Dr. Bortrum
04/01/2015
Birds and Watery Bodies
CHAPTER 55 Water, Water Everywhere?
Longtime readers will know that one of my favorite topics is intelligent birds, my all time favorite being Alex, the African grey parrot that warranted a New York Times obituary when he passed away some years ago. Although somewhat annoying when they sound off early in the morning, crows have shown surprising instances of intelligent behavior. A few weeks ago, our editor Brian Trumbore called my attention to an article on the BBC News Magazine Web site about gift-giving crows. The article indicates that crows and other members of the crow family such as magpies and ravens are caring individuals that appreciate being treated kindly. The news magazine had published a previous article about a young girl in the USA who liked to feed crows and the crows responded by bringing her gifts of such things as bits of glass, jewelry, buttons. etc.
The article generated responses from a number of readers who had their own experiences crows bringing gifts. Judging from the responses, crows or their relatives all over the world share this penchant for gift-giving, the responses coming from locales ranging from Germany to Kathmandu in Nepal. One of the more humorous and interesting responses was from a pretty young lady in the U.S. who is pictured in the article with Sheryl Crow, a crow she adopted when she found it as an injured baby crow. The crow grew up, learned to fly and kept returning with gifts such as a yellow dart from a game and a Santa Claus figurine among the treasures. Each time Sheryl arrived with a gift it would spread its wings and bow.
Others reported similar instances of gift-giving but one lady in Germany reported that her crow's gift was in the form of performing a chore. The lady gardened and had the habit of removing bad leaves and other debris from the plants and then tearing them into smaller pieces. A crow had become a regular visitor when the lady started feeding it bread or cat food. After eating the food the crow would sit there and "observe" her doing the gardening. Sure enough, one day she had pulled some bad leaves off a zucchini plant when the crow ran up and ripped the leaves with his beak and claws until they were in tiny bits. The crow continued to "help" in this fashion in the days that followed.
So much for birds. This past month or so has been such a productive time in the space field I have to include some recent findings or feats. With all the news coverage of the trial of the Boston marathon bomber, it was good to hear a happier marathon story. You probably heard or read about the Mars rover Opportunity having logged a total roaming distance of 26.219 miles in a mere 11 years and two months on the Red Planet. I noted the JPL rover team planned a marathon-length relay run to celebrate the event. Hey, those JPL guys and gals are smart; they're not all going to run individual marathons! Seriously, I find it amazing that Opportunity still is able to move around after more than 11 years. Among its achievements was finding evidence of flowing liquid water in Mars' distant past and conditions that might have favored some form of life in that past.
NASA had more to say about Mars' past history in a press release stating that ground-based measurements over a period of three years of the relative amounts of hydrogen and its heavier form, deuterium, in the Martian atmosphere over the polar region of Mars indicates that Mars may have had an ocean containing as much water as our Arctic ocean back over 4 billion years ago. NASA scientists estimate that about 87 percent of the water has evaporated and today what's left of that water is in the form of ice. Continuing on Mars, NASA's MAVEN spacecraft orbiting Mars has turned up the presence of dust and an aurora in the atmosphere of Mars. The presence of dust and the aurora are both surprises and the source of the dust is not known. It is likely that the aurora is caused by high energy particles ejected from the Sun. Mars doesn't have the protective magnetic field that we have on Earth.
Auroras have also been spotted on Jupiter's moon Ganymede. I didn't know that Ganymede is the largest moon in our solar system and the only one to have a magnetic field. Score one more triumph for the Hubble Space Telescope, which celebrates its 25th anniversary in space this month. NASA reports that Hubble has been monitoring the auroras over Ganymede and the results indicate that Ganymede has a saltwater ocean over 60 miles deep and covered by a 95-mile thick crust of mostly ice!
OK, you ask, "How can measurements of auroras be used to conclude that an ocean exists below the surface of a moon?" NASA puts it this way. Ganymede has a magnetic field. Jupiter has a magnetic field. Jupiter's magnetic field would induce a secondary magnetic field in a saltwater ocean; this induced magnetic field would counteract Jupiter's magnetic field. Magnetic fields affect the auroras. What NASA says is that as Ganymede orbits Jupiter and the magnetic fields interact, there's a "sloshing" of the fields due to the saltwater ocean. Without an ocean, the auroras would be expected "rock" some 6 degrees. Hubble observed the rocking of the auroras in ultraviolet light and the rocking is only 2 degrees. Conclusion: there's this huge saltwater ocean that explains the dampening of the aurora rocking. And, where there's an ocean, one can speculate that life of some sort might exist.
But Hubble wasn't the only player in the ocean game. NASA's Cassini spacecraft is still meandering around the vicinity of Saturn and has turned up evidence that Saturn's moon Enceladus may also be in the running for the existence of life. Cassini had previously observed plumes of water ice and vapor ejected from cracks in the surface of Enceladus. Last year, researchers on the Cassini team postulated that Enceladus has a 6-mile deep ocean beneath a crust of ice of about 19 to 25 miles thick. For me, that's good enough to allow speculation about life. But now Cassini has found evidence of "hydrothermal" activity in the ocean. You've no doubt seen or heard of hot volcanic type vents on ocean floors here on Earth. Life abounds in the vicinities of these vents, where hot water meets cold water deep under the oceans' surfaces.
So, where would you expect to find evidence of hot water in the depths of Enceladus? As with the auroras, I would not have expected the answer would lie in dust in the atmosphere of the planet. And not just in the immediate atmosphere. A press release from JPL last month cites the 4-year effort of an international team devoted to analysis of the data collected by a cosmic dust analyzer (CDA) instrument on Cassini. It seems that way back in 2004, even before entering Saturn's orbit, Cassini was detecting tiny grains of material rich in silicon. When I say tiny, they were only nanometers in size and it was finally concluded they were grains of silica, which is sand or quartz here on Earth.
Workers in Germany and Japan collaborated on experimentally verifying conditions that would result in forming silica grains of the small size found by Cassini. The conclusion is that the grains form where hot water from the interior of Enceladus meets cold water at the ocean bottom. The tiny grains are thought to be transported quickly up to vents on the surface where they are ejected into the atmosphere. There's also been a bunch of methane detected in the plumes erupting from Enceladus and one possible source of methane generation would be a hydrothermal process.
I would be remiss if I didn't recognize another major NASA achievement. Last month its Dawn spacecraft become the first spacecraft to go into orbit around a dwarf planet. The dwarf planet is Ceres, which is all of about 590 miles in diameter and resides in the asteroid belt between Mars and Jupiter. It was just last year that the European Space Agency's Herschel mission made the first definitive detection of water on Ceres. There may be more water in the form of ice on Ceres than all the fresh water here on Earth. The Dawn spacecraft is slated to spiral down in its orbit to obtain close-up views of this little dwarf planet. Stay tuned. Oh, stay tuned also for NASA's New Horizons spacecraft's close flyby of that other dwarf planet, Pluto, coming up in July.
I can't close this column without mention of the fact that this year marks the centennial of Einstein's publication of his general theory of relativity. The journal Science and Discover magazine have both pictured him on their covers and devoted considerable space to discussing the achievements of the theory and the continuing efforts to find errors or chinks in the theory. So far, it's held up with remarkable precision. I must close with an incident cited in Science that I found humorous. In his later years, Einstein and a collaborator submitted a paper to the prestigious journal Physical Review. In this paper, Einstein calculated that his earlier proposal of gravitational waves was wrong and that they did not exist. As is usual today with most high quality journals, Physical Review sent the paper out for review. The reviewer returned the paper with the recommendation that it be rejected! Einstein was not happy with this, saying he hadn't given permission for his work to be shared with another person prior to publication. He rejected the criticism.
He submitted the unchanged paper to the Journal of The Franklin Institute. I don't know if Einstein ever knew, but the reviewer was a colleague at Princeton University who had found an error in Einstein's mathematical analysis. Gravity waves did exist in the correct theory! The colleague had a chat with Einstein pointing out the error and Einstein was spared the humiliation of publishing an erroneous repudiation of his own theory. The paper was corrected with a change in title before publication in the Franklin Institute journal. There's still a huge amount of money being spent searching for those gravity waves! Einstein never submitted another paper to Physical Review.
I was going to end by saying that I only managed to publish one paper in Physical Review. However, I just looked up my publications and surprisingly found I had three Phys. Rev. papers, but only one as senior author. In that one, I was proud to point out a very minor error in a formula published by one of our Bell Labs theoretical physicists. Oh to have been the one who corrected my scientific hero, Albert Einstein!
Next column, hopefully, on or about May 1.
Allen F. Bortrum
