Dr. Bortrum
06/03/2015
Color Matching and Avian Evolution
CHAPTER 57 Colored Salt and Bird Beaks
As mentioned previously in these columns, after finishing graduate school at Pitt in 1950 I joined the National Advisory Committee for Aeronautics (NACA, now NASA John H. Glenn Research Center at Lewis Field) in Cleveland. The group I was in had as its principal objective the study of materials problems related to the building and operation of a nuclear powered aircraft. (This ill-conceived project fortunately was abandoned sometime after I left NACA for Bell Labs in 1952.) When I arrived at NACA one of the projects in the group involved studies on so-called "color centers". If color centers are formed in, for example, a salt such as sodium chloride that is normally colorless the salt becomes colored.
One way to produce color centers in sodium chloride is to heat the salt in sodium vapor, introducing an excess of sodium into the crystal lattice. Another way is by irradiation, which can knock ions out of their normal place in a crystal lattice. Either process produces vacancies in the lattice where chloride ions normally reside and these vacancies are filled by electrons from the sodium. These electron-filled vacancies are the color centers.
Why do I bring this up here? I was reminded of those color centers when I read a May 12 news release from NASA about the apparent detection of sea salt on the surface of Jupiter's moon Europa. Europa is known to have a deep ocean underneath its surface and eruptions or geysers of water from that ocean have been observed. It has been speculated that the ocean is a salty ocean, as are our own oceans here on Earth. Of course, one has to think, "Hey, if there's an ocean could there be life?"
Previously, dark areas have been observed around fissures and relatively young geological features on Europa. Some dark areas on Europa have been attributed to compounds involving sulfur and magnesium. However, the surface of Europa is under bombardment by ions and electrons hitting the surface at high energies, thanks to the large magnetic field of Jupiter. If the ocean within Europa is salty, could there be salt on the surface left over from those eruptions of water? Kevin Hand and Robert Carlson at the Jet Propulsion Lab set up experiments in which sodium chloride was placed in a vacuum chamber at a temperature of minus 280 degrees Fahrenheit, corresponding to the temperature on the surface of Europa. They bombarded the salt with a beam of electrons for a period of time that would be the equivalent of a century's worth of irradiation on Europa. The salt turned color, changing from white to a yellowish brown, strongly resembling the color of the dark patches on Europa.
This apparent confirmation that Europa has a salty ocean reinforces my feeling that instead of concentrating effort on a manned trip to Mars we should be working towards some sort of mission to Europa to see if there's any evidence of life in the samples of ocean that have made their way to the surface of that member of our solar system.
There is another coming event in our solar system that will surely make the headlines. The New Horizons spacecraft is fast approaching Pluto and should come within a few thousand miles of that dwarf planet in a couple of weeks. Who knows? If Pluto turns out to be a truly interesting body the astronomical community may promote it back to a regular planet. NASA can certainly be proud of its far-flying spacecrafts they've sent to the farthest reaches of our solar system.
Speaking of flying far, a brief item in the April 3 issue of Science tells of the tiny blackpoll warbler, weighing in at a mere 12 grams or just a bit more than our U.S. half dollar. These little guys fly from Canada to the Caribbean islands. Researchers tagged 20 of these warblers before their flight from Canada. Surprisingly to me, they managed to recover 5 of the 20 tags from the birds making the trip. The birds did fly from Canada to the Caribbean islands and then continued on to Venezuela. You might say that's not impressive. After all, some Monarch butterflies go from Canada to Mexico. However, the blackpoll warblers fly from Canada to the Caribbean islands, roughly 1500 miles, over the Atlantic Ocean. Quite a trip!
Continuing the bird theme, a couple days ago I was having breakfast and looked out the window at a robin gathering materials for making a nest. I was impressed by the bird's ability to select the dried up grass in a patch of mixed green and brown grass and store quite a big pile of grass in his beak before taking off to construct its nest. Were I as mentally sharp as I was in my younger days, I might have wondered how it was that birds evolved to have beaks. After all, when some dinosaurs started on the path to becoming birds, they gave up those front feathered paws or arms, whatever you want to call them, with claws. These appendages became wings. The evolving birds needed something to enable them to pick up or handle food or construction materials.
Actually, I was alerted to the beak development problem by an article by Elizabeth Pennisi titled "How birds got their beaks" in the May 15 issue of Science. The article discusses work published in Evolution by Harvard biologist Arhat Abzhanov and his former student Bhart-Anjan Bhullar, now at The University of Chicago. Specifically, these two researchers were interested in trying to determine how the snout evolved into a beak. They studied fossils of dinosaurs, early birds and animals such as the alligator, which is as close as I can imagine to looking like a dinosaur as anything else living today. In the alligator, as in reptiles and other animals, there are two bones, known as the premaxillary bones, that form the end of the snout. In the alligator, these bones are rounded and do not fuse together. On the other hand, in birds these bones are slender and pointed and fuse together to form the bill of the beak.
In trying to figure out how evolution of the beak proceeded, the researchers looked at genes known to be involved in facial development. They found two genes that earlier workers had shown to be involved in the development of the premaxillary bones. The Harvard workers noted that the activities of these genes were concentrated at different areas of the face in the alligator and in chick embryos. In the chick embryos, activities concentrated at the front part of the face while in the alligator and other animals the activities concentrated at the side of the face.
Now comes the key part of their work. The researchers used certain chemicals to inhibit the activities of these genes in chick embryos and the results were interesting, to say the least. When the activities of the genes were most inhibited, the premaxillary bones in the chick embryos did not fuse and were rounded. The chick embryos were more like their dinosaur relatives. In addition, another bone was affected, a palate bone forming the roof of the mouth. In birds it's reduced and disconnected, allowing the top part of the bill to open wide. In other animals it's typically flat and connected to the surrounding bones. the chick embryos' palate bones were more like those in the other animals. These chick embryos were indeed unusual and the experiments would seem to open the way to some degree of reverse evolution. Could Jurassic Park be on the way?
Perhaps you're wondering, how did the chicks do when hatched? The Science article said nothing about that topic. But I did find the answer on a Nature Web site. The chicks were not hatched. Hatching was not in the approved protocol for the project and I can imagine the researchers hesitation at the prospect of facing a possible storm of controversy hatching might have generated. Controversy has arisen anyway, as it so often does in the field of evolution. The Science article points out that biologist Ralph Marcucio, who has also worked on the beak problem, had proposed that another gene was involved in the beak formation and also is concerned that the chemical inhibitors themselves could be affecting the embryo development.
I was going to close here with a comment on how interesting science is when by doing experiments here on Earth we can determine what has happened on a moon millions of miles away and how evolution shaped an animal millions of years ago. However, a coincidence happened to me this morning that I thought worthy of mention.
I was having coffee with a couple at the local mall this morning after my walk there. The wife mentioned that they had given a gift of a telescope to one of their grandchildren and that he was really into astronomy. I told Ken and Leah that I would be an astronomer if I had a chance to live another life and mentioned the salt on Europa that I was including in this column. I also suggested that their grandson might want to get on the NASA/JPL emailing list and, as an aside, mentioned that our former neighbors' daughter Barbara had married William Weber. I've mentioned Bill Weber previously in this column in connection with his being employed at JPL and one responsibility was being manager of JPL's Deep Space Network. Leah noted that she had been to JPL in connection with some consulting work.
I came home and was about to post this column when the phone rang and who should be calling but Barbara Weber, saying she and Bill were in the area and could they stop by for a brief visit! Of course, my answer was yes and we had a delightful visit. Bill is now retired from JPL but is volunteering in other activities related to our past space endeavors. I was especially interested to hear about their son, who is married to an Italian woman and is a professor at the University of Trento in Italy. He is involved in a European Space Agency program called LISA Pathfinder. The eventual goal of the LISA program is to detect those elusive gravitational waves that we've discussed before. It's good to see the space gene has been passed down to the next generation of the Weber family. If I'm still among the living and still writing these columns, if LISA does indeed detect gravitational waves, you will certainly read about it here.
Next column, hopefully, on or about July 1.
Allen F. Bortrum
