View Full Version : Podcast: Comets, Our Icy Friends from the Outer Solar System

2007-Jan-16, 01:51 AM
The sudden brightening of Comet McNaught has reminded us what a treat it can be to see a comet with the unaided eye. A diffuse ball with a long tail stretching across the sky. ...

Read the full blog entry (http://www.universetoday.com/2007/01/15/podcast-comets-our-icy-friends-from-the-outer-solar-system/)

2007-Jan-16, 05:39 PM
Dr. Gay needs to update her notes. Both the Stardust and Deep Impact missions returned OBSERVATIONAL RESULTS that are dramatically at-odds with prior THEORETICAL textbook explanations. Most notable it the presence of mineral clays that form at a variety of temperatures, both simple and complex organics, and a much higher proportion of ‘dirt’ than water-ice.

Scientists have long thought of comets as cold, billowing clouds of ice, dust and gases formed on the edges of the solar system. But comets may not be so simple or similar. They may prove to be diverse bodies with complex histories. Comet Wild 2 certainly is made up of components with a more complex history than thought.

We have found very high-temperature minerals, which supports a particular model where strong bipolar gas jets coming out of the early sun propelled material formed near to the sun outward to the outer reaches of the solar system," said Michael Zolensky, NASA cosmic mineralogist and Stardust co-investigator at the Johnson Space Center (JSC), Houston. "It seems that comets are not composed entirely of volatile rich materials but rather are a mixture of materials formed at all temperature ranges, at places very near the early sun and at places very remote from it.


The presence of clays and carbonates is particularly surprising. Comets are thought to contain material, unchanged from the very earliest days of the solar system. But clays and carbonates need liquid water to form, suggesting the early solar system was rather different than we currently imagine, with much more mixing of the material that went on to form the planets.
None of the four comets we have looked at closely confirm the ‘dirty iceball’ model used by Dr. Gay. They may be “Icy dirtballs”, but the current data suggest they are highly friable wet clay and organics of unknown origin. At this time we can only conclude other comets will follow suit.