As you may know, Canada is absolutely full of impact craters. In fact, of the 10 largest craters on Earth, Canada contains 5 of them - but it just might contain 6. In Northwestern Ontario lies North Caribou Lake- another 20 km wide reminder that Canada once had glaciers. Yet from a satellite view it appears to occupy a vast egg-shaped formation made obvious by the Eyapamikama Lake to the north and an unnamed river to the south. Continuing to look around the area will reveal more features appearing to make a circular shape around 52.59706 N 90.824734 W. In total, the crater appears to measure at least 50 kilometers wide, making it the 15th largest possible crater on Earth (not including uncomfirmed craters)
Unfortunately the crater is in the middle of nowhere, the nearest town to it is Pickle Lake, with a population of only 425.
I could of course try to report it to the Earth Impact Database but they require evidence of an impact crater versus a geologic dome or volcanic crater - shatter cones, shocked quartz, impact breccia, etc etc. All of this would require a visit to the crater, yet I have neither the money or the time to do this any time soon. So I ask, by the off-chance anyone lives near the crater, consider taking a trip there and look for any of the above mentioned features.
In the mean time, I'll be saving up to go there myself.
Either way, happy New Year!
Wednesday, December 31, 2014
Monday, December 8, 2014
happy MJD 2457000.0!
Most of us know today as a rather unimportant day, as days go, with the rather unimportant number of December 8th. However if you're familiar with a timekeeping method used in many astronomy fields, then you'll know that from 12:00 today to 12:00 tomorrow is the julian date 2,457,000.
First, a brief history. The Julian date is a count of the days that have passed since January 1st, 4713 BC. It is used in timekeeping for astronomy to count individual days since that date, and in the case that I most often see, to provide epochs for minor planets' orbits. Today, exactly 2,457,000 days have passed since the count was started. 2456000 was March 14th, 2012 and 2458000 will be on September 4th, 2017.
So, happy JD 2457000!
First, a brief history. The Julian date is a count of the days that have passed since January 1st, 4713 BC. It is used in timekeeping for astronomy to count individual days since that date, and in the case that I most often see, to provide epochs for minor planets' orbits. Today, exactly 2,457,000 days have passed since the count was started. 2456000 was March 14th, 2012 and 2458000 will be on September 4th, 2017.
So, happy JD 2457000!
Wednesday, December 3, 2014
67P/Churyumov-Gerasimenko's double lobed shape
By far the most interesting and defining quality of comet 67P, when the Rosetta Probe visited it earlier this year, was its double-lobed shape. While not being completely new, this was the first example of such a process happening with a comet.
Contact binaries are assumed to have been two asteroids (or comets) that joined together through a collision slow enough that they wouldn't fly past each other, or destroy each other. A defining quality for these is the notable double-lobe nature of them when a telescope points itself at them. Naturally, based on the images, that's what I would have thought if I didn't know better. However I have a couple of reasons to believe otherwise.
First, long exposure images of the comet have found that both lobes of the comet are erupting. And, based on a JPL small-body database search, asteroids outnumber comets just a bit over 200:1. The chances of two comets merging together is less than 0.1%. To further this, every picture taken shows most of the outgassing coming from the center of the comet, along with the shape of the comet indicating that the area was dug away rather than gravitationally connected- a contact binary owuld have a distinct divider between each asteroid, with gravitational attraction flattening only the closest parts to one another, giving it more of a bowling pin look than an apple-core look.
Second, the density of the comet is 0.4 g/cm<sup>3</sup>, which is typical of a comet, but based on such a size and a density, a contact binary alone would not be sufficient to mold the two lobes of the comet together to such a high degree. Plus, you would expect the density to be higher had two asteroids collided with each other, pushing each other together and giving a density of at least a few more decimals than the found density.
Lastly, notice that, contrary to the rest of the comet, the 'bridge' is relatively smooth, without any craters. This shows that the surface is young in comparison, and that any craters that form are quickly wiped away as the dust that they are imprinted upon flies off the comet.
Based on the given evidence, I can conclude that 67P is a single comet, but through an unknown force, the center of it is being melted away quicker than the rest of the comet, and that we are perhaps observing live exactly how comets fragment. It may be quite a while before this one fragments, but I think the mechanism behind this quicker core sublimation would be a good target for more in-depth study, and that it will help us better understand exactly how comets work.
Contact binaries are assumed to have been two asteroids (or comets) that joined together through a collision slow enough that they wouldn't fly past each other, or destroy each other. A defining quality for these is the notable double-lobe nature of them when a telescope points itself at them. Naturally, based on the images, that's what I would have thought if I didn't know better. However I have a couple of reasons to believe otherwise.
First, long exposure images of the comet have found that both lobes of the comet are erupting. And, based on a JPL small-body database search, asteroids outnumber comets just a bit over 200:1. The chances of two comets merging together is less than 0.1%. To further this, every picture taken shows most of the outgassing coming from the center of the comet, along with the shape of the comet indicating that the area was dug away rather than gravitationally connected- a contact binary owuld have a distinct divider between each asteroid, with gravitational attraction flattening only the closest parts to one another, giving it more of a bowling pin look than an apple-core look.
Second, the density of the comet is 0.4 g/cm<sup>3</sup>, which is typical of a comet, but based on such a size and a density, a contact binary alone would not be sufficient to mold the two lobes of the comet together to such a high degree. Plus, you would expect the density to be higher had two asteroids collided with each other, pushing each other together and giving a density of at least a few more decimals than the found density.
Lastly, notice that, contrary to the rest of the comet, the 'bridge' is relatively smooth, without any craters. This shows that the surface is young in comparison, and that any craters that form are quickly wiped away as the dust that they are imprinted upon flies off the comet.
Based on the given evidence, I can conclude that 67P is a single comet, but through an unknown force, the center of it is being melted away quicker than the rest of the comet, and that we are perhaps observing live exactly how comets fragment. It may be quite a while before this one fragments, but I think the mechanism behind this quicker core sublimation would be a good target for more in-depth study, and that it will help us better understand exactly how comets work.
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