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ISON: Lackluster Showing at Mars

comets mars ison mars reconnaissance orbiter

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#1    Waspie_Dwarf

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Posted 05 October 2013 - 06:02 PM

ISON makes lackluster showing in images from Mars


spaceflightnow.com said:

Comet ISON made its closest approach to Mars this week, and scientists in charge of the sharp-eyed camera aboard NASA's Mars Reconnaissance Orbiter say the long-awaited comet did not live up to expectations.

It's too early to say what that means for ISON's swing by the sun in November, when observers on Earth are expected to get their best chance to see the comet in the sky

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#2    Professor Buzzkill

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Posted 05 October 2013 - 07:54 PM

How can those images be of any use? A pixel, compared to other images of Ison which show the comet in far greater detail.


#3    Waspie_Dwarf

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Posted 05 October 2013 - 08:42 PM

View PostProfessor Buzzkill, on 05 October 2013 - 07:54 PM, said:

How can those images be of any use? A pixel, compared to other images of Ison which show the comet in far greater detail.

The article explains how the images can be useful. For example:

Quote

"Based on preliminary analysis of the data, the comet appears to be at the low end of the range of brightness predictions for the observation," HiRISE scientists Alan Delamere and Alfred McEwen wrote on the instrument's website. "As a result, the image isn't visually pleasing but low coma activity is best for constraining the size of the nucleus."

Or this:

Quote

The comet's nucleus does not fill a single pixel in HiRISE's snapshots, but scientists can estimate ISON's size by observing the brightness of its coma, or atmosphere, composed of dust and water vapor streaming away from its rock-ice core.

Is it possible that you didn't understand what was being said about the "less than one pixel" image.

Quote

The comet's nucleus does not fill a single pixel in HiRISE's snapshots

Not the comet but the nucleus. There are no more detailed images of the nucleus because there are no images of the nucleus at all.

The nuclei of comets are hidden by the coma, which is reflective dust and gas which evaporates from the nucleus. As the comet gets closer to the sun the coma expands and the nucleus is harder and harder to see.

In fact no comet nucleus had ever been seen until spacecraft flew close to Halley in 1986.

As MRO is observing ISON from Mars orbit it is observing from a father away from the sun than the best views Earth based observatories will get. It is seeing the comet when there is less obscuring material around the nucleus.

The best opportunities for Earth based observation will be after the comet has made its close pass of the sun. It is likely that the coma will be hugely expanded by then.

Besides, there is a chance the comet will not survive it's pass of the sun intact, in which case the MRO observations could be the best opportunity we have to observe this comet.

THAT is how these images can be of use.

Edited by Waspie_Dwarf, 05 October 2013 - 09:08 PM.
on re-reading came across as unnecessarily sarcastic.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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Also tagged with comets, mars, ison, mars reconnaissance orbiter

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