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Mars Orbiter Beams Back Images of Comet's Surprisingly Tiny Nucleus
astroengine writes The High-Resolution Imaging Science Experiment (HiRISE) camera on board NASA's Mars Reconnaissance Orbiter (MRO) has become the first instrument orbiting Mars to beam back images of comet Siding Spring's nucleus and coma. And by default, it has also become the first ever mission to photograph a long-period comet's pristine nucleus on its first foray into the inner solar system. Interestingly, through analysis of these first HiRISE observations, astronomers have determined that the icy nucleus at the comet's core is much smaller than originally thought. "Telescopic observers had modeled the size of the nucleus as about half a mile, or one kilometer, wide," writes a NASA Jet Propulsion Laboratory news release. "However, the best HiRISE images show only two to three pixels across the brightest feature, probably the nucleus, suggesting a size less than half that estimate."
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Well, I guess that takes a bit of the sting out of the missed impact opportunity.
If the nucleus really had been 50km in diameter (original estimated maximum), and if it had hit Mars, it would've significantly increased Mars' atmosphere with one blow. I'll confess that I was a bit disappointed when we realized that wasn't going to happen.
A comet this small would still have made an impressive boom, but it would have been perhaps a bit less world-changing.
0.8 kilometer (1/2 mile) is about one kilometer. Claiming more precision ("1/2 mile, or 0.8 kilometer") would actually be misleading.
Within their measurement errors bounds, yes ½mile == 1km
don't link to Discovery.com for TFA. The last time I tried to load a page there, the NoScript menu got half a mile long. Every domain I enabled trying to get the site to display correctly, added 5 more script domains to the list. You end up downloading half the Internet just to display one page.
Comets are named after whoever spots it first. Siding Spring is an observatory in Australia.
There is no water coming out of comets. What is detected are OH- ions, that are believed to be derived from water - which is not there
This is flat out wrong in the sense that water, as opposed to OH-groups, have been confirmed. This includes the v2 bending mode and v3 asymmetric stretching mode ~1600 cm^1 and ~3750 cm^-1, plus other combination vibration modes such as v1+v3. These modes do not exist in just the OH ion, and involve frequencies specific to water (although some combination modes overlap with other detected vibration modes). This stuff has been seen since at least the 80s.
The other name for the mountain is: Mount Woorat, part of the Warrumbungle National Park. So in comparison, not as Siding Spring is not as strange.