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Cratering on Eros: Insights from Impact Studies and Observations

lael-potts avatar
lael-potts
19 diapositives · 341 Views · Nov 19, 2014

This presentation explores the intricate impact cratering processes on the asteroid Eros. It aims to understand projectile population distributions, determine the cratering age of Eros, and investigate secondary cratering effects. Observations reveal a unique landscape comprised of large craters, boulders, and unusual geological features shaped by low-gravity conditions. The study highlights how Eros compares to other small bodies and the mechanisms behind its surface evolution, emphasizing the complexities of cratering on asteroids and the implications for planetary science.

#cratering on eros: insights from impact studies and observations #cratering on eros: insights from impact studies and observations ppt #powerpoint #presentation
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  1. Cratering on Small Bodies: Lessons from Eros Clark R. Chapman SouthwestResearchInstitute Boulder, Colorado, USA Impact Cratering: Bridging the Gap between Modeling and Observations Lunar & Planetary Inst., Houston, 9 Feb. 2003

  2. Goals of Studying Cratering on Eros Planetary craters provide an historical record. We must understand not only their formation but also their degradation and ancillary processes (e.g. secondary cratering). • Chief goal of cratering specialists: study moderate-scale cratering on a nearly gravitationless body • Some of my goals: • Determine projectile population size-distribution in main asteroid belt (where Eros lived most of its life) • Determine “cratering age” of Eros • How old Eros is since its creation as an independent body or since its last global resurfacing event • Evidence (at high res) indicating its duration in near-Earth orbit • Understand ejecta/secondary cratering processes • Understand regolith evolution on a small body • Learn (from surface expression) about interior of Eros

  3. Eros in Context of Asteroids Imaged by Spacecraft Mathilde • Eros is typical in size, though an Earth-approacher • All are S-types, except C-type Mathilde; Mathilde’s unique giant craters are probably due to its high porosity/low density • Angular Gaspra has low crater density, perhaps due to metallic composition • Craters similar on Eros & Ida Ida Gaspra Eros

  4. Some Aspects of the Larger Craters on Eros • Two of largest craters (Himeros and Psyche) are large relative to the width of Eros • Compressive ridge extends around to other side of Eros • Bowl-shaped Psyche has markedly different shape from youngest large crater (Shoemaker, not shown here) • Bright/dark interior slopes indicate downslope slippage, unusual space weathering

  5. Eros’ Surface from Low Orbit

  6. “Ponds” from Low-Altitude Flyover

  7. NEAR-Shoemaker’s Landing Spot on Eros Inset shows Himeros Estimated positions of last images end within a 50 meter diameter crater • How typical is the edge of Himeros of Eros? • How typical is Eros of other asteroids?

  8. Fifth Last Image (largest boulders are 3 meters across)

  9. Eros is Covered with Rocks

  10. Final Landing Mosaic

  11. Closest Image of Eros

  12. “Ponds” and “Beaches”? • “Ponds” are flat, level, and are sharply bounded • “Beaches” (not always seen) surround some ponds and are relatively lacking in either craters or boulders • Although stratigraphically younger, ponds may have more small craters than typical terrains, suggesting that boulders may armor crater production • How are they formed? Electrostaticlevitation, seismicshaking? If mass-wasting, why don’t lunar ponds exist?

  13. The Relative Plot (R-Plot) • Shows spatial densities of craters as function of size relative to saturation

  14. R-Plot: Eros Craters & Boulders

  15. Eros R-Plot (annotated)

  16. Eros is NOT Like the Moon! Eros has rocks. The Moon has craters.

  17. Summary of NEA Population Estimates (A. W. Harris, 2002)

  18. Whyis Eros so Different from the Moon at Small Scales? ??? • Covering-up by mass-wasting, seismic shaking, ejecta blanketing -- doesn’t work: boulders would be covered, too. • Unless...Shoemaker crater formed “yesterday”! • Armoring by boulders: impactors strike but few craters are formed -- probably explains factor of 3…we need orders of magnitude (note: few craters in ponds). • Yarkovsky Effect (meteorite-sized bodies depleted from asteroid belt, some delivered to Earth) -- hasn’t worked quantitatively, yet.

  19. Final Comment... Cratering on asteroids is unexpectedly weird and varied