Bumps and ripples in the otherwise flat ring system of Saturn cast long shadows at equinox. Image credit: NASA/CassiniImagine a vast, flat plain spreading out before you for tens of thousands of miles in all directions, with no Earthly curvature to give the horizon its slightly finite look. Instead, it stretches seemingly to the infinite blackness of space in one direction, and slices straight into the streaky, wind-smoothed clouds of Saturn in the other…

Hard to imagine what it would be like to float just above the rings of Saturn, but what a sight it must be! As a kid, one of my favorite astronomical pass-times was imagining the view from other places in the Solar System.

Now imagine a towering bulge of frosty mist rising up out of this super-flat plane of ice chunks, literally the size of a mountain. Such is what was beheld by NASA's Cassini spacecraft last month–albeit, from a distance–when it turned its cameras to Saturn's vast rings during the few days surrounding Saturn's equinox (August 29, 2009), giving us a view never before seen.

Equinox on Earth, when the Sun is positioned directly over our equator, happens twice a year. Due to Earth's tilted rotational axis, as we orbit the Sun the latitude over which the Sun shines directly cycles north and south between the latitudes of the Tropics. On its way north to warm our (Northern Hemisphere) summers or south to leave us in the chill, the Sun crosses the equator on the equinoxes (Fall and Spring).

The same thing happens on Saturn, with two differences. First, Saturn takes nearly 30 years to orbit the Sun, so equinox comes only about every 14 years. Second, Saturn has its system of rings that encircle the planet directly above its equator, serving as a visible extension of the equator. At Saturn's equinox, the Sun is not only directly over the equator, but sunlight strikes the rings edge-on, like a flashlight shining on a flat piece of paper from the edge, the light just grazing over the surfaces on either side.

When this happens, any deviations from the flatness of the ring system—bumps and ripples–cast long shadows across the rings, making the features much easier to see. The same thing is seen on that piece of paper with shadows from creases and bumps leaping across the page.

As seen from Earth, equinox on Saturn means the rings appear to vanish as we look at them edge-on. This behavior puzzled astronomers long ago before they understood the rings for what they are. During the August 2009 Saturn equinox, however, for the first time in history we had a bird's-eye view of the rings during equinox, from Cassini. Cassini has been in orbit around Saturn for five years now.

Cassini spotted a number of prominent shadows trailing bright spots and ridges—bumps and ripples of different sorts rising above the ring plane.

Some of the bumps–icy ring material kicked up by the gravitational disturbance of a small moonlet inside the rings–were measured at over two miles high, the height of the Rocky Mountains. Other rippling features, such as long ridges running along the direction the rings encircle Saturn, are waves created by the gravity of moons orbiting outside the ring system. Still other types of disturbances observed are possibly caused by the impact of meteoroids or chunks of ice with the rings.

Saturn's rings are tens of thousands of miles across, but are extremely thin—perhaps no thicker than the height of a four-story building! So a bump or ripple as high as a mountain is a big deal!

Ah, to be on Saturn, now that equinox is here…

Map of Moon water; blue indicates higher concentrations of detected water molecules. Credit: NASA/Moon Mineralogy Mapper instrument.Here it comes! A veritable tidal wave of discovery on Earth's Moon….

In one short week, NASA's LCROSS (Lunar Crater Observation and Sensing Satellite) mission will quite literally come to an end—a fiery, spectacular end as it deliberately crashes into the lunar South Pole crater Cabeus A in hopes of kicking up enough material for us to detect the presence of water. If you want to see the action as it happens, come up to Chabot Space & Science Center on Friday morning, October 9, 3:00 AM to watch NASA's live simulcast and–weather and the gods of astronomy permitting–the view through Chabot's 36-inch telescope, "Nellie."

In recent months, NASA has been sending a lot of acronyms—excuse me: spacecraft—to the Moon: LRO with it's LROC, LEND, and LOLA instruments; LCROSS (which I've heard some call "LaCROSS," for the record) with its VIS, NIR, MIR, TLP, VSP, NSP—oh, the list goes on!

The fact of the matter is MOON spells "Moon." Whether or not we do end up returning humans to the Moon in the next decade, which is partly what reconnaissance by LRO and LCROSS and their arrays of acro-instrumentation is for, there are still things to be learned about our nearest neighbor in space—and water is the word at present.

Even as LCROSS and its Centaur-booster-rocket-turned-lunar-clobbering-device follow their final fatal trajectory toward Cabeus A, its launch buddy LRO, now in an orbit around the Moon and beginning to send back scientific results and images, may have already detected telltale signs of the wet stuff—which on the Moon won't be wet, but frozen solid, of course; liquid water cannot persist in the Moon's airless environment.

LRO's LEND (Lunar Exploration Neutron Detector) instrument is designed to find signs of water molecules by measuring neutron radiation emanating from the lunar surface. The Moon is constantly bombarded by high energy cosmic radiation, which forms radioactive isotopes in the soil that in turn emit neutrons. By measuring the abundance and speed distribution of the neutrons, details of soil chemistry can be inferred. The presence of light atomic nuclei–in particular the lightest of all, hydrogen, a component of water—in the soil reduces the levels of neutron emission. That drop in neutron radiation is the telltale scientists are looking for.

While LRO scientists want to make further measurements before concluding the presence water ice concentrations, observations from three other spacecraft—NASA's M3 instrument (Moon Mineralogy Mapper) aboard India's Chandrayaan-1 spacecraft and the Cassini and EPOXI spacecraft—have mutually confirmed the presence of water and hydroxyl molecules (hydroxyl is a water molecule missing one of its two hydrogen atoms) in the soils of the Moon, across much wider expanses than the confines of dark polar crater floors.

Cassini and EPOXI made measurements as they flew past the Moon to their respective destinations (Saturn, and a comet), and measurements have been made by M3 from lunar orbit. The detection of water by these spacecraft doesn't mean seas of liquid or glaciers of ice, or even blanketing layers of gaseous water vapor, but rather relatively small amounts of water and hydroxyl molecules attached to, or "stuck to," other materials in the top few millimeters of soil.

This thin "confetti" of water molecules appears to come and go with lunar daytime, forming during the cold, dark two-week-long lunar night and diminishing under the baking light of the Sun.

So, right now, MOON spells water (M3 et al), water (LRO), and possibly more water (LCROSS, on October 9th)—at least, the evidence seems to be mounting!

The LCROSS satellite, launched on June 18th, is slowly making itself ready to smack into the moon in late October. A plume of dust 37 miles high will be produced, which may be visible from Earth (most likely Hawaii). The envy of the Mythbusters, this explosion is designed to find water in permanently shadowed areas of the moon. Much has been written on LCROSS, from historical perspectives to cost containment.

As the impact grows closer, NASA is making an effort to talk about the locally driven mission. Many of the upcoming talks are suitable for any audience, from kids to adults.

Luna Philosophie: Hitch-hiking to the Moon

Where: Scribd, 539 Bryant St. (2nd Floor), San Francisco

When: Wednesday, 9/23 6-8 PM

Cost: Free, RSVP to Delia.L.Santiago@nasa.gov

Details: Dr. Kim Ennico, LCROSS Payload Scientist and the LCROSS Payload Integration & Test Manager, will provide an overview of the NASA LCROSS mission and discuss how NASA has been expanding the concept of “participatory exploration” with LCROSS as an example. This will be a lively discussion.

Andrew Chaikin on LCROSS

Where: Chabot Space & Science Center

When: Saturday, 9/26 3-430 PM

Cost: Free with Museum Admission

Details: Author, speaker, and space journalist Andrew Chaikin joins Chabot visitors for a night of moon conversation and exploration. Using the detailed program Google Moon, which he helped to develop, Chaikin takes the visitor on a guided tour of the moon’s surface. Chaikin will also discuss the recent LCROSS mission and his extensive knowledge of the Apollo missions.

To the Moon: A Look at NASA’s Upcoming Lunar Impact Mission and the History of Moon Exploration

Where: Exploratorium

When: Sunday, 9/27 2-4 PM

Cost: Free with Museum Admission

Details: Take a trip to our nearest neighbor in space with renowned science journalist and space historian Andrew Chaikin. Relive the achievements of Apollo lunar astronauts and learn about the ambitious LCROSS mission, which will send a rocket crashing into the moon’s permanently shadowed regions to kick up huge plumes of debris in the hopes of uncovering deposits of ice. In addition, Exploratorium educators will give an entertaining and interactive overview of moon science.

QUEST on KQED Public Media.

Block Island—a half-ton meteorite found on Mars by NASA's Opportunity rover.Image credit, NASA/MER OpportunityEver been driving down a lonely desert highway when you suddenly glimpse something in the corner of your eye that makes you think, "What was that?!" You brake, tires screech, you spin the wheel and make a wild U-turn, cutting into the shoulder and leaving a rooster-tail of dust as you floor the gas to get back to what you thought you saw….

Okay, dramatic desert car scene ended. That would be the Hollywood movie version of what NASA's Mars Exploration Rover Opportunity did recently, on the lonely desert highway that it's scouting on Mars.

On its determined long trek from Victoria Crater to the larger Endeavour Crater (a 12-mile span that Opportunity has completed about one fifth of over the past year), the rover passed by an X-box-sized block of iron that presented the appearance of a meteorite. It snapped a picture in passing, which was eventually transmitted to Earth and examined. By this time, Opportunity had already traveled about 180 meters beyond the block (dubbed "Block Island"). This is when the rover was commanded to backtrack all the way to the find (though it's doubtful it worked up a rooster tail).

Upon returning to Block Island—quite obviously an iron-nickel meteorite by appearance alone, but whose composition was confirmed by the rover's alpha particle X-ray spectrometer instrument—Opportunity took more pictures, including extreme close-ups with its microscope camera, which revealed surface patterns similar to those found on Earth iron-nickel meteorites that have been exposed to long-term weathering by wind and sand.

As interesting as stumbling upon a half-ton meteorite on the dusty plains of Mars' Meridiani Planum is, what this particular chunk of weathered iron is telling scientists sparks the imagination. In a nutshell, given the thinness of Mars' current atmosphere, scientists wouldn't expect a meteorite of this size to survive impact intact, at the speed it would be going. One of the possible explanations for Block Island's rock-houndable state is that when it fell to Mars, Mars' atmosphere was substantially thicker than it is now.

Further examination of the meteorite may reveal clues as to how long ago it fell through Martian skies. Evidence that Mars' atmosphere was warmer and thicker in the distant past, as well as the possibility that there was liquid water on the surface, has been mounting over the years. The age of this meteorite-fall could shed more light on the history of Mars' environment. If it fell billions of years ago, Block Island would weigh in as more evidence to support our current suspicions. If, however, we find that it fell more recently, then this could indicate that the atmosphere was more substantial later in Mars' history than we thought.

Imagine, if you will, a Mars that looks even more Earthlike than it does now: seas of water with waves rolling into shorelines, great clouds sending downpours of rain and snow onto mountains and plains, streams and rivers snaking through the landscape. Maybe, maybe, even some form of life?

All that from a rock? Yes, rocks talk, if we listen.

Neil Armstrong’s left boot print on the Moon—the celebrated ‘one small step’. Credit: NASA
What were you doing 40 years ago, on July 20th, 1969, when the first human foot (booted, not bare) made its impression on the gritty surface of the Moon? That is, if you're over 40 yourself….

I was in Oakland, lying on the green carpet of my family's living room floor, watching our black and white Zenith television set—the kind that would take a minute or so to warm up before delivering the handful of local VHF TV broadcasts within range of our aerial antenna.

Right. It was definitely another era. As archaic as the telecommunications technology may sound to those born after, oh, 1980, it was nevertheless the Space, not Stone, Age…. Never forget, the Apollo 11 landing on the Moon was the culminating moment of the whole adventure that started the Space Age.

It didn't really matter that our Zenith was a b/w set, as all the images from Apollo 11 and the Moon's surface were transmitted in black and white anyway. My eyes were riveted to the TV, the grainy, fuzzy image of the Eagle's landing strut and ladder as yet empty.

"What's taking them so long?" I complained impatiently (I was seven years old). I remember waiting for what seemed a couple of hours for the astronauts to come out.

"They're probably playing poker inside," was my dad's reply. I don't recall if I believed him or not. Finally, there was a booted foot at the top of the ladder, attached to the bulky white and gray form of a human in a space suit—Neil Armstrong, of course. And, history was made—twice: Buzz Aldrin came down the ladder soon after.

Some of you younger crowd may have been born into a world where humans walked on the Moon a long time ago, but I was born around the time it was actually happening. (In fact, I was born the year after the first human went into space; similarly my grandfather was born the year of the Wright Brothers' first aerial success—how time flies….)

On Monday, we not only mark four decades since that singular historic event, we do so at a time when there are plans afoot for humans to step onto the Moon once again.

Several robotic probes have gone Moonward in recent years, paving the way: Clementine, Lunar Prospector, and only last month the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS) were launched in tandem. LRO will give us our most detailed and comprehensive view of the Moon's surface appearance and conditions to date, and will help to identify future possible landing sites. LCROSS will look for water ice in a crater floor at the Moon's South Pole by impacting it with an empty booster rocket and studying what is blasted skyward. Water on the Moon would be a resource to future human missions far more valuable than gold.

Neil's left boot print is still up there, next to the Eagle's landing foot, most likely as fresh and new looking as when it was made (unless it got bulls-eyed by a one in a million meteorite strike!).

As there is no air, and thus no erosion, on the Moon, the print serves equally well as a monument to that decades-ago venture, or as a logo for the enterprise of our return. Fitting, too, as the Moon could serve as a stepping stone to destinations beyond….

Credit: NASA.

When the LCROSS satellite, nicknamed Centaur, smacks into the south pole of the moon in late October, it is expected to produce a plume of dust 37 miles high, which may be visible from Earth with a good backyard telescope. It will be visible in an arc from Hawaii to Texas.

If you'd like to catch the impact, the Chabot Space and Science Center in Oakland is hosting a Shooting the Moon star party on the night of impact. Morrison Planetarium in San Francisco may host a star-gazing event, as well, but it hasn't been announced yet. And you could check in on other observatories in the Bay Area, as well: Lick observatory in the Santa Cruz mountains, Foothill observatory in Los Altos Hills, Sonoma State observatory in Rohnert Park, and the Fremont Peak observatory in the East Bay.

Not all of them will be open to the public; for instance, Foothill Observatory will be closed to the public, because they’ve been asked to take photographs of the event.

If you know anyone with a 10-inch telescope (that's the diameter of the lens), you can bet that telescope will be lined up to look skyward when the LCROSS probe hits the moon.

If the impact goes well, then the plume above the moon's surface could hover there for hours. It will make its own crater on the moon about 6 feet deep and 30 yards wide, so the plume of dust will not be visible to the naked eye, or even through binoculars.

The exact date, time and even the exact location of the impact have not yet been determined. Keep your eye on NASA's site for more information.

And one aside: This impact will not hurt the moon, or send it off its orbit. That may seem apparent to many people, but NASA Ames officials say those are the most-asked questions about the project.

Listen to the Crash Landing radio report online.

The Hubble Space Telescope being serviced by Space Shuttle
Atlantis astronauts in May 2009. Credit: NASAFour hundred years ago, Galileo built his telescope and became the first on record to point the new device (invented the previous year) at objects in the sky. Today (in fact, even as I write!) what has become a symbol for the current state of evolution of the telescope—the Hubble Space Telescope–is being repaired and upgraded by the crew of the Space Shuttle Atlantis…for the last time.

Galileo's telescope had a magnification of only about 27x, allowing him to see that Venus has phases like the Moon, Jupiter has four large moons of its own, Saturn does not appear as a simple disk but has unusual "projections" to either side, and the Milky Way contains far more stars than is apparent to the naked eye. And though these are features that can be seen through the least powerful home telescopes today, Galileo's observations changed the way we look at the universe.

Hubble has done the same thing, but on a modern scale of magnitude. Not a large telescope by the standards of ground-based behemoths like Keck in Hawaii (Hubble's primary mirror is 2.4 meters in diameter), Hubble's "edge" is it's location in space, orbiting the Earth over 300 miles high, outside of our atmosphere. Particularly in its earlier days before ground based telescopes were using adaptive optics techniques to compensate for atmospheric distortion, Hubble's vision on the universe was unparalleled in its clarity.

Here's is a recap of a few of the many big discoveries Hubble has made possible:

Dark Energy: By accurately measuring the distance and velocity of distant supernovae, over a large range of distances, Hubble has refined out knowledge of the rate of expansion of the universe–leading to the discovery that the expansion of the universe is actually accelerating, contrary to what was expected. Scientists suggest the existence of a mysterious "dark energy" throughout the universe that exerts an antigravitational repulsive pressure on the cosmos.

Age of the Universe: Since Edwin Hubble (for whom the Space Telescope was named) discovered that the universe is expanding, astronomers have been trying to determine how long ago the expansion began–how long ago the "starting gun" of the Big Bang was fired, and thus the beginning of the universe. Through precise observations with the Hubble, astronomers in recent years have been able to peg it between 12 and 14 billion years. (Most recently, observations made with the WMAP mission have honed that down to 13.7 billion years, give or take 0.13 billion.)

Supermassive Blackholes: Hubble found the clues that point to the existence of "supermassive" blackholes at the heart of maybe most–or every–galaxy. The Milky Way's own central blackhole has a mass equivalent to four million Suns.

Stellar Dust Disks: Before the first extrasolar planets were actually detected, Hubble observations revealed that flat disks of dust encircling young and developing star systems–aka "protoplanetary disks"–is commonplace. This has given us a glimpse at what our own solar system may have looked like before the planets formed.

It has been seven years since the last Hubble servicing mission, with another servicing scheduled a few years ago cancelled in the wake of the Columbia disaster. Several failing systems will be repaired or replaced this time, and other instruments are receiving upgrades that will make Hubble more powerful than ever in its declining years.

This mission to service the Hubble will be the last. Since NASA is retiring the Space Shuttle fleet after 2010, we will no longer have a space vehicle large enough to carry upgrade and replacement equipment to and from the Hubble. After that, the next new big space-based descendent of Galileo's spyglass will be the James Webb. Stay tuned…

Cal Poly's CP-4 mini-satellite in orbit. Credit: The Aerospace
Corporation.

It's a classic engineering story – a garage inventor spends years working in isolation, only to produce something that gets the attention of the world. Ok, the CubeSat story may not be quite as romantic, but it does have a lot of the same ingredients.

Professors at Stanford University and Cal Poly created CubeSats – 10 by 10 by 10 centimeter mini-satellites – as enginneering projects to give their students hands-on experience. Compared to standard satellite missions, which can run hundreds of millions of dollars and take years to complete, CubeSat missions are mean to be done cheaply and quickly.

CubeSat is also a standard – a basic blueprint that any university program can use. CubeSats are actually known as "FedEx satellites," since universities can mail them to Cal Poly to arrange a ride into space. They've created launching devices called P-Pods (a box that fits the CubeSats perfectly) so they can piggyback on larger rocket launches. Once the main cargo is deployed, the P-Pod releases the CubeSats into orbit. Depending how high they are, CubeSats can orbit for more than a decade before they burn up in the atmosphere.

What started at universities has spread – NASA, Boeing and other aerospace companies all have mini-satellite programs. Despite the small size, CubeSats are actually able to do valuable research. They can space test new technology, submitting it to all the rigors of space travel like solar radiation and launch stress. Recreating those conditions on the ground can be very expensive.

CubeSats can also gather scientific data. On Tuesday, NASA will be launching Pharmasat, which they hope will be their second nano-satellite in orbit. It will carry yeast samples, and once in orbit will hit them with an anti-fungal to see if their resistance is increased in space. NASA has previously observed that some bacteria are more resistant to antibiotics in space, something that could be dangerous for future human space travel.

You can tune in on Tuesday evening for the Pharmasat launch. Three other CubeSats from Cal Poly and other organizations will also be getting a lift into space.

Listen to the Do-It-Yourself Mini-Satellites radio report online, and see our Web Extra: Mini-Satellites Slideshow.

Artwork from Jules Verne’s 1865 novel, From the Earth to the MoonLaunching a spacecraft bound for the Moon with the deliberate intention of striking the Moon in a spectacular impact!

Sounds like something out of a Jules Verne novel… but that's exactly what NASA's up to this year with the upcoming LCROSS (Lunar Crater Observation and Sensing Satellite) mission, scheduled for launch on June 2nd and impact sometime in October– exact date TBA.

And it's not unprecedented, either: the Lunar Prospector spacecraft back in 1998/1999, whose instruments detected possible signs of water ice in craters around the Moon's poles, was crashed into the Moon's South Pole at the end of its mission. The aim was to blast up a cloud of material from the lunar surface and spectroscopically analyze the plume in search of water vapor. None was detected then, but that's where LCROSS comes in.

LCROSS will seek to verify the presence or absence of water ice and related hydrated materials buried at the bottom of a permanently shadowed crater floor on the Moon's South Pole. Water ice cannot persist on any part of the Moon's surface that is subjected to sunlight, but because of the Moon's low axial tilt with respect to the ecliptic (the Sun's apparent annual path in the sky)– only about 1.5 degrees– there are craters at the Moon's poles whose floors never see the light of day, all month long and year round. Water ice could persist near the surface in these places.

LCROSS consists of two pieces: a "Shepherding Spacecraft" that will guide the whole affair to the proper location on the Moon's South Pole, and the Centaur rocket stage that propelled the spacecraft to the Moon. The pair will separate, and the Centaur rocket will become the primary impactor, striking ground and producing a crater and plume of ejected material. Viewing the event from above, the Shepherding Spacecraft will use cameras and other instruments to analyze the plume from a distance, and will then follow the same course as the Centaur, descending four minutes after impact through the ejected plume and analyzing material samples as it falls.

Then, the Shepherding Spacecraft, too, will impact the Moon– and the plume it kicks up may well be visible through modest sized telescopes on Earth. We're planning to watch the explosion live through our telescopes at Chabot, weather permitting. Keep an eye on our website for details.

Now, back to Jules Verne for a moment. The launching of a projectile with the intent of striking the Moon was indeed the subject of one of his novels, From the Earth to the Moon, published in 1865. Fired from an enormous cannon, the goal of that post Civil War mission was to catch the attention of anyone living on the Moon, to open up a line of communication with their civilization.

My wife asked me if crashing a probe into the Moon would have any harmful effects, particularly if in fact there is any form of life (subsurface microbes or such) living there. Well, certainly, if you happen to be a lifeform living at ground zero of the impact… but the fact is the Moon is frequently struck by meteorites much larger than the LCROSS impactor anyway. To paraphrase Douglas Adams, "that kind of thing goes on all the time."

One last fun tidbit about the Jules Verne novel: the launch site for his cannon-fired projectile was a place in Florida, 50 miles south of Tampa Bay, and only about 135 miles from the Kennedy Space Center, from which LCROSS will be launched…

NASA/Mars Reconnaissance Orbiter; Fans of dark dust on Mars'
southern ice cap, apparently blasted from beneath the ice
by thawing carbon dioxide."

It's spring again, that time of year when my thoughts return to…blasts of carbon dioxide gas jetting up from beneath the frigid layer of dry ice below, carrying rusty red dust in plumes that jet toward the pale skies….

At least, that's what happens at the polar ice cap on the planet Mars. I'd sure love to be there to see it, even if there are no flowers in bloom. Still, there seems to be plenty of "blossoming" going on….

NASA's Mars Reconnaissance Orbiter—the spacecraft with that high powered camera that could spot a beach ball on Mars' surface—has captured images of the aftermath of some of Mars' springtime polar action. Appearing as dark fan-shaped bursts strewn across the thinning springtime polar ice, these features are explained as plumes of Martian dust that have settled after being blasted into the air by releases of gas pressure from under the surface of the ice.

To describe what's going on, let me paint a picture of the Martian polar region as it emerges from the deep freeze of winter into spring.

Mars' year is almost twice as long as Earth's—and so too are its seasons. Winter at the southern pole of Mars lasts almost six months. In that time, the normally freezing temperatures on the Red Planet plummet to as low as -225 degrees Fahrenheit at the pole. During this time, Mars' permanent water ice cap acquires a layer of frozen carbon dioxide (dry ice) on top, formed from carbon dioxide freezing directly out of the atmosphere.

This seasonal dry ice cap also forms around the edges of the water ice cap, covering adjacent ice-free surfaces as well. The carbon dioxide ice cap may grow to as much as a meter thick.

Then, as spring approaches and the ice cap gradually comes out of the dark and receives more and more sunlight, it begins to warm up (though don't get the impression that it is ever "warm" anywhere on Mars' surface! Air temperatures recorded by the Viking landers in Mars' more temperate latitudes was barely ever higher than 1 degree Fahrenheit). Spring Equinox in Mars' southern hemisphere was on December 26th.

As the layer of solid carbon dioxide heats up, its ices turn to gas, both at the top of the layer and beneath it as well. The gases forming underneath build up pressure, which seeks a path to escape. Evidently the pressurized carbon dioxide gas can actually carve channels in the Martian soils under the ice as it flows—said channels have been seen in the past after the seasonal ice cap dissipates entirely.

When the gases find a weak point in the ice, they can erupt upward, bursting into the air, sometimes carrying dust with it. The dust rockets skyward and is blown by prevailing winds, settling out on the ice in great dark fans—which is what Mars Reconnaissance Orbiter has shown us.

Ah, to be on Mars in springtime….