Open Space 83: Dr. Jamie Molaro on Asteroid Bennu and OSIRIS-REx | Summary and Q&A

June 15, 2020
Fraser Cain
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Open Space 83: Dr. Jamie Molaro on Asteroid Bennu and OSIRIS-REx


Planetary scientist Dr. Jamie Millar discusses the weathering processes on asteroids and moons, focusing on the mechanical breakdown of rocks over time due to factors like heat and cooling cycles and impacts. The research aims to understand how these processes shape the surfaces of these celestial bodies.

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Key Insights

  • 💦 Weathering processes on asteroids and moons differ from those on Earth due to the absence of water, wind, and biogenic factors.
  • 🖐️ Thermal fracturing plays a significant role on asteroid surfaces, causing cracks, fractures, and other related features.
  • ✋ High-resolution images have revealed the effects of thermal fracturing on Bennu, showing cracked rocks and splintered boulders.
  • 💩 Asteroids like Bennu started as rubble piles and have undergone extensive surface changes over time.
  • 🧗 The suitability of landing sites on asteroid surfaces is influenced by the presence of boulders and the potential for thermal fracturing and weathering.
  • 🏍️ Seasonal and annual cycles affect temperature changes on asteroids, contributing to phenomena like exfoliation and fracturing.
  • 💦 Comparative studies of different asteroids and their surfaces provide valuable insights into the variety of geological processes at work.


all right should be live hey everyone welcome to open space for Monday June 15 2020 of course this is our more open concept free ranging discussion about space and astronomy honestly I have no idea what we're going to talk about I suspect asteroids and that's because I'm joined by dr. Jamie Millar oh who is a planetary scientist Jamie welcome to op... Read More

Questions & Answers

Q: How do rocks weather in space without factors like water, wind, and biogenic processes?

While these factors don't exist in space, the Sun's heat and impacts can cause rocks on asteroids and moons to experience changes over time. Thermal fracturing is one such process where rocks crack and fracture due to heating and cooling cycles.

Q: Can thermal fracturing cause larger fractures to develop on asteroids, like splitting a boulder in half?

Yes, thermal fracturing can cause larger fractures to develop on asteroid surfaces. High-resolution images of Bennu have shown dramatic features where rocks, sometimes as large as 30 feet across, split apart due to these fractures.

Q: What determines the duration of the day/night cycle on an asteroid like Bennu?

Bennu has a day/night cycle of approximately four and a half hours. The surface layer of boulders, especially the upper several inches, is most affected by the diurnal cycle, where it undergoes heating and cooling.

Q: Do asteroids like Bennu have an annual cycle that affects temperature changes?

Yes, the elliptical orbit of Bennu results in an annual cycle, causing temperature changes as it moves closer or farther away from the Sun. This yearly cycle can penetrate through the materials, potentially leading to fractures in larger boulders.

Summary & Key Takeaways

  • Dr. Jamie Millar studies the mechanical weathering processes that cause rocks to break down and fracture over time on the surfaces of moons and asteroids.

  • On Earth, weathering is driven by factors like water, winds, and biogenic processes, but in space, the Sun and impacts play a significant role in weathering.

  • Recent images from the Bennu asteroid reveal the effects of thermal fracturing, where rocks on the surface crack and fracture due to heating and cooling cycles.

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