Stockton Astronomical Society
Valley Skies - October 2004 Issue
Following Dr. Neil Lark's retirement in 1999, the position of Department Chair of the Physics Department at UOP was taken over by Dr. James Hetrick. We are pleased to welcome Jim back to the SAS for our October program, after a six-year absence. (Jim was our speaker for two meetings in 1998, one about his year doing research at the South Pole, the second on "Neutrinos have Mass!").
On October 14, Jim will tell us why...
"It's a Great Time to be a Physicist"
Dr. James E. Hetrick
B.S., Case Western Reserve University, 1982
Ph.D., University of Minnesota, 1990
Dr. Hetrick joined the (physics) department at UOP in 1997. After receiving his B.S. degree he spent a year at the South Pole Station in Antarctica, conducting upper atmosphere, solar-terrestrial, and cosmic ray experiments for the Bartol Research Foundation. Since receiving his Ph.D. he has been a Postdoctoral Research Fellow and Research Associate at the Swiss Federal Institute of Technology (ETH) in Zurich, the University of Amsterdam in the Netherlands, the University of Arizona in Tucson AZ, and Washington University in St. Louis MO.
Dr. Hetrick's research interests include theoretical physics, particle physics, computer simulation, and astrophysics.
Welcome back, Jim.
Planet Watch & Lunar Eclipse
Brilliant Venus rises later each morning, about three hours ahead of the Sun. Paired closely with Regulus at the beginning of the month, Venus will move into Virgo, approaching Jupiter at month's end.
Jupiter will rise about 3 minutes earlier each morning, in Virgo, rising at 5 a.m. by month end.
Saturn will remain in Gemini, rising by about 11:15 p.m. by the end of the month.
Mars is marginally observable in morning twilight late in October. Mercury will be too close to the Sun after sunset. Forget it for this month. See the sky chart on page 10 of the newsletter for locations of Neptune, Uranus and Pluto.
*The Total Lunar Eclipse on October 27 is the big story this month. Here in N. California, the timing will be perfect for observing the whole visible eclipse sequence:
|Full Moonrise:||6:04 p.m.|
|Partial eclipse begins:||6:14 p.m.|
|Total eclipse begins:||7:23 p.m.|
|Total eclipse ends:||8:45 p.m.|
|Partial eclipse ends:||9:45 p.m.|
Lunar eclipses bring out the crowds. We will have to coordinate with Delta College about the observing location. I think their preference will be for us to use the Shima 2 parking lot, as we did for the Mars opposition in August '03, to accommodate the number of visitors.
The Science Directorate at NASA's Marshall Space Flight Center sponsors the Science@NASA web sites. The mission of Science@NASA is to help the public understand how exciting NASA research is and to help NASA scientists fulfill their outreach responsibilities.
Secrets of a Salty Survivor
by Patrick L. Barry
A microbe that grows in the Dead Sea is teaching scientists about the art of DNA repair.
September 10, 2004
You can learn a lot from a microbe. Right now, a tiny critter from the Dead Sea is teaching scientists new things about biotechnology, cancer, possible life on other worlds.
And that's just for starters: This microbe, called Halobacterium, may hold the key to protecting astronauts from one of the greatest threats they would face during a mission to Mars: space radiation. The harsh radiation of interplanetary space can penetrate astronauts' bodies, damaging the DNA in their cells, which can cause cancer and other illnesses. DNA damage is also behind cancers that people suffer here on Earth.
Cells of Halobacterium as seen through a high-powered microscope. The individual cells in this image are about 5 microns long.
Halobacterium appears to be a master of the complex art of DNA repair. This mastery is what scientists want to learn from: In recent years, a series of experiments by NASA-funded researchers at the University of Maryland has probed the limits of Halobacterium's powers of self-repair, using cutting-edge genetic techniques to see exactly what molecular tricks the "master" uses to keep its DNA intact.
"We have completely fragmented their DNA. I mean we have completely destroyed it by bombarding it with [radiation]. And they can reassemble their entire chromosome and put it back into working order within several hours," says Adrienne Kish, member of the research group studying Halobacterium at the University of Maryland.
Being a virtuoso at repairing damaged DNA makes Halobacterium one hardy little microbe: in experiments by the Maryland research group, Halobacterium has survived normally-lethal doses of ultraviolet radiation (UV), extreme dryness, and even the vacuum of space.
The Dead Sea is not so dead.
The Dead Sea is 5+ times saltier than Earth's oceans. As water evaporates, salt is left behind. When the saturation point is reached, the salt forms these pillars. Credit: Purdue University.
But why is Halobacterium such a tenacious survivor? What caused it to evolve such dexterous DNA repair mechanisms? And how do those mechanisms work? Jocelyne DiRuggiero, leader of the Maryland research group, has been exploring these questions for the last five years. She believes the answer stems from the fact that Halobacterium naturally lives in some rather inhospitable places: ultra-salty bodies of water such as the Dead Sea.
Most sea life would quickly shrivel up and die in the Dead Sea's briny water, which is 5 to 10 times saltier than normal seawater. The extreme saltiness damages an organism's cells, and especially the DNA inside those cells. This happens because DNA molecules are accustomed to being surrounded by a dense swarm of water molecules, and the DNA actually depends on the influence of these water molecules to keep its double-helix structure intact and to avoid damage. But in ultra-salty waters, the dissolved salt crowds out the water molecules. Partially deprived of the contact with water they need, the long strands of DNA suffer damage and even break, causing the cell to malfunction or die.
Evolving to cope with a salty lifestyle could explain why Halobacterium is so good at surviving radiation and other ravages, DiRuggiero reasons: "High salt concentrations lead to the same type of lesion in the DNA that does radiation," she explains. "So if the organisms are adapted to extreme saltiness, they have the machinery to repair those lesions when they encounter radiation."
DiRuggiero and her research group have begun revealing this DNA-repair machinery in a recent series of experiments funded by NASA's Exploration Systems Mission Directorate.
In some experiments, they exposed Halobacterium cells to beams of intense UV radiation. "We used UV-C at 254 nm, which is the most lethal UV wavelength," says DiRuggiero. Most microbes, like E. coli that lives in the human gut, would have been completely exterminated, yet 80% of the Halobacterium cells survived. Indeed, they went on living and reproducing just fine.
In other experiments, the researchers used a vacuum chamber at NASA's Goddard Space Flight Center to expose cells of Halobacterium to a space-like vacuum (1 millitorr). Here, living in very salty water proved to be Halobacterium's saving grace: as the vacuum caused the water to evaporate away, the salt was left behind, forming salt crystals. The tiny cells of Halobacterium became trapped inside these crystals, along with a bit of entrapped water. "The salt crystal is like a little house in which the cells are protecting themselves from additional desiccation," DiRuggiero explains. The cells can live in a semi-dormant state within the crystals for a long time. When dissolved back into water, the cells spring to life again, repair all the damage to their DNA caused by the partial desiccation, and go right on living.
Some scientists even claim to have found living cells of Halobacterium encased in salt deposits that are 250 million years old. (see journal references below) The claim is controversial, but if true, it could have some profound implications for the hunt for microbial life on Mars. Evidence from the Mars Exploration Rovers, Spirit and Opportunity, announced in March suggests that the Martian surface once had pools of salty water, which slowly evaporated away.
"So if microbial life evolved on Mars and then the water evaporated, and if the microbes are trapped in salt crystals, they could still be there, and still viable. Given the data that we have from Earth, that's entirely possible," Kish says.
Reading the "book of life"
A DNA microarray, as seen through a microscope. Each tiny dot corresponds to one of the organism's thousands of genes, and the color of the dot indicates the activity level of that gene. Image credit: James Smiley.
To understand how these cells of Halobacterium managed to survive in their experiments, DiRuggiero's team sent the "victims" of their tests to the Institute for Systems Biology in Seattle. There, scientists used a modern genetics tool called a "DNA microarray" to see a complete picture of Halobacterium's response to being damaged: the full set of molecular tools that spring into action in the wake of a UV dose or exposure to space-like vacuum.
These "molecular repair tools" belong to a category of proteins called enzymes. Enzymes are the workhorses of all living cells: they catalyze the thousands of chemical reactions necessary for life, such as breaking down food or repairing flaws in DNA. Halobacterium always keeps a certain amount of repair enzymes on hand, so when a radiation dose occurs, this stash of enzymes can quickly administer "first aid" to the DNA. But then it must also ramp up production of other repair enzymes to continue the repair, activating the genes that produce those enzymes. It's that boost in gene activity that the microarray tests can detect, thus showing which enzymes are important for Halobacterium's remarkable DNA-repair abilities.
From those microarrays, DiRuggiero's team has learned that when it comes to DNA repair, Halobacterium is something of a "Renaissance bug." It dabbles in a bit of everything. Its genome of only 2,400 genes contains several distinct sets of DNA-repair mechanisms. Some of these sets of tools are like the DNA-repair tools found in plants and animals, other sets are more like those of bacteria, and still others are characteristic of a lesser-known group of life called "Archaea" (the group that Halobacterium belongs to). Halobacterium has them all. Beyond even that, Halobacterium has a few novel DNA-repair mechanisms that no one has ever seen before!
A repair enzyme correcting an error in a DNA molecule. The enzyme is on the right in orange and green, and part of the double-helix-shaped DNA is on the left in blue. Image credit: Albert Lau.
Learning how all these repair mechanisms work could teach scientists a lot about how DNA repair occurs in humans, and perhaps point to ways to enhance people's natural ability to cope with damage to their DNA - a possible boon to astronauts.
"Many of the repair proteins in the Archaea are very similar to that of Eukarya - [the group of life that includes] you and me - and therefore Archaea can be used as a simple model system to study the more complex processes that occur in eukaryotes," DiRuggiero explains.
Some of these novel molecular tools could also prove to be useful for industry and biotechnology, DiRuggiero suspects. After all, it was in studying a cousin of Halobacterium - a heat-loving microbe - that scientists found the DNA-copying protein that made it possible to sequence entire genomes. The Human Genome Project would have never happened without it.
Not bad for a humble microbe.
Hunting Gravitational Waves: Space Technology 7
by Patrick L. Barry and Dr. Tony Phillips
Among the mind-blowing implications of Einstein's general theory of relativity, direct verification is still missing for at least one: gravitational waves. When massive objects like black holes move, they ought to create distortions in space-time, and these distortions should spread and propagate as waves - waves in the fabric of space-time itself.
If these waves do exist, they would offer astronomers a penetrating view of events such as the birth of the Universe and the spiraling collisions of giant black holes. The trick is building a gravitational wave detector, and that's not easy.
Space Technology 7 will test a technology to be used in detecting gravitational waves in space.
Ironically, the gravitational waves spawned by these exceedingly violent events are vanishingly feeble. Gravitational waves exert a varying tug on objects, but this tug is so weak that detecting it requires a device of extraordinary sensitivity and a way to shield that device from all other disturbances.
Enter Space Technology 7 (ST-7). This mission, a partnership between NASA's New Millennium Program and the European Space Agency (ESA), will place a satellite into a special orbit around the Sun where the pull of the Earth's and Sun's gravities balance. But even the minute outside forces that remain - such as pressure from sunlight - could interfere with a search for gravitational waves.
To make the satellite virtually disturbance-free, ST-7 will test an experimental technology that counteracts outside forces. This system, called the Disturbance Reduction System (DRS), is so exquisitely sensitive that it can maintain the satellite's path within about a nanometer (millionth of a millimeter) of an undisturbed elliptical orbit.
DRS works by letting two small (4 cm) cubes float freely in the belly of the satellite. The satellite itself shields the cubes from outside forces, so the cubes will naturally follow an undisturbed orbit. The satellite can then adjust its own flight path to match that of the cubes using high-precision ion thrusters. Making the masses cube-shaped lets DRS sense deviations in all 6 directions (3 linear, 3 angular).
ST-7 is scheduled to fly in 2008, but it's a test mission; it won't search for gravitational waves. That final goal will be achieved by the NASA/ESA LISA mission (Laser Interferometer Space Antenna), which is expected to launch in 2011. LISA will use the DRS technology tested by ST-7 to create the ultra-stable satellite platforms it needs to successfully detect gravitational waves.
If ST-7 and LISA succeed, they'll confirm Einstein (again) and delight astronomers with a new tool for exploring the Universe.
Read more about ST-7 at http://nmp.jpl.nasa.gov/st7.
For kids in a classroom setting, check out the "Dampen that Drift!" article at http://spaceplace.nasa.gov/en/educators/teachers_page2.shtml.
This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
New Comet Machholz on its Way
Colfax resident and amateur astronomer Don Machholz has found another one!
In an era when most comets are discovered by automated search programs, using large telescopes and computer software to eliminate known objects, many comet hunters have given up the pastime. The process was tough enough before, often requiring many hundreds or thousands of hours of systematic searching through the wee hours before enjoying the exhilaration of a new discovery. Kinda like the definition of "genius" - 1% inspiration, 99% perspiration!
Don started searching the skies on January 1, 1975, maintaining a careful log of every session. He found his first comet on September 12, 1978 after 1700 hours of searching.
Don made his new discovery at about 4:12 a.m. on the morning of Friday, August 27, from his back yard, using a 6" Criterion Dynascope, an f/8 reflector that he bought for Christmas in 1968. This is his 10th Comet Machholz, officially designated Comet C/2004 Q2 (Machholz). It is expected to be visible to the naked eye by January '05.
Don has spoken before the Stockton Astronomical Society on previous occasions, discussing the processes of comet hunting and Messier marathons, another of his specialties. We hope to have him back again at the November meeting to tell us all about his latest find.
Dr. Fred Lawrence Whipple: 1906-2004
One of the giants of 20th century astronomy, Dr. Fred Whipple died on August 30, aged 97.
Fred Whipple is credited with the "dirty snowball" description of comets, first proposing in 1950 that comets are made of mostly ice.
It was Dr. Fred Whipple who set up the worldwide network of amateur astronomers, including Dr. Clarence Custer, John Gabrian and many other early SAS members, that monitored the Russian satellite Sputnik in 1957.
It was the observation that comets did not conform to the laws of simple Newtonian mechanics that gave Dr. Whipple the clue to what comets really were. He postulated that they were large masses of ice and rock - "icy conglomerates" - and that evaporation of the ice due to the sun's radiation could change the velocity of a comet. Close-up images of Halley's comet in 1986 by the ESA's Giotto spacecraft validated his theories.
Dr. Fred Whipple was director of the Harvard-Smithsonian Center of Astrophysics in Cambridge, Mass. Until his retirement in 1977. According to the New York Times, "...he continued to bicycle to the center six days a week until he was 90."
Dragon Skies: Astronomy of Imperial China
"A great show, and well worth the visit," reported SAS members Jim and Emelia Seiferling.
Even though the planetarium was closed for some maintenance work, Jim and Emelia were very impressed with the Chabot Space and Science Center.
"The Chinese exhibit was wonderful," said Emelia, "but there's a lot to see in the rest of the Science Center as well."
Located in the Oakland Hills, the Chabot Space and Science Center is easy enough to find. From Stockton take Hwy 205 east to I-580, then take Hwy 13 (Warren Freeway). Take the Joaquin Miller/Lincoln Avenue exit. Turn right and proceed up the hill to the crest. Turn left on Skyline Blvd. The Center is 1.3 miles up Skyline on the right.
The Dragon Skies exhibit will be there through January 2, 2005. To check on other events such as films, planetarium shows, telescope viewing, etc., check the website at: www.chabotspace.org or call (530) 336-7300.
Copyright © 2004 by Stockton Astronomical Society
Last Updated: 10/14/2004