I will observe this week with the new crescent coming up if the weather allows. There is a storm coming in for Monday and then it clears up and is really nice for the rest of the week. I am going to start posting my double star observations and more lunar observations and practices of lunar sketching. I've done three more since the post so I'll probably post those with the originals I have from my September observations.
So in light of the clouds, I've done some researching and found some interesting things about impact craters and extinction events here on Earth. Most know that the K-T Extinction event that killed off the dinosaurs about 65 million years ago. I had a general knowledge that the Permian-Triassic period ended with a much larger extinction with about 96% of the marine species and 70% of land species wiped out. The Permian-Triassic extinction event also included the mass loss of insect species in the land species, the only time this has happen. There are several theories to what caused the extinction There seems to have been from one to three events that triggered the "Great Dying." The first event was probably a gradual environment change that was on-going. The second trigger may have been increased in volcanism, a quick release of large amounts of methane clathrate or a large bolide impact or multiple bolide impacts.
Possible impact crater sites for this event have been suggested by at the Bedout structure located off the northwest coast of Australia; or the Wilkes Land Crater in Antarctica. One scientist has even suggested that the Gulf of Mexico is the impact that cause the P-Tr extinction event.
From what I read it is quite possible that the Siberian Traps with the overflow of lava and CO2 into the atmosphere caused the extinction event. I also read that perhaps it was a combination of the Siberian Trap lava and an impact that caused the extinction event. We do know that of the extinction events, the nine (some list five) listed, that one, the K-T event was caused by an impact from space.
This though led me to look at massive impact craters that are found on the earth located in the following links:
10 Greatest Impact Craters
Google Map of Major Crater Impacts
List of Visible Craters in the United States
So I played around for a while and seeing if any of the large craters were in the time frame of any of the extinction events. Here is one example where I could easily connect the dots.
Lake Manicouagan in Canada, or the Eye of Quebec is a large, eroded impact crater that was formed by a 62 mile impact crater (100 km) caused by a 3 mile (5 km) asteroid (see the first link above) that hit about 212 million years ago. Well, at this same time we know that the end Triassic extinction event occurred from 199 million to 214 million years ago. Chicxulub was about 105 miles in diameter so certainly this "minor" impact had to have had a major impact on the extinction that occurred at this time. I should state that scientists believe that the Triassic extinction was
"most likely caused by massive floods of lava erupting from the central Atlantic magmatic province -- an event that triggered the opening of the Atlantic Ocean."Was it? Probably, but I just am curious about what the impact of the bolide that caused the 62 mile crater at Lake Manicouagan on the environment, and on species? I have more research to do on this one. Guess I need more time to connect the dots.
I don't really promote the knowledge in Wikipeidia except for a starting reference point but here are two sites I used to play connect the dots:
List of Impact Craters This has the crater size and its estimated age.
Extinction Event: List the major and minor events and dates.
Now on to another side of this fun time searching. The finding of major impact craters and sites related to them.
In Siberia most people know of the Tunguska event from the early 20th century. What many may not know is that there is a major impact crater there already. It is called the Popigai Crater. Picture of the Day from Jan. 7th, 2008 has a nice post on it located here.
Taking off from some links on that site are some other impact craters Picture of the Day has posted. There is:
Libya's Kebira Crater
Wilkes Land Crater in Antarctica
So, if nothing else, at least I was able to raise some questions that I can research now to find out if these were impact events or something else. If they are impact craters, which they seem to be, then what was their impact on the earth and life here? Sounds interesting as a winter project. I hope your skies are better than mine right now.