A Mission to Earth: OSIRIS-REx

Episode Summary

Executive Summary: This holiday Planetary Radio episode previews OSIRIS-REx’s early science at asteroid Bennu, highlighting water-bearing minerals, the value of sample return, and the mission’s Earth flyby used to test instruments. Bill Nye reflects on 2019’s space outlook, while Bruce Betts covers eclipses, space history, and a New Horizons trivia contest tied to Ultima Thule.

Main Topics: OSIRIS-REx at Bennu: The episode centers on the spacecraft’s arrival at Bennu, early observations, and the promise of returning pristine samples to Earth in 2023. Earth flyby as instrument calibration: Vicki Hamilton explains why OSIRIS-REx pointed its spectrometers at Earth during its gravity assist: to verify calibration, test performance, and collect real targets before Bennu operations. Water-bearing minerals and Bennu’s composition: The team reports evidence of water inside minerals on Bennu, reinforcing the asteroid’s similarity to carbonaceous chondrite meteorites and validating target selection. Bill Nye on the future of planetary exploration: Bill Nye frames 2019 as part of a larger, hopeful decade for Mars sample return, life-finding missions, Europa Clipper, and sustained NASA support. Why sample return matters: Hamilton explains that meteorites alter after entering Earth’s atmosphere and biosphere, so returning an untouched sample is essential for accurate scientific study. What's Up: sky events and space trivia: Bruce Betts summarizes upcoming eclipses, notes space-history anniversaries, and runs a New Horizons/Ultima Thule contest.

Key Arguments: OSIRIS-REx is successfully uncovering Bennu’s properties early in the mission, validating the choice of target. Evidence of water in Bennu’s minerals supports the idea that the asteroid is compositionally similar to carbonaceous chondrites. Sample return is crucial because meteorites found on Earth are already chemically altered by the atmosphere, hydrosphere, and biosphere. Using Earth as a known target allows instrument teams to calibrate spectrometers that otherwise would only see deep space during cruise. The Earth flyby required careful coordination between scientists and engineers to avoid risking the spacecraft while still obtaining valuable data. Bill Nye argues that the 2020s could be transformative if Mars sample return, life-search missions, and Europa Clipper proceed as planned. OSIRIS-REx’s observations of Earth demonstrated that its instruments and cameras can work on both a bright target and a spectrally rich atmosphere. The New Horizons Ultima Thule encounter was framed as a major public-science moment made possible by NASA and Planetary Society support.

Data Points: Bennu diameter: about 500 meters - Hamilton describes Bennu as a very small target for sample return and orbital operations. Earth flyby follow-up observations: day 0, day +3, day +6, and day +10 - OSIRIS-REx repeated Earth observations after the gravity assist to provide backup data opportunities. Earth reflectivity: 20–30% of sunlight - Used to contrast Earth with Bennu’s much darker surface when discussing imaging challenges. Bennu reflectivity: about 4% of sunlight - Explains why OSIRIS-REx cameras were designed for a very dark object and had to avoid overexposure on Earth. Sample return date: 2023 - Hamilton notes the mission will not end until it brings a sample back to Earth in 2023. OSIRIS-REx travel time to Bennu: more than 2 years - The spacecraft reached Bennu after a long interplanetary cruise. Earth gravity assist distance: no more than 2 kilometers - Nye references OSIRIS-REx’s planned close pass around Bennu after the Earth assist. Ultima Thule orbital period: 296.44 Earth years - Bruce Betts explains why the object’s previous similarly aligned orbit occurred in 1722. Apollo 8 lunar orbits: 10 - Trivia answer discussed on the show and used as a listener contest highlight. January 6 eclipse: partial solar eclipse - Bruce Betts lists the month’s sky events. January 21 eclipse: total lunar eclipse - Bruce Betts notes it is visible across much of North and South America, parts of Europe, Africa, and the Pacific.

Pivotal Quotes: "we want to be able to study this object without any of those interferences" — Vicki Hamilton: Explaining why pristine asteroid sample return is scientifically valuable compared with meteorites on Earth. "we have these absorption features or these dips in the curve that tell you what is actually there interacting with the light" — Vicki Hamilton: Describing how the thermal infrared spectrometer identifies gases and minerals in Earth and asteroid observations. "it is an amazing thing to me that there is such a thing as 2019" — Bill Nye: Opening his New Year reflection on how far space exploration has progressed.

Implications: The episode underscores how sample return and instrument calibration drive planetary science, while also signaling a decade of high-value exploration ahead for Mars, Europa, and Kuiper Belt science.