Science In Action – "Asteroids, Comets and Where to Find Them"

BBC World Service – September 11, 2025
Broadcast from the European Planetary Science Congress, Helsinki

Overview

This episode of Science in Action explores groundbreaking missions and discoveries related to the smallest members of our Solar System: asteroids and comets. Recorded on location at the European Planetary Science Congress, host Roland Pease brings listeners the latest updates from leading scientists involved in NASA and global missions. The episode spotlights the Lucy mission's asteroid encounters, the rare opportunity to observe interstellar comet 3I Atlas, and the international excitement over the upcoming near-Earth flyby of asteroid Apophis in 2029.

Key Discussion Points and Insights

1. The Focal Point: Small Bodies of the Solar System

• Roland Pease sets the theme:
  • Rather than focusing on planets, this episode zeroes in on asteroids and comets—“small, but important, nonetheless, for what they tell us about how the solar system came to be.” (01:59)

2. NASA's Lucy Mission: Surprises in the Asteroid Belt

Speaker: Hal Levison, Principal Investigator, NASA Lucy Mission

• Asteroids as Fossils

  • "They're fossils of the solar system." (02:19)
  • The mission is named "Lucy" after the famous fossil, emphasizing their historical importance.

• Encounter with Donald Johansen

  • Purpose: Test instruments before approaching Jupiter’s Trojans.
  • “All the important science is being taken in 24 hours. We can't go back if we screw up.” (04:04)
  • Unique features: Bilobed, likened to a “rubber duck” or “bowling pin.” (04:06)
  • "The neck of the bowling pin turns out to be just weird. It's overly smooth... the craters are all there, but they're all deformed and warped." (04:17)
  • Geologically active: The material between the lobes is moving, thought to be caused by the YORP effect—a change in the asteroid’s spin due to sunlight. (05:08)

• First Flyby Learnings

  • Contrast in asteroid appearances: Dinkinesh was unexpected, Donald Johansen resembled predictions. (05:52)
  • “It’s like a crime scene that you’re going through.” (05:41) – Pease on interpreting rapid flyby data.

3. The Quest to Observe Interstellar Comet 3I Atlas

A rare observation window with multiple missions involved:

Speakers:

• Je Kot, Deputy Project Scientist, Europa Clipper Mission
• Tom Statler, Lead Scientist for Small Bodies, NASA HQ

Europa Clipper’s Opportunity

• “The Europa Clipper will... pass by the comet within one astronomical unit.” (08:15)
• Using navigation (star) cameras to observe, as main science cameras are unavailable. (08:50)
• The spacecraft will fly through the comet’s tail—allowing plasma and dust analysis: “We can determine the species and charge state.” (09:30)
• Urgency and improvisation: Mission team quickly mobilized after the opportunity was recognized. (10:06)

Coordinated NASA Observation Effort

• Tom Statler outlines multi-mission approach:
  • Other involved missions: Psyche (also near the comet), Mars orbiters and rovers, Heliophysics and Sun-observing missions, and James Webb Space Telescope. (12:10-13:47)
  • The challenge and value of observing from different viewpoints: “One of the most interesting things you can do to observe a comet is to look at the scattered sunlight off of the dust from different angles and at different colors, different wavelengths." (13:47)
• Statler on the significance:
  • “It’s a sample probably from the early stages of the formation of a completely different planetary system.” (15:02)
  • Opportunity to compare with Solar System comets: “How is it similar to and different from our own homegrown comets.” (15:18)
  • “It’s an exciting time to be a planetary scientist… especially to be interested in our solar system’s small bodies.” (15:39)

4. Apophis 2029: Seismic Science, International Collaboration, and Ambition

European Seismic Mission on Apophis

Speaker: Naomi Murdoch, French Space Agency, CENS

• Mission Plans and Science Goals

  • RAMSES: Deploying two cubesats; one will land a seismometer on Apophis, an asteroid about 340m across. (19:05)
  • Unprecedented science: “First ever seismic measurements on the surface of an asteroid.” (19:30)
  • Why seismic? Earth’s close approach will “pull on Apophis... probably going to be the spin rate. So how fast it's moving. And as it changes its spin rate, the body is going to reorganize internally.” (20:07)
  • Excitement: “It’s a once in a lifetime opportunity.” (19:35)
  • Seismometer prepared for tiny signals – hoping to “detect these very small amplitude signals... and then we're just going to hope for the best.” (20:47)

• Assurances

  • Landing won’t disturb the asteroid: “Low velocity landing... is not going to change anything for Apophis.” (21:18)
  • Timeline: Deployed “several hours before the close encounter… expect[ing] to see the majority of these seismic signals” a few hours after closest approach. (21:59)
  • Personal enthusiasm: “This is really, really special. It's a really special mission for lots of reasons.” (22:07)

China’s Apophis Flyby Mission

Speaker: Jiang Yang Li, Sun Yat Sen University

• China planning a quick flyby and observation; will park in a stable halo orbit at L1, “wait for the asteroid to come by.” (24:15-24:49)
• Tiny 44 kg spacecraft; will observe and measure Apophis’ surface and estimate its mass using a secondary satellite: “Maybe micrometers change [in the distance between satellites] over tens of kilometers.” (27:00)
• Goal: Detect surface changes post-encounter with Earth’s tidal forces, and weigh Apophis using relative satellite movement. (26:22, 27:07)

International Collaboration and Historic Parallels

• Li draws parallel between Apophis 2029 and the 1986 Halley’s Comet flybys, a global festival of planetary science. (22:46)
• Pease and Li agree this event is “a unique science opportunity the whole world can take part in.” (23:24)

Notable Quotes and Memorable Moments

• Hal Levison: “I look at these small bodies and I say, they're fossils of the solar system.” (02:19)
• Roland Pease: “It’s like a crime scene that you’re going through.” (05:41)
• Je Kot: “The Europa Clipper mission will luckily be on the right side of the sun and will pass by the comet within one astronomical unit.” (08:15)
• Tom Statler: “Who doesn't love an interstellar comet? Everybody is excited by this, everybody wants to do it.” (13:22)
• Naomi Murdoch: “Earth is going to pull on it and it's going to change a lot of things about Apophis, but one of them is probably going to be the spin rate... And as it does that, the blocks are going to move against each other and they're going to create seismic signals inside the body.” (20:07)
• Jiang Yang Li: “...this festival for this tiny object. That’s exciting.” (23:24)
• Tom Statler: “It’s an exciting time to be a planetary scientist... a wonderful time to be doing such groundbreaking science that really enlightens the history of our solar system and benefits all of humanity.” (15:39)
• Naomi Murdoch: “We've done seismology on the moon, we've done seismology on Venus, we've done seismology on Mars. We've never done seismology on an asteroid, so it's a first.” (22:07)

Key Timestamps

| Timestamp | Segment | |-----------|--------------------------------------------------------------------| | 01:16 | Conference virtual opening; planetary science context | | 02:19 | Hal Levison on asteroids as “fossils”; Lucy mission overview | | 03:04 | First results from Lucy flyby of asteroid Donald Johansen | | 05:08 | YORP effect and asteroid surface activity explained | | 07:17 | Je Kot on Europa Clipper’s trajectory and new science opportunity | | 08:15 | Je Kot details plan to observe comet 3I Atlas with Europa Clipper | | 10:46 | Tom Statler on NASA’s coordination for 3I Atlas observations | | 12:10 | Psyche, Mars orbiters/rovers, James Webb, and multiple missions collaborating | | 13:47 | Statler explains the value of multi-angle, multi-wavelength observations | | 15:02 | The significance of 3I Atlas as an interstellar “sample” | | 17:58 | Naomi Murdoch on Europe's Apophis mission and its seismometer | | 19:05 | Design and challenge of seismometry on Apophis | | 20:07 | Apophis expected to "creak" under Earth's gravity | | 22:46 | Jiang Yang Li contextualizes international collaboration – Halley parallel | | 24:15 | Details of China’s L1 orbit Apophis flyby mission | | 27:07 | Using twin satellites to measure Apophis’ mass |

Conclusion

In this packed episode, Roland Pease provides an immersive journey into humanity’s innovative efforts to study asteroids and comets—small bodies with outsized importance for understanding the solar system. From NASA’s Lucy revealing “crime scenes” in the asteroid belt, to the rush of multiple spacecraft preparing to catch fleeting glimpses of an interstellar comet, and the unprecedented international focus on Apophis’ close approach, planetary scientists are harnessing rare opportunities for fundamental discoveries. The prevailing tone is one of excitement, collaboration, and ambition—a testament to a scientific community captivated by the mysteries of the smallest objects in space.