The first pictures of Comet ISON taken by the Mars Reconnaissance Orbiter (MRO) are finally here. That’s it? OK, they’re probably not what we were expecting, but they do give astronomers information about the comet’s size from a different perspective than Earth. Keep in mind that the spacecraft’s cameras were optimized to stare down at the sunlit surface of Mars, not poke around the sky looking for comets.
Even though ISON was only 8 million miles (12.9 million km) when the pix were shot on Sept. 29, the comet is very faint. According to predictions this puts ISON at the low end of brightness expectations. It also constrains the size of the comet’s nucleus, a key indicator of whether it will survive it fiery brush with the sun late next month. Bigger is better of course!
“The image has a scale of approximately 8 miles (13.3 km) per pixel, larger than the comet, but the size of the nucleus can be estimated based on the typical brightness
of other comet nuclei,” according to today’s press release.
Three more observations of Comet ISON are planned for today and tomorrow.