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Updated: Jul 18, 2026

Bringing the Visible Universe into Focus with Robo-AO
Published on: February 12, 2013
Deep Impact: excavating comet Tempel 1
M F A'Hearn1, M J S Belton, W A Delamere
1University of Maryland, College Park, MD 20742, USA. ma@astro.umd.edu
Abstract:
Deep Impact collided with comet Tempel 1, excavating a crater controlled by gravity. The comet's outer layer is composed of 1- to 100-micrometer fine particles with negligible strength (<65 pascals). Local gravitational field and average nucleus density (600 kilograms per cubic meter) are estimated from ejecta fallback. Initial ejecta were hot (>1000 kelvins). A large increase in organic material occurred during and after the event, with smaller changes in carbon dioxide relative to water. On approach, the spacecraft observed frequent natural outbursts, a mean radius of 3.0 +/- 0.1 kilometers, smooth and rough terrain, scarps, and impact craters. A thermal map indicates a surface in equilibrium with sunlight.
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