If you want to help save all life on Earth, get out to a national park and see the Orionid meteor shower this weekend. Perhaps I should explain. Unless you've been avoiding all media for the last three years, you are probably aware that the world is prophesied to end this year. As an astronomer I've been inundated with 2012-apocalypse questions more than three years now (I got my first question from the guy slicing cheese at the supermarket). At first I had no clue what these folks meant, but boy, were they worried. Magnetic pole flips, sunspots, solar flares, and mysterious beams of energy from the black hole at the galactic center sounded bizarre enough. Add to that list ancient Mayan calendars, Egyptian codexes, Atlantis, and Lords of Light and Shadow and you really send the topic into ultra tinfoil hat territory. There's nothing to all of this, of course, but you don't have to take my word for it, I just have a Ph.D. Listen to the whole sordid mess straight from the source.
Then last week a student who'd been surfing the Web stopped me and said, "Why are we worried about 2012 when there are comets and asteroids out there? That stuff is really terrifying!" He's right. If you want to believe the universe is out to kill you, it's easier to do it with a random piece of space rock than with a Mayan death ray from the black hole in Sagittarius.
Appropriate, then, that this last month has included several important comet and asteroid discoveries. Ever hear that an asteroid or comet impact may have killed off the dinosaurs 65 million years ago? Now there is strong evidence that a much more recent impact may have done the same to the woolly mammoths and even impacted the development of human civilization here in North America. A team of scientists at the University of South Carolina just announced in the Publications of the National Academy of Sciences that a comet impact 12,900 years ago near the current Great Lakes is thought to have altered the climate at just the moment the Earth was coming out of the last ice age. This impact killed off large land mammals and lead to the fall of the Clovis people, some of the earliest inhabitants of the continent.
Much more recently, amateur astronomers caught what appears to be a comet or asteroid collision with the cloud tops of Jupiter. On September 10, amateur astronomers including Dan Petersen of Racine, Wis., witnessed a flash on Jupiter as something smacked at supersonic speeds through the dense atmosphere. This is the third collision with the solar system's most massive planet witnessed in the last 20 years. Jupiter's great mass (300 times that of the Earth's) gobbles up the wandering flotsam of space and is perhaps one of the reasons the Earth can go millions of years between extinction-level impacts. If not for Jupiter, Earth would probably not be left alone long enough for intelligences like ours to worry about ancient calendrical cycles.
All of this comes the same month as amateur astronomers in Eastern Europe discovered a new comet that has the potential to become the comet of the century in November 2013 (sorry, 2012 conspiracy buffs). Comets are giant balls of ice, dust and rock that spend the vast majority of their lives far from the sun. When the vagaries of gravitational attraction bring them into the inner solar system, the heat of the sun turns the ice to gas and comets develop a gauzy cloud and tail that can span interplanetary distances (and make them the biggest things in the solar system). Sometimes, though, the sun's heat can crack the comet into pieces and the whole thing boils away to nothing before any spectacular tail can form. While cometary orbits can be easy to predict, what they develop into, and when they get here is notoriously hard. The fact that Comet ISON is still beyond the orbit of Jupiter and already beginning to blow off gas is a good sign, that like Comet Hale Bopp 15 years ago, this could be a comet visible to the naked eye in even light polluted city skies (with some predictions claiming it could be visible during broad daylight).
One effect of comets entering the inner part of our solar system is they leave behind a giant stream of dust as sunlight evaporates the ice on their frozen surfaces. When the Earth passes through this dust we see a meteor shower from all these brief, fiery encounters with our atmosphere. The next meteor shower is this weekend, and it is due to dust left behind by the most famous of all comets: Halley's Comet. If you want a good view of this, or any meteor shower, do yourself a favor and get away to a national park. A hundred years of the National Park Service preserving the natural landscape from development has also preserved some of the last remaining spectacular views of the night sky. The park service now recognizes that seeing the Milky Way and a starry night sky is now as rare for most visitors as seeing grizzlies, geysers and glaciers. Amateur astronomers have realized this, too, as they are frequently set up with their telescopes on clear, dark summer weekends. And for those interested in searching the skies for new comets, the dark night skies of the national forests, wildernesses and national parks are the places to go since the rise of light pollution above the populated (and even not so populated) parts of our world have made it increasingly hard to discover potential threats from deep space. It would be truly ironic if the rise of our civilization should be the very thing that hindered its preservation from destruction. The night sky of the national parks made be the thing that saves us all (provided we survive 2012).