Home Page

Valley Skies

Newsletter Home Page


Editor's Corner...

To the Nitty Gritty and Beyond

When we sit under the simulated night sky in the Clever Planetarium, we see a few hundred stars from our own "neighborhood" of the Milky Way Galaxy. Whether there or under the real night sky at Peddler Hill, what we see is but a tiny fraction of the 100 billion stars in our galaxy. When we contemplate the cosmos, with 100 billion galaxies like our own, extending billions of light years from us, the numbers and distances are mind numbing, virtually impossible to grasp.

On October 13, when Dr. Theresa McRae, Chair of the Science and Mathematics Division at San Joaquin Delta College, leads us on a tour of the new Center for Microscopy and Allied Sciences on the Delta College campus, we will have an opportunity to contemplate the equally mind boggling universe of inner space.

Where astronomy and cosmology have been empowered by the development of gargantuan telescopes capable of "seeing" with various segments of the electromagnetic spectrum, from infrared to gamma rays, so has the study of the extremely small been facilitated by optical and electron microscopes.

And just as increasingly sophisticated telescopes continue to challenge and expand our understanding of the cosmos, so do continued enhancements in electron microscopy open new doors. Optical microscopy enabled the study of minute life forms and greatly expanded the science of materials technology. However, the wavelength of visible light is a limiting factor that determines how small an object can be resolved under an optical microscope. The development of the electron microscope, using a focused beam of electrons instead of visible light to obtain an image, allowed scientists to attain resolution down to the level of atoms and molecules.

Continued refinement of the technology has enabled techniques for actually manipulating molecules to produce new forms of materials, structures and machines with unique new properties, with potential for all manner of exotic applications.

The possibilities appear to be limited only by the imagination...and there's some wild imagining going on!

For more on the Delta microscopy program, go to the SJDC Web site: http://www.deltacollege.edu/dept/electmicro/whatis.html

...Trevor Atkinson


Earth Science Week 2005 -- Contrail Count-a-Thon

In recognition of Earth Science Week, the GLOBE Program and NASA invite you to join in a scientific exploration on Thursday, October 13, 2005, to observe the sky over your area and report on the presence or absence of contrails. Teachers, students, and anyone interested in helping to develop a better understanding of Earth are welcome to participate.

Contrails are cirrus clouds formed when water vapor condenses and freezes around small particles (aerosols) in aircraft exhaust. Some of the water vapor comes from the surrounding air, some from the aircraft exhaust. Contrails, especially thin ones, are very hard to see from satellites, and may have an impact on Earth's atmosphere. In order to improve contrail prediction models, scientists need observations both of contrail occurrence and absence.

Visit http://www.globe.gov/earthsciweek2005 for more information on contrails and clouds.

Instructions on how to participate in this event and report your information can be found at this Website. The observations that are reported will be tallied and analyzed by NASA scientists looking for clues to contrail prediction. A report on their findings will be posted to the website.

Nancy Leon
Education and Public Outreach Lead
NASA New Millennium Program/Space Place
NASA/JPL 4800 Oak Grove Drive
Mailstop 301-235
Pasadena, CA  91109


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.

Crackling Planets

by Trudy E. Bell

Astronauts on the Moon and Mars are going to have to cope with an uncommon amount of static electricity.

August 10, 2005:  Have you ever walked across a wool carpet in leather-soled shoes on a dry winter day, and then reached out toward a doorknob? ZAP! A stinging spark leaps between your fingers and the metal knob.

That's static discharge-lightning writ small.

Beware the door knob.

Static discharge is merely annoying to anyone on Earth living where winters have exceptionally low humidity. But to astronauts on the Moon or on Mars, static discharge could be real trouble.

"On Mars, we think the soil is so dry and insulating that if an astronaut were out walking, once he or she returned to the habitat and reached out to open the airlock, a little lightning bolt might zap critical electronics," explains Geoffrey A. Landis, a physicist with the Photovoltaics and Space Environmental Effects Branch at NASA Glenn Research Center in Cleveland, Ohio.

This phenomenon is called triboelectric charging.

The prefix "tribo" (pronounced TRY-bo) means "rubbing." When certain pairs of unlike materials, such as wool and hard shoe-sole leather, rub together, one material gives up some of its electrons to the other material. The separation of charge can create a strong electric field.

Here on Earth, the air around us and the clothes we wear usually have enough humidity to be decent electrical conductors, so any charges separated by walking or rubbing have a ready path to ground. Electrons bleed off into the ground instead of accumulating on your body.

But when air and materials are extraordinarily dry, such as on a dry winter's day, they are excellent insulators, so there is no ready pathway to ground. Your body can accumulate negative charges, possibly up to an amazing 20 thousand volts. If you touch a conductor, such as a metal doorknob, then-ZAP!-all the accumulated electrons discharge at once.

On the Moon and on Mars, conditions are ideal for triboelectric charging. The soil is drier than desert sand on Earth. That makes it an excellent electrical insulator. Moreover, the soil and most materials used in spacesuits and spacecraft (e.g., aluminized mylar, neoprene-coated nylon, Dacron, urethane-coated nylon, tricot, and stainless steel) are completely unlike each other. When astronauts walk or rovers roll across the ground, their boots or wheels gather electrons as they rub through the gravel and dust. Because the soil is insulating, providing no path to ground, a space suit or rover can build up tremendous triboelectric charge, whose magnitude is yet unknown. And when the astronaut or vehicle gets back to base and touches metal-ZAP! The lights in the base may go out, or worse.

Physicist Joseph Kolecki and colleagues at NASA Glenn first noticed this problem in the late 1990s before Mars Pathfinder was launched. "When we ran a prototype wheel of the Sojourner rover over simulated Martian dust in a simulated Martian atmosphere, we found it charged up to hundreds of volts," he recalls.

Electrostatic discharge points at the base of Sojourner's antenna.

That discovery so concerned the scientists that they modified Pathfinder's rover design, adding needles half an inch long, made of ultrathin (0.0001-inch diameter) tungsten wire sharpened to a point, at the base of antennas. The needles would allow any electric charge that built up on the rover to bleed off into the thin Martian atmosphere, "like a miniature lightning rod operating in reverse," explains Carlos Calle, lead scientist at NASA's Electrostatics and Surface Physics Laboratory at Kennedy Space Center, Florida. Similar protective needles were also installed on the Spirit and Opportunity rovers.

On the Moon, "Apollo astronauts never reported being zapped by electrostatic discharges," notes Calle. "However, future lunar missions using large excavation equipment to move lots of dry dirt and dust could produce electrostatic fields. Because there's no atmosphere on the Moon, the fields could grow quite strong. Eventually, discharges could occur in vacuum."

"On Mars," he continues, "discharges can happen at no more than a few hundred volts. It's likely that these will take the form of coronal glows rather than lightning bolts. As such, they may not be life threatening for the astronauts, but they could be harmful to electronic equipment."

So what's the solution to this problem?

Here on Earth, it's simple: we minimize static discharge by grounding electrical systems. Grounding them means literally connecting them to Earth-pounding copper rods deep into the ground. Ground rods work well in most places on Earth because several feet deep the soil is damp, and is thus a good conductor. The Earth itself provides a "sea of electrons," which neutralizes everything connected to it, explains Calle.

There's no moisture, though, in the soil of the Moon or Mars. Even the ice believed to permeate Martian soil wouldn't help, as "frozen water is not a terribly good conductor," says Landis. So ground rods would be ineffective in establishing a neutral "common ground" for a lunar or Martian colony.

Note the marsdust clinging to Sojourner's wheels. This is indirect evidence of electrostatic charging.

On Mars, the best ground might be, ironically, the air. A tiny radioactive source "such as that used in smoke detectors," could be attached to each spacesuit and to the habitat, suggests Landis. Low-energy alpha particles would fly off into the rarefied atmosphere, hitting molecules and ionizing them (removing electrons). Thus, the atmosphere right around the habitat or astronaut would become conductive, neutralizing any excess charge.

Achieving a common ground on the Moon would be trickier, where there's not even a rarefied atmosphere to help bleed off the charge. Instead, a common ground might be provided by burying a huge sheet of foil or mesh of fine wires, possibly made of aluminum (which is highly conductive and could be extracted from lunar soil), underneath the entire work area. Then all the habitat's walls and apparatus would be electrically connected to the aluminum.

Research is still preliminary. So ideas differ amongst the physicists who are seeking, well, some common ground.




Where No Spacecraft Has Gone Before

by Dr. Tony Phillips

In 1977, Voyager 1 left our planet. Its mission: to visit Jupiter and Saturn and to study their moons. The flybys were an enormous success. Voyager 1 discovered active volcanoes on Io, found evidence for submerged oceans on Europa, and photographed dark rings around Jupiter itself. Later, the spacecraft buzzed Saturn's moon Titan--alerting astronomers that it was a very strange place indeed! -- and flew behind Saturn's rings, seeing what was hidden from Earth.

Beyond Saturn, Neptune and Uranus beckoned, but Voyager 1's planet-tour ended there. Saturn's gravity seized Voyager 1 and slingshot it into deep space. Voyager 1 was heading for the stars-just as NASA had planned.

Now, in 2005, the spacecraft is nine billion miles (96 astronomical units) from the Sun, and it has entered a strange region of space no ship has ever visited before.

"We call this region 'the heliosheath.' It's where the solar wind piles up against the interstellar medium at the outer edge of our solar system," says Ed Stone, project scientist for the Voyager mission at the Jet Propulsion Laboratory.

Out in the Milky Way, where Voyager 1 is trying to go, the "empty space" between stars is not really empty. It's filled with clouds of gas and dust. The wind from the Sun blows a gigantic bubble in this cloudy "interstellar medium." All nine planets from Mercury to Pluto fit comfortably inside. The heliosheath is, essentially, the bubble's skin.

"The heliosheath is different from any other place we've been," says Stone. Near the Sun, the solar wind moves at a million miles per hour. At the heliosheath, the solar wind slows eventually to a dead stop. The slowing wind becomes denser, more turbulent, and its magnetic field-a remnant of the sun's own magnetism--grows stronger.

So far from Earth, this turbulent magnetic gas is curiously important to human life. "The heliosheath is a shield against galactic cosmic rays," explains Stone. Subatomic particles blasted in our direction by distant supernovas and black holes are deflected by the heliosheath, protecting the inner solar system from much deadly radiation.

Voyager 1 is exploring this shield for the first time. "We'll remain inside the heliosheath for 8 to 10 years," predicts Stone, "then we'll break through, finally reaching interstellar space."

What's out there? Stay tuned...

For more about the twin Voyager spacecraft, visit voyager.jpl.nasa.gov. Kids can learn about Voyager 1 and 2 and their grand tour of the outer planets at spaceplace.nasa.gov/en/kids/vgr_fact3.shtml .

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.


Copyright © 2005 by Stockton Astronomical Society
Last Updated: 10/5/2005
http://www.stocktonastro.org/Newsletter/VS0510.html