy and we are planning to repurpose the spacecraft and send it to rendezvous with another asteroid — the near-Earth asteroid Apophis. After sample return, the OSIRIS-REx spacecraft will therefore transition to being known as the OSIRIS-APEX (Apophis Explorer) spacecraft. OSIRIS-APEX will reach Apophis shortly after the asteroid’s close approach to Earth in April 2029 and it will complete a planned 18-month investigation (similar to that of Bennu) of the 340-meter-diameter asteroid from orbit. Some of the major objectives of OSIRIS-APEX will be to better understand Apophis’ internal configuration, study possible observable consequences of tidal effects, connect ground-based observations to in situ data, and help planetary defense hazard mitigation studies.
But we definitely won’t be able to sit back and rest on our OSIRIS-REx laurels because in between the OSIRIS-REx sample return and our release of the first look at the samples, the launch period for our Psyche spacecraft will open (running from October 5 to 25). Psyche will launch on a SpaceX Falcon Heavy from Cape Canaveral and start its journey to the asteroid of the same name. Observations from Earth indicate that asteroid Psyche has a very high metal content (perhaps up to about 60%) and is one of only a handful that we know has this kind of compositional makeup. For this reason, the Psyche mission will provide a unique view of what may be the remnant of a larger body’s metallic core and, thus, incredible insights into planetary formation processes. After a cruise of almost six years, the spacecraft will orbit the asteroid for 26 months and its payload (including a gamma-ray and neutron spectrometer, a multispectral imager, a magnetometer, and an X-band radio telecommunications system) will be used to map the asteroid’s surface elemental composition and mineralogy, measure the gravity field and investigate the interior structure, characterize any remnant magnetic field, and much more.
And, yet, that is still not all! Asteroid autumn will also see the one-year anniversary of the DART spacecraft’s astoundingly successful impact with Dimorphos on September 26, 2022. I still get an immense thrill watching the final series of images that took us right to the moment of impact. More importantly, in the year since impact, the DART team has confirmed that the orbital period of Dimorphos around its parent asteroid, Didymos, changed from 11 hours and 55 minutes to 11 hours and 22 minutes — a whopping 33-minute change — because of DART’s impact. DART has showed us that the kinetic impactor technique — once only an idea for planetary defense — is a viable technique that could potentially be used to help protect Earth and humanity from a future asteroid threat. There are now several DART publications available (e.g., in a special issue of Nature) that document and discuss many aspects of the impact and its aftermath, with many more still to come.
Rounding out our asteroid autumn will be the first asteroid flyby of the Lucy spacecraft on November 1. Since launching in October 2021, Lucy successfully completed its first Earth gravity assist last October and is currently on a two-year heliocentric orbit that will bring it around for another Earth gravity assist next October. In the meantime, the flyby of asteroid Dinkinesh in the inner edge of the main asteroid belt in November will serve as a risk reduction and a test of Lucy’s autonomous terminal tracking system. Before heading out on its tour of the Trojan asteroids (asteroids orbiting the Sun at the same distance as Jupiter that are probably remnants of the primordial material that formed the outer planets), Lucy will make a flyby of a second main-belt asteroid, Donaldjohanson, in April 2025. All told, the Lucy spacecraft will be making flybys of 10 asteroids over a 12-year mission — an incredible feat.
I hope this has managed to whet your appetite for asteroid autumn and that you’ll find a way to share in the excitement of all these events. Go OREx! Go Psyche! Go Lucy! Go asteroids!
— Lori S. Glaze, Director, NASA’s Planetary Science Division, August 2023