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Space Topics: Planetary AnalogsStars Above, Earth BelowAstronomy and Space Exploration in America's National Parks
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Winter Snows on Grand Canyon South Rim
Winter storms keep bringing new snow to Grand Canyon's South Rim. Stunning scenery has made for slightly less stunning nights. Eventually the clouds cleared, and Grand Canyon's dark starry skies allowed for evening ranger programs. Credit: Tyler Nordgren |
Grand Canyon National Park -- I just walked back up from the bottom of the Grand Canyon. Every other kind of walking I do in my daily life seems so … pedestrian by comparison now. The relevance of this to astronomy is not obvious, so I will come back to it later.
Grand Canyon is a wonderful place for astronomy and planetary science. The sky is dark and the altitude is high, so the air is clean and crisp. I have been asked if there is something special about the stars that makes them so bright (jokingly, I start to say that we are a full 7,000 feet closer to them than back home in Los Angeles, but then I stop).
The Interpretation staff at Grand Canyon knows they have something special here and so tries to offer some sort of evening astronomy program every week all year round. One of my duties as a park service volunteer here is to train the entire Interpretation staff on aspects of the night sky so that they will all be able to give night sky talks. This is a far cry from most of the other parks I have visited, where astronomy talks are the province of one or two rangers who happen to have an interest in the topic.
Part of the reason for this difference at Grand Canyon is the sheer number of visitors coming through this place. On a random cold winter day here I have seen far more visitors than other parks I visited in the height of summer. Tonight was a cold, frigid night and a Full Moon Walk along an icy canyon rim easily drew 60 people. By summer the numbers will be at least three times that, and multiple talks given by multiple rangers leaving from the same spot on the same evening will be necessary. Since evening astronomy programs are easily the most attended parks programs, proper training of the park staff will allow me to reach a staggering number of visitors.
The Milky Way Above Lipan Point
The Milky Way in Cygnus is still faintly visible over the western rim of the Grand Canyon. Lights from distant cities like Las Vegas light the undersides of clouds along the horizon. Credit: Tyler Nordgren |
The park has taken a similar view towards training all of their staff to be able to give geology talks about the canyon. Obviously, the giant hole in the ground is a major draw for the tourists, and its connections to planetary science are plentiful. The forces at work in this part of the country, deposition and erosion in Grand Canyon, volcanism in nearby Flagstaff, cratering at Meteor Crater near Winslow, all lead to wonderful comparisons with geological processes on the other terrestrial planets. One major connection I can make is to Mars, especially as it hangs high in the sky right now. However, since comparisons to Mars are the main reason for traveling up to the Red Rock country of Utah in April, I am going to hold off on writing more about that until then.
What I’d like to get back to is that walk I took. I was invited by the rangers down at the Phantom Ranch Ranger Station, located at the bottom of the canyon, to come down and give an evening talk to the public. I was also asked to have a look at the lighting around the area and see if there were any suggestions I could offer about improvements. I hiked down the South Kaibab Trail on Tuesday. The trail is 8.5 miles (14 kilometers) long and descends almost 5,000 feet (1,600 meters) along a bare ridge jutting out into the canyon. Over the course of seven hours I had a lot of time to think about what I would talk about during my public program. At the bottom of the inner canyon gorge, the view of the sky is quite limited by the granite walls all around and so there would be no Milky Way to point out. A first quarter moon would also be visible and so the sky probably wouldn’t be that dark, so talking about light pollution would be kind of unnecessary. There was also no way I was carrying my telescope down on my back, and it was too heavy for the mules, so anything I was going to talk about had better be visible to the naked eye.
All of this I thought about as my hands trailed along on the sandstone walls along my side. Here there was elaborate cross-bedding of yellow sandstone layers. Two hours later and 1,000 feet (300 meters) lower, yellows turned to reds. Still later, red gave way to crumbly brown, purple, and green limestones. And later still, there were red and black granites and schists. Each of these layers was formed at successively earlier epochs in time. By inches I walked eons into the canyon. The interpreters do a good job of describing the processes that made the canyon, but the concept of the vast periods of time required to first deposit the layers, and then to slowly erode them away is difficult to grasp. Standing at the Yavapai Observation Station on the South Rim where the park service has many excellent geology exhibits, I time and again heard people talk to one another about the formation of the canyon, if not with incredulity, then at least with a decided lack of conviction when it came to the span of time involved.
The Sky Above Mather Point
Just as most visitors have never seen anything like the Grand Canyon before, the dark starry sky is unlike anything they have seen from their homes. This is the view of the canyon and sky from the most heavily used overlook in the canyon. Parking times are limited to a single hour. The lights at the bottom of the canyon are Phantom Ranch. Credit: Tyler Nordgren |
In astronomy, and especially in cosmology, I get this all the time with my students when I talk about the enormous distances and amounts of time involved in the structure and formation of the universe. They just don’t get a personal sense of these huge numbers. As I kept walking down in to the canyon I slowly hit upon a talk that might have more emotional appeal to those who had made the trek down there as well. Start by looking at your feet. You are looking across a distance of one meter (to the nearest order of magnitude). Since most American non-scientists don’t have an intuitive feel for a meter, I can now claim that a meter is just another name for You. Thus the rest of the talk is all relative to You the listener. Looking across the amphitheater where we all gathered we were looking at distances on the order of 10 meters. Looking up out of the inner gorge of the Grand Canyon we were looking across 100 meters. Up to the rim of the canyon was 1,000 meters. Across the canyon took us to 10,000 meters, and at 100,000 meters we were seeing to the edge of space. On that order of magnitude the International Space Station could be seen going by.
Star Trails Above the Colorado River at Phantom Ranch
Star trails reveal the passage of time along the river that carved the canyon. The rock walls of the inner gorge are of rough black schists and bright pink granites. Credit: Tyler Nordgren |
Following a “Powers of 10” approach we progressively worked our way out into the Universe. At surprisingly many of those steps we found something we could see. At a million light years, we came to the Andromeda Galaxy, the most distant object visible to the naked eye. Here I concluded with a quote from Teddy Roosevelt, who declared Grand Canyon a national monument exactly 100 years ago last week. According to his longtime friend, the naturalist William Beebe:
After an evening of talk, perhaps about the fringes of knowledge, or some new possibility of climbing inside the minds and senses of animals, we would go out on the lawn, where we took turns at an amusing little astronomical rite. We searched until we found, with or without glasses, the faint, heavenly spot of light-mist beyond the lower left-hand corner of the Great Square of Pegasus, when one or the other of us would then recite:
That is the spiral galaxy in Andromeda.
It is as large as our Milky Way.
It is one of a hundred million galaxies.
It is 750,000 light years away.
It consists of one hundred billion suns,
each larger than our own sun.After an interval Colonel Roosevelt would grin at me and say: “Now I think we are all small enough! Let’s go to bed.
And so we did, all of us at the bottom of the Grand Canyon.
I will be conducting astronomy training this next week for the park staff, but after that I head up to Yellowstone. I’m looking forward to seeing the familiar geothermal features surrounded by a layer of frost and snow. That should make their similarity to analogous features on Io and Enceladus all the more authentic. I am, however, beginning to get a little cold.
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