Pluto, Arrokoth, and What’s Next — with Dr. Alan Stern

Watch the episode: https://www.youtube.com/watch?v=jo4TziASLP8

Dr. Fredrick Jenet co-hosted This Week in Space Episode 176 (“Beyond the Solar System”), featuring planetary scientist Dr. Alan Stern, principal investigator for New Horizons. The conversation walks through what New Horizons revealed at Pluto, why Arrokoth matters for planet formation, and what the mission could still do at the edge of the solar system.

Pluto was the last major “first visit” in planetary exploration. New Horizons showed a world far more complex than expected: active surface processes, varied terrains, and evidence that pushed scientists to rethink how small worlds evolve. The possibility of a subsurface ocean is part of that updated picture.

After Pluto, New Horizons flew past Arrokoth in the Kuiper Belt. Its distinctive “contact binary” shape—two lobes gently merged—points strongly to low-speed accretion, a result that helped settle a long-running debate about how the building blocks of planets grow.

The team is now searching for one more flyby target in the Kuiper Belt. They are using powerful survey facilities (Subaru now, with future help from the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope). The spacecraft is healthy and has the power and fuel to keep working, but the window narrows once it exits the Kuiper Belt in the 2030s—continued support and a timely target are both important.

Meanwhile, New Horizons continues to collect valuable data on the heliosphere—the outer boundary of the Sun’s influence—offering a long baseline of measurements as it heads outward.

The episode also puts these topics in current context: concerns about the U.S.–China lunar timeline, NASA naming a new Associate Administrator, and a third interstellar comet observed with a notable CO₂ cloud. Together, these headlines underscore why steady funding and clear priorities matter for deep-space science.