In fact, last year, I poked around the net to see if the pending WISE could “see” these cometary ghosts. I managed to locate references to asteroid and NEO detection as planned tasks for WISE — but, strangely, no mention of the terms or “dark comet,” or “dead comet,” in connection with the WISE mission.
Around the same time, I had the good fortune to exchange an email with Dr. Napier on another subject, and I took the opportunity to ask him whether the pending WISE mission would indeed be capable of and tasked appropriately to locate his ‘dark’ comets. I should dig up the email, but I recall Napier told me it would NOT be capable of performing such tasks. I was disappointed.
Now, less than two month into the mission, NASA confirms the agency is indeed looking for “dark” or “dead” comets:
Though this particular body is actively shedding dust, WISE is also expected to find dark, dead comets. Once a comet has taken many trips around the sun, its icy components erode away, leaving only a dark, rocky core. Not much is known about these objects because they are hard to see in visible light. WISE’s infrared sight should be able to pick up the feeble glow of some of these dark comets, answering questions about precisely how and where they form.
“Dead comets can be darker than coal,” said Mainzer. “But in infrared light, they will pop into view. One question we want to answer with WISE is how many dead comets make up the near-Earth object population.”
The mission will spend the next eight months mapping the sky one-and-a-half times. A first batch of data will be available to the public in the spring of 2011, and the final catalog a year later. Selected images and findings will be released throughout the mission.
If the Mark Bosloughs, Allan Harisses and David Morrisions of the world are correct in their confident estimates of the Near Earth Object population — a critical figure in estimating impact frequency — they would need to account accurately for these elusive dark beasts. As far as I can find they have never even mentioned them.
Moreover, as far as I can tell from exhaustively searching the the JPL and NASA web sites, NASA has never once mentioned (as far the internet is concerned) that locating “dark” or “dead” comets was a task for WISE. Until this week.
So why does NASA now casually slip into a press release a stated objective of finding “dark” comets using WISE? Could it be because they intended to look for them, but wanted to find some prior to admitting their existence was on the table — thus revealing the built-in uncertainty in impact threat estimates?
That seems highly likely to me now. Unless, of course, there are some ‘dark’ facts not visible on the Internet indicating NASA has been forthright about their interest in dark objects.