Martian dunes, captured by NASA's Mars Reconnaissance Orbiter

The motor in question powers a fan in an exhibit built to demonstrate the physical processes of duning—the fluid transport and deposition of solid particulates into collections and patterns. The fan blows up a constant micro-gale within the exhibit enclosure, and visitors get to play Mother Nature by turning a handle and redirecting the wind. Meanwhile, a mass of tiny white glass beads is constantly whipped up into a fair recreation of a sand storm on planet Arakis….

After the chore of installing the new motor, I rewarded myself by enjoying the exhibit a bit. I piled up all of the sand on one side of the tank to see how the fan would redistribute it; I sent the wind from different directions, watching how the freshly blown grains were scattered across the pristine black undersurface; I placed all of the pyrite rocks, which serve as wind obstacles, in one pile. It was a lot of fun.

One thing I noticed that I hadn't paid much attention to in the past was how the dune actually moved, or migrated. Maybe I hadn't watched long enough before, or maybe it was easier to witness because I had stacked the deck by mounding the sand all in one corner, but it was fascinating to see the process.

On the windward side of the giant dune, the scouring wind picked up the sand and carried it racing to the top—slowly peeling away the front face of the dune. As soon as the sand-laden wind reached the crest and took a sudden turn downward, it was slowed a bit, becoming less able to support the sand grains, which then fell out onto the leeward side of the dune in a sandy-wind version of precipitation. The buildup of sand on the lee side eventually formed small avalanches that slid down the face in little dry floods.

In this fashion, the dune moved along, slowly being erased on its windward side and formed on the lee.

Almost coincidentally, a few days later I read a report from NASA about sand dunes on Mars. In some areas, dunes have been observed to migrate over time, while on others the patterns have remained stock-still—some of them for perhaps thousands of years, or longer.

So I had successfully created the right conditions for a migrating sand dune. What about static dunes? Well—I had noticed already that some of the pyrite rock obstacles that I placed in the sand stream formed small dunes in the wind-shadows of their leeward sides. The rocks weren't moving, and so the dunes they were nurturing and protecting remained in place.

Some of the static dune ripples observed in Meridiani Planum—where the rover Opportunity is exploring—have been explained as possibly being protected by the presence of "blueberries": tiny nodules of gray hematite that have eroded out of Martian rocks, but which themselves are erosion-resistant, and too large (1-3 millimeters) to be carried by the wind. The blueberries, as the explanation goes, embed in the sand and form a protective "armor" layer for the dune ripples, which remain safe and still in their lee.

Where else do we find dunes, other than Earth? Well, you need wind of sufficient strength and sand of sufficiently small size, for starters. We don't know about dunes on Venus; Venus has a thick enough atmosphere, but the winds may be too sluggish to whip up much of a sand storm. The only other object with a thick enough atmosphere and a solid surface is Saturn's moon Titan—and in fact we have pictures of Titanian dunes taken by Cassini.

Now I'm feeling that old itch to make another trip to my favorite place in the Solar System, Death Valley, to explore the macroscopic dunes of Stovepipe Wells . I'll send a postcard….

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Sand dunes near Stovepipe Wells, in Death Valley. Photo: Craig Miller.

Now, okay, "quiet" is a somewhat subjective thing. When I lived on the upper (way upper) west side of Manhattan in the 1980s, any interval without hearing a car alarm seemed like blessed relief. Quiet can be measured, of course, with sound pressure meters. Anything below about 40 decibels is pretty darn quiet for most people's purposes.

The National Park Service (NPS) says the quietest place it has yet measured is a spot in Great Sand Dunes National Park, where Vicki McCusker, who helps oversee the natural sounds program for the Park Service, says it was "bottoming out" their meters.

I've never been there but it's hard to imagine greater quietude than an afternoon I spent in Death Valley. Coincidentally this was also on a sand dune, near Stovepipe Wells. It was also Christmas Day, which kept the tourist traffic to a minimum. It was at a point in my life when I was in desperate need of some deep introspection, so I parked my car along Highway 190 and trekked into the dunes, found an accommodating slope and sat down. Occasionally a fly (or something) would buzz by. Other than that, the loudest thing was the buzzing in my own head, which I can only hope would've been inaudible to anyone with me.

It's interesting how, when things get really quiet, our bodies try to make up for it with ringing ears and internal chaos. The noted bioacoustician Bernie Krause talks about the time he and his wife, Kat were hosting guests from New York, who literally had to leave the Krause's semi-secluded Glen Ellen "sanctuary" because the night-time quiet was creeping them out.

I asked Krause what he could draw from that. "Well, it tells me that we’re more insane than I ever thought in the first place," he mused. "I mean, we’re definitely verging on pathological.  Because it’s exactly those kinds of sounds–the urban acoustic envelope in which we enfold ourselves–that kind of urban noise that’s driving up the numbers of prescriptions for Prozac."

Surveys of national park visitors would seem to bear that out.  In the early 1990s, NPS surveyed 15,000 visitors in 39 parks, about noise issues (NPS manages 391 "units" nationwide, 58 of which are designated as "parks"). More than nine out of ten visitors surveyed cited "enjoyment of natural quiet" as a reason for visiting. This survey provided some juice for the ongoing natural sounds program in the parks.

An open question is: where does it go from here? Much of the current effort in the parks appears to be geared toward developing "air tour management plans," a response to concerns that first arose over the increasingly crowded skies above the Grand Canyon. McCusker told me that while aircraft overflights are the most pervasive noise issue across the parks, the most common complaint is probably over loud motorcycles (note to "straight-pipe" Harley owners).

Krause, who conducted a year-long project documenting soundscapes in Sequoia-Kings Canyon National Park, hopes the research will also be used to develop new rules governing on-the-ground noise pollution. "If the parks can set aside places where people can go and hear the natural world as it is, at any season of the year, then that will be a really big benefit for visitors coming to the parks," he says. "Otherwise, you’re seeing the parks with the wrong soundtrack. It’s like watching Star Wars without a soundtrack."

So check out this four and a half minute “journey” I produced with Bernie Krause, founder of Wild Sanctuary. It takes you from the familiar cacophony of the urban soundscape to a serene spot in Sequoia Park.

QUEST on KQED Public Media.

Listen to the radio report, "Soundscapes of National Parks" online.

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Mockup of Phoenix (top) and 'Robinson Crusoe on Mars'
(bottom)—both set in Death Valley National Park…
Credit: NASA (top), Paramount Pictures (bottom)

This time the flavor of the day is the Phoenix Lander, courtesy of NASA, scheduled to land on May 25th at about 4:38 PM PDT. We'll be watching live NASA coverage of the landing at Chabot Space & Science Center that afternoon, if you'd care to join us…

Following somewhat in the footsteps of the Viking landers of the 1970s, Phoenix's primary mission is to look for evidence of life, or at least the chemical conditions that might be suitable for life to exist. The two Viking landers carried small chemical laboratories that analyzed soil samples scooped up from the surface, as does Phoenix.

While its mission parallels that of Viking, one big difference from Phoenix is its destination: the Northern Polar Ice Cap of Mars. The Vikings landed much farther south in the mid latitudes. Phoenix is targeting the ices of Mars' arctic region.

Growing up, one of my favorite sci-fi films was Robinson Crusoe on Mars. Made in 1964, the same year that Mariner 4, the first space probe to Mars, was launched, RCOM made a descent stab at imagining what it was like. So what if the main character walked around in apparent t-shirt weather and with sufficient atmospheric pressure to keep his blood from boilin–he still wore a respirator that doled out oxygen from an ever-dwindling supply tank, a nod to Mars' thin atmosphere.

A couple of other things our astronaut Robinson Crusoe found on that fictional Mars that we are now looking for on the real one: liquid water and life…Our hero found small caches of water (with the help of a monkey) in grottos between the rocks, and, lo and behold, living in that water was a vine-like life form with edible fruit or tubers. He even took a foot-trek, along with his guy Friday, to the polar ice cap…

(I also loved the film because some of its "Martian terrain" scenes were shot in my favorite spot on Earth, Death Valley…)

Though evidence of past liquid water action seems to be all about the planet, Phoenix certainly won't find any brooks or pools or grottos of spring water, owing at least in part to the frigid arctic region it will set feet on–an arctic zone on a world where the warmest temperatures in the tropics might reach levels of the coldest climates on Earth. What's important about landing on Mars' ice cap is that Phoenix is almost certain to dig up some water–albeit frozen.

And it is the chemical compounds either locked up in that ice or preserved by its proximity that Phoenix is interested in. (Similarly, climatologists on Earth study ice cores from Antarctica to analyze the trapped and preserved gases of Earth's atmosphere of past millennia.)

We wish Phoenix a happy landing, and look forward to the first images and discoveries from the Martian North Pole. And I'm fairly confident the epic polar adventure ahead won't resemble in the least another "great" film of 1964: Santa Claus Conquers the Martians….

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.

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The Milky Way in the skies of Death Valley's
Devil's Racetrack. Credit: Dan Duriscoe, U.S. National
Park ServiceI just got back from my semi-yearly pilgrimage to my favorite spot on Earth: Death Valley National Park. My main reasons for returning to this place again and again have mostly to do with hiking in the stunning natural beauty of the place, reconnecting with good times in my childhood, and reflecting spiritually on life, the Universe, and everything.

But, I can't go to a place like that and not feel more connected with outer space. Not only is the night sky a celestial spectacle–but it's darned cold there too, this time of year! Cold, like space. Each turn of the Earth through its own shadow is like a quick dip in the icy pool of space….

After twilight had faded, after the campfire had burned to embers–and as the frigid cold of the desert winter night started seeping through my layers of clothing–I lay down on the picnic bench and raised my binoculars to my eyes…

…and that's all I had to do. Arcing overhead was the section of the Milky Way around the constellations Cassiopeia, Perseus, Andromeda, Pegasus–a section of the sky rich in a variety of "deep sky" objects (objects typically only visible through binoculars or telescopes).

There was the Double Cluster in Perseus–a pair of "open" clusters of stars.

Open clusters are stars bound together gravitationally, still clinging to each other after their "group infancy" in the gaseous cloud that gave birth to them. Stars in these clusters are young–and because of their youth, open clusters often contain a number of large, bright, blue stars that shine brilliantly–but which have short life spans as stars go, being more prolific hydrogen-burners (gas guzzlers). (In a word, you can't find an old blue giant star.)

You can't avoid seeing open clusters in this region; the place is positively littered with them….

This is also where the famous Andromeda Galaxy can be found, in the constellation Andromeda (where else?). What's special about the Andromeda Galaxy? For one, it's the closest large galaxy to our own, as well as the most distant object in the Universe that can be seen with the unaided human eye (without telescopic help). Looking at the Andromeda is like looking through a peephole into the realm beyond our Milky Way…

I could go on and on yakking about what I got to see in the clear, dark Death Valley skies last week, so I'll have to stop myself now. Suffice to say that with a dark sky, a pair of binoculars, and a segment of the Milky Way in view, encountering the celestial wonders of the Universe in a very personal way is like shooting ducks in a barrel.

But don't let the light polluted skies of the Bay Area stop you from trying it from your own backyard; there's a lot to behold despite the city lights…

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.