What causes air currents to organize into self-sustaining tornados that can generate wind speeds up to 200 mph?

Tornados twist because Earth rotates. Our overall weather patterns would be much different if Earth didn’t spin once about every 24 hours.

Large-scale wind currents, the winds we feel every day, are first generated by pressure differences in the atmosphere. Like all fluids, air flows naturally over level terrain from areas of high pressure to areas of low pressure. That’s why air quickly rushes out of a car tire when it is punctured: the pressure inside the tire is significantly higher than outside.

Our atmosphere is not spatially uniform. Large areas of slightly higher than average pressure and areas of slightly lower than average pressure are distributed here and there across the oceans and continents, and air flows develop between them. These air flows tend to smooth out the large-scale pressure variations that cause them.

But high- and low-pressure systems persist for days and weeks, so some contributing effect must act to sustain the pressure differences while the wind is trying to equalize them.

One of the dominate effects that helps high- and low-pressure systems persist is the so-called Coriolis effect, named after the French scientist who first described it in 1835.

All objects, large and small, including tiny air molecules, move in a straight line at constant speed if left to themselves. Left to themselves, air molecules would rush straight from a high-pressure region to a low-pressure region to quickly equalize the pressure. But that’s not what happens here on Earth.

On Earth, in the Northern hemisphere, moving bodies apparently get deflected to the right – always to the right, here in the Northern hemisphere.

In the Northern hemisphere, as air flows into a low-pressure center to “fill it up”, the persistent deflection to the right builds up a wind field that spirals counter clockwise around the low. And low-pressure centers, then, don’t get “filled up” as quickly as they would without this persistent rightward deflection.

The rightward deflection of moving objects in the Northern hemisphere (leftward in the Southern hemisphere), Coriolis noted, is an apparent oddity that crops up because the Earth spins. Isolated moving objects really do move in straight lines, but fixed to the ground of a spinning Earth, our reference frames spin out from underneath, causing us to perceive deflections from straight-line paths.

One experiment I have always wanted to try is to watch drunks stumble out of a bar late at night. If there is anything the Coriolis effect, more Northern-hemisphere drunks would stumble to the right than to the left.

One thing you may have heard about the Coriolis effect that isn’t true is that it causes sink and bathtub drains – and toilets – to spin counter clockwise in the Northern hemisphere and clockwise in the Southern hemisphere. Testing this notion would be a great science-fair project.

It turns out that residual random motions of stumbling drunks and water in sinks, bathtubs and toilets can cause them to spin and fall either way.

The Coriolis effect is not noticeable on the small scales of our everyday lives; however, on flows of air in the atmosphere it can build up to tremendous proportions.

In the Northern hemisphere, all hurricanes and nearly all tornados spin counter clockwise because of the Coriolis effect.

This article originally appeared in the Grand Haven Tribune on 28 April 2011.

When a planet is at opposition, it rises at sunset, climbs high in the sky in the middle of the night, and sets at sunrise.

This is notable because at opposition, an outer planet – a planet with an orbit larger than Earth’s – is closest to earth and best situated for viewing.

Presently you will find Saturn above the horizon in the Southeast a couple hours after sunset, rising higher and higher as the night wears on. In the early morning hours, you will find Saturn above the horizon in the Southwest, eventually setting as the dawn sky brightens.

Saturn in the SE after sunset. Image renedered using Stellarium software. Click for larger image.

To the unaided eye, Saturn appears as a bright star; through a small telescope, Saturn’s rings are clearly visible.

Italian all around top-notch scientist Galileo Galilei was the first person to see Saturn’s rings when he turned his small telescope skyward in 1610, although he didn’t know what to make of what he saw. Drawings in Galileo’s hand of his blurry view of Saturn show Saturn with flanking blobs of light that don’t look much like rings.

Dutch astronomy Christian Huygens is widely believed to be the first to propose, in 1655, that observations of Saturn’s appearance could be explained by a thin ring surrounding the planet.

If you read my article in March 2008 and are now reading this article in April 2011, you can figure out something important about Saturn’s orbit.

Saturn was exactly at opposition on Feb. 24, 2008, and again on Apr. 3, 2011.

Let’s visualize what has happened in the past 3 years, 5 weeks and 4 days (there was a leap day in there).

On Feb. 24, 2010, Saturn stood exactly opposite the sun from our perspective. So, on a sheet of paper, with a dot representing the sun marked in the center, a line drawn straight out to the right would pass through Earth and Saturn (with Earth between the sun and Saturn).

On Apr. 3, 2011, Saturn stood again exactly at opposite the sun from our perspective. Since the last opposition, Earth has orbited the sun exactly three times… plus a bit more… 5 weeks and 4 days, or 39 days.

Why wasn’t Saturn at opposition again on Feb. 24, 2009, or again on Feb. 24, 2010? Because in the time it takes Earth to orbit the sun once, Saturn made some small amount of progress along its own orbit about the sun.

The orbits of Earth and Saturn (not to scale). Saturn was at opposition - opposite the sun in the sky - on 2/24/2008 and again on 4/3/2011.

Saturn orbits the sun much more slowly than earth does, and it is Saturn’s orbital period that we can figure out from these observations.

Since it took 39 days more than a year for Saturn to drift from opposition 2008 to opposition 2011, we know that Saturn has drifted just about 38 degrees around its orbit. This is so because the earth moves 360 degrees around the sun in 365 days, or a tiny bit less than 1 degree per day.

Saturn has made it only about 38/360 = 0.106 of the way around its orbit in 3 years, 5 weeks and 4 days, or 3.11 year’s time. Therefore, Saturn must go around the sun once in about 3.11/0.106 = 29.3 years.

According to NASA’s Saturn Fact Sheet, Saturn’s orbital period is 10,759 days – or 29.456 years.

Our calculation is pretty good!

Orion the hunter followed by his faithful hunting dog Canis Major both perpetually chasing their prey, mighty Taurus the Bull, have dominated the sky all winter long. But now these characters are setting shortly after sunset, replaced from the East by less severe constellations like Canis Minor (the little dog), Leo the Lion and Virgo the Virgin.

This changing of the guard is a sure sign that spring really is in the air. It’s hard to knock astrology in this regard.

Year after year, it’s cold and dark when Orion hunts high in the sky in the middle of the night. But the days always grow lighter and longer by the time he has chased his prey to the Western horizon in the early evening.

A most famous astrological connection is that between the annual flooding of the Nile River in Egypt and the brightest nighttime star: Sirius.

Sirius marks the nose of Orion’s hunting dog Canis Major. This time of year, Sirius is easily spotted in the Southwest an hour or two after sunset, an outstretched hand or two down and to the left of Orion.

Every year beginning in August and running into September, the Nile River spills over its banks and floods the plains through which it runs.

These plains have been fertile farm lands for thousands of years, and the flooding of the Nile has long punctuated the calendar of civilizations settled in the Nile River valley.

An ancient Egyptian farmer would need to be ready to plant after the flood of the Nile and must be sure to harvest before the next.

The bright star Sirius foretold the flood of the Nile. About 5,000 years ago, the bright star Sirius underwent what is called its helical rising – that is, Sirius rose with the sun – in early September.

Short term weather clues can be misleading – like week-long stretches of below-freezing nights in early spring. But ancient Egyptian farmers could know that the Nile flood was eminent when Sirius rises with the sun, regardless of the prevailing weather.

In modern times, Sirius’ heliacal rising is in the very beginning of August, some weeks before the flooding of the Nile.

All the signs have drifted since the hay days of astrology. The drift is caused by the slow wobble of Earth’s rotational axis. Today, for example, Polaris in the Big Dipper is the North Star, but 12,000 years ago, Vega in the constellation Lyra was the North Star.

Our astrological or birth signs have drifted too.

Born in late September, I’m a Libra, making me inclined to doggedly seek balance in my life – but yet never to achieve it.

True enough, I do seem to seek balance without achieving it, but on the day I was born the sun was in the constellation Virgo.

Astrology – the study of connections between arrangements in the heavens and our affairs on Earth – is not without merit, however, especially if cause is not attributed to these arrangements.

Maybe I am the way I am less because the Sun was in a certain constellation on the day I was born and more because I suffered my first Midwestern winter during the most formative first six months of my life.

Maybe my lively and more cheerful wife, a Gemini who reaches a milestone birthday this year in late May, is the way she is because she spent her first months laying on a blanket in the warm sun picking at grass leaves and playing with ladybugs.

The article originally appeared in the Grand Haven Tribune on 1 April 2011.

While our circumstance in this regard may sound dire, biological systems on Earth have a fair amount of built-in, although limited, resiliency when it comes mitigating the effects of radiation exposure.

Radiation is a form of matter/energy that mankind has known about since the last years of the 19th century when Bavarian physics professor Wilhelm Roentgen discovered “X-rays”, the same X-rays that are used in medicine and security to image our insides.

X-rays are a form of what scientists call ionizing radiation: radiation with sufficient energy to strip orbiting electrons from atoms and molecules, forming electrically-charged atoms called ions and electrically-charged molecules called free radicals.

Ionizing radiation, as you might imagine, is damaging to living systems. Ions and free radicals don’t behave as their neutral counterparts do, and they generally mess up the physics and chemistry of life.

Radiation is a little mysterious and very frightening. Consider the events unfolding around the damaged nuclear reactors in Japan.

News reports of the radiation tragedy in Japan cause concern for our personal safety here in the US, more than 7,000 miles away.

Here is what you need to know about radiation to evaluate radiation risks.

First, know that radiation does not exist apart from normal matter. A radioactive atom of iodine, for example, differs from a normal atom of iodine in the nucleus; radioactive iodine has one or two more neutrons than does normal iodine.

Scientists call atoms of a particular material that have different number of neutrons isotopes.

These extra neutrons make a radioactive isotope unstable, and eventually it will fragment into lighter, more stable elements and in the process, it will release a relatively large amount of energy in the form of high-speed subatomic particles (like electrons) and high energy photons (like X-rays) – what we call radiation.

Most radiation does not travel very far. It is absorbed by most anything it hits, including air molecules.

Some radioactive materials – normal materials like dust particles and gas molecules, but containing some radioactive isotopes – can be transported by wind, for example, after they are formed.

We call material like this that settles out onto the landscape radioactive fallout. Radioactive fallout in high concentrations can render large swaths of land uninhabitable for generations.

Second, know that radioactive fallout does not travel long, long distances in high concentrations.

While there are reports that radioactivity from the disaster in Japan has reached the U.S., for example, these reports are mostly a testament to our ability to detect the presence of unbelievably tiny amounts of radioactivity.

For example, with modern instruments it is easy to detect the radioactive decay of just ten radioactive atoms in a sample of material the size of a sugar cube.

Lastly, know that we are bathed in background radiation on a daily basis. About half of our average annual exposure is natural, coming from terrestrial and extraterrestrial sources. We accumulate the other half of our exposure from medical tests and procedures.

Living cells are damaged by exposure to radiation, but at low exposure rates, cells either repair themselves or die of more or less natural causes.

At high exposure rates, however, cells are damaged and die off in large numbers, leading to illness and eventually to death.

The events unfolding in Japan are a tragedy to be sure for the people of Japan living and working near the damaged nuclear reactors.

But there is no risk to us here in the U.S.

This article originally appeared in the Grand Haven Tribune on 25 march 2011.

The Milky Way in a very dark sky.

On a clear night when the sky is truly dark one can see literally thousands of stars.

Most of us, however, see far fewer when we take the opportunity to look, because for most of us the night sky is washed out by ambient, artificial light.

The fact is we are all afraid of the dark. We put exterior lights on our houses, we burn streetlights all night to illuminate our streets and neighborhoods, and businesses illuminate their store fronts and parking lots with lights that sometimes rival the brightness of the mid-day sun.

At night all of this light adds up to wash out the night sky, constituting what some call light pollution.

Light Pollution in Los Angeles, CA -- the City of Lights.

For six years now a consortium of scientific organizations has organized a `citizen science’ effort that you can participate in to quantify and map the extent of light pollution around the globe.

The program is called GLOBE at Night, and it is a collaboration between the National Optical Astronomy Observatory (NOAO), the Environmental Systems Research Institute, Inc. (ESRI), the International Dark-Sky Association (IDA) and Centro de Apoyo a la Didactica de la Astronomia (CADIAS) with past sponsorship from The Global Learning and Observations to Benefit the Environment (GLOBE) Program.

The idea is pretty simple: citizen scientists are encouraged to go outside and observe the constellation Orion and then report their observations at the program’s website at www.globeatnight.org.

This year, two campaigns are planned. One is running from Feb. 22 to Mar. 6; the next will run from Mar. 22 to Apr. 4. These observing windows are set to avoid the bright moon which will do its part to light up the night sky during the middle two months of March.

If you would like to contribute an observation or two to this fun global effort, you will need only to follow a simple observing protocol, and you will need to know your latitude and longitude.

The observing protocol (described in more detail at www.globeatnight.org) involves going outside an hour or more after sunset, letting your eyes adapt to the darkness for a short time, then comparing your view of Orion – the number of stars you can see – to one of eight “magnitude charts.”

Observations are reported at the GLOBE at Night website by filling out a simple form.

In order to submit an observations – and you can make as many as you like from many different places – you will need to find the latitude and longitude of your observing spot. You’re cell phone might provide this, or maybe you have a GPS. As a last result you can look up latitude and longitude on line using Google maps or Mapquest.

In past years tens of thousands of observers contributed data to the project.

We don’t need to see a dark, star-filled sky, free of light pollution. But some of us want to. Debate about light pollution cannot rise to the level of debate about more exciting issues like climate change.

But there is one practical consideration. Any man-made light that makes it up to the sky and heads out to the stars is surely wasted. Calling attention to light pollution might help us make more energy-efficient decisions about artificial lighting.

This article originally appeared in the Grand Haven Tribune on 4 March 2011.

Artist rendering of Stardust-NExT spacecraft nearing comet Tempel 1 (courtesy NASA).

The spacecraft is NASA’s Stardust probe, a 300-kilogram solar-powered spacecraft that has been working in the inner solar system since its launch on 2 Feb. 1999.

Long before Stardust began chasing it, Comet Tempel 1 was the focus of a NASA mission called Deep Impact.

The Deep Impact spacecraft was launched relatively recently, in Jan., 2005, with the aim of chasing down, photographing, and bombarding Tempel 1.

In late June, 2005, Deep Impact released a probe called the Smart Impactor (that’s a nice professional wrestling stage name) which was a spacecraft with small maneuvering engines, cameras, and communications gear of its own.

But the Smart Impactor was mostly inert mass – about 800 lbs of pure copper – designed to smash into Tempel 1 so Deep Impact could analyze and photograph the resulting crater and debris.

The impact went off as planned on July 4, 2005, when the Smart Impactor maneuvered itself into the path of comet Tempel 1 and hit the brakes.

So “technically” (as my seven-year-old has become very fond of saying) Tempel 1 hit the Smart Impactor, producing a tremendous collision which scientists analyzed thoroughly.

Images of the impact on Tempel 1 (courtsey NASA). Click the image for a high-res version and NASA's Deep Impact website.

Stardust’s primary mission, however, didn’t involve Tempel 1.
In 2006, after flying by a comet called Wild 2 (pronounced “Vilt 2”, it delivered back to Earth a small capsule containing material picked up in space near the comet.

This was the first time cometary material had ever been brought back to Earth for scientists to study.

After the successful sample return, NASA managers nudged Stardust into retirement by shutting down all but the most essential systems aboard the spacecraft. But several years later, like a high-profile sports star, Stardust came out of retirement for one more mission: Stardust-NExT.

For its encore, Stardust flew by the comet Tempel 1 on Valentine’s Day, 2011, this time taking only pictures.

Image of Tempel 1 taken by Stardus (courtesy NASA). Click the image for a link to NASA's Stardust-NeXt site.

But the pictures will are valuable because we’ve pestered Tempel 1 before.

Since Deep Impact visited in 2005, Tempel 1 has made nearly a complete orbit around the sun.

Comets are often modeled as dirty snowballs, and when comets slip close to the sun, the story goes much like “Frosty the Snowman.”
Scientists are interested to see specifically how the surface of Tempel 1 has changed since we last had a good look at it in 2005.

Stardust’s Valentine’s Day 2011 encounter will make Tempel 1 easily the best studied comet in history.

You can read much more about the Stardust-NExT mission and watch for pictures as they become available at the mission website stardustnext.jpl.nasa.gov.

This article originally appeared in the Grand Haven Tribune on 11 February 2011.

NanoSail-D’s primary mission is to “… deploy a highly compact solar sail/boom system and validate de-orbit functionality,” according to the published mission overview.

Artist's conception of NanoSail-D in orbit. Image courtesy NASA. Click the image for a (PDF) NanoSail-D fact sheet.

NanoSail-D’s sail isn’t designed to sail the satellite to the stars; rather, its purpose of “validating de-orbit functionality” means that the sail is supposed to help the satellite dissipate energy and crash back into Earth’s atmosphere in about 100 days.

The sail, made of an aluminized space-age fabric, is about 10 square meters in area – a bit larger than the sail on a Laser sailing dinghy.

Launched by NASA on Nov. 19, 2010 from a launch pad on Kodiak Island, Alaska, aboard a larger host satellite called FASTSAT (a `bacronym’ for Fast, Affordable, Science and Technology SATellite), NanoSail-D was commanded to eject from its berth and unfurl its solar sail on Dec. 5, 2010.

But inexplicably, when it was commanded to eject from FASTSAT, the blender-sized microsatellite became stuck. The spring that was to push NanoSail-D from its housing didn’t get the job done.

Mission managers were disheartened, until Jan. 17, when surprisingly NanoSail-D sprung free. Three days later it’s sail deployed as planned and the mission was off and running.

NanoSail-D is equipped with a low-power radio transmitter that operates on a frequency allotted to amateur radio operators. Powered by a small battery, the beacon sent telemetry packets what were received by amateur radio operators around the world and forwarded to mission control at Santa Clara University in Santa Clara, CA.

On-orbit mission control for the NanoSail-D mission is being provided by the students, staff and faculty of the Robotics Systems Laboratory at SCU.

The beacon went silent on Jan. 21, when the battery went dead as expected. But people around the world are still making contact with NanoSail-D visually.

In fact, NASA and the publishers of the website spaceweather.com are sponsoring a photo contest “… to encourage photography of NanoSail-D, the first solar sail to circle Earth in low orbit,” according the contest website nanosail.org.

The rules go on to stipulate that “Cash prizes will be awarded to the first ($500), second ($200), and third ($100) place photos, judged by a NASA-appointed panel on the basis of beauty and technical merit.”

You can view predictions for catching a glimpse of NanoSail-D at a number of satellite-spotting websites, including spaceweather.com, heavens-above.com and calsky.org.

While on average not a bright as the International Space Station, NanoSail-D can produce extremely bright flares if sunlight glints off its shiny sail just right.

But don’t procrastinate. NanoSail-D is expected to re-enter Earth’s atmosphere in a fiery spectacle as early as April of this year. As the tiny spacecraft descends, it should, however, get brighter and brighter.
More information about NanoSail-D is available online at nanosail.org.

This article originally appeared in the Grand Haven Tribune on 4 Feb. 2011.

Although I am bigger than both my dog and cat, either one of them could easily beat me in a race across the yard.

If I were empty handed and really hungry, I would have to eat plants and worms because I surely couldn’t catch a bird, rabbit, squirrel, chicken or even a fish; and while I might be able to catch a sleepy cow or an inattentive pig, what would I do then? Both are bigger than me.

The famous British astrophysicist Sir Arthur Eddington (1882-1944) noted in the introduction of his 1932 book entitled Stars and Atoms that “Nearly midway in scale between the atom and the star there is another structure no less marvelous — the human body.”

A representative star – a star a bit bigger than our sun, because our sun is on the smallish side as stars go – is about 10 billion meters across.

An atom is very small, maybe just 10 billionths of a meter across.

What is the average of a star and an atom? To average two numbers, you add them up and divide by 2.

In this case the result is exactly half the size of a star, because 10 billion meters plus one 10 billionth of a meter is still 10 billion meters, half of which is 5 billion meters, or half the size of a star.

Clearly this isn’t what Sir Arthur Eddington meant.

Another way to quantify the midpoint between two numbers is to determine what mathematicians call the geometric mean.

The geometric mean of two numbers is the square root of their product. In other words, to find the geometric mean of two numbers you multiply them and take the square root of the result.

The geometric mean is useful when one number is much, much bigger than the other; it is a way of averaging that doesn’t let the really big number take over.

For example, the average of 1 and 100 is nearly 50, but their geometric mean is 10.

In the case of an atom and a star, one 10 billionth times 10 billion equals 1, and the square root of 1 is 1. So the geometric mean of the size of an atom and a star is 1 meter, a length that is on par with the size of a human.

So the next time you are feeling small and insignificant, just remember you are by this measure halfway between an atom and a star.

Here is another way to put yourself into perspective: the Milky Way galaxy contains 100 billion stars, yet the number of cells in your body is 1,000 times greater – 100 trillion.

And every cell in your body contains in its DNA all the information needed to make another copy of you.

Highlighting how big we humans actually are, the famous American physicist Richard Feynman (1918-1988) gave a talk he entitled “There is plenty of room at the bottom” at the 1959 meeting of the American Physical Society. A transcript of his talk is available here.

Feynman’s talk was about nanotechnology, and at one point he mused that if bits of information were to be encoded into bits of matter consisting of 100-atom chunks, it would be possible to put the sum total of mankind’s collective wisdom – the contents of Earth’s major libraries – into a speck of dust just barely visible to the unaided eye.

Viewed in this light, we humans are really much bigger than it seems… or we just don’t know that much.

This article originally appeared in the Grand Haven Tribune on 28 Jan. 2011.

If I hold this conviction as a result of a brainwashing at the hands of a nefarious conspiratorial organization, the brainwashing was first-rate because I don’t remember it at all.

What I do remember is spending a lot of time studying objectively how the physical world around me works. I remember influential teachers and interesting books, real-world experiences and long periods of quiet introspection. What is in my brain I am pretty sure I put there myself.

I remember reading that the first life forms on Earth were algae cells and later, microscopic bacteria, that thrived in Earth’s primordial atmosphere, which consisted of a rich mixture of noxious gases like methane, ammonia, chlorine, sulfur dioxide and carbon dioxide. The prolificacy of these life forms is well documented in the geologic record (i.e. fossils).

The single-celled Earthlings lived in the oceans. First they generated their energy for life by consuming inorganic materials and the abundant atmospheric carbon dioxide. Then they developed the ability to digest organic matter using sunlight as a catalyst, still consuming carbon dioxide but now farting little bubbles of oxygen – the process we call photosynthesis.

At this time in Earth’s history, the planet was on average much warmer than it is now. Warmer, even though the sun itself was only about seventy percent as bright as it is now. Earth was warmer in spite of the young, cool sun because of all the atmospheric carbon dioxide.

It is a well established fact that carbon dioxide and other similar gases concentrated in the atmosphere trap infrared light reradiated from Earth’s surface, and make Earth warmer.

Over time, all the little oxygen farts added up. So prolific and so industrious were the first of Earth’s little beasties that as time rolled on they consumed nearly all the carbon dioxide and increased to today’s level the concentration of oxygen in Earth’s atmosphere – a deadly poison to the creatures themselves.

The Earth cooled, the algae and bacteria that couldn’t survive in the now heavily polluted atmosphere died off, and other forms of life developed that needed oxygen to generate their energy for life.

Earth recycles everything. All the carbon that was locked in carbon dioxide in Earth’s primordial atmosphere four billion years ago is still here on Earth. And Earth’s global ecosystem can accommodate anything that can scratch out a way to survive.

Earth’s global ecosystem has long accommodated balanced populations of oxygen-consuming/carbon dioxide-producing species (“animals”) and carbon dioxide-consuming/oxygen-producing species (“plants”).

And the human species thrives, easily the most industrious of Earth’s present day inhabitants.

It is undeniable that since the industrial revolution, human activity – mostly the combustion of fossil fuels to heat our homes, run our businesses, and provide long-distance transportation – is increasing significantly the concentration of carbon dioxide and other “greenhouse” gases in the atmosphere.

“Animals” are producing way more carbon dioxide than “plants” can process back into oxygen.

Earth’s global climate and ecosystem is finding a new balance.

We argue over the details as we try to sense, quantify and predict the way Earth’s global climate and ecosystem are changing. And each of us decides for ourselves what is important.

But Earth will go on and our offspring will adapt or die out as the climate changes as a result of our activity.

I have heard the message passed on from Earth’s first inhabitants: climate change is for real.

This article originally appeared in the Grand Haven Tribune on 21 Jan. 2011.

JPL manages the Cassini mission for NASA and the European Space Agency. Cassini is an interplanetary spacecraft orbiting Saturn loaded up with a number of instruments, but most importantly, for Saturn’s facebook page, a fine digital camera.

The Casini spacecraft (image courtesy NASA).

Saturn is the patriarch of our solar system. In Roman mythology, Saturn is the father of Jupiter; ancient Greeks called him Cronus, the god of time.

Saturn is most known for its spectacular system of rings, which were first discovered by Galileo more than four hundred years ago now. Saturn’s rings are easily visible to a careful observer with a small telescope held steady on a tripod. They are composed of small chunks of rock and ice, material that would have formed into a moon were it further away from Saturn itself.

Even though Saturn’s ring material never formed into a moon, he is not deficient in this statistic. It’s difficult to decide when to stop counting the tiny bodies that orbit Saturn, but conventionally, it is believed that Saturn has twenty four regular satellites.

Saturn’s largest moon Titan, oddly enough, is often said to be the other place in the solar system that is most like Earth. Titan is about 40% the size of Earth, with a substantial atmosphere composed mostly of nitrogen, just like Earth.

But the most recent updates to Saturn’s facebook page have focused on images of his lovely wife Rhea. Rhea is Saturn’s second-largest moon. She is about half the size of our moon, completely lacking an atmosphere, like our moon, also heavily cratered.

Rhea's cratered surface imaged as Casini sped past in March 2010. Image courtesy NASA and JPL.

The Cassini spacecraft, with the camera that is taking the most recent pictures of Rhea, was launched on Oct. 15, 1997. Cassini traveled 3.5 billion km (2.2 billion miles) to reach Saturn on June 30, 2004. Since then, Cassini has been in orbit, taking pictures and doing experiments, including launching a probe that sped into Titan’s atmosphere six years ago on Jan. 14, 2005.

Cassini’s orbit around Saturn and its rings and moons is managed and updated by mission controllers back here on Earth. It is interesting to note that the commands sent to the spacecraft by radio and the data that the spacecraft sends back, streaming through empty space at the speed of light, take about an hour and twenty minutes each way to make the trip. Controllers must work with Cassini in the past.

The high-resolution images coming down from the spacecraft were captured when Cassini sped past Rhea swooping to within just sixty miles of its cratered surface. But the encounter happened in March of 2010! Cassini is capturing so much data that the data must be buffered and sent back to Earth when time and orientation permit.

The images that are coming down now of Rhea show remarkable detail. On one hand, the images look like many other pictures of our moon one might see in books or online. On the other, it is mindboggling to think where these images are coming from and how we are getting a look at them – what a spectacular accomplishment.

An accomplishment that largely goes unnoticed, given the things that compete for our attention these days.

Take a look for yourself at Saturn’s facebook updates at http://saturn.jpl.nasa.gov.

This article originally appeared in the Grand Haven Tribune on 15 January 2011.