A large dust/ice ratio in the nucleus of comet 9P/Tempel 1

摘要: NASA's Deep Impact spacecraft met its intended fate on 4 July this year when it collided with Comet Tempel 1 at a relative velocity of over 36,000 km per hour. Telescopes all around the world and beyond were trained event in order to glean information about internal structure comet. Results from OSIRIS cameras ESA's Rosetta provided continuous coverage 3 days before 10 after impact. The impact created crater 60 metres diameter nature debris points comet as an ‘icy dustball’ rather than more familiar concept ‘dirty snowball’. Comets spend most their life low-temperature environment far Sun. They are therefore relatively unprocessed maintain formation conditions planetary system, but composition nuclei poorly understood. Although situ1 remote2 measurements have derived global properties some cometary nuclei, little is known interiors. mission3 shot projectile into 9P/Tempel investigate interior. Here we report water vapour content (1.5 × 1032 molecules or 4.5 106 kg) cross-section dust (330 km2 assuming albedo 0.1) by corresponding dust/ice mass ratio probably larger one, suggesting that comets dirtballs’ snowballs’ commonly believed4. High velocities (between 110 m s-1 300 m s-1) imply acceleration comet's coma, sublimated solar radiation. We did not find evidence enhanced activity impact, general impacts meteoroids cause outbursts.