G=EMC^2 Glazier wrote:
As I'm typing I'm looking at pictures I have of both,and they both look
like Mars moons. Mars moons are asteroids. Tempel 1 does not look like
a dirty snow ball. Its potato shaped,has dusty creators,and made of
rock. Structure wise it is hard for me to look at Tempel 1 and say its a
comet. Its nice to have close up pictures of both Deep impact probe of
Tempel 1,and Gaspra photographed by the Galileo spacecraft as it went by
in 1991. This has bothered me a lot. Can I say a rock asteroid and a
rock comet are physically the same? Bert


Analysis: Deep Impact Comet All Fluff
By Robert Roy Britt
Senior Science Writer
posted: 06 September 2005
01:05 pm ET


"The shape and surface features of the comet rammed this summer by
NASA's Deep Impact probe are quite different from the two other comets
whose cores have been studied, scientists said today.

Comet Tempel 1, hit in early July by an 820-pound probe, appears to be
coated with fine powder rather than solid ice and rock. The powder is
even finer than sand, scientists had reported shortly after the impact.

A thorough analysis confirms that and other preliminary conclusions
about the 7-mile-long icy world, which appears to be rather fluffy.

Weak and porous

The outer tens of meters (yards) of the comet is less strong than a
snow bank, said Deep Impact's Principal Investigator Michael A'Hearn,
an astronomer at the University of Maryland.

Still, the object's gravity holds it all together.

Dust emanates from the comet in frequent outbursts, likely a result of
being warmed by the Sun. The dust kicked up by the impact was not the
same as surface dust, but it spread through space and dissipated in a
manner similar to the natural outbursts.

While more analysis is needed, the interior is clearly different from
the surface.

Inside, the comet harbors a relatively high concentration of organic
compounds, the stuff from which life is made. The organics were more
prevalent during and after the outburst than the water and carbon
dioxide that routinely escape from the nucleus, or hard core of the
comet.

The results were presented to reporters in a teleconference today and
will be published later this week by the journal Science.

Comets are leftovers from the formation of the solar system. They're
frozen vaults of primordial material, stuff that escaped the
planet-formation process and therefore holds clues to what the raw
materials of Earth and other worlds was like.

Before Deep Impact, scientists had gotten close-up looks at the nuclei
of only two comets, Borelly and Wild 2. Tempel 1 is much different from
either of those, yet in the grand scheme it is likely still a garden
variety comet, A'Hearn and his colleagues said.

Snowy dirtball

In recent years, our impression of comets has shifted from dirty
snowballs to snowy dirtballs. That latter description holds true with
comet Tempel 1, A'Hearn said.

There is more dust than ice, A'Hearn said, but the ratio is less than
10-to-1. More significant to the new data is the revelation that
there's not much there.

"The comet is mostly empty," A'Hearn said, adding that it is probably
more than 75 percent porous with perhaps no solid core. Instead, it's
likely made of ice grains loosely packed through and through.

That conclusion would not alter how comets might have delivered water
and organic material to early Earth, A'Hearn said. One leading theory
for the formation of life on our planet holds that the raw material was
delivered by comets.

A'Hearn explained that when a comet plummets through the atmosphere, it
creates a shock wave in front. Such a shock wave, not a comet's
composition, is the primary factor that allows a large comet to make it
to the surface intact, delivering water and organics.

A'Hearn said scientists are still analyzing the chemicals that came out
of the Tempel 1, from ammonia and acetylene to hydrogen cyanide. None
of the molecules are different from what previous ground-based
observations had revealed, however.

Tempel 1 is also dotted with round depressions that the scientists
think are impact craters, which have not been seen before on comets."

http://www.space.com/scienceastronom...l1_update.html

Double-A